N904AW

1.1 HISTORY OF FLIGHT

On September 20, 1999, at 1623 mountain standard time, the flight crew of America West Flight 2208, a Boeing 757-2S7, N904AW, executed an escape maneuver when the ground proximity warning system (GPWS) activated near Agua Caliente, Arizona. The aircraft was not damaged; however, 2 flight attendants received serious injuries while 2 others received minor injuries. The remaining flight attendant, the flight crew of 2, and the 170 passengers onboard were not injured. The aircraft was being operated by America West Airlines, Inc., under 14 CFR Part 121 as a scheduled domestic passenger flight when the accident occurred. The flight originated from the Los Angeles International Airport, Los Angeles, California, at 1535 Pacific daylight time that afternoon. Instrument meteorological conditions prevailed at the in-flight altitude of the event and an instrument flight plan was filed.

A review was conducted of the recorded air-ground communications transcripts between the airplane and Albuquerque Air Route Traffic Control Center (ARTCC) and Phoenix Terminal Radar Approach Control. Data plots from the Digital Flight Data Recorder (DFDR) were also compared to the transcript and recorded radar data to reconstruct the events surrounding the GPWS warning and subsequent escape maneuver. In addition, pertinent conversations recorded on the Cockpit Voice Recorder were reviewed.

The flight checked in with ARTCC Sector 91 at 1618 at Flight Level (FL) 300 (30,000 feet msl) with a previous sector's clearance to fly direct to ARLIN intersection. The sector 91 controller acknowledged the flight and assigned a 120-degree heading for traffic separation. Shortly thereafter the controller asked the flight what their indicated airspeed was and the crew replied "265 indicated." The controller turned the flight further right to a 125-degree heading, instructed the flight to descend and maintain FL270, and to increase their indicated airspeed to 300 knots or greater. At 1621, the controller advised the flight to expedite their descent to FL270 and to expect a lower altitude in 2 minutes due to opposite direction traffic below FL270. The controller pointed out the traffic as "11 o'clock 10 miles westbound at flight level 260 [FL260]." The flight responded that they were unable to visually acquire the traffic because they were in instrument meteorological conditions.

At 1623, the controller told the flight to descend and maintain FL240 at a "good rate of descent." The flight responded, "We just got a terrain warning and had to climb out of it." The controller queried, "You mean aircraft warning [because of] that guy below you?" The flight responded, "Negative, must have been a nuisance warning."

According to the crew's written and oral statements, the first officer was the flying pilot. The airplane had been cleared to descend to FL270 and was descending at a rate of about 4,000 feet per minute in instrument meteorological conditions. Albuquerque center issued a traffic advisory for opposite direction traffic at 12 o'clock and passing 1,000 feet below. The traffic was being displayed on the traffic alert and collision avoidance system (TCAS) indicator as an amber traffic alert (T/A) symbol showing "-1700 warning." The TCAS also provided the aural alert, "Traffic, Traffic." As the traffic disappeared from the TCAS indicator, a GWPS "terrain, terrain, whoop, whoop, pull up" warning was received. The first officer said that he looked briefly at the captain who said, "Let's do it." The first officer said he then executed the GPWS escape maneuver as the aural warnings sounded continuously. He increased power to maximum thrust and pitched the nose up to about 8 degrees. The aircraft began a climb at 3,400 fpm. As he reached FL 280, the aural warning ceased and the aircraft entered visual meteorological conditions. As he leveled the aircraft, the captain advised Albuquerque Center that they had received a GPWS warning and had responded. Albuquerque Center asked if was a TCAS alert to which they answered "no." [The four injured flight attendants were standing in the rear galley when the escape maneuver was performed. The events in the cabin are contained in summary form in the SURVIVAL FACTORS section of this narrative; complete statements from all cabin crewmembers can be found in the Survival Factors Group Factual Report, which is appended to this document.]

The crew stated that Albuquerque Center told them to descend and maintain FL 240. As the aircraft began its descent with a vertical speed of about 300 to 500 fpm, the GWPS resumed the same aural warning with an occasional "sink rate." The volume level of the warning made communications in the cockpit difficult, and it was silenced only after the first officer pulled the circuit breaker.

