What happened
On June 26, 2013, a Piper PA23-250 Aztec, registration F-OIJT, was conducting a multi-engine rating extension training flight from Pointe-à-Pitre / Le Raizet aerodrome. The crew, consisting of a student pilot, an instructor, and one passenger, had been performing various maneuver exercises. During the approach for a landing on runway 12, the pilot attempted to extend the landing gear and flaps. However, the landing gear indicator remained amber, and the flaps failed to deploy.
The crew attempted to use the manual emergency pump to extend the gear, but this was unsuccessful. They then proceeded to the emergency gas cartridge procedure. While this action successfully extended and locked the right main gear, the left main gear and the nose gear remained unlocked. The instructor took control and attempted several maneuvers to lock the remaining gear. During the landing roll, the right main gear touched down first, and the left main gear eventually locked as the aircraft slowed. However, during deceleration, the nose of the aircraft struck the runway, causing the plane to slide approximately 200 meters. The aircraft sustained slight damage.
The investigation
Investigators examined the aircraft and discovered traces of hydraulic fluid in the nose gear bay and found the hydraulic reservoir to be empty. Upon refilling the reservoir and testing the gear, a leak was identified at the battery compartment access panel. Specifically, a perforation was found in an aluminum hydraulic line supplying the nose gear actuator, located near a mounting clamp.
Metallurgical analysis of the perforation revealed the presence of foreign iron and manganese, as well as evidence of heating to at least 600 °C. The clamp and its elastomer coating remained undamaged. The findings were consistent with rapid, localized heating caused by an electrical arc during a short circuit. While the electrical components in the compartment showed no anomalies, the origin of the arc could not be determined.
Findings
- The hydraulic reservoir emptied during the flight's various maneuvers due to the leak.
- Once the fluid level was depleted, the hydraulic system could no longer extend the flaps or the landing gear, even when using the emergency gas cartridge, as the gas escaped through the perforation.
- The perforation of the hydraulic line caused by an electrical arc was the primary cause of the system failure.