What happened
On August 16, 2018, a Tecnam P2002-JF, registration HB-KOP, was conducting a flight training mission between Yverdon-les-Bains and Lausanne-La Blécherette. During an earlier leg of the flight, the crew noticed a faint smell of burning plastic in the cockpit, which dissipated before landing. Following a routine pre-flight inspection after landing, the aircraft departed Lausanne for Yverdon at approximately 17:30 local time.
During the initial climb, smoke began to fill the cockpit from the left side. While engine parameters remained normal and power was unaffected, the instructor took control of the aircraft. The crew declared a Pan-Pan emergency and requested an immediate landing on the opposite runway. The aircraft successfully performed a turnaround and landed at Lausanne. The smoke cleared once the canopy was opened during taxiing. The crew sustained no injuries.
The investigation
An inspection of the aircraft conducted on August 17, 2018, revealed damage to the engine compartment. Investigators found burn marks and minor damage on the left-side lower engine cowling and its mounting, which had been deformed and partially carbonized. The investigation established that the end of the exhaust outlet pipe had broken off inside the engine compartment.
Further examination of the cabin heat exchanger housing showed that the unit was not properly sealed. Two of the four mounting screws were loose, and the housing was not flush against the firewall, leaving a gap of approximately 3 to 4 mm. Additionally, the cabin heat valve was improperly adjusted; even in the "OFF" position, the flap did not close completely, allowing contaminated air to enter the cabin.
Findings
- The primary cause of the smoke was the failure of the exhaust outlet pipe, which allowed exhaust gases and hot particles to escape.
- The smoke and odors entered the cockpit because the cabin heat exchanger housing was improperly secured and not airtight.
- An improperly adjusted heat valve allowed bypass airflow from the engine compartment into the ventilation system.
- The broken exhaust pipe was located in close proximity to the cabin heat exchanger, facilitating the leak into the cabin.
- A carbon monoxide detector on the dashboard confirmed that the crew was not exposed to carbon monoxide poisoning during the incident.