Examination of the radar data and mode C altitude reports form both aircraft obtained from Albuquerque ARTCC disclosed that the true ground track of the flight was 131 degrees in a descent while the opposite direction aircraft's true ground track was 280 degrees while level at FL260. At 1623:27, the opposite direction aircraft was 1.52 nautical miles and on a relative bearing of 350 to America West flight 2208; the radar target returns merged at 1623:34. Based upon calculations of the ground tracks and the timing, the opposite direction aircraft passed laterally behind flight 2208 by about 1,300 feet with a vertical separation of 1,200 feet. The direct distance between the two aircraft at the closest point of approach was about 1,770 feet. The radar data and mode C altitude reports showed that flight 2208's vertical profile changed from a descent to a climb at 1623:38; the change occurred at FL272 and the airplane climbed to FL282 before leveling briefly and then resuming a descent.

Data readout from the DFDR disclosed that the GPWS escape maneuver began at subframe reference 47924 (subframe reference is the number of seconds from beginning of the recording) at an altitude of 27,100 feet. The data traces for the vertical acceleration (g's) oscillated during the escape maneuver from 1 to 2.5 to 0.5 over a 2-second period. Nose-up and down elevator inputs consistent with the vertical acceleration oscillations were recorded during this same 2-second interval. The data plot shows that coincident with engine spool-up, and within about a 2-second interval, the right elevator moved to a 5-degree deflection and the nose pitch attitude achieved 8 degrees. The right elevator then moved to a zero or slightly minus deflection as the nose pitch attitude decreased to 5 degrees. The pitch attitude then increased back to 8 degrees over a 6-second interval, where it remained until the airplane leveled off at 28,250 feet. The plot traces for the Radio Altitude parameter were noted to be erratic from the time of liftoff at Los Angeles until touchdown at Phoenix, with jumps every so often from 1,700 feet to 500. About 5 seconds before the initiation of the escape maneuver, the Radio Altitude jumped from 1,700 to 500, then back to 1,200, then down to 200 before resuming a 1,700 reading. Following that, the Radio Altitude parameter oscillated in 6-second cycles from 1,700 to 200 and back again; this oscillation continued until touchdown at Phoenix.

After the flight resumed a normal descent, it was handed off to ARTCC sector 42, and that controller gave the flight further descent instructions down to FL110 and cleared the flight for the ARLIN 1 arrival procedure into Phoenix. Subsequently, sector 42 handed the flight off to Phoenix Terminal Radar Approach Control (TRACON) at 1628. The flight declared an emergency at 1637 with Phoenix TRACON, announcing, "We need to get to [runway] 26 right and expedite to gate A14…we have injured flight attendants and a couple are going into shock." The TRACON controller gave the flight priority direct to the runway and the airplane landed at 1641.

The CVR was transcribed and is appended to this report. The recording begins at some point after the aircraft has parked at the gate with the captain noting that the Auxiliary Power Unit (APU) is running and that the "secure checklist" is complete. During the next 5 minutes, the captain and first officer are discussing the event. The first officer remarked, "you know when you're strapped in, and doing that kind of thing in the sim [simulator], you don't realize what kind of an effect [unintelligible word]. I was totally surprised when she said what happened back there." He then went on to note that a status message, "ground prox byte" was on the EICAS in flight after the event.

The crew then had a discussion on the radio with maintenance control informing them of the nature of the event and that the EICAS is now displaying the "ground proximity byte message." Shortly after that, the assistant chief pilot entered the cockpit and the crew discussed the event with him. Comparison of this conversation with the crews later written and oral statements revealed that they are consistent. The conversation then turns toward the need to secure the CVR for readout and how to write up the event on the log page.

A maintenance technician then entered the cockpit and had a discussion first on pulling the CVR, then on the event. After the crew described the GPWS warning and subsequent events, the technician states "This aircraft had a tremendous history on radio altimeter problems…did you have any associated radio altimeter messages or warnings or anything like that?" The first officer responded that they did not.

1.2 PERSONNEL INFORMATION

The America West personnel, flight and training records for both of the flight crew were reviewed. In addition, the FAA Airman and Medical Certification files were examined.

1.2.1 Captain

The captain held an Airline Transport Pilot certificate with a class rating for multiengine land airplanes, with commercial privileges in single engine lan...