What happened
On May 6, 2021, a Beechcraft King Air C90A, registration VT-JIL, was operating a non-scheduled air ambulance flight from Nagpur to Mumbai. The flight carried two crew members, a medical doctor, a medical attendant, and a patient.
During the takeoff roll at Nagpur airport, the left-hand main landing gear wheel detached from the aircraft as it became airborne. While the flight crew was initially unaware of the separation, airport security personnel observed the event and notified Air Traffic Control (ATC). Once the crew was informed that a wheel had been found on the runway, they coordinated with their engineering team to assess the situation.
To determine the extent of the damage, the crew performed a low-altitude pass over runway 27 at Mumbai airport with the landing gear extended. Following confirmation that the left-hand wheel was missing, the crew decided to perform a controlled belly landing. To minimize impact force, the crew held in a pattern to burn off fuel, reducing the aircraft's weight. The landing was completed on runway 27 with no injuries reported to the five occupants. However, the aircraft sustained substantial damage to its propellers and underbelly.
The investigation
AAIB India investigators examined the wreckage and the detached wheel assembly. Laboratory analysis conducted by CSIR-NAL focused on the left-hand main landing gear. The investigation revealed that the primary failure originated in the outer bearing of the left-hand wheel assembly.
Technical examination showed that the failure was a progressive process. High frictional heat generated during the takeoff roll caused the components of the bearing lock assembly—including the bearing cone, washer, and lock-nut—to fuse together. This intense heat led to the shearing of the cotter pin and the subsequent dislodgement of the bearing cup and rollers from the wheel hub.
Furthermore, the investigation of the starboard (right-hand) main landing gear revealed significant pitting, spalling, and scoring on the roller surfaces. This suggested that the bearings on the opposite side had also reached the end of their reliable service life.
Findings
- The catastrophic failure of the outer bearing on the left-hand main wheel assembly was the direct cause of the wheel separation.
- The failure occurred over a period of time, likely due to the deterioration of the rolling surfaces.
- The secondary damage to the brake assembly rotor plates was a result of the misalignment caused by the failing bearing.
- The condition of the starboard gear bearings suggests that the entire landing gear wheel assembly was subject to advanced wear, potentially due to lubrication issues, contamination, or usage beyond its technical life.