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 '''National Transportation Safety Board. 2000. Controlled Flight Into Terrain, Korean Air Flight 801, Boeing 747-300, HL7468, Nimitz Hill, Guam, August 6, 1997. Aircraft Accident Report NTSB/AAR-00/01. Washington, DC.'''

Abstract: This report explains the accident involving Korean Air flight 801, a Boeing 747-300, which crashed into high terrain at Nimitz Hill, Guam, on August 6, 1997. Safety issues in the report focus on flight crew performance, approach procedures, and pilot training; air traffic control, including controller performance and the inhibition of the minimum safe altitude warning system at Guam; emergency response; the adequacy of Korean Civil Aviation Bureau and Federal Aviation Administration oversight; and flight data recorder documentation. Safety recommendations concerning these issues are addressed to the Federal Aviation Administration, the Governor of the Territory of Guam, and the Korean Civil Aviation Bureau.

The National Transportation Safety Board is an independent Federal agency dedicated to promoting aviation, raiload, highway, marine, pipeline, and hazardous materials safety. Established in 1967, the agency is mandated by Congress through the Independent Safety Board Act of 1974 to investigate transportation accidents, study transportation safety issues, and evaluate the safety effectiveness of government agencies involved in transportation. The Safety Board makes public its actions and decisions through accident reports, safety studies, special investigation reports, safety recommendations, and statistical reviews.

Recent publications are available in their entirety at . Other information about available publications may also be obtained from the Web site or by contacting:

National Transportation Safety Board Public Inquiries Section, RE-51 490 L'Enfant Plaza, East, S.W.  Washington, D.C. 20594 (800) 877-6799 or (202) 314-6551

Safety Board publications may be purchased, by individual copy or by subscription, from the National Technical Information Service. To purchase this publication, order report number PB00-910401 from:

National Technical Information Service 5285 Port Royal Road Springfield, Virginia 22161 (800) 553-6847 or (703) 605-6000

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NTSB/AAR-00/01 PB00-910401 Notation 6952B Adopted January 13, 2000

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

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Contents

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544 Bowie, Mrs., social leader, 146, 147 Boyle, John, sculptor, 396 Bradstreet, Anne, 309 Breitmann Ballads, 320, 456 Brennan, artist, 393 Brewster, Benjamin Harris, 342 Briggs, Richard, 424 Brillat-Savarin, 414 British Museum, 12, 309 Broad and Locust Streets, 257, 258, 259, 449 Broad and Walnut, 42 Broad Street, 324, 449, 489, 499-503, 529, 533 Broad Street, North, 459, 529 Broad Street Station, 12 Brook Farm, 347 Brown, Charles Brockden, 313, 363 Browning Societies, 352 Bryn Mawr, 98, 104, 173, 307, 364, 529 Bullitts, the, 107 Bunyan, John, 308 Burns's, 126, 210, 456 Burr, Anna Robeson, 363 Burr, Charles, 363 Burton's Gentleman's Magazine, 314 Business and Professional Club, 352

Cadwallader-Biddle, 343 Cadwalladers, 50, 145, 216 Caldwell, J. E. & Co., 125, 456 Callista, 59 Callowhill, Hannah, 417 Callowhill Street Bridge, 281 Camac Street, 351 Camden (N. J.), 293, 324-329 Campanini, opera singer, 401 Campbell, Helen, 338 Cape May, 170 Carlyle, Thomas, 243 Carpenter's Hall, 514 Carson, Hampton L., 6, 363 Cary (publisher), 313 Casket, The, 314, 428 Cassatt, Mary, 393 Castleman, Richard, 6 Cathedral, the, 120, 183, 184, 187, 198, 200, 203 Catholics, 176, 177-204, 258 Cavalcaselle, Giovanni B., 402 Centennial Exposition, 205-232, 233, 234, 253, 267, 276, 277, 357, 375, 390 Century, The, 337 Champs-Elysées, 405 Chapman, Miss, school, 258 Charles the Bold, 337 Chartres Cathedral, 199 Chartreuse, the old, 444 Chase, William M., 246 Chester, 54, 152 Chestnut Hill, 78, 123, 129, 170, 258 Chestnut Street, 125, 144, 226, 227, 325, 342, 368, 449, 456, 459, 499 Chestnut Street Theatre, 67, 459 "Chestnut, Walnut, Spruce, and Pine," 119, 123, 151, 158, 182, 263, 297, 464 Chew House, 297, 298, 518 Childs, George W., 113, 342, 499 Chippendale furniture, 289 Christ Church, 114, 120, 183, 188, 277, 517 Christ Church Burial Ground, 120, 281 Church (painting), 246 Church of England, 183 Cimabué, Giovanni, 402 City Companies in London, 152 City Hall, 259, 260, 405, 489, 526, 534 City of Homes, 481, 534 City Troop, 64, 452, 510 Civic Club, 494 Civil War, the, 130, 146, 518 Claghorn's collection of old prints, 376, 394 Clements, Gabrielle, 396 Clinton Street, 514 Clover Club, 152, 443 Club (Art), South Broad Street, 406 Coates, Mrs. Florence Earle, 336, 362 Cobbett, William, 440, 485, 513 Coghlan, Father, 193 Coleridge, Samuel Taylor, 324 College Club, the, 494 Colonial (American) art, 381, 389 Colonial Congress, 253, 267 Colonial Dames, 219, 221, 361, 522, 525 Colonial days, 283, 526 Colonial doorways, 361 Colonial history, 9


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552 Washington, George, 44, 119, 215, 290, 482, 526 Washington's Birthday, 63 Washington's household, 44, 166, 433 Washington, statue of, 386 Waterloo (eve of), 254 Water-works (Fairmount), 64, 67, 299, 533 Watson, John, 6, 356, 357, 413 Watts, Harvey M., 362 Waugh, Frederick J., marine painter, 406 Welsh, John, 50 West, Benjamin, 64, 389 West Philadelphia, 126, 294, 297, 468, 529, 538 Wharton, Anne Hollingsworth, 6, 361 Whartons, the, 50, 145, 216 Whelans, the, 31 Whistler, James A. McNeill, 16, 395, 396, 405, 534 White, Ambrose, 78, 120 White, Bishop, 290 White, Dr. (dentist), 64 White, William, 144 White, Willie, 144, 145 Whitefield, George, 177 Whitman, Walt, 119, 316, 324-331, 336, 337, 344, 347, 364 Whittier, John G., 320 Wide, Wide World, The, 59, 335 Widener, Peter A. B., 307, 406 Wilde, Oscar, 344, 347 Williams, Dr. Francis Howard, 336, 362 Williams, Dr. Talcott, 364 Willing's Alley, 184 Willings, the, 158 Willis, N. P., 316 Willow Grove, 213 Wilstach Collection, 405 Wise, Herbert C., 361 Wissahickon (creek), 127, 177, 298, 299 Wistar House, 297, 521 Wistar parties, 146 Wister, Mrs., authoress, 335, 336 Wister, Owen, 363 "Wister, Sally," 162, 356 Wisters, the, 107 Woman in White (German mystics), 176 Woman's School of Design, 405 Wood, Bishop, 200, 203 Woodland's, 126 Wren, Sir Christopher, 283, 289, 533 Wyck, 297, 521 Wyeth's, 126, 456

Yale (college), 162 Yearly Meeting, 289 Yellow Buskin, the, 405

Zantzinger, C. C, architect, 407 Zola, Émile, 259


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On August 6, 1997, about 0142:26 Guam local time, Korean Air flight 801, a Boeing 747-3B5B (747-300), Korean registration HL7468, operated by Korean Air Company, Ltd., crashed at Nimitz Hill, Guam. Flight 801 departed from Kimpo International Airport, Seoul, Korea, with 2 pilots, 1 flight engineer, 14 flight attendants, and 237 passengers on board. The airplane had been cleared to land on runway 6 Left at A.B. Won Guam International Airport, Agana, Guam, and crashed into high terrain about 3 miles southwest of the airport. Of the 254 persons on board, 228 were killed, and 23 passengers and 3 flight attendants survived the accident with serious injuries. The airplane was destroyed by impact forces and a postcrash fire. Flight 801 was operating in U.S. airspace as a regularly scheduled international passenger service flight under the Convention on International Civil Aviation and the provisions of 14 Code of Federal Regulations Part 129 and was on an instrument flight rules flight plan.

The National Transportation Safety Board determines that the probable cause of the Korean Air flight 801 accident was the captain's failure to adequately brief and execute the nonprecision approach and the first officer's and flight engineer's failure to effectively monitor and cross-check the captain's execution of the approach. Contributing to these failures were the captain's fatigue and Korean Air's inadequate flight crew training. Contributing to the accident was the Federal Aviation Administration's (FAA) intentional inhibition of the minimum safe altitude warning system (MSAW) at Guam and the agency's failure to adequately manage the system.

The safety issues in this report focus on flight crew performance, approach procedures, and pilot training; air traffic control, including controller performance and the intentional inhibition of the MSAW system at Guam; emergency response; the adequacy of Korean Civil Aviation Bureau (KCAB) and FAA oversight; and flight data recorder documentation. Safety recommendations concerning these issues are addressed to the FAA, the Governor of the Territory of Guam, and the KCAB.

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On August 6, 1997, about 0142:26 Guam local time, Korean Air flight 801, a Boeing 747-3B5B (747-300), Korean registration HL7468, operated by Korean Air Company, Ltd., crashed at Nimitz Hill, Guam. Flight 801 departed from Kimpo International Airport, Seoul, Korea, with 2 pilots, 1 flight engineer, 14 flight attendants, and 237 passengers on board. The airplane had been cleared to land on runway 6 Left at A.B. Won Guam International Airport, Agana, Guam, and crashed into high terrain about 3 miles southwest of the airport. Of the 254 persons on board, 228 were killed,, and 23 passengers and 3 flight attendants survived the accident with serious injuries. The airplane was destroyed by impact forces and a postcrash fire. Flight 801 was operating in U.S. airspace as a regularly scheduled international passenger service flight under the Convention on International Civil Aviation and the provisions of 14 Code of Federal Regulations (CFR) Part 129 and was on an instrument flight rules (IFR) flight plan.

