Event Description
On 7 October 2015, at approximately 1157 local time, an Aero AT4 light sport aircraft, registration 9M-EVA, veered off the taxiway at Seletar Airport, Singapore. The aircraft had landed on Runway 21 and was taxiing to its assigned parking bay at A2 via Taxiway EP. As the pilot approached the junction at Taxiway E2, he applied brakes to slow the aircraft. He reported that the right brake felt unresponsive and the aircraft began to veer left. Despite repeated pumping of the right brake pedal, the pilot could not correct the veer. The aircraft departed the taxiway and came to rest on a grass patch adjacent to a drain.
Aircraft Damage
The nose landing gear sheared off during the incident. The left landing gear sustained impact damage, including misalignment of the wheel and brake disc relative to the brake caliper, with rub marks on the internal interface of the left forward brake caliper. The leading edge of the left wing had dents, the left wing tip had scratch marks, and the canopy had a line crack.
Investigation Findings
Post-occurrence examination of the aircraft's control systems revealed no anomalies in the rudder, aileron, or elevator controls. A functional test of the brake system indicated normal operation. However, inspection of the brake linings showed that the installed part numbers did not match the manufacturer's recommendations, and there was no evidence of approval for use on this aircraft by the relevant authorities.
The investigation determined that the left brake had seized during taxi. Seizure of the left brake caused a sudden deceleration and a strong left turning moment that the pilot could not counteract. The seizure resulted from the detachment of non-approved brake linings from the brake disc, with loose fragments jamming the left brake calipers.
Meteorological conditions at the time included a dry runway, no precipitation, visibility of 7,000 meters, and wind from 050 degrees at 5 knots. The pilot held a Malaysian Private Pilot License with 97 total flying hours, 60 of which were on the Aero AT4. He was not injured, and toxicological tests showed no relevant factors affecting performance.
Regulatory Aspects
The aircraft was operated under a Permit-To-Fly (PTF) issued by the Department of Civil Aviation of Malaysia, valid only for flights within Malaysia. The aircraft had entered Singapore on three occasions without a PTF issued by the Civil Aviation Authority of Singapore (CAAS), as required. The pilot stated he assumed that acceptance of flight plans by air traffic services providers in both countries constituted permission.
Conclusion
The aircraft veered off the taxiway due to the seizure of the left brake, caused by the installation of brake linings not approved for use on the aircraft. The non-approved linings detached from the brake disc, and loose fragments jammed the left brake calipers, leading to the seizure.