American Airlines Flight 157

American Airlines Flight 157, a

The 15 surviving passengers escaped in the initial seconds after the crash, scrambling through a gaping hole in the forward fuselage and through the emergency exit doors over the wings.^[4][7] The cockpit section of the aircraft had separated from the fuselage, helping the flight crew to escape the fire. Most survivors escaped with only minor injuries.

Only one passenger would die of his injuries after managing to escape from the burning aircraft.^[2] The remaining 25 passengers and two flight attendants were trapped in the wreck as the flames quickly grew too intense to allow any rescue attempts. Firefighters fought the massive blaze for at least 30 minutes before the wreckage could be approached, by which time many of the victims were charred beyond recognition.^[2][5] The Dallas Aviation School and American Magnaflux buildings were almost destroyed and the hangar was extensively damaged. The parked airplane that was struck by the DC-6 burned so extensively that little remained of it afterwards.^[5]

Investigation

The Civil Aeronautics Board (CAB) held a hearing in Dallas in December 1949 to investigate the causes of the accident. During the hearings, it was revealed that neither Claude nor Forbes knew that Lewis had feathered the No. 4 propeller; Claude did not find out until hearing Lewis' statement being read to the CAB.^[6]

After investigating the remains of the aircraft, conducting flight tests to replicate the accident scenario, and completing the hearing, the CAB concluded in August 1950 that the probable cause of the accident was "the faulty execution of an engine-out approach."^[1] A series of significant mishaps by the crew contributed to the final outcome:

• The captain failed to align the aircraft with the runway centerline after the final turn.
• After realizing the misalignment, the captain attempted to correct it with a risky "S"-turn at low altitude. There is little room for error if a problem arises during this maneuver because as the angle of the bank increases, so does the probability of stalling the airplane.
• The crew made no attempt to balance the airplane's fuel load after the No. 1 engine failed. The DC-6 is equipped with four main fuel tanks that serve individual engines, while a network of valves allow fuel to be transferred from one engine's tank to feed other engines. The crew did not cross feed fuel from the tank serving the failed engine to balance the plane's weight as recommended in the flight operations manual. Flight 157 had flown for almost three hours with the No. 1 engine out, and the CAB concluded that the No. 1 main fuel tank was holding about 1,400 lbs (635 kg) more gasoline than the other three main tanks when the plane arrived at Love Field. The investigators primarily attributed the left wing's sharp drop to the excessive weight of the fuel at its outboard end.^[8]
• The captain applied excessive
  skid. This maneuver would have caused the plane's airspeed to drop, and according to the CAB findings, it caused the fuel in the No. 4 main tank to slosh away from the fuel outlet, lowering the engine's fuel pressure.^[8]
• The captain's application of full throttle to both right-hand engines caused to airplane to turn further to the left due to the relative lack of thrust from the single functioning left-hand engine. This exacerbated his loss of directional control.
• The first officer disobeyed the captain's order to raise the wing flaps, and did not tell the captain.[6]
• The first officer misinterpreted the No. 4 engine's fuel pressure drop as a sign of incipient engine failure and feathered the prop. However, the CAB partially exonerated Lewis for this act, concluding that the craft was so close to the ground at that point that his mistake probably had little influence on the final outcome.^[8]
• Excessive
  elevator
  input by the captain caused the aircraft to stall.

The CAB concluded that the accident could have been avoided if the crew had held the plane straight and level when the misalignment was first noticed, then raised the flaps, climbed to a safe altitude, circled the airport, and attempted another landing. The CAB concluded that there were no factors present that would compel the crew to land immediately despite the sloppy approach, such as rapidly deteriorating weather or a shortage of fuel.

See also

• Aviation safety
• American Airlines accidents and incidents
• List of accidents and incidents involving commercial aircraft

References