Flight 255 Northwest Airlines

Flight 255 was chartered by the company Northwest Airlines on a McDonnell-Douglas DC-9 (or MD-82) to connect the towns of Detroit to Phoenix with the the United States. The August 16th 1987 with 20:45 the plane was crushed shortly after its takeoff killing 154 of the 155 occupants of the plane and two motorists.

Plane

The plane was a DC-9-82, built in 1981 under serial number 48090/1040 and registered N312RC. At the time of the accident it added up 14928 hours of flight and was propelled by two engines Pratt & Whitney JT8D-217.

Crew

the commander : John Maus, 57 years, 20859 hours of flight including 1359 on DC-9.
the copilot : David Dodds, 35 years, 8044 hours of flight including 1604 on DC-9.
Personal of cabin : 4 people (Michael Kahle, Roberta Rademacher, Pamela Shaffer, Bruce Elfering).

Circumstances of the accident

Towards 20:32, on August 16th, 1987, the plane was towed door of loading towards the Taxiway. After having started the engines, the crew was authorized with rolling and accepted instructions to go to the threshold of the track 3C by taking the Charlie exit. They missed this exit and accepted new instructions.

With 20:42 they positioned in the axis of the track 3C and with 20:44 min4s they were authorized on takeoff. With 20:44 min21s the setting in output engine was applied. With 20:44 min58s the copilot announced " rotation" (the wheels leave the ground). With 20:45 min5s the warning signal of Décrochage started to vibrate (it will vibrate until the end) and vocal alarm resounds. The apparatus took off only of 15 meters and from right to left had a movement of Roulis before striking a standard lamp located on a carpark of rented cars. The plane continued to lean on the left and struck a second standard lamp. Witnesses affirmed that the plane was tilted with 90° on the left when it hung the roof of a hangar and that it had continued to lean before being crushed on the ground on a road. The flight had not lasted which 14 seconds.

The plane disintegrated on several tens of meters and put fire all around him.

Assessment

Surviving: 1 (a 4 year old child, seriously wounded)
Dead: 156 (6 team members, 148 passengers and 2 motorists on the ground)
the plane is destroyed with the impact.

Inquire

The investigation was entrusted to NTSB. The block boxes were recovered and analyzed.

While basing itself on the first visual testimonys, the investigators established that the plane had taken down without being able to gain altitude and thought initially that the plane had faced a shearing of wind. However, the examination of the parameters of flight made it possible to dismiss this assumption. The plane had taken off at a speed of 169 nodes (306 km/h) then had continued to accelerate up to 184 nodes while rising of 48 feet. These speeds did not go in the direction of a shearing of wind which, on the contrary, would have slowed down the plane.

The recordings showed that the warning signal of Décrochage (which makes tremble the orders of flight) had functioned during the 14 seconds of the flight and which vocal alarm had resounded four times. With the shutters extended in position takeoff and the nozzles deployed leading edges, the stalling speed of the plane was approximately 121 nodes. With the sunken shutters and the extended slats it went up to 128 nodes, well in-on this side speed of the plane at the time of the facts. However the stall warning indicator had persisted. The investigators showed that the only configuration which could activate the warning signal of the kind was the configuration of cruising, i.e. entirely sunken shutters and nozzles. In other words, it appeared to the investigators that plane had taken off without shutters and without nozzles deployed, which was confirmed by the analysis of the block boxes which showed, moreover, whom at any time the pilots had not actuated them. The analysis of the block box was corroborated by the examination of the remains. The shutters were found in sunken position. If the pilots had put them in position of takeoff and by imagining that the destruction of the hydraulic systems caused their re-entry, they would not have had time to retract completely before the impact on the ground. They would have been necessary approximately 6 seconds, but it ran out only less than two seconds between the impact on the hangar and the crash landing on the ground. In the same way the analysis of a piece of wing made it possible to conclude as the nozzles of leading edge had returned at the time of the crash landing.

The plane was thus not configured to take off.

However DC-9 was equipped with an alarm making it possible to inform the pilots who the plane was not in configuration of takeoff, but it appeared with the listening of the recordings of the block boxes that this alarm had not resounded, because of a problem of power supply whose origin could not be given. However, this alarm was there only as a last resort. It was up to the pilots to check that their plane was configured correctly and obviously they did not do it. With the listening of the recordings the investigators realized that the entries of checklist precisely making it possible to make sure of the deployment of the shutters and the nozzles, had not been recited. It is thus this error which was at the origin of the accident. An incredible and unacceptable error on this level of professionalism. The recordings even showed that the pilots had made several errors in the procedures of stating of the checklists.

If the pilots had only put the shutters in position takeoff, the plane would have taken off and passed above the standard lamps.

External bonds

Total return of the NTSB

Random links: