What happened
On 16 October 2012, a Britten-Norman Islander BN-2B-26, registration VP-MNT, was performing a scheduled commercial passenger flight from Antigua to Montserrat. The aircraft, carrying one crew member and six passengers, was on its third flight sector of the day when it approached John A Osborne Airport.
During the landing roll, after the main gear had touched down, the nosewheel made contact with the runway surface. Upon contact, the aircraft was struck by an intense nosewheel shimmy. The pilot attempted to mitigate the vibration by releasing the brakes and lifting the nosewheel off the runway, but the oscillation returned with greater intensity when the nosewheel was lowered again.
Fearing that the aircraft would not stop before the end of the runway—where the terrain drops away into a hazardous area—the pilot elected to steer the aircraft off the runway onto the grass at the edge of the airfield. The maneuver prevented a potential overrun, and the aircraft sustained no damage. There were no injuries to the crew or passengers.
The investigation
The investigation examined the aircraft's maintenance history, the pilot's landing technique, and the mechanical state of the landing gear. Engineers inspected the braking system, tyres, and the nosewheel assembly. While no mechanical failure was identified, investigators noted some hydraulic fluid on the nosewheel oleo strut, though it was unclear if this was caused by the shimmy itself.
Investigators also reviewed the pilot's approach, noting that the pilot had used GPS groundspeed as a primary reference rather than indicated airspeed. The investigation also considered the aircraft's flight manual, which provided no specific procedures for managing a nosewheel shimmy during landing.
Findings
- The primary cause of the incident was a severe nosewheel shimmy that became uncontrollable during the landing roll.
- The pilot's decision to steer the aircraft onto the grass was a necessary action to avoid a high-risk overrun into the terrain beyond the runway end.
- The pilot's technique of keeping the nosewheel off the runway for a period during braking likely increased the total landing distance and delayed the detection of the shimmy.
- No specific mechanical cause for the oscillation could be established, as the aircraft performed normally during subsequent taxi trials and following a component replacement.