What happened
On April 23, 2010, at 11:32 local time, a Piper PA-28R-200 Arrow II, registration OH-PAM, performed a forced landing in a wooded area near Emäsalo, Porvoo. The aircraft was conducting an instrument proficiency check flight from Helsinki-Malmi. The flight itinerary included an instrument approach to Helsinki-Vantaa and a simulated VOR/DME approach near the Porvoo VOR beacon.
During the simulated approach, while the pilot was attempting to increase power from a low setting, the engine failed at an altitude of approximately 400 meters. The pilot was unable to restart the engine, and the aircraft struck trees in the forest. The impact destroyed the aircraft, causing the wings to separate from the fuselage. The pilot sustained fatal injuries, while the flight examiner and a passenger both suffered serious injuries.
The investigation
The investigation examined the aircraft's technical condition, the weather conditions, and the flight crew's preparations. Investigators found no evidence of volcanic ash from the Icelandic eruption in the engine or air filters, and no mechanical defects were found that could have caused the failure. The investigation also noted that the aircraft's weight at takeoff exceeded the maximum allowable mass by approximately 24 kg, though this was not a factor in the crash. Additionally, the presence of a passenger during a proficiency check was noted as a violation of regulations.
Findings
Ice formation in the fuel injector unit caused the fuel-air mixture to become too lean, leading to the engine failure when power was increased. This icing occurred because the flight continued into a rain shower with temperatures between 0 and -5 degrees Celsius, accompanied by heavy snow, sleet, and hail.
Several contributing factors were identified:
- The flight crew had reviewed METAR and TAF reports but had failed to consult the Significant Weather Chart (SWC) or the General Aviation Forecast (GAFOR), which had predicted moderate icing in clouds.
- The flight examiner had an insufficient understanding of how the prevailing weather conditions would affect engine performance.
- There was a perceived need to complete the nearly finished check flight according to the original plan.
- The Piper PA-28R-200 operation manual lacked instructions for the preemptive use of the alternate air system to prevent fuel injector icing in such conditions.