According to Korean Air company records, the flight crew arrived at the dispatch center in the Korean Air headquarters building in Seoul about 2 hours before the scheduled departure time of 2105 (2005 Seoul local time) on August 5, 1997. The original flight plan for flight 801 listed a different captain's name. The captain aboard the accident flight had initially been scheduled to fly to Dubai, United Arab Emirates; however, because the accident captain did not have adequate rest for that trip, he was reassigned the shorter trip to Guam.

According to Korean Air personnel, the flight crewmembers collected the trip paperwork, conducted a self-briefing, and received a briefing from the assigned supervisor of flying (SOF). Flight 801 departed the gate about 2127 and was airborne about 2153.

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Factual Information According to the cockpit voice recorder (CVR), the captain was performing the pilot-flying (PF) duties, and the first officer was performing the pilot-not-flying (PNF) duties. Upon arrival to the Guam area, the first officer made initial contact with the Federal Aviation Administration's (FAA) Guam Combined Center/Radar Approach Control (CERAP) controller about 0103:18, when the airplane was level at 41,000 feet mean sea level (msl) and about 240 nautical miles (nm) northwest of the NIMITZ VOR/DME.

About 0105:00, the CERAP controller told flight 801 to expect to land on runway 6L, and the first officer acknowledged the transmission. About 0110:00, the controller instructed flight 801 to "...descend at your discretion maintain two thousand six hundred [feet msl]." The first officer responded, "...descend two thousand six hundred pilot discretion."

About 0111:51, the CVR recorded the captain briefing the first officer and the flight engineer about the approach and landing at Guam. The captain stated:

 * I will give you a short briefing...ILS [instrument landing system ] is one one zero three...NIMITZ VOR is one one five three, the course zero six three, since the visibility is six, when we are in the visual approach, as I said before, set the VOR on number two and maintain the VOR for the TOD [top of descent], I will add three miles from the VOR, and start descent when we're about one hundred fifty five miles out. I will add some more speed above the target speed. Well, everything else is all right. In case of go-around, since it is VFR [visual flight rules], while staying visual and turning to the right...request a radar vector...if not, we have to go to FLAKE ...since the localizer glideslope is out,13 MDA [minimum descent altitude] is five hundred sixty feet and HAT [height above touchdown] is three hundred four feet....

About 0113:33, the CVR recorded the captain saying, "we better start descent;" shortly thereafter, the first officer advised the controller that flight 801 was "leaving four one zero for two thousand six hundred." The controller acknowledged the transmission.

The CVR recorded the captain making several remarks related to crew scheduling and rest issues. About 0120:01, the captain stated, "if this round trip is more than a nine hour trip, we might get a little something...with eight hours, we get nothing...eight hours

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 do not help us at all." The captain also stated that "they make us work to maximum, up to maximum...." About 0120:28, the captain further stated, "probably this way [unintelligible words], hotel expenses will be saved for cabin crews, and maximize the flight hours. Anyway, they make us [747] classic guys work to maximum." About 0121:13, the captain stated, "eh...really...sleepy."

About 0121:59, the first officer stated, "captain, Guam condition is no good." About 0122:06, the CERAP controller informed the flight crew that the automatic terminal information service (ATIS) information Uniform was current and that the altimeter setting was 29.86 inches of mercury (Hg). About 0122:11, the first officer responded, "Korean eight zero one is checked uniform;" his response did not acknowledge the altimeter setting. About 0122:26, the captain stated, "uh...it rains a lot." About 0123:45, the captain stated, "request twenty miles deviation later on...to the left as we are descending." About 0124:02, the first officer questioned, "don't you think it rains more? in this area, here?" The captain then stated, "left, request deviation" and "one zero mile." About 0124:30, the controller approved the first officer's request to deviate "...one zero mile left of track [for weather]."

The CVR then recorded about 6 minutes of discussion among the flight crew regarding the weather conditions and the deviation around the weather. About 0126:25, the flight engineer stated, "it's Guam, Guam." About 0131:17, the first officer reported to the CERAP controller that the airplane was "...clear of Charlie Bravo [cumulonimbus clouds]" and requested "radar vectors for runway six left." The controller instructed the flight crew to fly a heading of 120?. After this transmission, the flight crew performed the approach checklist and verified the radio frequency for the ILS to runway 6L. About 0138:49, the CERAP controller instructed flight 801 to "...turn left heading zero nine zero join localizer;" the first officer acknowledged this transmission. At that time, flight 801 was descending through 2,800 feet msl with the flaps extended 10? and the landing gear up.

About 0139:30, the first officer said, "glideslope [several unintelligible words]...localizer capture [several unintelligible words]...glideslope...did." About 0139:44, the controller stated, "Korean Air eight zero one cleared for ILS runway six left approach...glideslope unusable." The first officer responded, "Korean eight zero one roger...cleared ILS runway six left;" his response did not acknowledge that the glideslope was unusable.

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 According to the CVR, about 0139:55 the flight engineer asked, "is the glideslope working? glideslope? yeh?" One second later, the captain responded, "yes, yes, it's working." About 0139:58, an unidentified voice in the cockpit stated, "check the glideslope if working?" This statement was followed 1 second later by an unidentified voice in the cockpit asking, "why is it working?" About 0140:00, the first officer responded, "not useable."

About 0140:06, the CVR recorded the sound of the altitude alert system chime. According to information from the flight data recorder (FDR), the airplane began to descend about 0140:13 from an altitude of 2,640 feet msl at a point approximately 9 nm from the runway 6L threshold (5.7 nm from the NIMITZ VOR). About 0140:22, an unidentified voice in the cockpit said, "glideslope is incorrect." About 0140:33, as the airplane was descending through 2,400 feet msl, the first officer stated, "approaching fourteen hundred [feet]." About 4 seconds later, when the airplane was about 8 nm from the runway 6L threshold, the captain stated, "since today's glideslope condition is not good, we need to maintain one thousand four hundred forty [feet]. please set it." An unidentified voice in the cockpit then responded, "yes." About 0140:42, the CERAP controller instructed flight 801 to contact the Agana control tower; the first officer acknowledged the frequency change. The first officer contacted the Agana tower about 0140:55 and stated, "Korean air eight zero one intercept the localizer six left." Shortly after this transmission, the CVR again recorded the sound of the altitude alert chime, and the FDR data indicated that the airplane was descending below 2,000 feet msl at a point 6.8 nm from the runway threshold (3.5 nm from the VOR). About 0141:01, the Agana tower controller cleared flight 801 to land.

About 0141:14, as the airplane was descending through 1,800 feet msl, the first officer acknowledged the landing clearance, and the captain requested 30? of flaps. No further communications were recorded between flight 801 and the Agana control tower.

About 0141:31, the first officer called for the landing checklist. About 0141:33, the captain said, "look carefully" and "set five hundred sixty feet" (the published MDA). The first officer replied "set," the captain called for the landing checklist, and the flight engineer began reading the landing checklist. About 0141:42, as the airplane descended through 1,400 feet msl, the CVR recorded the sound of the ground proximity warning system (GPWS) radio altitude callout "one thousand [feet]." One second later, the captain stated, "no flags gear and flaps," to which the flight engineer responded, "no flags gear and flaps." About 0141:46, the captain asked, "isn't glideslope working?" There was no indication on the CVR that the first officer and flight engineer responded to the this question. About 0141:48, the captain stated, "wiper on." About 0141:53, the CVR recorded the sound of the windshield wipers starting. The windshield wipers remained on throughout the remainder of the flight.

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 About 0141:53, the first officer again called for the landing checklist, and the flight engineer resumed reading the checklist items. About 0141:59, when the airplane was descending through 1,100 feet msl at a point about 4.6 nm from the runway 6L threshold (approximately 1.3 nm from the VOR), the first officer stated "not in sight?" One second later, the CVR recorded the GPWS radio altitude callout of "five hundred [feet]." According to the CVR, about 2 seconds later the flight engineer stated "eh?" in an astonished tone of voice.

About 0142:05, the captain and flight engineer continued the landing checklist. About 0142:14, as the airplane was descending through 840 feet msl and the flight crew was performing the landing checklist, the GPWS issued a "minimums minimums" annunciation followed by a "sink rate" alert about 3 seconds later. The first officer responded, "sink rate okay" about 0142:18; FDR data indicated that the airplane was descending 1,400 feet per minute at that time.

About 0142:19, as the airplane descended through 730 feet msl, the flight engineer stated, "two hundred [feet]," and the first officer said, "let's make a missed approach." About 1 second later, the flight engineer stated, "not in sight," and the first officer said, "not in sight, missed approach." About 0142:22, as the airplane descended through approximately 680 feet msl, the FDR showed that the control column position began increasing (nose up) at a rate of about 1? per second, and the CVR indicated that the flight engineer stated, "go around." When the captain stated "go around" about 1 second later, the airplane's engine pressure ratios and airspeed began to increase. However, the rate of nose-up control column deflection remained about 1° per second. At 0142:23.77, as the airplane descended through 670 feet msl, the CVR recorded the sound of the autopilot disconnect warning. At 0142:24.05, the CVR began recording sequential GPWS radio altitude callouts of "one hundred...fifty...forty...thirty...twenty [feet]." About 0142:26, the airplane impacted hilly terrain at Nimitz Hill, Guam, about 660 feet msl and about 3.3 nm from the runway 6L threshold. FDR data indicated that, at the time of initial ground impact, the pitch attitude of the airplane was increasing through 3°. The accident occurred at 13? 27.35 minutes north latitude and 144? 43.92 minutes east longitude during the hours of darkness. The CVR stopped recording about 0142:32.

Figure 1 shows the instrument approach chart for the Guam runway 6L ILS procedure that was in effect at the time of the accident. Figures 2 and 3 show FDR information for the last 5 ? minutes of flight, along with CVR comments and sounds and air traffic control (ATC) data.

