Nosewheel failure leads to aircraft excursion at Wycombe Air Park

Casualties unknown • Wycombe Air Park, Buckinghamshire, GB

A Pegasus/Flight Design CT2K Microlight experienced a nosewheel collapse while taxiing, resulting in damage to the propeller and nosegear.

What happened

On 18 February 2003, a Pegasus/Flight Design CT2CK Microlight, registration G-CBWA, was conducting a private air experience flight at Wycombe Air Park. Following a smooth landing on Runway 07L, the pilot taxied the aircraft toward the northern end of the runway. After traveling approximately 50 metres across a rough grass surface, the aircraft suddenly pitched forward. The impact caused a loud cracking sound and the propeller struck the ground, causing the engine to stop. There were no injuries to the pilot or the passenger, though the aircraft sustained damage to the nosewheel and propeller.

The investigation

Investigators examined the nosewheel assembly, which consists of two aluminium alloy wheel halves secured to a steel hub with five bolts. The inspection revealed that the nosewheel mounting bolts had been incorrectly installed through the 10 mm diameter lightening holes in the hub rather than the intended 6.5 mm mounting holes. This error meant the wheel halves were held in place only by the friction of the bolt clamping force.

Further examination showed that the wheel halves had been drilled with ten holes that aligned with the hub's lightening holes, making it difficult to distinguish between the correct and incorrect mounting points. The investigation also noted that the wheel halves had been replaced approximately 30 flying hours prior to the accident. The new replacement parts featured inaccurately drilled holes, which made it even more difficult to align the assembly correctly.

Findings

  • The nosewheel failed because the mounting bolts were inserted into the larger lightening holes instead of the correct mounting holes.
  • The lack of alignment markings on the hub or wheel halves increased the risk of incorrect assembly.
  • The absence of written instructions for replacing the nosewheel contributed to the error.
  • The design of the hub allowed for the possibility of mis-assembly due to the proximity of the lightening holes to the mounting holes.

Safety action

  • It is recommended that Pegasus Aviation modify the nosewheel assembly to eliminate the possibility of incorrect bolt insertion.
  • It is recommended that the manufacturer provide written instructions to owners regarding the correct installation of the nosewheel assembly.
  • It is recommended that measures be taken to ensure the correct installation of recently replaced nosewheel components.

Probable cause

The nosewheel failure was caused by the incorrect assembly of the nosewheel, where mounting bolts were placed through the hub's lightening holes. Contributing factors included a design that permitted mis-assembly and a lack of instructional documentation for owners.

Frequently asked questions

What happened in the 2003-02-18 Pegasus/Flight Design CT2K Microlight accident near Wycombe Air Park, Buckinghamshire, GB?

A Pegasus/Flight Design CT2K Microlight experienced a nosewheel collapse while taxiing, resulting in damage to the propeller and nosegear.

What aircraft was involved and where did it happen?

The accident on 2003-02-18 involved a Pegasus/Flight Design CT2K Microlight, registration G-CBWA, at Wycombe Air Park, Buckinghamshire, GB.

What was the probable cause of the accident?

The nosewheel failure was caused by the incorrect assembly of the nosewheel, where mounting bolts were placed through the hub's lightening holes. Contributing factors included a design that permitted mis-assembly and a lack of instructional documentation for owners.

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