Nose landing gear failure causes propeller strike during landing

Casualties unknown • Cascais, PT

A nose landing gear fork failure on a Grob G 115 led to a nosewheel collapse and propeller strike during a training flight in Cascais.

What happened

On November 3, 2014, a Grob G 115, registration D-EGXI, was conducting a local training flight at Cascais Airfield (LPCS) with an instructor and a student pilot on board. The flight was intended to prepare the student for their first solo flight. During the flight, the crew requested a touch-and-go maneuver on runway 3 and was initially denied due to wind conditions exceeding 15 knots. The instructor subsequently requested a go-around, which was authorized.

During the go-around, the aircraft encountered turbulence near Manique hill. Due to increasing wind intensity, the instructor requested and was granted a full-stop landing on runway 35. As the aircraft decelerated after touchdown, the nosewheel experienced significant vibrations, known as shimming. During this phase, the nose landing gear fork collapsed, causing the propeller to strike the ground.

The investigation

The GPIAAF conducted a safety investigation into the incident. The investigation team examined the mechanical elements of the aircraft, specifically focusing on the nose landing gear. A detailed laboratory analysis was performed on the nose wheel fork (P/N: 115-5200.03) to determine the failure mode. Additionally, a finite element analysis was conducted to assess the structural integrity of the component, considering the high number of landings (over 17,000) and the mechanical loads associated with training operations.

Findings

  • The investigation confirmed that the nose wheel fork fractured along two distinct lines.
  • Laboratory analysis revealed that the fractures occurred at the connection holes, which are areas of high stress concentration.
  • The presence of beach marks on the fracture surface is consistent with a material fatigue process.
  • No inherent material defects were found that would have caused the fracture.
  • The aircraft had accumulated 6,524 flight hours and 16,494 landings at the time of the event.
  • The use of aerodynamic wheel fairings, which were present on the aircraft, may have hindered effective visual inspections of the components by the crew.

Probable cause

The nose landing gear fork failed due to material fatigue caused by stress concentration at the attachment holes, exacerbated by the mechanical loads and vibrations (shimming) inherent in frequent training operations.

Frequently asked questions

What happened in the 2014-11-03 Grob G 115 accident near Cascais, PT?

A nose landing gear fork failure on a Grob G 115 led to a nosewheel collapse and propeller strike during a training flight in Cascais.

What aircraft was involved and where did it happen?

The accident on 2014-11-03 involved a Grob G 115, registration D-EGXI, at Cascais, PT.

What was the probable cause of the accident?

The nose landing gear fork failed due to material fatigue caused by stress concentration at the attachment holes, exacerbated by the mechanical loads and vibrations (shimming) inherent in frequent training operations.

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