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Cases › DCA18LA285 · Part 121 airline · Class 3

Boeing 757American Airlines

New York, NY, USA · 2018-09-06·N173AN

0
fatal
1
serious
Serious injury
highest injury
—
damage
Replay the flight data2,539,495 samples · 97 parameters09:25:00.0 – 17:01:20.0Read the cockpit voice recorder453 lines15:56:06.2 – 17:51:39.5AnalyseThe analystOne timeline · precedents · ask the docket · what the record saysGenerateInvestigation briefFacts, cause, recorder extremes, sequence, sourcesSourceNTSB docket9 documents on data.ntsb.gov

What happened

NTSB summary, verbatim

The airplane was descending toward the destination airport with the autopilot and autothrottle systems engaged. As the airplane was approaching 12,000 ft, and the autopilot was capturing the altitude, the captain adjusted the altimeter resulting in a displayed altitude of 12,100 ft. The captain (the pilot flying) selected flight level change mode on the autopilot to recapture the altitude and set the speed at 250 knots to slow from about 255 knots. As a result, the autothrottles went to Throttle Hold mode when the throttle levers reached the aft stop. As the captain was briefing the approach, the airplane slowed and pitched up as it tried to maintain altitude with a reduced throttle setting. An international relief officer who was in the cockpit at the time commented on the airplane’s decreasing speed three times when the airplane’s airspeed was about 186 knots before stating that the captain should push the nose over. The captain disengaged the autopilot and auto throttles, aggressively pitched down, and increased the throttles. These aggressive maneuvers caused the flight attendants in the aft galley to be thrown against the ceiling. One flight attendant sustained a compound arm fracture; two other flight attendants sustained minor injuries. The crew subsequently landed the airplane without further incident.

Photographs

1the aircraft, and what the investigators found
The aircraft before the accident
248ac - American Airlines Boeing 757-223, N173AN@MIA,21.07.2003 - Flickr - Aero Icarus
Aero Icarus from Zürich, Switzerland · CC BY-SA 2.0 · Wikimedia Commons

Probable cause

the Board's determination
The flight crew’s failure to adequately monitor the airplane’s airspeed, which led to the captain’s aggressive control inputs to increase airspeed; these aggressive inputs resulted in injuries to three cabin crewmembers.

Occurrence sequence

1 stepsNTSB coding · CICTT taxonomy
  1. 1 · Enroute-descent
    Abrupt maneuver
    defining event

Findings

1 causal · 0 contributing
  • CAUSE
    Personnel issues › Task performance › Use of equip/info › Aircraft control — Pilot

Sequence of events

26 timed eventsfrom the FDR factual report · claude-sonnet-5
  1. 09:25:00Pre-departurep.3
    Full incident flight FDR data range begins
  2. 09:28:24Departure/Climbp.4
    Aircraft departed EGPH and climbed to a cruising altitude of 36,000 feet
  3. 16:31:50Descentp.4
    Initial descent to 24,000 feet into KJFK began
  4. 16:37:49Descentp.4
    Aircraft reached 24,000 feet and held for about a minute
  5. 16:38:00Descentp.3
    Descent time range begins (24,000 feet)
  6. 16:39:04Descentp.4
    12,000 feet dialed into the mode control panel (MCP) and another descent began
  7. 16:45:39Descentp.4
    As aircraft neared 12,000 feet, Altitude Hold mode engaged
  8. 16:45:51 to 16:45:55Descentp.4
    Recorded altimeter setting changed from 29.92 inHg to 30.13 inHg (input change may have occurred any time in this window; altimeter setting recorded only once every four seconds)
  9. 16:45:55Descentp.4
    Flight change (FLCH) button activated on MCP; auto throttle system immediately transitioned to FLCH descent mode; MCP speed window switched to display current airspeed, slightly above desired 250 knots; MCP speed then manually dialed down to 250 knots; engine throttle lever angle began to decrease and airplane decelerated
  10. unspecified (after 16:45:55)Descentp.5
    Once throttles reached the aft stop, auto throttle system entered Throttle Hold mode
  11. unspecifiedDescentp.5
    With autopilot in FLCH mode targeting 12,000 feet and auto throttles in Throttle Hold mode, aircraft pitch attitude began to increase to attempt to hold 12,000 feet and airspeed started to decay below 250 knots
  12. 16:47:31Descentp.5
    Airspeed had degraded to 186.5 knots and pitch attitude was approximately 6 deg nose up
  13. 16:47:34Descentp.5
    At an airspeed of 185.5 knots, throttle lever angles increased rapidly, and the auto throttle system exited Throttle Hold mode; N1 on both engines began to increase
  14. 16:47:42Eventp.5
    Autopilot and auto throttle systems were disengaged; throttle lever angles began to decrease; airspeed was 195 knots and increasing
  15. 16:47:44Eventp.5
    Aircraft pitch attitude was approximately 10 degrees nose up and control column position moved quickly forward (to command nose down attitude)
  16. 16:46:00 to 16:49:00Eventp.3
    Event time range covering three minutes surrounding the event
  17. 16:47:44 to 16:47:55Eventp.5
    Vertical acceleration varied between 1.476 g and -0.156 g and pitch attitude varied between 10 degrees nose up and 3 degrees nose down
  18. 16:47:45Eventp.3
    Approximate time of the event during descent
  19. 16:48:01Post-eventp.5
    Auto throttle system briefly engaged again
  20. 16:48:08Post-eventp.5
    Auto throttle system disengaged
  21. unspecified (around 16:48:08-16:48:16)Post-eventp.5
    Aircraft continued to gain airspeed; pressure altitude was 11149 feet and decreasing
  22. 16:48:16Post-eventp.5
    Autopilot reengaged with a target altitude of 7,000 feet
  23. 16:49:31Post-eventp.5
    Auto throttle system reengaged (had remained disengaged since 16:48:08)
  24. 16:50:00Post-eventp.3
    End of descent time range (two minutes fifteen seconds after the event)
  25. 17:00:35Landingp.5
    Aircraft landed on runway 22L at KJFK, approximately 13 minutes following the event
  26. 17:01:20Landingp.3
    Approximate arrival at KJFK; end of full incident flight time range

NTSB analysis

from the final report

The airplane was descending toward the destination airport with the autopilot and autothrottle systems engaged. As the airplane was approaching 12,000 ft, and the autopilot was capturing the altitude, the captain adjusted the altimeter resulting in a displayed altitude of 12,100 ft. The captain (the pilot flying) selected flight level change mode on the autopilot to recapture the altitude and set the speed at 250 knots to slow from about 255 knots. As a result, the autothrottles went to Throttle Hold mode when the throttle levers reached the aft stop. As the captain was briefing the approach, the airplane slowed and pitched up as it tried to maintain altitude with a reduced throttle setting. An international relief officer who was in the cockpit at the time commented on the airplane’s decreasing speed three times when the airplane’s airspeed was about 186 knots before stating that the captain should push the nose over. The captain disengaged the autopilot and auto throttles, aggressively pitched down, and increased the throttles. These aggressive maneuvers caused the flight attendants in the aft galley to be thrown against the ceiling. One flight attendant sustained a compound arm fracture; two other flight attendants sustained minor injuries. The crew subsequently landed the airplane without further incident.