What happened
On 6 February 2011, a Gulfstream G150, registration D-CKDM, was preparing for a commercial passenger flight from RAF Northolt to Moscow. The flight crew intended to use a static takeoff technique due to the relatively short runway length, which involved holding the aircraft on the toe brakes until full power was achieved.
During the takeoff roll on Runway 2മുണ്ട, the aircraft's acceleration began to drop significantly below normal levels. As the aircraft approached its rotation speed, the commander attempted to pull the control column back to rotate the aircraft, but the plane failed to pitch up, maintaining a nose-down attitude. Realizing the aircraft would not rotate, the pilot not flying retarded the thrust levers, and both pilots applied the brakes. The aircraft decelerated rapidly and came to a stop near the end of the paved surface.
Following the stop, a fire broke out around the left main wheels. The aircraft's passengers were evacuated, though one passenger sustained a minor injury (a twisted ankle). The fire was quickly suppressed by the airport's rescue and fire fighting service.
The investigation
Investigators examined the aircraft's flight data recorder (FDR) and cockpit voice recorder (CVR). The FDR revealed that longitudinal acceleration was notably lower than expected for the aircraft's weight and environmental conditions. Specifically, the acceleration was approximately 0.1g lower than previous similar takeoffs at 50 and 100 knots, and dropped to nearly 0g just before the takeoff was aborted.
Technical examination of the braking system showed that the steel disks in all four brake assemblies had welded themselves together due to the intense heat of the high-speed rejected takeoff. The investigation also found that the left main gear tyres had suffered fire damage and one had deflated.
Findings
- The primary cause of the lack of rotation and reduced acceleration was the inadvertent application of hydraulic brake pressure during the takeoff roll.
- The commander's technique of holding the rudder pedals with the heels clear of the floor meant that any movement of the feet could potentially contact the pedals. It is likely that the commander applied pressure to the brakes without realizing it, possibly while using the pedals for extra leverage during the attempt to rotate the aircraft.
- The aircraft's acceleration was significantly below normal, a change that the crew did not detect during the initial stages of the roll.
- The fire was caused by leaking hydraulic fluid making contact with the overheated brake disks.