|Title:||Elevator jam on takeoff, HS748 Series 2A, G-ATMI, Liverpool|
|Micro summary:||Takeoff rotation was prevented by an elevator jam; the takeoff was rejected after V1.|
|Event Time:||1996-08-16 at 2357 UTC|
|Publishing Agency:||Aircraft Accident Investigation Board (AAIB)|
|Publishing Country:||United Kingdom|
|Site of event:||Takeoff, Liverpool|
|Departure:||Liverpool John Lennon Airport, Liverpool, England|
|Airplane Type(s):||HS748 Series 2A|
|Type of flight:||Revenue|
|Executive Summary:||The accident occurred when take-off rotation of the aircraft was prevented by an elevator control circuit jam. The take-off was rejected after reaching V1, and wheelbraking and selection of propeller ground fine pitch failed to stop the aircraft on the runway. During the overrun the aircraft collided with camera equipment mounted on a building, locally damaging the right wing. |
A number of potentially serious deficiencies in the flight controls gust lock system were found, although the system passed checks intended to verify its integrity. An undemanded re-locking of the system could not be reproduced during testing, but this could not fully simulate the accident circumstances. It was concluded that the accident was probably caused by a re-engagement of the elevator gust lock induced by the carrying out of a Full and Free controls check at the start of the take-off run.
Despite a series of modifications to the flight controls gust lock system by the manufacturer, particularly following a major fatal overrun accident which occurred at Sumburgh Airport on 31 July 1979, this accident at Liverpool Airport and other possible gust lock related incidents demonstrated that associated unlocking of the flight controls on HS748 aircraft before flight is still not sufficiently reliable.
The investigation identified the following causal factors:
1. Flight control gust lock system deficiencies which probably caused the elevator lock to reengage on completion of the crew's Full and Free check of the flight controls before the take-off.
2. Lack of any indication of a jammed elevator condition until the first officer attempted to pull the control column back at aircraft rotation speed, VR.
3. Lack of sufficient remaining runway distance to stop the aircraft on the runway following the rejected take-off at some 8 kt above V1 decision speed with the elevator jammed fully down.
4. Inadequacies in maintenance information and implementation that led to failure to correctly maintain a gust lock system the design of which is inherently sensitive to deficiencies.
5. Lack of fully effective modification action, following the fatal overrun accident to HS748, G- BEKF, at Sumburgh Airport on 31 July 1979 (AIB Report 1/81), to address the inherent design sensitivity of the flight controls gust lock system.
Fourteen Safety Recommendations have been made as a result of this investigation.
|Learning Keywords:||Operations - Maintenance|
|Operations - Rejected Takeoff after V1|
|Operations - Runway Overrun|
|Systems - Elevator, Stabilizer, Rudder, Ailerons|
|Systems - Flight Control System|
|Other - Certification|
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