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 Figure 2. Side view of FAA radar data with selected ATC and CVR communication excerpts.

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 Figure 3. Overhead view of FAA radar data with selected ATC and CVR communication excerpts.

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Table 1. Injury chart.

The airplane was destroyed by impact forces and a postcrash fire. The estimated value of the airplane was about $60 million.

The accident caused extensive ground scarring and fire damage to trees and foliage along the wreckage path and in the immediate vicinity of the main wreckage area. Also, a 12-inch fuel oil pipeline located along a vehicle access road that services the NIMITZ VOR was severed when it was struck by the airplane. The severed pipeline spilled about 1,000 gallons of oil in a localized area.

The captain, age 42, was hired by Korean Air on November 2, 1987. He was previously a pilot in the Republic of Korea Air Force. He held an Airline Transport Pilot (ATP) certificate issued by the Korean Ministry of Construction and Transport (MOCT) on April 19, 1992, with type ratings in the Boeing 727 and 747. The captain qualified as a 727 first officer on December 19, 1988, and as a 747 first officer on February 13, 1991. He upgraded to 727 captain on December 27, 1992, and 747 captain on August 20, 1995. The

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 captain held Korean and FAA First Class Airman Medical certificates, both issued on March 13, 1997, without limitations.

According to Korean Air records, the captain had accumulated a total of 8,932 hours of flight time, 2,884 hours as a military pilot and 6,048 hours as a civilian pilot. He had logged a total of 1,474 and 1,718 hours as a 747 first officer and captain, respectively. Also, Korean Air's 747 chief pilot stated, in a post accident interview, that the captain had received a Flight Safety Award in May 1997 from the company president for successfully handling an in-flight emergency involving a 747 engine failure at a low altitude.

The captain had flown 235, 144, 90, and 17 hours in the last 90, 60, 30, and 7 days, respectively, before the accident. Between December 1992 and August 1993, he had flown from Seoul to Guam eight times as a 727 captain. In addition, he had flown from Seoul to Guam as a 747 captain on July 4, 1997 (about 1 month before the accident). National Transportation Safety Board investigators interviewed the first officer from the July 4, 1997, flight. That first officer stated that the captain had contacted him by telephone 1 day before the trip and proposed that they obtain a charter briefing for Guam because they did not regularly conduct 747 operations at that airport. Consequently, the captain and first officer arrived several hours before the trip departure time and received a charter briefing from a Korean Air instructor, even though the briefing was not required. The captain and first officer watched the Guam airport familiarization video presentation and studied the approach charts for the airport. During that time, the captain commented that the area where the NIMITZ VOR is located was mountainous and required extra attention (referring to this area as a "black hole"). The first officer said the trip to Guam was routine and that the weather was good, with scattered cumulous clouds and good visibility at the airport. Further, the first officer said that the captain briefed and executed the ILS 6L approach to a routine landing.

The captain's last route check was on a round trip flight from Seoul to Narita, Japan, on July 19, 1997. A company check airman told Safety Board investigators that, although the weather conditions at Narita and Seoul were above instrument approach minimums, the captain executed the full ILS approach to each airport and received an "above standard" evaluation for the flights. The captain's last proficiency check was conducted in a Korean Air 747 simulator on June 11, 1997. According to Korean Air, the captain executed a nonprecision VOR/DME approach to runway 32L at Kimpo Airport during the proficiency check. The simulated weather conditions for the approach were 900 feet overcast and winds 290? at 11 knots. The captain received an "excellent" evaluation. A Korean Air representative told Safety Board investigators that the captain had passed the company's Level 3 Pilot English Test and had attended crew resource

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 management (CRM) training from October 24 to 27, 1989. The captain had not flown with the flight 801 first officer before the accident flight.

Korean Air records indicated that the captain flew a round trip flight sequence from Seoul to San Francisco, California, from July 28 to July 30, 1997. He was off-duty until August 2, when he flew two round trip domestic flights between the hours of 1100 and 2000. On August 3, the captain flew an international trip to Hong Kong that arrived in the early evening. The return flight was delayed because of inclement weather. The captain remained in Hong Kong overnight and flew back to Seoul the next morning, arriving about 1230. After the accident, the captain's wife told Safety Board investigators, through a family representative, that the captain normally awoke between 0600 and 0630 and went to bed between 2200 and 2300. She stated that, on August 2, the captain awoke between 0600 and 0630 and went to bed about 2300. On August 3, the captain awoke about 0630 for the trip to Hong Kong and remained there overnight. The captain's wife stated that, after arriving home on August 4 from the trip, he was involved in routine activities and went to bed at his accustomed time. According to the captain's wife, on August 5, he awoke at 0600, worked out in a gym for an hour and returned home for breakfast. He later studied the flight schedule for the trip to Guam, took a nap from 1100 to 1340, and then ate lunch. She also stated that the captain departed for the 20-minute drive to Kimpo Airport about 1500 and that the captain had left early to allow time to prepare for the flight to Guam.

The first officer, age 40, was hired by Korean Air on January 10, 1994. He was previously a pilot in the Republic of Korea Air Force. He held an ATP certificate issued by the FAA on July 10, 1994, and a Korean ATP certificate issued by the MOCT on March 28, 1997. He received a 747 type rating on March 11, 1995, and qualified as a 747 first officer on July 23, 1995. The first officer held Korean and FAA First Class Airman Medical certificates, both issued on June 13, 1997, with no limitations. According to company records, the first officer had accumulated a total of 4,066 hours of flight time, 2,276 hours as a military pilot and 1,790 hours as a civilian pilot. He had logged a total of 1,560 hours as a 747 first officer. The first officer had flown 189, 132, 67, and 20 hours in the last 90, 60, 30, and 7 days, respectively, before the accident. The first officer had flown from Seoul to Guam in August and September 1995 as a 747 first officer. According to company records, he viewed the Guam airport familiarization video on July 8, 1997, in preparation for a future flight to Guam. The first officer's last route check was conducted in July 1995. The first officer's last proficiency check was conducted in a Korean Air 747 simulator on March 28, 1997. During the proficiency check, the first officer executed a nonprecision VOR/DME approach to runway 32L at Kimpo Airport. The simulated weather conditions for the

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 approach were clouds 900 feet broken and winds 260° at 11 knots. An instructor noted, in an overall simulator session evaluation, that the first officer's "control skills and knowledge [were] above standard." The first officer received a "standard" evaluation for his nonprecision VOR approaches. However, the instructor noted that the "altitude management on nonprecision approach [was] somewhat less than desirable." Another instructor noted that the first officer was "somewhat slow to carry out directions." According to Korean Air records, the first officer had passed the Level 3 Pilot English Test but had not attended CRM training.

Korean Air records indicated that the first officer returned from an international trip to the United States on the afternoon of August 2, 1997. He was off-duty on August 3 and flew a round trip domestic flight on August 4, 1997, between 0930 and 1245. The first officer was then off-duty until the accident flight. Safety Board investigators interviewed the first officer's relatives after the accident. They stated that he telephoned his mother about 1700 on August 5 and that "everything seemed routine." Because his family lived in New Zealand, the first officer's relatives could not be specific about his activities before the accident flight.

The flight engineer, age 57, was hired by Korean Air on May 7, 1979. He was previously a navigator in the Republic of Korea Air Force. He obtained his flight engineer's certificate on December 29, 1979, and was qualified on the Boeing 727 and 747 and Airbus A300 airplanes. The flight engineer held a Korean First Class Airman Medical Certificate issued on June 5, 1997. According to company records, the flight engineer had accumulated a total of 13,065 hours of flight time, including 11,088 hours as a flight engineer (1,573 hours of which were as a flight engineer on the 747). Korean Air records also indicated that the flight engineer had flown 165, 120, 77, and 28 hours in the last 90, 60, 30, and 7 days, respectively, before the accident.

The flight engineer's last two route checks were in April 1997. He received an "above standard" evaluation for the first route check and an "excellent" evaluation for the second route check. The flight engineer's last proficiency check was in a Korean Air 747 simulator on March 7, 1997. He received an "above standard" evaluation for the session, and an instructor note stated, "control skills and knowledge are above standard." The flight engineer's crew coordination was also rated as "above standard." According to Korean Air records, the flight engineer passed the Level 3 Pilot English Test and attended CRM training from April 28 to May 1, 1987. A Korean Air official indicated that the flight engineer had never flown to Guam.

The flight engineer had returned to Seoul on August 3, 1997, after completing a 3-day international trip to Anchorage, Alaska, and San Francisco. Although he was off-duty on August 4 and was assumed to have engaged in routine activities at home, the flight engineer's wife and son could not provide Safety Board investigators with details of his activities or sleep patterns before the accident flight.

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Fourteen flight attendants were working on the accident flight. The lead flight attendant (or purser), age 37, had been hired by Korean Air on July 18, 1988. According to company records, the purser had completed her basic training on August 28, 1988, and her most recent recurrent training was completed on December 10, 1996.

One flight attendant, age 43, was hired by Korean Air in August 1981; the other 12 flight attendants, ranging in age from 21 to 25, were hired between November 1992 and March 1997. According to company records, all had completed their basic training, and their most recent recurrent training was completed between June 1996 and April 1997.

1.5.5.1 Combined Center/Radar Approach Control

The CERAP controller, age 39, was hired by the FAA on May 30, 1982, in Los Angeles, California, and initially qualified as a terminal radar approach control (TRACON) controller. He transferred to the Guam CERAP facility on September 3, 1995, where he was certified as a full-performance level controller. Before his employment with the FAA, the controller worked as a radar and tower controller in the U.S. Navy. His last duty station in the Navy was at Naval Air Station Cubi Point, Philippines, from 1978 to 1982. He was medically certified as a controller without waivers or limitations.

1.5.5.2 Air Traffic Control Tower The Agana tower controller, age 39, was hired by Barton ATC International, Inc.-- a nonfederal contract ATC service company--as an air traffic controller at the Guam Federal Control Tower on May 15, 1995.

