What happened
On 4 September 2018, a Piper PA-28R-200, registration EC-HSZ, was performing a private flight from Burgos to Cuatro Vientos Airport in Madrid. Following takeoff from Burgos, the pilot attempted to retract the landing gear but noticed that the amber gear-transit light remained illuminated. The pilot sought visual confirmation from a nearby aircraft, which reported that the nose gear was retracted while the main gear remained in an intermediate position.
Despite several attempts to cycle the gear lever and performing maneuvers such as pitching and yawing the aircraft to encourage locking, the gear failed to extend. The pilot also attempted to use the manual emergency extension procedure but found the lever could not be moved to the necessary position. After approximately two hours of flight, the pilot proceeded to Cuable Vientos, notifying the tower of the emergency. Following a low pass to confirm the gear position, the pilot was cleared to land on runway 27. Upon touchdown, the landing gear collapsed, causing the aircraft to skid approximately 80 meters along the runway. The pilot was uninjured, but the aircraft sustained heavy damage to the propeller, landing gear, and fuselage underside.
The investigation
Investigators examined the aircraft's landing gear systems and the history of its maintenance. The investigation focused on why the manual emergency extension system failed to function. Technicians discovered that the emergency gear lever's travel was physically obstructed. Specifically, a rod responsible for relaying motion to the hydraulic valve was blocked by a pin connected to the Backup Gear Extender (BGE) system.
Although the BGE system had been removed in accordance with Service Bulletin SB 866A, the investigation found that the diaphragm assembly from the removed system had been left in place. This diaphragm had become stuck to the inside of its housing, preventing the mechanical rod from moving into the position required to release hydraulic pressure and allow the gear to drop.
Findings
- The inoperative condition of the manual emergency system was the primary cause, resulting from improper and undocumented maintenance tasks.
- The diaphragm assembly within the BGE housing had adhered to the casing, physically blocking the emergency gear lever's movement.
- The electric pump for the landing gear showed signs of poor maintenance, including excessively worn and dislodged brushes.
- The pilot correctly followed the emergency procedures and executed a landing that minimized the impact of the gear collapse.
- The aircraft's weight and the prevailing meteorological conditions were within safe limits for the operation.