What happened
On May 11, 2024, an Embraer 170, registration F-HBXI, operated by HOP!, was conducting a chartered passenger flight from Paris-Charles de Gaulle to Toulouse–Blagnac. During the initial approach to runway 14R, the crew attempted to extend the landing gear, which triggered a "LANDING GEAR" aural warning and a landing gear disagreement message. The left main landing gear position sensor failed to indicate a locked status.
Following an initial aborted approach, the crew performed the abnormal landing gear extension and partial or gear-up landing procedures. During the second approach, the aircraft landed successfully, but the crew stopped the aircraft on the runway to allow for an inspection. While the crew initially found no signs of fire or leaks, they discovered they could not steer the aircraft due to the nose gear steering being inoperative following the emergency extension procedures. A ground mechanic subsequently identified a mechanical rupture in the left main landing gear assembly.
The investigation
The investigation focused on the structural failure of the left main landing gear's locking-stay bracket. Investigators examined the bolts and nuts used to secure the bracket to the shock strut. Using scanning electron microscopy, the BEA identified fatigue cracking on one bolt and an overload failure on another. The investigation also reviewed the crew's execution of emergency procedures and the cockpit's circuit breaker configuration.
Findings
- The primary cause of the landing gear indication error was the separation of the locking-stay bracket from the left main landing gear shock strut, which misaligned the position sensors.
- The structural failure was caused by the use of incorrectly sized nuts (type MS17826) on the bottom bolts. These nuts could not withstand the torque values required by the manufacturer's documentation, leading to the destruction of the assembly.
- The fatigue and subsequent breakage of the bolts caused the bracket to move, preventing the gear from being detected as locked.
- During the emergency procedure, the crew accidentally pulled the wrong circuit breaker (C32 instead of C31), which prevented the inhibition of the continuous aural warning during the approach.
- The aircraft sustained slight damage, and there were no fatalities or injuries among the 52 passengers and 4 crew members.