According to company and FAA records, the controller was fully certified on all positions of operations in the tower, including clearance delivery, ground control, local control, and controller-in-charge. He was medically qualified for his duties and held an FAA Second Class Airman Medical Certificate issued on April 9, 1997, without waivers or limitations. Before his employment with Barton ATC International, the controller held a similar position in the U.S. Navy from 1983 to 1992. During this time, the controller was trained and qualified in various TRACON positions, including radar approach control, arrival radar, radar final, departure radar, and precision and surveillance radar. He was assigned to the Naval Air Station Agana tower in 1989. The controller told Safety Board investigators that, at the Agana Naval tower, he was qualified in all tower positions and worked as a flight data controller, radar final controller, tower supervisor, facility watch

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 supervisor, and radar branch chief. The controller remained on Guam after he was discharged from the Navy.

The accident airplane, HL7468, serial number 22487, was one of three Boeing 747-300s in Korean Air's fleet. The airplane was delivered new to the company on December 12, 1984, and had been operated and maintained continuously by Korean Air until the accident. Every Korean-registered aircraft is subject to annual renewal of its airworthiness certificate from the Korean Civil Aviation Bureau (KCAB); this airplane's last airworthiness certificate was issued on July 7, 1997.

At the time of the accident, the airplane had accumulated about 50,105 hours total time in service and about 8,552 cycles. The airplane was equipped with four Pratt & Whitney JT9D-7R4G2 engines with total times and cycles since new of 26,014 hours and 4,699 cycles (No. 1), 36,611 hours and 6,137 cycles (No. 2), 25,904 hours and 4,383 cycles (No. 3), and 33,889 hours and 5,701 cycles (No. 4). The most recent engine change before the accident was the replacement of the No. 3 engine on June 11, 1997, after a compressor surge incident.

According to Korean Air, the airplane was maintained according to the company's Continuous Maintenance Program, which was approved by the KCAB. The maintenance program comprised "A" checks performed at 350-hour intervals and "C" checks at 4,000-hour intervals. (Approximately 12 A checks are performed between each C check.) The last A check was performed on July 12, 1997, at 49,874 hours. The last C check was performed on December 16, 1996, at 47,918 hours. During the C check, operational/functional test work cards were completed for the transponders, radar altimeters, VOR/ILS navigation receivers, central air data computers, GPWS, autopilot, automatic direction finder (ADF), altitude alert, inertial navigation systems, weather radar, DME, and high-frequency radios. Further, the FDR was read out, and the altimeters were calibrated.

The accident airplane's logbooks indicated that, from December 1996 (the time of the last C check) to August 1997, all mechanical discrepancies identified by flight crews or maintenance personnel had been corrected before the next scheduled flight. Several discrepancies were deferred, in accordance with Korean Air minimum equipment list guidelines, and the airplane was flown to Seoul for repair. The airplane's logbook entries during this time period detailed the following maintenance deficiencies and corrective actions:

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 *Between December 18, 1996, and January 5, 1997, five airspeed-related writeups were logged, including one that identified a discrepancy of up to 50 knots between the captain's and first officer's airspeed indicators while in cruise. Corrective actions were taken.
 * On April 9, 1997, the GPWS failed the "below glideslope" test. Contamination was cleaned from a connector.
 * Between May 3, 1997, and June 23, 1997, six writeups were logged about erroneous fuel quantity indications on the No. 1 fuel quantity indicator. The system was checked after each event.
 * On July 3, 1997, the first officer's altimeter was replaced.

 * On July 30, 1997, during an autocoupled approach at Seoul, autopilot channel "A" disengaged at a radar altitude of 1,000 feet. (According to a Boeing representative, because the autopilot is a triple-redundant system, it would have continued to control the airplane using the "B" and "C" channels.) A pin on one of the autopilot system's electrical connectors was subsequently cleaned.

Korean Air records indicated that the accident airplane had no deferred maintenance items when it was dispatched on August 5, 1997, and that no discrepancies had been identified in the airplane's logbook for the previous 12 flights. The partially completed logbook page for the accident flight was recovered from the wreckage, and no maintenance writeups had been logged.

The captain's and first officer's instrumentation panels from the Boeing 747 Classic are shown in figures 4 and 5, respectively. A discussion of the accident airplane's autopilot system, GPWS, and ILS follows.

1.6.2.1 Autopilot System

The accident airplane was equipped with a Sperry-Rand (now Rockwell Collins) autopilot, model SPZ1. The autopilot system consists of a mode control panel and three pitch and roll computers (with a landing rollout function) that drive the pitch and roll actuators. In addition, two separate yaw damper computers provide control to the "split" rudder system (two individual rudder panels).

Boeing engineers stated that, when the autopilot's ILS mode is selected by the pilot and a sufficient glideslope signal exists, the glideslope "armed" indicator is annunciated in the cockpit with an amber light. The pitch and roll computers maintain pitch control and operate in any of the following modes: "Altitude Hold," "Altitude Select," "Indicated Airspeed Hold," or "Vertical Speed." When the deviation of the glideslope signal reaches a predetermined level, the vertical beam sensor automatically switches the landing rollout computer function to control the pitch axis of the elevator. The glideslope signal is

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 validated before the system can arm the glideslope "engage" logic and the vertical beam sensor. According to Boeing, if the glideslope signal is invalid, the failure will be annunciated in the cockpit with a steady red "autopilot" warning light. The altitude alert system is coupled to the autopilot.

The altitude alert is armed by the pilot when the desired altitude is set into the "ALT SEL" (altitude select) window on the pilot's control panel (or glareshield). The amber "ALTITUDE ALERT" light illuminates steadily, and a 2-second aural tone sounds when the aircraft is approaching the selected altitude from either 900 feet above or below. The light remains illuminated until the aircraft is within 300 feet of the desired altitude. The light then flashes, and the 2-second aural tone sounds when the aircraft deviates 300 feet above or below the selected altitude until the deviation exceeds 900 feet, at which time the light extinguishes and the system automatically resets for subsequent altitude alerting. The "deviation from altitude" mode of the altitude alert system deactivates when the landing gear is extended.

1.6.2.2 Ground Proximity Warning System

The accident airplane was equipped with an AlliedSignal Mark VII GPWS Warning Computer. The mode 2 warnings "TERRAIN" and "PULL UP" were desensitized during flight 801's approach while the airplane was in the landing configuration (gear down/flaps extended). The advisories and alerts that remained active in the landing configuration were those for excessive descent rate (sink rate); excessive terrain closure rate; excessive glideslope deviation; minimums (radio altitude decision height) callout; and 1,000, 500, 100, 50, 40, 30, 20, and 10 feet radio altitude callouts.

On October 3, 1997, postaccident testing of the GPWS installed on flight 801 was performed at AlliedSignal facilities in Redmond, Washington. The testing found that the GPWS was capable of normal operation. 1.6.2.3 Instrument Landing System The accident airplane was equipped with three Rockwell International/Collins Model 51RV-5B ILS receivers. No recorded malfunctions or abnormalities with the three receivers were recorded between the time of their respective installations (from November 1996 to May 1997) and the accident.

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 In a normally functioning system, ILS information is displayed in the cockpit on the captain's and first officer's raw data indicators on the attitude director indicator (ADI) and the horizontal situation indicator (HSI) if they are receiving localizer and glideslope information. In addition, the ADI's flight directors (FD) display ILS information if the appropriate FD mode is selected. The ADI and HSI are equipped with a warning flag that is displayed over the ILS indications (localizer and glideslope) to alert a pilot if either the ground or airborne system fails or if the receivers are not set to the correct radio frequency.

According to the manufacturer, the glideslope warning flag will appear if the navigation receiver is tuned to an ILS frequency and any of the following conditions exist:
 * there is an absence of a glideslope radio-frequency signal or 90- and 150-Hertz (Hz) modulations;
 * the percentage of modulation of either the 90- or 150-Hz signal is reduced to zero and the other is sustained at 40 percent or more; or
 * the level of a standard glideslope deviation signal produces 50 percent or less of the standard deflection of the deviation indicator.

The weight and balance form signed by the captain and the dispatcher for the accident flight included the following data: * zero fuel weight, 197,897 kilograms (kg);
 * departure fuel, 51,847 kg;
 * trip fuel, 36,923 kg;
 * takeoff weight, 249,744 kg;
 * estimated landing weight, 212,821 kg;
 * passenger weight (including cabin baggage), 17,694 kg;
 * cargo in compartments, 7,333 kg;
 * takeoff weight center of gravity, 24 percent mean aerodynamic cord; and
 * takeoff stabilizer trim setting, 4.4 units.

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Guam's climate is relatively uniform throughout the year. Guam averages 247 days each year with measurable amounts of precipitation (rain), and most days begin with scattered layers of clouds that become broken to overcast by afternoon.

From August to October, visual meteorological conditions (VMC) prevail about 80 percent of the time, and instrument meteorological conditions (IMC) prevail predominately during the afternoon hours. The rainy season lasts from July to November. During that time, precipitation averages about 24 days per month, and the prevailing winds are usually from the east, averaging about 9 knots.

A weather synopsis prepared by the Guam National Weather Service (NWS) Office on the day of the accident stated:

 * ...a weak low pressure trough is moving slowly [through] the Mariana Islands...resulting in gentle to moderate easterly winds and scattered showers. The effects of the upper level low far to the northeast have diminished during the past 12 hours or so. Light to moderate showers should be expected except for isolated afternoon thunderstorms due to solar heating.

About 0122:06 during the accident flight, the flight crew was informed by the CERAP controller that ATIS information Uniform was current. The content of that report was as follows:

 * Agana tower information UNIFORM, time one four five zero zulu, wind calm, visibility seven, [clouds] one thousand six hundred scattered, two thousand five hundred scattered, temperature two seven [Celsius], dew point two four, altimeter two niner eight six, runway six in use. NOTAMs [Notices to Airmen ], runway six left ILS glideslope out of service until further notice, advise on contact you have information UNIFORM.

