Case Study: 6 Flight Attendants Represented in Major Continental Airlines Lawsuit
Continental Airlines Flight 75, a McDonnell Douglas DC-10 aircraft, was en route from Los Angeles to Honolulu on May 21, 1998 when it experienced an unexpected pitch-up. The aircraft was climbing in smooth air with the No. 1 autopilot engaged when it began a sudden and hard un-commanded pull up. The captain reported that he immediately grabbed the control yoke and disengaged the autopilot in order to level the aircraft. During the pull up, and subsequent corrections by the pilot, nine people were injured, four seriously. There were 285 passengers, 10 flight attendants, and 3 cockpit crew onboard. The aircraft was not damaged.
The seat belt sign was reported to be on at the time of the upset. During the event, the aircraft pulled up suddenly, causing all who were not buckled-up to be thrown to the floor. There were a few more reversals of force as the pilot attempted to gain control of the aircraft. These forces caused three flight attendants and one passenger, who was in the aft lavatory at the time, to be bounced up into the ceiling and then slammed back against the floor. A flight attendant said that what followed was a ‘roller coaster’ type of movement. The captain later reported that during the upset the aircraft had gained 1,200 feet in altitude and lost 30 knots of airspeed before he was able to disconnect the autopilot and regain control. After the aircraft had been steadied, a few doctors on board attended to the wounded as the crew turned the aircraft back towards Los Angeles where it was taken out of service for detailed examination.
Following an investigation of the incident and an examination of the aircraft, the National Transportation Safety Board found that a contaminated strain gage lead to the “excessive autopilot initiated elevator movement, and excessive elevator actuation during recovery by the captain.” Investigators also reviewed maintenance records for the year preceding the accident and found over 50 discrepancies for autopilot systems. One item stated “A/C [aircraft] has a long history of pitch oscillations, both autopilots.” Investigators then discovered that this particular aircraft was involved in a similar accident in 1986, which resulted in one injury.
According to the NTSB, post-accident testing of the first officer’s control wheel sensor unit showed an out of tolerance and drifting null signal for the strain gage which provides pitch signal input to the No. 1 autopilot. Analysis showed the material was a silver based conductive substance, lying below a factory applied sealing layer, which was introduced during manufacture. The solder on the lugs and the wire used between the lugs and terminals was found not to be consistent with the manufacturer’s specifications.
In addition, the NTSB found that the failure of the airplane maintenance department to diagnose and correct these historical problems with the autopilot systems led to the in-flight disturbance. Also at fault, said the investigators, was the manufacturer’s inadequate quality assurance program.