Korean Air Flight 801 investigation/IIC
Gregory A. Feith
On August 6, 1997, about 0142 Guam Local Time, a Korean registered Boeing 747-300, operated by Korean Air Company, Ltd., as Korean Air flight 801, crashed about 3 nautical miles southwest of the Guam International Airport in Agana, Guam, while executing the Instrument Landing System (ILS) approach to runway 6 left.
The Safety Board was notified of the accident on August 5, about 1200 noon eastern daylight time. I was assigned as the Investigator-in-Charge, and the Go-Team assembled at Andrews Air Force Base (AFB) in Maryland, and departed later that evening via a United States Air Force C-141 transport airplane to Fairchild AFB in Washington. The trip to Guam was subsequently completed on a KC-135R, and the team arrived in Guam about 0830 Guam time, on August 7. The Board Member on duty at the time of the accident was George Black and he accompanied the team to Guam.
The investigative team consisted of various specialists from the Safety Board's headquarters, the South Central Regional and Southwest Regional Offices. The specialty areas were: Aircraft Operations, Human Performance, Structures, Systems, Powerplants, Maintenance Records, Air Traffic Control, Survival Factors, Aircraft Performance, Meteorology, and Search/Fire/Rescue. Specialists were also assigned to conduct the readout of the flight data recorder (DFDR) and transcribe the cockpit voice recorder (CVR) in the Safety Board's laboratory in Washington, D.C. The initial CVR transcript was produced in English by the group members. However, the CVR group reconvened and produced a more detailed transcript in both English and Korean languages.
The following organizations were given party status and provided technical assistance to the Safety Board: the Federal Aviation Administration, Korean Air Company, Inc., Boeing Airplane Company, Pratt & Whitney Engines, the National Air Traffic Controllers Association, the United States Navy, and emergency response personnel from Guam.
In addition, Mr. Ham of the Korean Civil Aviation Bureau (KCAB) was designated as the Accredited Representative and leader of the Korean delegation in accordance with the provisions of Annex 13 to the Convention on International Civil Aviation. Annex 13 dictates the procedures for cooperation during the investigation of international aviation accidents.
Further, two Air Safety Investigators from the Australian Bureau of Air Safety Investigations (BASI) participated in the investigation as technical observers.
History of Flight
Korean Air flight 801 was a regularly scheduled passenger flight that departed Kimpo Airport, in Seoul Korea, at 2153. The flight proceeded uneventfully en route to Guam. An audio examination of the CVR revealed that the captain was the "flying pilot" and the First Officer (F/O) was performing the radio communications and non-flying pilot duties at the time of the accident.
At 0103, the first officer contacted the Guam Air Traffic Control Center and Radar Approach Control (CERAP) and stated that they were at flight level (FL) 410 (41,000 feet) and over MIXSS intersection, which is located about 240 nautical miles northwest of the Nimitz VOR.
About 0111:51, the CVR recorded the captain briefing the other flightcrew members about the approach to Guam. The captain stated, in part, "I will give you short briefing...since the visibility is six [miles] when we are in the visual approach, as I said bcfore, set the VOR on number two and maintain the VOR for the TOD [top of descent]... in case of go-around, since it is VFR, while staying visual and turning to the right... request a radar vector...since the localizer glideslope is out, MDA [minimum descent altitude] is five hundred sixty feet and HAT [height above touchdown] is three hundred four feet..."
At 0122, the Guam CERAP controller informed flight 801 that the automatic terminal information scrvice (ATIS) report was "uniform" and the current altimeter setting was "29.86." The first officer acknowledged the transmission and said, "checking uniform," however, he did not acknowledge the altimeter setting.
At 0124, flight 801 began deviating around cumulonimbus clouds that were scattered along their route of flight. About 6 minutes later, the first officer reported to the Guam CERAP they were clear of the weather and requested radar vectors to runway 6 left.
At 1031, the CERAP controller provided radar vectors to flight 801 and approximately 7 minutes later the controller transmitted, "Korean Air eight zero one, turn left heading zero nine zero, join the localizer." The first officer acknowledged the transmission.
At 0139, the CERAP controller transmitted," Korean Air eight zero one...cleared for thc ILS runway six left .. glideslope unusable." The first officer responded, Korean eight zero one roger .. cleared ILS runway six left," however, he did not acknowledge that the glideslope was unusable.