The special surface weather observation for 0132 on August 6, 1997, was as follows:
 * Wind 090? at 6 knots; visibility--7 miles; present weather--shower vicinity; sky condition--scattered 1,600 feet, broken 2,500 feet, overcast 5,000 feet; temperature--27? C; dew point--25? C; altimeter setting 29.85 inches Hg; remarks--showers vicinity northwest-northeast.

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 The special surface weather observation for Guam International Airport for 0147 on August 6 was as follows:

 * Wind variable at 4 knots; visibility--5 miles; present weather--light rain shower; sky condition--few 1,500 feet, scattered 2,500 feet, overcast 4,000 feet; temperature 26° C; dew point 24° C; altimeter 29.85 inches Hg.

The Safety Board examined the NWS surface weather observation logs and found that heavy rain showers were reported at the airport between 0020 and 0029, between 0114 and 0116, and between 0153 and 0158. The weather logs also indicated that light rain showers were reported at the airport between 0016 and 0020, between 0029 and 0033, between 0106 and 0114, between 0116 and 0128, and between 0138 and 0148. Further, light rain and mist were also reported between 0148 and 0153. The maximum windspeed recorded at the airport between 0130 and 0150 was about 10 knots.

The following terminal aerodrome forecast (TAF) for Guam International Airport, which was issued by the NWS on August 6 at 0030 as an amendment to an earlier TAF, was valid at the time of the accident:
 * Wind 120° at 7 knots, visibility greater than 6 miles, scattered 1,600 feet scattered 4,000 feet scattered 8,000 feet overcast 30,000 feet. Temporary August 6, 0100 to August 6, 0600, wind 130° at 12 knots gusting 20 knots, visibility 3 miles, heavy rain shower, broken 1,500 feet cumulonimbus overcast 4,000 feet.

The radar antenna of the Guam Weather Surveillance Radar-1988, Doppler (WSR-88D) was located about 5 nm east of the accident site. Data recorded about 0143 on August 6 (1543 UTC time on August 5, 1997) indicated an area of precipitation over higher terrain about 4 nm southwest of the airport, including Nimitz Hill. The precipitation was oriented east to west, about 7 to 8 nm long and 3 to 4 nm wide, and was moving toward the west. Figure 6 shows the WSR-88D four-panel base reflectivity product for 0143.

The CERAP radar controller stated that, although areas of weather were in the vicinity of the VOR and airport, he had not received any pilot reports from midnight to the time of the accident. The controller stated that a "relatively small cell,"38 which he believed to be of light to moderate intensity, was depicted on the Airport Surveillance Radar (ASR)-8 display. Further, the controller said that the "relatively small cell" observed on radar extended about 3 to 5 miles on the final approach course and was about 2 to 3 miles across in the largest area. The controller said that he had no means of determining the intensity of this or any other weather cell because, unlike other weather radar displays, the ASR-8 radar display is monochromatic, and it is difficult to differentiate precipitation intensity without color. However, the controller also said that he

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 Figure 6. WSR-88D four-panel base reflectivity product for Guam.

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 interpreted the intensity of precipitation by the different levels of opaque (white) shading and his experience as a controller.

The CERAP controller stated that he did not advise the flight crew or the Agana tower controller that he had observed the precipitation on radar while flight 801 was on the approach course to the airport. The controller said that he had assumed that the flight crew was using cockpit radar because they had asked him twice for deviations around weather. The controller stated that the airplane's cockpit radar was more accurate and more precise than the radar he was using at the CERAP. The controller further stated that he did not observe (on radar) the airplane entering the precipitation.

FAA Order 7110.65, "Air Traffic Control," paragraph 2-6-4 (a) states that a controller is to "issue pertinent information on observed/reported weather or chaff39 areas. Provide radar navigational guidance and/or approved deviations around weather or chaff when requested by the pilot...." Paragraph 2-6-4 (c) states that a controller is to "inform any tower for which you provide approach control services if you have any weather echoes on radar which might affect their operations." Further, paragraph 2-9-2 states that, in the event of "rapidly changing conditions," a new ATIS is to be recorded and that the information is to be issued by ATC.

The Agana tower controller stated that, although it was not raining at the airport when flight 801 was inbound, a rain shower was moving in from the northeast over the airport and down the runway to the southwest. The tower controller said that he did not know when the rain began at the airport because he was using binoculars to try to locate flight 801 on the approach. He estimated that the visibility was 7 miles and stated that no low clouds were visible.

A certified Navy weather observer on Nimitz Hill, about ¾ mile northwest from the accident site, stated that the cloud ceiling about the time of the accident was approximately 700 to 800 feet above ground level (agl), or 1,300 to 1,400 feet msl, during a heavy rain shower. Also, he stated that visibility was about 200 to 300 meters and that the windspeed was not more than 10 knots. The NWS forecaster on duty at the time of the accident stated that no SIGMETs [Significant Meteorological Information] were valid for Guam and that the night was "pretty routine." The flight crew of Continental Air Micronesia flight 960, a Boeing 747 that landed at Guam about 30 minutes before the accident, stated that visibility was "excellent" from PAYEE intersection (located about 240 nm north of the NIMITZ VOR) and that scattered thunderstorms were occurring around the area. Further, the pilots indicated that their on-board radar depicted rain showers over the NIMITZ VOR but not over the airport. They also stated the visibility was "good" under 2,000 feet and that they maintained visual contact with the airport throughout the approach.

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 The flight crew of Ryan International flight 789, which landed shortly after the accident occurred, stated that the visibility was sufficient to see the lights of Guam from about 150 nm away. The first officer stated that on-board weather radar indicated showers northeast of the airport but no thunderstorms.

Additionally, the Ryan flight crew initially requested a visual approach when the flight was about 15 nm from the VOR, but the airplane encountered clouds and rain on approach to runway 6L shortly thereafter. The first officer stated that the airplane remained in the clouds until it was in proximity of the VOR, at which time the airplane broke out and the flight crew was able to acquire and maintain visual contact with the airport. The captain stated that, although clouds and rain were over the island's shoreline, the air around the airport and in the vicinity of the accident site was smooth. Further, the captain, who was also a check airman based at Guam, said that he "noticed that once [flight] crews are given a visual approach [to Guam International Airport] they have a tendency to press on even when they lose visual contact in hopes of regaining visual contact again.... That's because so many approaches are visual and the clouds and rain showers are so localized."

In addition, a witness who was hunting on Nimitz Hill at the time of the accident stated that it was not raining when he observed flight 801 pass over his position (100 feet north of the VOR beacon) and crash a very short distance away. He said that there had been intermittent rain showers shortly before the accident but that, when he saw the airplane crash, he could see stars directly over the accident site. The witness also said that the visibility was "very good" at the time of the accident and that, although he could not see the airport lights, he could see the lights of the town of Tamuning (3 to 4 miles northeast of his location). He said that the wind was "normal" and that no thunder or lightning was in the area.

Guam International Airport is serviced by three navigational aids: the NIMITZ VOR/DME (UNZ); the Mount Macajna nondirectional beacon (NDB), which was not operational at the time of the accident; and the ILS glideslope and localizer.

The colocated VOR and DME transmitters were equipped with a "selfmonitoring" system that samples radiated transmitter signals to ensure that the system is operating within prescribed tolerances and parameters. If these tolerances are exceeded, the monitoring system automatically shuts down the equipment. According to the facility logs, the VOR was not shut down at the time of the accident.

On the day of the accident, the FAA conducted a flight check of the localizer, outer marker, and NDB at Guam. The VOR and DME at Guam were not checked by the FAA until the day after the accident because of rescue operations. The FAA's flight checks determined that the respective systems were functioning properly and within prescribed tolerances. The flight checks did not examine the glideslope because it was out of service and removed at the time (see section 1.10.2 for more information).

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No communications problems were reported between the crew of flight 801 and any of the FAA or contract ATC facilities. (See sections 1.7.2 and 1.10.1 for more information.)

The A.B. Won Pat Guam International Airport is located about 3 nm northeast of Agana on the west-central coast of Guam at an elevation of 297 feet msl. The airport is leased to the Guam International Airport Authority by the U.S. Navy, and the associated navigational facilities are owned and operated by the FAA. The airport has two parallel runways oriented northeast/southwest: runway 6R/24L, which is 8,001 feet long and 150 feet wide, and runway 6L/24R, which is 10,015 feet long and 150 feet wide.

Runway 6L is equipped with high-intensity runway edge lights and a mediumintensity approach lighting system with runway alignment indicator lights. The runway was not equipped with runway end identifier lights, centerline lights, or touchdown zone lights. Runway 6L is also equipped with a four-box visual approach slope indicator (VASI) calibrated for a 3° visual glidepath angle. The touchdown elevation of runway 6L is 256 feet but rises to 297 feet at the departure end of the runway.

Guam International Airport was certified by the FAA as an Index D aircraft rescue and firefighting (ARFF) facility under 14 CFR Part 139. In accordance with this index, the airport is required to maintain a minimum of three ARFF vehicles capable of carrying a total quantity of at least 4,000 gallons of water.

1.10.1.1 Combined Center/Radar Approach Control

The Guam CERAP, located at Andersen Air Force Base (AFB), provides both TRACON and en route ATC services. To do so, the CERAP is equipped with two

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 independent radar data processing systems that receive radar information from different radar sites: terminal ATC services are provided by an Automated Radar Terminal System (ARTS) IIA analog display processor connected to an ASR-8 radar system; en route ATC services are provided by a digitized, narrow-band Micro-En route Automated Radar Tracking System (EARTS) processor connected to an FPS-93 long-range radar. Each of these systems independently performs its own minimum safe altitude warning (MSAW) processing (see section 1.10.1.2) but uses different algorithms that have been optimized for either terminal or en route operations. Both the FPS-93 and ASR-8 sensors are located about 1,500 feet apart on Mount Santa Rosa.

