What happened
On March 31, 2019, a Piper PA31-350, registration HK5229, was conducting a non-scheduled passenger flight from Popayán (SKPP) to López de Micay (SKZI). Shortly after departing Popayán at 12:25 HL, the pilot noticed a drop in oil pressure and fluctuating temperatures in the number one engine. The crew declared an emergency and decided to return to Popayán.
To ensure safety, the crew shut down the number one engine and feathered the propeller. During the approach to runway 26, the aircraft encountered an 11-knot tailwind. The aircraft touched down, but due to a high ground speed, the crew applied heavy, progressive braking. This intense braking caused the brakes to overheat and lose effectiveness, resulting in a prolonged runway excursion past the end of runway 26, stopping 28 meters into the safety area. All 10 occupants (2 pilots and 8 passengers) were uninjured.
The investigation
The GRIAA investigation examined the engine, the braking system, and the flight maneuvers. Investigators reviewed video footage provided by a passenger, which confirmed the landing sequence and showed approximately 1,605 meters of runway remaining at touchdown.
Technical inspections of the number one engine revealed no evidence of mechanical failure, oil leaks, or metal shavings in the oil, suggesting the initial pressure drop may have been an erroneous indication. The investigation also found that while the braking system was functional, the high energy of the landing exceeded the system's capacity to stop the aircraft. The aircraft sustained no structural damage, though the tires and brakes showed excessive wear.
Findings
- The primary cause of the excursion was the execution of an emergency landing with a single engine inoperative.
- The pilot maintained an approach speed significantly higher than the manufacturer's recommended limits for single-engine operations.
- The high ground speed, combined with an 11-knot tailwind, led to a landing speed that exceeded the braking system's ability to dissipate energy.
- The crew's decision to maintain high speed was intended to ensure safe flight conditions with one engine inoperative.