What happened
On June 9, 2011, a PIPER PA-34-200T “Seneca II”, registration EC-KDP, was performing a flight training check flight at Tenerife North Airport (GCXO). The flight, which involved an examiner and an examinee, was in its approach phase when the pilot in command noticed that the left landing gear was not properly locked. The green light for the left gear remained off, while the red "gear in transit" light was illuminated and the cockpit warning horn was sounding.
In an attempt to rectify the situation, the crew cycled the landing gear twice and even attempted the emergency extension procedure as outlined in the Pilot Operating Manual. Despite these efforts, the cockpit indications did not change. After requesting a visual check from the airport tower personnel—who could see the gear was down but could not confirm it was locked—the crew proceeded to land with extreme caution.
Upon touchdown, the aircraft initially made contact with the right gear. However, as the left wheel touched the runway, the gear leg collapsed. This caused the aircraft to yaw sharply to the left and depart the runway near the E3 exit taxiway, eventually coming to a stop 40 meters from the runway centerline at a 180-degree angle to its original heading. The aircraft sustained damage to the left wing, pitot tube, and underside of the fuselage, but there were no injuries to the two occupants.
The investigation
Investigators examined the aircraft's maintenance history and the condition of the landing gear mechanism. The aircraft, which was used for flight training, experienced long periods of inactivity, having flown only 59 hours in the previous year.
During inspections at the incident site and later in a hangar, investigators found that while the hydraulic pump and fluid levels were functional, the left gear leg failed to fully extend or lock. The mechanism required significant manual force and the use of tools to engage the locking tabs. The investigation revealed that the left gear system was dusty and exhibited visible signs of corrosion and a lack of lubrication. Notably, some corroded areas had been painted over, masking the underlying degradation.
Findings
- The primary cause of the incident was a restriction in the left landing gear deployment and locking system, which prevented the locking tabs from fully engaging.
- The aircraft was frequently parked outdoors in a highly humid and saline environment, which, combined with the aircraft's low utilization, allowed dust and moisture to accumulate in the gear mechanism.
- The accumulation of debris and corrosion caused the mechanical restriction that went undetected until the gear was cycled during the approach.
- Maintenance challenges, including the aircraft's primary maintenance center being located on a different island, likely contributed to the difficulty in detecting and correcting the corrosion early.