The CERAP airspace comprises concentric circles centered around the Mount Santa Rosa radar antenna site. The 250-nm-radius outer ring, which encompasses all of the airspace from above the surface, is classified as oceanic airspace. A 100-nm-radius inner ring, which extends over the Saipan radio beacon and from the surface to 28,000 feet, is classified as domestic airspace. The CERAP airspace is adjoined on all sides by the Oakland Air Route Traffic Control Center oceanic sectors. The airspace over Saipan and Guam is classified as approach control airspace, and its boundaries extend from the surface to 17,000 feet. The CERAP was classified as a Level II facility at the time of the accident.

The CERAP facility has two en route and one approach control radar positions. The R-1 en route radar position is responsible for the 100-nm inner circle; the R-4 en route radar position is responsible for the 250-nm outer circle. The D-3 approach control radar position, which is located between the en route R-1 and R-4 radar positions, is responsible for a 25-nm inner ring that extends from the surface to 17,000 feet and includes the NIMITZ VOR and the Andersen TACAN. At the time of the accident, one controller was performing the functions of all three positions from the R-4 position.

Authorized staffing for the Guam CERAP comprises 14 full-performance level controllers, 3 supervisors, an Automation Specialist, a Quality Assurance/Training Specialist, an Air Traffic Manager, and a secretary. According to FAA quality assurance staff at Guam, afternoon traffic at Guam is primarily overflights of aircraft traveling northbound, and evening traffic is primarily aircraft traveling inbound from Asia.

The CERAP controller on duty at the time of the accident told Safety Board investigators that, after arriving at the facility at 2345 on August 5, 1997, he assumed the duties at the R-4 en route radar position (and the colocated R-1 en route and D-3 approach control radar positions). A coworker arrived at the facility and assumed the duties at the

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 D-3 position from midnight to 0110, at which time he went on a break. The controller then resumed the duties of the D-3 position. (His coworker was not in the control room at the time of the accident.)

The CERAP controller stated that he was monitoring the EARTS (en route) radar display, which was set to 265 nm (but normally covers 250 nm). The controller also said that the en route radar display (which was located directly in front of him) was set to show the MSAW area in the lower right corner. (Controllers are able to set radar information to any position on the radar screen.) According to the controller, the en route radar system was displaying only secondary radar (beacon) target information throughout his shift. (The system was set up that way when he relieved the previous controller on duty.) He said the en route radar system was not able to display weather information because the part of the system that would normally display such information was out of service.

Further, the CERAP controller told investigators that the TRACON radar display (which was located to his immediate right) was set to a 60-nm range. The controller also stated that the approach control radar was set to display the MSAW area in the lower center of the screen. In addition, the controller said that the approach control radar was displaying primary and secondary radar return targets and areas of weather that were moving through the Guam area throughout his shift.

The CERAP controller also told investigators that the traffic complexity and density, that is, the number of aircraft under his control, from the time of initial radio contact with flight 801 (about 0103:18) to the time he advised the flight crew to contact the Agana tower (about 0140:42) was "light to moderate traffic and routine complexity." The controller estimated that he was handling 10 to 15 aircraft during that time, including flight 801. After the CERAP controller initiated the communications change (instructing flight 801 to contact the Agana tower controller), he was still responsible for radar monitoring of the flight because the Agana tower was a VFR facility and none of the criteria for automatic termination of radar service, as stated in FAA Order 7110.65, "Air Traffic Control," paragraph 5-1-13, had been met. However, the CERAP controller was no longer able to directly contact the airplane after it had switched to the Agana tower frequency. During a postaccident interview, the controller stated that he did not monitor the progress of flight 801 after the communications changeover because he was performing other duties that might have precluded further monitoring. According to the transcript from the recorded voice communications of radio and interphone lines during the period that flight 801 was in communication with the Agana tower, the CERAP controller made a radio transmission to another aircraft about 0140:54. From about 0141:14 to 0141:30, he was on the interphone with a controller at the Oakland Center. About 0142:05, the CERAP

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 controller acknowledged a transmission from the flight crew of Ryan International flight 789. The transcript indicated no further activity until about 0143:49, when the CERAP controller called the Agana tower with a flight plan. The CERAP controller said that he last observed the target of flight 801 on the terminal radar display when the airplane was 7 miles from the airport at an altitude of 2,600 feet.

Between 0150 and 0151, the CERAP controller was queried by the Agana tower controller about flight 801. About 0154:44, the CERAP controller contacted Ryan flight 789 and stated, "ryan seven eighty nine roger we may have lost an airplane...." About 0156:03, the CERAP controller requested the Ryan flight crew to "...look for signs of an accident west of the airport." About 0156:35, a Ryan flight crewmember advised the CERAP controller, "...about fifteen minutes ago we saw the clouds light up bright red it was kinda weird we thought it was just our eyes or something." About 0156:58, the crewmember advised the controller, "we got a big fireball on the hillside up here...about our three o'clock and two miles?ah a mile."

1.10.1.2 Minimum Safe Altitude Warning System

Beginning in 1977, MSAW functions were incorporated into the ARTS software installed in FAA terminal radar data processing systems. According to FAA technical document NAS-MD-684, MSAW provides general terrain monitoring for all aircraft, including those not on approach, within a predetermined geographic area and approach path monitoring for certain aircraft operating within an approach capture box (a rectangular area surrounding a runway and final approach course). The document also states that aircraft on approach are to be monitored based on their current or predicted altitude compared with the lowest MDA for the approach and that warning alerts are based on an "aircraft's relative position to a runway threshold and final approach course centerline."

The ARTS IIA MSAW system uses computer software that contains a terrain database customized for the environment around each airport that utilizes ARTS processors. The MSAW system is designed to visually and aurally alert a controller whenever an IFR-tracked target with an altitude encoding transponder (Mode C) descends below, or is predicted by the software to descend below, a predetermined safe altitude. The ARTS IIA and EARTS MSAW systems use approach capture boxes aligned with runway final approach courses to identify aircraft that are landing. Within these boxes, MSAW applies special rules specific to approach and landing operations. The ARTS IIA adaptation allows the use of a "pseudo-glideslope" that underlies the actual glideslope. Predicted or actual descent below this pseudo-glideslope normally produces a low-altitude alert. EARTS approach adaptation is less sophisticated and does not include glideslope monitoring; instead, a single base altitude is used for the entire approach capture box.

According to FAA records, the Guam terminal (approach) MSAW system was originally installed in 1990 to provide altitude protection within a 55-nm radius around the Guam ASR-8 site. In March 1993, a new software package was developed and evaluated

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 by FAA technicians for installation at Guam. The new software was designed to inhibit MSAW alerts inside a 54-nm radius of the Guam ASR-8 site. Thus, the MSAW was only available (uninhibited) for a 1-mile radius (from 54 to 55 nm around the Guam ASR-8 site). According to FAA representatives, this change, designed as a temporary solution to reduce false, or "nuisance," warnings, was submitted by the Guam CERAP and approved by the FAA's Western Pacific Regional Office. The Safety Board requested documentation of the reasons for the changes, but the FAA was unable to explain the specific reason(s) for the change in the MSAW configuration. The FAA Technical Center in Atlantic City, New Jersey, modified the software and delivered it to Guam in January 1994, but the software did not become operational until February 1995. (The EARTS MSAW system at Guam only generates visual MSAW alerts, and these alerts were not inhibited at the time of the accident.)

The ARTS IIA system recorded no alerts for Korean Air flight 801 at any time. The EARTS MSAW alert records showed that a visual approach path warning was generated at 0142:20, about 6 seconds before the crash of flight 801, and continued until at least 0142:49.

At the Safety Board's public hearing, the FAA's Deputy Program Director of Air Traffic Operations testified that, in some circumstances, controller issuance of an MSAWbased safety alert could be a first-priority duty equal to separation of aircraft. FAA Technical Center management testified that MSAW is a safety-critical service.

An FAA quality assurance evaluation report, dated July 31, 1995, on the Guam CERAP facility stated that the MSAW system had been inhibited and that a NOTAM had been issued about the inhibited MSAW. An FAA representative stated that, because no "established policy" existed for MSAW operations at the time of the 1995 evaluation, the MSAW inhibition was noted only as an "informational" item in the evaluation team's report and, as a result, did not require corrective or follow-up action. The report also indicated that a new digital terrain map had been ordered and was scheduled for delivery in April 1995 but that the delivery date had been rescheduled for August 1995.

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 FAA documents revealed that new MSAW software became operational in April 1996, but it contained the same 54-nm-radius inhibition as the February 1995 version. About 1 year after the installation of the new software, the FAA conducted another facility quality assurance evaluation of the Guam CERAP. The evaluation report, dated April 1997, did not note that the ARTS IIA MSAW system remained inhibited.

According to the FAA, the MSAW system at Guam was restored to full, uninhibited operation on August 23, 1997 (17 days after the flight 801 accident), after the monitoring software parameters were adjusted to reduce false alert incidents. The FAA indicated that, since that time, controllers had been experiencing about 18 nuisance alarms per day and that work was ongoing to reduce these alarms.

1.10.1.3 Air Traffic Control Tower

The Agana tower is responsible for operations within the surrounding Class D airspace, which is defined as the airspace within a 5-statute mile radius from the center of the Guam International Airport up to, but not including, 2,500 feet agl. The tower facility is located on the south-southwest side of the airport and is operational 24 hours a day. The controller positions are arranged in a semicircular pattern that face generally from the southwest to the northeast. The four operational positions are the controller-in-charge, local control, ground control, and flight data. All of the positions are typically worked by one controller as a combined function, but the positions may be separated depending on traffic conditions and staffing levels.

In August 1994, Barton ATC International, Inc., was awarded the contract to provide ATC services at the Agana tower. Barton was purchased by Serco Aviation Services, Inc., in January 1997. According to a Serco official, 6 controllers with an average of 15 years of experience worked at the tower at the time of the accident. Three of these staff members, including the Air Traffic Manager, had worked at the facility when it was operated by the U.S. Navy.

