With two pilots and two passengers a Learjet 45 was being operated on a charter flight from Edinburgh Turnhouse Airport (Scotland) to Keflavik (Iceland), 5 years ago. Before the engines were started a TLD 150 Max tug was connected with a towbar to the nose landing gear. After all flight preparations were completed both engines (Honeywell TFE731-20BR-1B) were started at the parking position. After the engines were started pushback clearance was obtained and the pushback towards the taxiway was started.
The aircraft in its final position (Source & © AAIB)
As the aircraft was being turned to line up on the taxiway the nose landing gear failed backwards, resulting in the aircraft coming to a rest on the rearward folded nose landing gear and the towbar. The engines were shut down and the aircraft was depowered. There were no injuries.
The AAIB (Air Accident Investigation Branch) was alerted and an investigation was launched into the accident. The nose landing gear on this aircraft is a forward retracting design. The retraction actuator is attached to the aircraft structure in the nose landing gear bay and to the front of the nose landing gear with a bracket. It was found that the bracket on the nose landing gear had failed, allowing the nose landing gear to fail backwards.
The bracket was removed and sent to a metallurgical laboratory for analysis. This analysis revealed that the bracket had failed due to an overload. There were no indications of a pre-existing condition or fatigue that could have led to the failure.
Learjet 45 brake system schematic (source & © Bombardier)
Pictures of the damage sustained by the aircraft were sent to the aircraft for their review. They stated that similar damage had been sustained to another aircraft when the aircraft brakes were applied during the pushback. The manufacturer also informed the AAIB that they were aware of two other accidents in which the application of the aircraft brakes, during a pushback, had led to the rearward failure of the nose landing gear.
During the crew interview after the accident, the co-pilot stated that he had been completing checks and had just started to adjust the rudder pedal position. He was bringing the pedals aft (towards his seat) and indicated that he might have inadvertently tapped the brakes at that time, but was not aware of doing so.
A Learjet 45 Nose Landing Gear the bracket that failed on the accident airplane circled (Source; Public Domain)
The AAIB concluded that the nose landing gear collapse was most likely caused by inadvertent brake application during the pushback.
The AAIB report on this accident, which served as a source for this blog, can be accessed by clicking on the .pdf file below;