Shortly after being cleared for the ILS approach, the CVR recorded the flight engineer say, "is the glideslope working..." to which the captain responded "...yes, yes, it's working." At 0139:58, the CVR recorded an unidentified flightcrew member say, "check the glideslope if working," followed by "why is it working." The first officer rcsponded, "not useable." About 23 seconds later thc CVR recorded an unidentified flightcrew member say, " glideslope is incorrect."
At 0140:33, the first officer stated, "approaching fourteen hundred." The captain responded, "since today's glideslope condition is not good, we need to maintain one thousand four hundred forty. Please set it." Approximately 20 seconds later the sound of the altitude alert was recorded on the CVR.
At 0141:14, the controller cleared flight 801 to land on runway six left. The first officer acknowledged the clearance and the crew began to reconfigure the airplane for landing. About 0141:42, the CVR recorded the ground proximity warning system announcing "one thousand [feet]; and the captain saying, "no flags, gear, flaps." About 4 seconds later the captain said, "isn't glideslope working." However, there was no acknowledgement of this statement recorded on the CVR. The crew continued to complete the landing checklist items and at 1542:15 the CVR recorded the GPWS announcing "minimums" followed by "sink rate." This announcement was followed shortly thereafter by the first officer saying "sink rate okay," and the flight engineer announcing "two hundred [feet]."
At 0142:19, the first officer said "let's make missed approach," and the flight engineer said "not in sight, missed approach." These two comments were followed immediately thereafter by both the first officer and the flight engineer saying "go-around." Approximately 1 second later the CVR recorded the sound of the auto-pilot disconnect and the altitude announcements by the GPWS. The sounds of the airplane impacting the ground were recorded by the CVR at 0142:25
The published approach procedure for the ILS to runway 6 Left with the glideslope inoperative depicts a series of "step down" altitudes that the pilot is required to maintain during the execution of the approach. The step down altitudes ensure sufficient obstruction/terrain clearance. The lowest altitude for the first segment is 2,000 feet until 1.6 nautical miles from the VOR; this is followed by a step down to 1,440 feet until the VOR. Upon crossing the VOR, the pilot can descend to 560 feet, which is the minimum descent attitude or MDA. Once the pilot descends to the MDA, he/she must have visual contact with the airport environment/runway to continue the descent. If visual contact with the airport does not occur within 2.8 miles of crossing the VOR, or visual contact cannot be maintained, the pilot must execute a missed approach.
According to data recorded by the DFDR, flight 801 began to descend from 2,600 feet when the airplane was about 5 miles from the VOR, or 8.5 miles from the airport. The DFDR and radar data indicate that flight 801 descended at a rate of approximately 950 feet per minute and continued at this rate through the intermediate altitudes of 2,000 and 1,440 feet. The airplane struck rising mountain terrain about one tenth of mile west of the VOR.
Mr. Chairman, in an effort to present a clear picture of the accident related events, I would like to present a video that depicts both the flight track and the flight path of flight 801 as it approached Guam. The video will run approximately 10 minutes and you will see a split-screen view showing the plan and profile views.
Text summary of video
Flight 801, while in U.S. airspace, was being operated under 14 Code of Federal Regulations (CFR) Part 129. Of the two pilots, one flight engineer, one purser, 19 flight attendants (including 6 deadheading flight attendants) and 231 passengers that were aboard at the time of the accident, 225 received fatal injuries. Further, of the 25 passengers and 4 flight attendants that survived the accident with minor to serious injuries, 2 passengers and one deadheading flight attendant succumbed to their injuries in the 30 day period following the accident.
The following are a brief synopsis of some of the facts revealed thus far:
The captain had been a pilot in the Korean Air Force prior to his employment with Korean Air in November 1987. During his tenure with the airline, he flew the Boeing 727 and the Boeing 747, and had accumulatcd 8,932 hours of total flight time; 3,192 hours in the Boeing 747 and 1,718 hours as a 747 captain. According to company records, the captain had operated a Boeing 727 into Guam for approximately one year in 1993. His last video familiarization training and line experience into Guam occurred on July 4,1997, and was conducted in thc Boeing 747 during night-VFR conditions.
The first officer was also a pilot in the Korean Air Force prior to his employment in January 1994 with Korean Air. He had accumulated 4,066 hours of total flight time, with 1,560 hours as a first officer and in the 747. The first officer received familiarization training for operations into Guam on July 8' 1997, and had previous operating experience in the Boeing 747 in 1995.
