

Unfallbericht:
Northwest Airlines Flight 18 had departed from Hong Kong for a flight to New York-JFK with an intermediate stop at Tokyo-Narita, Japan. The flight, touchdown, and initial landing rollout at Narita, were routine. Engine thrust reversing was normal on all four engines until the flight crew moved the engine power levers out of reverse thrust at about 90 knots. During the rollout, the No. 1 engine and pylon rotated downward about the midspar pylon-to-wing fittings into a position in which the lower forward part of the engine nose cowl contacted the runway. The airplane was subsequently stopped on a taxiway, with the front of the No. 1 engine still contacting the ground. The lower forward engine nose cowl had been ground away as it slid along the runway. A fire near the No. 1 engine was rapidly extinguished by local fire fighters, and all passengers remained aboard. They were subsequently deplaned via portable boarding stairs about 30 minutes after the airplane was brought to a stop. There were no injuries.
Maintenance and inspection personnel who worked on the airplane were not adequately trained and qualified to perform the required maintenance and inspection functions. In addition, the work environment for the heavy maintenance of the airplane was inadequate and contributed to an effort producing situation for the workers.
PROBABLE CAUSE: "When C check of the aircraft was conducted, the retainer for the diagonal brace aft fuse pin of No.1 nacelle strut was removed and the aircraft was returned to service without reinstalling the retainer. In the course of the flights after this, the fuse pin moved, disconnecting the diagonal brace at the aft joint.
It is estimated that when the thrust reverser was deployed during the landing roll under such circumstances, the forward fuse pin of the upper link was fractured due to a load in excess of the design rupture strength, dangling the forward portion of No.1 engine and a fire on leaked oil and fuel broke out in the aft portion of the nacelle strut."
accident date: 01-03-1994
type: Boeing 747-251B
registration: N637US
accident date: 01-03-1994
type: Boeing 747-251B
registration: N637US
accident date: 01-03-1994
type: Boeing 747-251B
registration: N637US
| Status: | Accident investigation report completed and information captured |
| Datum: | Dienstag 1 März 1994 |
| Zeit: | 13:38 |
| Flugzeugtyp: |  Boeing 747-251B |
| Fluggesellschaft: | Northwest Airlines |
| Kennzeichen: | N637US |
| Werknummer: | 23548/644 |
| Baujahr: | 1986-05-10 (7 years 10 months) |
| Betriebsstunden: | 31798 |
| Triebwerk: | 4 Pratt & Whitney JT9D-7R4G2 |
| Besatzung: | Todesopfer: 0 / Insassen: 18 |
| Fluggäste: | Todesopfer: 0 / Insassen: 227 |
| Gesamt: | Todesopfer: 0 / Insassen: 245 |
| Sachschaden: | schwer beschädigt |
| Konsequenzen: | Repaired |
| Unfallort: | Tokyo-Narita Airport (NRT) ( Japan)
|
| Flugphase: | Landung (LDG) |
| Betriebsart: | Internationaler Linienflug |
| Flug von: | Hong Kong-Kai Tak International Airport (HKG/VHHH), |
| Tokyo-Narita Airport (NRT/RJAA), Japan | |
| Flugnummer: | 18 |
Northwest Airlines Flight 18 had departed from Hong Kong for a flight to New York-JFK with an intermediate stop at Tokyo-Narita, Japan. The flight, touchdown, and initial landing rollout at Narita, were routine. Engine thrust reversing was normal on all four engines until the flight crew moved the engine power levers out of reverse thrust at about 90 knots. During the rollout, the No. 1 engine and pylon rotated downward about the midspar pylon-to-wing fittings into a position in which the lower forward part of the engine nose cowl contacted the runway. The airplane was subsequently stopped on a taxiway, with the front of the No. 1 engine still contacting the ground. The lower forward engine nose cowl had been ground away as it slid along the runway. A fire near the No. 1 engine was rapidly extinguished by local fire fighters, and all passengers remained aboard. They were subsequently deplaned via portable boarding stairs about 30 minutes after the airplane was brought to a stop. There were no injuries.
Maintenance and inspection personnel who worked on the airplane were not adequately trained and qualified to perform the required maintenance and inspection functions. In addition, the work environment for the heavy maintenance of the airplane was inadequate and contributed to an effort producing situation for the workers.
Probable Cause:
PROBABLE CAUSE: "When C check of the aircraft was conducted, the retainer for the diagonal brace aft fuse pin of No.1 nacelle strut was removed and the aircraft was returned to service without reinstalling the retainer. In the course of the flights after this, the fuse pin moved, disconnecting the diagonal brace at the aft joint.
It is estimated that when the thrust reverser was deployed during the landing roll under such circumstances, the forward fuse pin of the upper link was fractured due to a load in excess of the design rupture strength, dangling the forward portion of No.1 engine and a fire on leaked oil and fuel broke out in the aft portion of the nacelle strut."
Accident investigation:

|
Informationsquelle:
» NTSB/SIR-94/02Sicherheitsempfehlungen
The NTSB made several recommendations to the Federal Aviation Administration concerning human engineering principles in maintenance operations, and the critical assessment of maintenance work environments. Recommendations were made to Northwest Airlines concerning the same subjects. NTSB issued 9 Safety Recommendations
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Fotos
accident date: 01-03-1994
type: Boeing 747-251B
registration: N637US
accident date: 01-03-1994
type: Boeing 747-251B
registration: N637US
accident date: 01-03-1994
type: Boeing 747-251B
registration: N637US
Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Hong Kong-Kai Tak International Airport to Tokyo-Narita Airport as the crow flies is 2920 km (1825 miles).
Accident location: Exact; deduced from official accident report.
Distance from Hong Kong-Kai Tak International Airport to Tokyo-Narita Airport as the crow flies is 2920 km (1825 miles).
Accident location: Exact; deduced from official accident report.
This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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