The Guam Air Traffic Manager said that the FAA evaluated the tower facility at Guam in October 1995 to determine whether a new tower should be constructed or the existing facility should be upgraded. The FAA also evaluated the Guam tower in September 1996, and the Air Traffic Manager learned that the facility would be upgraded with digital bright radar indicator tower equipment (D-BRITE) displays.

In February 1997, two D-BRITE systems were delivered to the Agana tower, and the radar displays were installed by the FAA in July 1997. The tower controller on duty at

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 the time of the accident stated that the D-BRITE radar display was operational but had not been certified for use. (At the time of the accident, the associated control panels for configuring the Guam tower D-BRITE video maps and settings were located at the Andersen AFB tower. According to the FAA, the equipment at the Agana tower was not certified or commissioned for use because of missing hardware and computer software.) The tower controller stated that the display showed secondary radar targets but that the radar setting selected by the Andersen AFB controllers determined whether Mode C targets would be displayed. He said that the controllers at Guam were not able to determine an airplane's position on the video map because it did not depict any final approach courses or runway orientations for the airport.

By December 1997, the two D-BRITE systems had been tested, and the Agana tower controllers received training on the systems' operation. The D-BRITE systems were certified and commissioned for use on April 11, 1998. The video map has been modified to depict the airport with extended centerlines for both runways 6L and 6R, and the system is controlled at the Guam tower.

The Agana tower controller on duty at the time of the accident told Safety Board investigators that he arrived for duty about 2215 on August 5, 1997. After that time, he and the controller on duty performed a position relief briefing, which covered airport conditions, navigation aid conditions, traffic clearances that had been issued, and the facility equipment status. After midnight, the controller performed daily administrative duties. The controller said that he was working at the local control position, which was located in the center of the tower cab facing the runway. The controller also stated that he was aware of the NOTAM regarding the out-of-service glideslope.

The tower controller said that, when Korean Air flight 801 made initial radio contact (about 0140:55), it was the only airplane that he was controlling. The tower controller said that, when flight 801 did not visually appear within 3 to 4 minutes after the airplane was cleared to land (about 0141:01), he commenced a communications search for the aircraft. The controller attempted to contact flight 801 about 0145:13 and 0150:06. Between about 0150:00 and 0151:00, the tower controller queried the CERAP controller, the ramp controller, and an Andersen AFB controller about flight 801.

FAA Form 6030-1, "Air Traffic Control Facility Maintenance Log," for July 7, 1997, showed that the Agana tower had been notified by an FAA maintenance technician that the glideslope portion of the ILS would be out of service starting that day for extensive reconstruction. The reconstruction work included the replacement of the glideslope's equipment shelter and all cabling and the upgrade of the power systems and grounding. A NOTAM issued by the FAA on July 7, 1997, indicated that the glideslope would remain out of service until September 12, 1997. The complete ILS system was

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 flight checked, certified, and returned to service on August 31, 1997. The Safety Board's review of the facility maintenance log revealed no entries of pilot reports regarding the ILS or related navigation systems from July 7 to August 6, 1997.

The accident airplane's CVR recorded conversation among the flight crew regarding the operational status of the ILS glideslope as they approached the airport. For example, as previously stated in section 1.1, about 0139:55, the flight engineer asked, "is the glideslope working? glideslope? yeh?" About 0139:56, the captain answered, "yes, yes, it's working." About 0140:00, the first officer responded, "not useable." About 0141:46, the captain asked, "isn't glideslope working?"

In a postaccident interview, the captain of a Continental Air Micronesia 727-200 stated that, about 1530 on August 5, 1997, he was conducting an in-flight functional test of a newly installed global positioning system (GPS) when the airplane's instrumentation showed an indication of the ILS glideslope, even though the glideslope was out of service. Specifically, the captain stated that he was on approach to runway 6L at Guam International Airport and was centered on the localizer when he noticed that the glideslope was also centered and that no warning flags were associated with the ILS. In addition, the captain said that the glideslope always indicated "center" with no warnings even when the airplane was above the normal glidepath. The first officer confirmed the captain's observations. However, the flight crew did not indicate any anomalous glideslope indication to ATC personnel or submit any maintenance writeups containing such information.

The Continental Micronesia captain told Safety Board investigators that he originally assumed that the anomalous glideslope indication he experienced was caused by an airplane anomaly. The captain further stated that he thought the anomaly might have been a result of the GPS wiring installation. The captain did not report the glideslope anomaly to his chief pilot until 2 days after the Korean Air accident. The first officer stated that he and the captain "never thought twice" about the glideslope indications because they knew the glideslope was inoperative.

According to the maintenance records for the Continental Air Micronesia airplane, the first officer's ADI and HSI were removed and replaced on August 5, 1997, after the functional test flight. In addition, the records showed repeated squawks for the first officer's ADI and HSI between August 8 and 25, 1997.

Instrument approaches available for runway 6L at the time of the accident were the ILS (localizer only, glideslope out of service), the VOR/DME, and the VOR.

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 1.10.3.1 The Nonprecision Runway 6L Instrument Landing System Localizer-only (Glideslope Out) Procedure

The execution of the Guam ILS runway 6L localizer-only (glideslope out) approach requires the use of the NIMITZ VOR as a step-down fix between the final approach fix (FAF) and the runway and DME to identify the step-down points. The DME is not colocated or frequency paired with the localizer transmitter (which is physically located at the airport); rather, it is colocated and frequency paired with the NIMITZ VOR. The nonprecision localizer-only approach requires the use of the localizer to obtain lateral guidance to the runway, the DME to identify the step-down points, and the VOR to identify the final step-down fix to the MDA. According to Jeppesen Sanderson's August 2, 1996, 11-1 ILS Runway 6L approach plate, the airplane should cross the FLAKE initial approach fix (IAF)--located at 7 DME from the VOR--at or above 2,600 feet msl.

The nonprecision approach procedure prohibits descent below 2,000 feet msl (1,744 feet above airport elevation) before reaching the outer marker identified as GUQQY, which is the FAF and is located 1.6 DME from the VOR. Upon crossing the FAF, the procedure prohibits descent below 1,440 feet msl (1,184 feet above airport elevation) until passing the VOR. The procedure calls for a descent to 560 feet msl (the MDA, 304 feet above airport elevation), and the pilot is required to count up from less than 1 DME, as the airplane passes over the VOR, to 2.8 DME, the published missed approach point (MAP) and location of the middle marker. If a missed approach is not required, the airplane can continue its descent to the runway 6L threshold, located 3.3 DME from the VOR.

According to the FAA, the DME and localizer at Guam are now frequency paired and colocated. In addition, the August 27, 1999, Jeppesen instrument chart for the ILS runway 6L approach (which became effective on September 9, 1999) states "DME or RADAR required" and includes "ILS DME" in the frequency box.

1.10.3.2 Instrument Approach Charts for Guam International Airport

During postaccident examination of the cockpit area (which had separated from the main wreckage, as discussed in section 1.12), investigators found a clear plastic sleeve, measuring approximately 8 ½ by 11 inches, that contained the following Jeppesen approach charts for Guam International Airport, all of which were dated January 19, 1996: 11-1, ILS Runway 6L; 13-1, VOR Runway 6L; 13-2, VOR DME Runway 6L; 16-1, NDB Runway 6L; and 16-2, NDB DME Runway 24R.

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 Charts 11-1 and 13-2 were found side by side and were visible through one face of the plastic sleeve. Chart 16-1 and the blank side of an approach plate were visible through the opposite face of the plastic sleeve. Chart 11-1, which is shown in figure 7, had the following items highlighted with a green fluorescent tint:

 * Plan view
 * ILS facilities box: 063° (inbound magnetic course), 110.3 (ILS frequency), IGUM (identifier), and FLAKE (IAF).
 * VOR facilities box: 115.3 (NIMITZ VOR frequency) and UNZ (identifier).

 * Profile view
 * 2500' (msl altitude crossing FLAKE).
 * 1900' (msl altitude crossing the outer marker).
 * 256' (touchdown zone elevation-runway 6L).

The instrument approach charts for Guam International Airport in effect at the time of the accident were issued on August 2, 1996 (with an effective date of August 15, 1996). Changes incorporated in the August 2, 1996, 11-1, ILS runway 6L approach chart (shown in figure 1) included the location names, crossing altitudes, and the missed approach procedure. Table 2 details the specific differences between the January and August 1996 instrument approach charts.

The accident airplane was equipped with a Sundstrand Data Corporation model 573A FDR, serial number 2663, which was configured to record 51 parameters. The FDR recorded information digitally on four tracks using ?-inch-wide magnetic tape that had a recording duration of 25 hours before the oldest data were overwritten. Even though the FDR case was damaged by impact forces, data could be retrieved and analyzed. Examination of the data indicated that the FDR had operated normally, except for a loss of synchronization about 3 seconds before the transition to 25-hour-old data. About 3 hours 48 minutes of data were transcribed for the entire accident flight (takeoff to impact).

After an initial readout of the FDR, Korean Air provided the Safety Board with documentation that indicated that 11 additional sensors had been retrofitted after the airline took delivery of the airplane. These retrofitted sensors--exhaust gas temperature and oil quantities for the airplane's four engines, static air pressure, and the left No. 4 and right No. 12 spoiler positions--were not reflected in the FDR documentation provided by the manufacturer or the airline at the time of the initial FDR readout. Documentation for the additional sensors provided by Korean Air did not include the equations necessary to

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Figure 7. The January 19, 1996, 11-1 ILS runway 6L instrument approach chart.

Reproduced with the permission of Jeppesen Sanderson, Inc. NOT TO BE USED FOR NAVIGATION.

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 Table 2. Information differences between the January 19 and August 2, 1996, Guam ILS runway 6L approach charts.

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 convert the recorded information into engineering units. The Safety Board applied equations used in previous readouts of FDRs from similar 747s, but the validity of the conversion equations could not be verified.

