McDonnell Douglas MD-11 N1768D

Summary

On 14 July 1996 at about 00:40 local time, a McDonnell Douglas MD-11 registered N1768D, operated by American Airlines, was involved in an accident near Westerly, Rhode Island, United States. 180 people were on board and one was seriously injured, 3 had minor injuries. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

14 July 1996 at 00:40

Classification

Accident

Location

Westerly, Rhode Island, United States

Coordinates

Not recorded

Aircraft

McDonnell Douglas MD-11

Registration

N1768D

Category

Airplane

Engines

3

Operator

American Airlines

Operating rule

Part 121: Air Carrier

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

London, Uk → Jamaica

Aircraft damage

Not recorded

Weather

VMC

Light

Day

NTSB number

NYC96LA148

1 person was seriously injured.

insufficient information from the manufacturer in the airplane flight manual and flightcrew operating manual regarding the hazards of applying force to the control wheel or column while the autopilot is engaged and adjusting the pitch thumbwheel during a level off. Also causal was the flightcrew's lack of understanding of these items and the captain's improper decisions to overpower the engaged autopilot and then to disconnect the autopilot while holding back-pressure on the control yoke.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The first officer (F/O) was making a descent from FL350 to FL240 in smooth air in VMC conditions with the autopilot (A/P) engaged. As the flight (flt) neared FL250, the captain became concerned that the airplane would not level off at FL240. He instructed the F/O to slow the rate of descent. The F/O attempted this by using the pitch thumbwheel on the A/P control panel. The captain then took control, attempted to overpower the A/P, and pulled back on the control yoke. With back pressure on the control yoke, he disengaged the A/P. With the reduced control column resistance after the A/P was disengaged, there was further excursion of the elevators to the up position. According to the flt data recorder, the airplane was subjected to a +2.28 G-load. A passenger in the aft lavatory suffered a fractured ankle. A 2nd passenger and 2 flt attendants received minor injuries. The MD-11 Flight Crew Operating Manual (FCOM) advised against attempting to overpower the A/P; however, this was contained under the title, 'SEVERE TURBULENCE AND/OR HEAVY RAIN INGESTION.' Each use of pitch thumbwheel interrupted the automatic level off, and the system would wait for 2 seconds after release of the thumbwheel before initiating a level off sequence again. Continued use of the thumbwheel precluded the A/P from performing the level off at FL240. The manufacturer has issued FCOM changes to warn pilots about the hazards of applying force to the control wheel or column while the A/P is engaged and adjusting the pitch thumbwheel during a level off.

Quoted verbatim from the NTSB record.