American Airlines Flight 96
| American Airlines Flight 96 | |
|---|---|
 An identical DC-10 from American Airlines |
|
| Accident summary | |
| Accident type | Structural failure |
| place | Windsor , Ontario |
| date | June 12, 1972 |
| Fatalities | 0 |
| Survivors | 67 (all) |
| Injured | 0 |
| Aircraft | |
| Aircraft type | McDonnell Douglas DC-10-10 |
| operator | American Airlines |
| Mark | N103AA |
| Departure airport | Detroit Metropolitan Wayne County Airport |
| Destination airport | Buffalo Niagara International Airport |
| Passengers | 56 |
| crew | 11 |
| Lists of aviation accidents | |
American Airlines Flight 96 was a scheduled flight on June 12, 1972 from Detroit Metropolitan Wayne County Airport to Buffalo Niagara International Airport . When American Airlines' McDonnell Douglas DC- 10-10 flew over Windsor , Ontario , the rear cargo door opened. Hence the incident is also known as the Windsor incident . As a result of the explosive decompression in the cargo area, part of the cabin floor broke into the cargo hold below, damaging various control elements of the aircraft. Despite the partial restriction of the control surfaces, the pilots managed to return to Detroit Airport safely without causing serious injuries to the occupants.
Course of the incident
Flight AA 96 was a scheduled flight from Los Angeles to LaGuardia Airport in New York City with stops in Detroit and Buffalo . On June 12, the route was flown by the DC-10-10 with the registration number N103AA. The cockpit crew consisted of the 52-year-old Captain Bryce McCormick, the 34-year-old First Officer Peter Whitney and the 50-year-old flight engineer Clayton Burke. McCormick was a very experienced pilot with over 24,000 hours of flying experience. Whitney and Burke were also very experienced crew members with approximately 7,900 and 13,900 hours of flight respectively. All three, however, had only completed 176 hours on the DC-10.
The flight took off at 1:30 p.m. ( EST ) in Los Angeles 46 minutes after the scheduled take-off due to the lengthy boarding process and general traffic , and arrived in Detroit at 6:36 p.m. This was where most of the passengers disembarked and the plane took on new passengers and cargo. 56 passengers and 11 crew members remained on board for the flight between Detroit and Buffalo. The aircraft took off at 7:20 p.m. and climbed to 6,000 feet (~ 1830 m) before being cleared for a climb to 21,000 feet (~ 6400 m) after reaching airway V-554.
At 7:25 p.m., at an altitude of approximately 11,750 feet (~ 3580 m) and a speed of 260 knots (~ 480 km / h), the crew heard a dull noise and dirt and dust particles were thrown up in the cockpit. The sound came from the rearmost cargo door, which had popped open and torn off. The resulting explosive decompression exerted such a load on the cabin floor that it collapsed in the rear of the aircraft. During the investigation, Captain McCormick later stated that he first suspected an air collision and a destroyed windshield. At the same time the pedals for the rudder were fully deployed, i.e. H. the left to the rear and the right to the front and the thrust levers moved back to the zero position. McCormick deactivated the autopilot , took manual control of the aircraft, and tried to increase the thrust. The thrust levers of engines 1 and 3 could be moved so that the thrust on these two engines could be increased again. The thrust lever of engine 2, however, did not move, because the control cables (Engl. Control Cable ) had been severed by the collapsed cabin floor. McCormick brought the plane into a stable straight flight and maintained the speed at 250 knots (~ 480 km / h), although the elevator control was very sluggish in contrast to the aileron control. The crew declared an air emergency and announced their return to Detroit.
The flight attendants observed the formation of fog in the cabin and immediately recognized the situation as a drop in pressure. Two flight attendants were in the rear of the passenger cabin, and the floor partially collapsed into the hold, sustaining minor injuries. Despite these circumstances, the cabin crew attempted to verify that the oxygen masks were deployed for the passengers, which they did not because the aircraft was below 14,000 feet (~ 4,270 m). Only then are the oxygen masks automatically triggered. One of the flight attendants took a portable oxygen cylinder and informed the cockpit of the damage in the rear of the aircraft. At the instructions of the cockpit, the flight attendants went through the emergency procedure with the passengers. Some passengers later reported that the security cards turned out to be helpful in finding the nearest emergency exit. The coffin of a deceased woman fell from the hold during decompression near Windsor , Canada .
The plane turned back to Detroit. A slow, gentle descent was initiated. When the cockpit crew extended the landing gear on the landing approach and set the landing flaps to 35 degrees for landing, the rate of descent increased to 1,900 feet / min (~ 9.7 m / s), which was far too steep for a stabilized approach. By increasing the thrust of engines 1 and 3, McCormick was able to reduce the rate of descent to 800 feet / min (~ 4.0 m / s). The aircraft landed on runway 03R at 7.44 p.m., immediately yawed to the right with the full rudder and left the runway. After Captain McCormick first switched both running engines to reverse thrust after touchdown, First Officer Whitney deactivated the thrust reverser of the right engine so that it remained idle, and let the left engine run at full counter-thrust, which resulted in a yaw moment in the other Direction and the aircraft turned back towards the runway. The machine came to a stop 880 feet (~ 270 m) from the end of the runway. The left landing gear and nose landing gear were on, the right landing gear next to the runway. When McCormick had trained for retraining on the DC-10, the simulator practiced how to control the aircraft exclusively with the engines after a total hydraulic loss. Similar technique was used on another DC-10 in 1989 during an incident on United Airlines Flight 232 following a total hydraulic loss.