The flight engineer was a navigator in the Korean Air Force prior to his employment with Korean Air, May 1979. He had flown as engineer on the Boeing 727, Airbus A-300, and Boeing 747, and had had accumulated approximately 13,000 hours of total flight time, of which over 11,000 was as a civilian flight engineer.
One issue developed during the investigation evolved from the operational status of the glideslope portion of the ILS approach. On August 6, the glideslope portion of the ILS was out-of service and only the localizer was available for lateral guidance to the runway. However, the CVR recorded statements by various flightcrew members questioning the operational status of the glideslope, thus, the Safety Board became concerned about the possibility of "spurious" radio signals and the influence that these radio signal may have had on the aircraft navigation Systems. We will have a witness testify about this issue later in the hearing.
The investigation team also examined the weather conditions at the time of the accident and found that the reported conditions were: wind from 090 degrees at 6 knots; the visibility was 7 miles in rainshowers; there were scattered clouds at 1,600 feet, a broken layer of clouds at 2,500 feet and an overcast layer at 5,000 feet. However, examination of weather data, doppler radar images, other weather satellite information, and witness statements, indicated there was a rain shower event occurring along the final approach path when flight 801 was executing the approach. Based on these data, this weather event produced heavy rain, gusting wind conditions and reduced visibility.
The en route and approach radar positions at Guam are typically performed by one controller using two independcnt radar systems. Both systems are equipped with a minimum safe altitude warning (MSAW) system that is designed to alert the controller both aurally and visually when an aircraft, in a predetermined geographic area, is below or predicted to be below a specified safe altitude. The investigation revealed that the MSAW system at Guam was not operating as designed or intended at the time of the accident. Detailed information about the MSAW system and its operation, both at Guam and nationwide, will be addressed by several witnesses testifying later today.
The Safety Board found during the investigation that the post-accident emergency response to the accident site was delayed several minutes because the air traffic controller was not immediately aware that flight 801 had crashed off the airport. In addition, the emergency response vehicles were delayed in arriving on-scene because access to the accident site was initially stopped by a fenced gate that encircled the property where the accident occurred; response was further hampered by a narrow paved road that was blocked by a broken pipeline that had been struck by the airplane and disable parked vehicles that congested the access road and prevented fire trucks from maneuvering close to the wreckage. Several witnesses will testify regarding these issues later in this public hearing.
In addition, the Safety Board will also be examining several other issues, including flightcrew training, crew resource management or CRM, and instrument approach procedures and charting.
Post-Accident Investigative Activities
Although the Safety Board's investigation team completed the on-site wreckage examination August 28, 1997; several other investigative activities have either been completed or on-going. These activities involved examination and tear down of various electronic components, an aircraft performance study and video simulation, follow-up demonstrations of the FAA's MSAW system, and the detection of "spurious" radio signals in the vicinity of Guam International Airport.
The latter issue regarding the spurious signals led the Safety Board to convene a meeting at Boeing Aircraft Company to discuss spurious radio signals and discuss the effect that these unwanted radio signals may have on aircraft navigation systems. A witness from the FAA will testify during the hearing to discuss this issue.
In addition to the investigative activities, a meeting was convened in Guam in January 1998, and was attended by all of the parties. The purpose of the meeting was to review the progress of the investigation, review the draft group chairman factual reports, and determine future work items. Since this meeting, all of the parties and the KCAB have reviewed the factual reports and their comments have been either addressed or incorporated in the respective reports.
The issues stated by the Chairman in his opening remarks, and those described briefly in this statement, will be addressed by the witnesses that were selected based on their expertise, experience or extensive knowledge of the relevant subjects or issues. Their testimony will provide additional factual information which the Safety Board will use in its analysis of the accident and its determination of the probable cause.
Before I conclude my statement, I would like to take a moment to publicly thank Mr. Ham and the Korean delegation for their continuing support and active participation in this investigation; the Safety Board's investigative staff who continually go above and beyond the call of duty to complete the investigative activities in a timely manner under very difficult and stressful conditions, the U.S. Air Force and Navy for their cooperation and logistical support, and finally, the officials and citizens of Guam for their support and generous hospitality while the team was on-scene.
Mr. Chairman, this concludes my remarks. The record of investigation is contained in the documents in our public docket and the court reporter has been provided a list of such materials.