National Airlines Flight 27

National Airlines Flight 27 was a scheduled passenger flight between Miami and San Francisco with intermediate stops at New Orleans, Houston, and Las Vegas, operated by a DC-10-10 aircraft (N60NA).

National Airlines Flight 27
A National Airlines DC-10-30 similar to the aircraft involved
Accident
DateNovember 3, 1973
SummaryUncontained engine failure
Siteen route over New Mexico
Aircraft
Aircraft typeMcDonnell Douglas DC-10-10
Aircraft nameBarbara[1][2]
OperatorNational Airlines (NA)
RegistrationN60NA
Flight originMiami International Airport
1st stopoverNew Orleans International Airport
2nd stopoverHouston Intercontinental Airport
3rd stopoverMcCarran International Airport
DestinationSan Francisco International Airport
Occupants128
Passengers116
Crew12
Fatalities1
Injuries24
Survivors127

On November 3, 1973, at about 4:40 p.m., while the aircraft was cruising at 39,000 feet (12,000 m) 65 miles southwest of Albuquerque, the No. 3 (starboard) engine fan assembly disintegrated in an uncontained failure. Its fragments penetrated the fuselage, the Nos. 1 and 2 engine nacelles, and the right wing area. The resultant damage caused decompression of the aircraft cabin and the loss of certain electrical and hydraulic systems.[3]

One passenger[4] was partially forced into the opening made by a failed cabin window, after it too was struck by engine fragments. He was temporarily retained in that position by his seatbelt. "Efforts to pull the passenger back into the airplane by another passenger were unsuccessful, and the occupant of seat 17H was forced entirely through the cabin window."[5]

The flight crew initiated an emergency descent, and the aircraft was landed safely at Albuquerque International Sunport 19 minutes after the engine failed. 115 passengers and 12 crew members exited the aircraft by using the evacuation slides. Of those, 24 people were treated for smoke inhalation, ear problems, and minor abrasions. The plane was repaired and was later flown by Pan Am (as Clipper Meteor).

The New Mexico State Police and local organizations searched extensively for the missing passenger who was sucked out of the window. A computer analysis was made of the possible falling trajectories, which narrowed the search pattern. However, the search effort was unsuccessful, and the body of the passenger was not recovered until two years later, when a construction crew working on the tracks for the Very Large Array radio telescope came upon his skeletal remains, which took another year for the medical investigator in Albuquerque to identify.[6]

Investigation

The National Transportation Safety Board determined the probable cause of this accident was the disintegration of the No. 3 engine fan assembly as a result of an interaction between the fan blade tips and the fan case. According to the NTSB, "the precise reason or reasons for the acceleration and the onset of the destructive vibration could not be determined conclusively," but enough was learned to prevent the occurrence of similar events. The speed of the engine at the time of the accident caused a resonance wave to occur in the fan assembly when the tips of the fan blades began to make contact with the surrounding shroud. The engine was designed to have a rearward blade retaining force of 18,000 pounds to prevent the blades from moving forward in their mountings slots and subsequently departing from the fan disk. The rearward force was not enough. As a result of this accident, GE re-designed the engine so that the blade retaining capability was increased to 60,000 pounds, and that change was incorporated into all engines already in service.[3]

In addition to this, it was found that between the 8th of August and the 12th of September 1973, there had been 15 problems reported about the third engine.[7] The engine had been taken off the aircraft for repairs, and between the time it was replaced and the accident, a further 26 faults had been reported by the pilots. It was found that the bolts that had held the front covering in place, which had failed in the accident, were outside the tolerances laid down. An engineering dispatch was sent out to inspect these engines, and six more discrepancies were found in National Airlines fleet alone. Therefore, this dispatch was made compulsory for all early DC-10s in order to prevent the issue occurring again.[7]

The NTSB expressed concern about the cockpit crew conducting an unauthorized experiment on the auto-throttle system. They had been wondering where the system took its engine power readings from and to see if it was the N1 tachometer readout "the flight engineer pulled the three N1 tachometer [circuit breakers]" and then adjusted the autothrottle setting. The cockpit voice recorder proved that the engines altered their power setting when requested, proving to the crew that the system was powered from another source. The crew then manually reset the throttles to the normal cruising power before the flight engineer had closed the tachometer circuit breakers. It was considered whether the crew had accidentally over-speeded the engine when setting power without the tachometers, but there was insufficient evidence to deliver a certain verdict. Nonetheless; "regardless of the cause of the high fan speed at the time of the fan failure, the Safety Board is concerned that the flightcrew was, in effect, performing an untested failure analysis on this system. This type of experimentation, without the benefit of training or specific guidelines, should never be performed during passenger flight operations."[3]

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See also
  • United Airlines Flight 232, a 1989 accident involving a DC-10 which suffered an uncontained engine failure, resulting in 111 fatalities.
  • Aloha Airlines Flight 243, a 1988 incident that involved an explosive decompression of the fuselage with one fatality.
  • British Airways Flight 5390, a 1990 incident where a crew member was partially ejected from a window in flight.
  • Southwest Airlines Flight 3472 and 1380, two incidents in 2016 and 2018, respectively, on two similar Boeing 737-700, both with the same engine model, where the number one engine (left side) exploded in an uncontained engine failure (the latter resulting in one fatality).
  • Delta Air Lines Flight 1288, another uncontained engine failure where the engine exploded during take off that killed two.
  • Air France Flight 66, a 2017 incident where an engine exploded during cruise with no injuries.
  • Qantas Flight 32, a 2010 incident where the #2 engine suffered an uncontained failure with no injuries.

References
  1. Stephen Barlay. Aircrash Detective. Coronet. 1975. ISBN 0-340-19890-7
  2. Macarthur Job. Air Disaster Volume 1. Aerospace Publications Pty Ltd. 1994. ISBN 1-875671-11-0
  3. "NTSB Report AAR75-02" (PDF). NTSB. pp. 6, 7, 8, 20, 35, 36.
  4. "Featured Maps: Decompression Defenestration (3 November 2010)". Retrieved 2010-11-21.
  5. Mondout, Patrick. "Curious Crew Nearly Crashes DC-10". Archived from the original on 2011-04-08. Retrieved 2010-11-21.
  6. Harden, Paul (2010-06-05). "Aircraft Down". El Defensor Chieftain. Retrieved 2018-10-24.
  7. Godson, John (1975). The rise and fall of the DC-10. D. McKay Co. p. 188. ISBN 0679505288. OCLC 1245951.

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