Investigations
The problem that had caused the accident was evident after landing, as the rear cargo door had disappeared and the left elevator was badly damaged. Investigators studied the aircraft's repair log and found that on March 3, 1972, three months before the accident, ground crew reported that the door did not close electrically and had to be closed manually. On May 30th, McDonnell Douglas published Service Bulletin 52-27, DC-10 SC 612, which recommended reinforcing the cables that supplied power to the motors for the locking latches because three operators were experiencing problems with the electric motors on and off Unlocking the cargo hatch. However, the change was not mandatory and was not carried out on the aircraft involved in the incident.
Investigators interviewed people working on the ground at Detroit Airport and learned that the loader who operated the rear door found it very difficult to close it. He testified that he had electrically closed the door and waited until the noises of the motors could no longer be heard. When these stopped, he tried to move the lever, noticing that it was very stiff. Only with the help of his knee could he close the door. He saw that the vent was not completely closed and reported this to a mechanic on site, who nevertheless cleared the flight. The flight engineer reported that the indicator light for the door on his instrument panel did not come on during taxiing on the ground or during the flight.
Investigations of the aircraft and the cargo door, which was recovered largely intact in Windsor, showed that the bolts were out of the secured position during the entire flight. In the closed, safe position, the pressure inside the aircraft closes the bolts further and the drive of the cargo door itself is not stressed. Since the safety latches were not or only partially closed, force was transmitted to the drive, which gave way at a pressure of about 6600 pounds, so that the door opened. The subsequent drop in pressure caused the ground above it to collapse. This stretched the rudder cable to the limit, which resulted in full rudder deflection. Other control cables were also damaged.
consequences
The NTSB proposed several changes to the locking system, including so that the door could no longer be forcibly closed and a ventilation slot in the rear cabin floor to equalize pressure between the cabin and the hold.
The Federal Aviation Administration (FAA), which was in charge of enforcing these proposals, agreed with McDonnell Douglas' argument that the additional ventilation slot would be very difficult to install. However, they implemented the modification of the locking mechanism and a small window on the cargo door through which the ground staff could check that the locking bolts were in the correct position. Together with the changes recommended by McDonnell Douglas on May 30, 1972, this should prevent this incident from happening again.
Shortly after the incident, Dan Applegate, director of product engineering at Consolidated Vultee Aircraft Corporation (Convair), wrote a memo to management to highlight several door design issues. McDonnell Douglas had commissioned Convair to design the fuselage, and Applegate had watched developments that he believed could compromise safety. In particular, he noted that they had switched from a hydraulic to an electric drive system, which he thought was less safe. He noted that if the cargo door opened in flight, the floor would be prone to collapse, which would likely sever the control cables under the cabin floor, resulting in the loss of the aircraft. Finally, he pointed out that this had already been found in soil tests carried out in 1970 and concluded from this that such an incident would very certainly occur again.
Despite these recommendations and warnings, on March 3, 1974, less than two years after the near-loss of American Flight 96, a DC-10 crashed on Turkish Airlines Flight 981 outside Paris due to an identical cargo door failure all 346 inmates were killed. In contrast to flight AA 96, on which the crew retained sufficient control over the control surfaces, the pilots on flight TK 981 lost control of the elevators and all hydraulic systems. Investigators discovered that the improvements had never been made to the aircraft, despite the fact that it was recorded in the aircraft's log. A modification was made: the installation of the verification window with a notice next to the door explaining in English and Turkish how to properly close and check the door. The loader in Paris was Algerian and spoke neither English nor Turkish. He was only instructed that everything would be safe when the locking lever is closed. He noticed that he didn't have to apply any force to the lever. The investigators concluded that it had already been bent on a previous flight.
In the aftermath of Flight TK 981, the Applegate memorandum was discovered and cited as evidence during a massive civil litigation that followed. Many commentators blamed aircraft manufacturer McDonnell Douglas and aviation authorities for not having learned from the Windsor incident. Although there was a revised design of the cargo door, this was only retrofitted voluntarily and arbitrarily by several airlines. If the warnings from Flight AA 96 had been heeded, the crash of the Turkish plane could probably have been prevented.
N103AA was disassembled at Phoenix Goodyear Airport in 2002 .
filming
- The story of this incident, together with Turkish Airlines Flight 981 in the fifth season of the series Mayday - alarm in the cockpit in the episode "Behind Closed Doors" (English title: Behind closed Doors ) treated.
- The episode "Crash Detectives" from Survival in the Sky also covers this incident.
Individual evidence
- ↑ a b Nicholas Faith (1996, 1998). Black Box: pp. 157-158
- ↑ a b c d Aircraft Accident Report. American Airlines, Incorporated McDonnell, Douglas DC-10-10, N103AA near Windsor, Ontario, Canada, June 12, 1972 , NTSB PB-219370, Washington February 28, 1973 (PDF)
- ↑ Air Disaster Volume 1, Chapter 15, pg 137 & 138. Macarthur Job - Aerospace Publications Pty Ltd 1994
- ↑ Air Disaster Volume 1, Chapter 15, pg 139. Macarthur Job - Aerospace Publications Pty Ltd 1994
- ↑ a b The DC-10 case (English)
- ↑ Macarthur Job: Air Disaster Volume 1 , pp. 136-144