The accident airplane was equipped with Fairchild model A-100A CVR, serial number 61216. The CVR case revealed no evidence of structural damage, and the interior of the recorder and the tape showed no evidence of interior heat or impact damage. The recording consisted of four channels of "good quality" audio information, which included the captain, first officer, and flight engineer microphones; audio panels; and the cockpit area microphone. The fourth channel also recorded the interphone and the public address system.

The audio portion began about 0111:42 and continued uninterrupted until 0142:32.53. The recording ended shortly after the airplane crashed and the power to the CVR was lost. The CVR group, consisting of representatives from the parties to the investigation and the KCAB, collectively transcribed the 31-minute 1-second tape in its entirety. A bilingual (English and Korean) transcript was produced of the entire recording (see appendix B).

Examination of the ground scars and the debris pattern revealed that the accident airplane impacted high terrain with the left outboard engine, main landing gear, and left wing at an elevation of about 660 feet msl and on a magnetic heading of approximately 063°.

The Safety Board performed a complete survey of the accident site and airplane structure. The main wreckage site area was in a gully covered with dense vegetation, located approximately 2,000 feet southwest of the NIMITZ VOR. The wreckage distribution area was about 2,100 feet long and 400 feet wide and included airplane debris, tree strikes, and ground impact marks. All major structural components of the airplane and control surfaces that were not consumed by the postimpact fire were identified along the wreckage path. The terrain along the wreckage path was hilly and ranged from about 673 feet msl at the first tree strikes to about 582 feet msl at the main wreckage area.

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 The initial point of impact was evidenced by several cut treetops that extended along the wreckage path. Several ground impact marks, consistent with the main landing gear, were found in the vicinity of the broken oil pipeline, located about 400 feet from the point of initial impact. A ground scar, about 89 feet long, 6 feet wide, and 2 feet deep, was found about 415 feet from the point of initial impact, and several pieces of the No. 1 engine cowl were found embedded in this area, along with parts of the left wing leading and trailing edge flap structure.

Numerous parts of the left main landing gear, including two wheels and tires, were found embedded in a small berm about 1,430 feet from the initial impact point. Most of the fuselage structure was located in the main wreckage area and was found separated into five major sections: the empennage, the aft fuselage, the center fuselage, the forward fuselage, and the cockpit.

Figures 8a and 8b are photographs of the wreckage from Korean Air flight 801. Figure 8a shows the airplane wreckage in relation to runway 6L, the NIMITZ VOR, and Apra Harbor. Figure 8b provides a closer view of the wreckage and the VOR.

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 Figure 8b. Closer view of the wreckage from Korean Air flight 801 and the NIMITZ VOR.

The cockpit section was located down an embankment beyond the large portion of the forward fuselage. The airplane's VHF [very high frequency] navigational radio control panels were recovered from the wreckage. To determine which radio frequencies were selected on both the captain's and the first officer's control panels in the cockpit, an examination was conducted on October 2, 1997, under the Safety Board's supervision, at Pacific Aero Tech, an FAA-approved repair station for the control panel, in Kent, Washington. The captain's frequency selector was found tuned to 110.30 megahertz (MHz), which was the Guam localizer frequency. The captain's control panel had been damaged by impact forces, and the frequency depicted was locked into a position that could not be changed by turning the frequency selector knob. The first officer's control panel selector knob could be easily rotated, and the frequency selector was found tuned to 116.60 MHz, which did not correspond to any voice or navigation frequencies at Guam.

The cockpit section was found separated about station 400. Most of the aft nose wheel well structure (nose gear attachment point) was relatively intact with the trunnion

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 support fittings, drag brace fittings, and transverse beam still attached. Examination of the nose landing gear and the wing- and body-mounted landing gear revealed that they were in the extended position at the time of impact. This section of fuselage structure revealed no evidence of fire damage.

The forward fuselage section approximately from stations 400 to 1120 was located on the upslope of a hill beyond the center fuselage section. The fuselage structure was split above the main deck floor on the right side, and most of the internal structure (frames, stringers, and fractured floor beams) remained attached. The structure exhibited extensive fire damage, including burn-through of the crown area (upper forward fuselage), sidewalls, and floor.

Examination of doors 1L, 1R, 2L, and 2R could not be performed in detail because the airframe structure around these doors was heavily burned, and only portions of the doors were located in the main wreckage site. The door identified as 3L was found closed and locked. Door 3R was found separated from the fuselage, with more than one-half of the door frame area missing because of fuselage separation in this area. According to Korean Air records, the 3L and 3R doors were deactivated before the company took delivery of the airplane. The doors identified as 4L and 4R were found detached from their respective mounted positions, and approximately one-third of the 4R door frame was missing. Door 5L was found closed and locked. Door 5R was found in the open position; however, the door handle was not in the full open position. The upper deck doors were not located; these doors were mounted in an area of the fuselage that sustained extensive fire damage.

The center portion of the fuselage structure, extending from stations 1120 (left side) to 1240 (right ride) and aft to station 1780, was found attached across the crown area and to the right wing by the landing gear beam. The landing gear beam at station 1350 was attached to the fuselage section. The entire center section was found rotated about 180° to the debris path, with the forward end of the section facing the aft body and empennage. The interior was extensively damaged by fire throughout the section. The exterior fuselage skin bore fire damage primarily adjacent to the break, and the right-side fuselage skin was heavily burned between doors 3R and 4R.

The exterior fuselage surface was lightly sooted on the left side of the center section, and the exterior of the right side bore evidence of light soot and areas of fire damage around the periphery of door 5R. The interior was damaged by fire from the main deck floor level to the belly; however, the upper portions of the internal structure were not burned significantly. The aft pressure bulkhead was intact, with the lower portion deformed. The bulkhead was not damaged by fire. The empennage was found separated from the aft fuselage in an upright position.

The empennage had sustained impact damage and some light fire damage. The left- and right-side horizontal stabilizers, their respective elevators, and the vertical fin (with the rudder attached) remained attached in their respective mounted positions.

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The left and right wings were located on the left side of the airplane in the main wreckage area. The right wing remained attached to the fuselage center section, and the left wing was located under the fuselage and right wing.

The outboard section of the left wing was located approximately parallel to and under the right wing section. This portion of the left wing structure was approximately 80 percent intact and had sustained extensive postimpact fire damage to the upper skin and midspar (between wing stations 470 and 1200), including the midspar web and chord structure. The corresponding lower skin and stringers also exhibited considerable fire damage. Exposure to the postimpact fire resulted in various degrees of damage to the remaining wing structure, including the leading edge and trailing edge flap structure. The outboard wing tip, which comprised 10 composite aluminum and fiberglass structures, was found separated from the wing box at the surge tank end rib at wing station 1548 and was not damaged by fire.

Most of the right wing inboard and outboard trailing edge flaps and support structure were found intact and attached to the wing box, except for approximately 6 feet of the inboard fore, mid, and aft flap structure of the inboard-most section of the flap. This section had separated and was found in the debris path in the vicinity of the initial impact point. Examination of the ball screw indicated the flap extension was approximately 25°.

All of the leading edge variable camber flap and inboard Krueger flap structure was destroyed by impact forces and the postcrash fire. The trailing edge flaps and control surfaces were found relatively intact with some localized fire damage, except for the inboard flap system, No. 4 flap track, and No. 6 spoiler, which separated from the wing box during initial impact.

The No. 1 through No. 5 flight spoilers were found in place in a neutral position at the in-spar box structure. The spoilers exhibited extensive fire damage. The No. 6 ground spoiler had separated from the wing and could not be located among the wreckage. Examination of the spoiler support beam revealed evidence consistent with overload from impact forces.

The full combination of outboard flap and support structure on the left wing was found in place on the wing box with a detent extension indicative of approximately 25°. All of the inboard flap and most of the support structure had separated from the wing box and was found along the wreckage path, with numerous parts in the area of the initial impact point.

All four of the engines were found separated from their respective mounted positions on the airplane. The No. 1 engine was located about 970 feet from the initial

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 impact point and about 1,300 feet from the main wreckage site. The other three engines were all located within the main wreckage site.

All of the engines sustained damage to the fan blades, with the tips and leading edges bent opposite to the direction of rotation. Further, vegetation and dirt had been ingested into the fans and low-pressure compressors of each of the engines. Examination of the rotating parts within each engine revealed evidence of rotational smearing, rubbing, and blade fractures that were consistent with the engines producing power at the time of impact. Further, none of the four engines exhibited any evidence of uncontained failures, case ruptures, or in-flight fires. All of the thrust reverser actuators that were found indicated that the thrust reversers on each of the engines were in the stowed position.

Tissue and fluid samples from both pilots and the flight engineer were transported to the FAA's Civil Aeromedical Institute (CAMI) for toxicology analysis. The CAMI laboratory performed its routine analysis for major drugs of abuse and prescription and over-the-counter medications, and the results were negative. The analysis detected ethanol in the blood and tissue samples of both pilots and the flight engineer, but no ethanol was detected in the vitreous (eyeball) fluid sample taken from the captain. All specimens were noted in the laboratory report to have been received by CAMI in a "putrefied" condition.

According to the captain's medical records, he consulted a personal physician on July 27, 1997, and was diagnosed with bronchitis. The physician prescribed three medications: Copan (clenbuterol), a medication to open the upper airways; Vibramycin (doxycycline), an antibiotic; and Sentil (clobazam), a medication in the benzodiazepine class of drugs that is frequently used as a sedative. The postmortem tests conducted by CAMI on the captain's blood specimen were negative for benzodiazepines, and no CAMI testing was available for the detection of Copan or Vibramycin.

The remains of deceased airplane occupants were examined by the Disaster Mortuary of Guam to determine the cause of death. Because many of the remains were fragmentary, the total number of remains sets (300) exceeded the number of accident fatalities. Autopsy examinations and toxicological analysis determined that the airplane occupants died of blunt force trauma, thermal injuries, and carbon monoxide inhalation. Complete autopsies and toxicological evaluations were performed on the remains of the three flight crewmembers (as discussed previously.) Of the 297 non-flight crewmember

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