|Title:||Uncommanded pitch-down on landing, Boeing 747-236B, G-BDXJ|
|Micro summary:||Just prior to landing, the nose of this Boeing 747-236B pitched down, causing a hard landing.|
|Event Time:||2000-05-15 at 0800 UTC|
|Publishing Agency:||Aircraft Accident Investigation Board (AAIB)|
|Publishing Country:||United Kingdom|
|Site of event:||London Heathrow Airport|
|Departure:||Miami International Airport, Miami, Florida, USA|
|Destination:||London Heathrow Airport, London, England|
|Airplane Type(s):||Boeing 747-236B|
|Type of flight:||Revenue|
|Executive Summary:||During an automatic landing the aircraft nose pitched down just prior to touchdown causing the aircraft to land heavily. The aircraft experienced minor airframe damage but there were no injuries to the passengers or crew. |
After the incident the 747 Maintenance Manual Chapter 5-51-05 Heavy Landing Inspections were performed. Damage was found to the keel beam behind the wing and on the Number 3 engine pylon skin. The pylon skin damage was repaired and after assessment the keel beam damage was considered acceptable for further service, subject to periodic re-inspection.
The validity of the radio altimeter data was established by checking the QAR data, which indicated that the radio altimeter system had been operating correctly.
The LCLUs were tested on the aircraft but as no faults were found and the component life histories for these units showed no history of related failures or early removals, it was not considered necessary to replace them.
Autoland Triple Channel Ramp Down checks were performed in accordance with 747 Maintenance Manual Chapter 22-00-00 with each of the three autopilot channels 'first in command'. These ground-based tests simulate an automatic approach and landing using dummy radio height, localiser and glideslope data signals supplied by test equipment. The approach and flare manoeuvre were performed satisfactorily in each case. No explanation could be found for the nose-down pitch during the flare.
The aircraft was returned to service and after completion of a successful automatic landing, the autopilot system was upgraded to triple autopilot landing operational status. The aircraft has since performed several successful automatic landings. As a precaution, the airline continued to monitor the performance of the autopilot for a short period. The aircraft has no history of this problem and no further problems have been reported since this incident.
|Learning Keywords:||Operations - Upset - Uncommanded or excessive Pitch|
|Systems - Autopilot/Autothrottle|
|Close match:||In-flight upset, China Airlines, Boeing 747 SP, N4522V, 300 Nautical Miles Northwest Of San Francisco, California, February 19, 1985|
|Uncommanded pitch-up, McDonnell Douglas MD-11, July 13, 1996|
|Maneuvering injury, Boeing 767-332, September 27, 1999|
|In-flight upset, Boeing 737-3M8, December 11, 1994|
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