B1/2010L Aircraft accident in Porvoo on 23 April 2010

An accident occurred at Emäsalo near the city Porvoo on 23 April 2010 at 11:32 Finnish time. A Piper PA-28R-200 Arrow II, owned by Espoon Moottorilentäjät ry (ESMO Flying Club), made a forced landing in the woods during an instrument check flight. The pilot was fatally injured and the flight examiner as well as the passenger was seriously injured.

The aircraft took off for an instrument check flight from Helsinki-Malmi aerodrome at 10:37. The intention was to carry out a similar check flight for the passenger on the following flight. To begin with, the pilot flew an instrument approach to Helsinki-Vantaa aerodrome, as per the flight’s programme, after which he flew close to the VOR beacon at Porvoo. Before returning to Helsinki- Malmi, the itinerary included a simulated VOR/DME approach. The engine failed during the simulated approach. The aircraft crashed into the woods and was destroyed in the subsequent forced landing.

Prior to the flight pilots checked the actual (METAR) and forecasted (TAF) weather, but not the Significant Weather Chart (SWC) or the General Aviation Forecast (GAFOR). The forecast included moderate icing in cloud on their intended route. The weather in the accident area kept changing. For approximately four minutes prior to the collision with the ground the aircraft was flying in conditions where the ambient temperature varied between zero and a few degrees below freezing. Furthermore, on their route they encountered heavy snow, rain and snow mixed (a.k.a. sleet) and hail, which made horizontal visibility poor.

Ice formed on the fuel injector unit, which made the fuel-air mixture too lean. This caused the engine to fail when engine power was increased from a low power setting. The engine failed at the approximate altitude of 400 m in a descent during the simulated VOR/DME approach. The engine would not restart.

No traces of volcanic ash resulting from the eruption in Iceland were found in any parts of the aircraft or the engine’s air filter. Technical inspections found no such defects that could have contributed
to the accident.

The accident was caused because the engine failed due to ice formation in the fuel injector unit and because of the subsequent forced landing. Ice formed in the fuel injector unit when the flight was continued into a rain shower during the final simulated approach where the conditions for icing were favourable.

Contributing factors included the flight examiner’s insufficient understanding of the consequences of the prevailing weather conditions on engine performance as well as the need to wrap up the almost completed check flight as planned. Moreover, the Operation Manual (OM) of the PA-28R-200 does not provide instructions for the preventive use of alternate air to avert ice formation in the fuel injector in icing conditions.

The investigation commission made a safety recommendation to the Federal Aviation Administration (FAA) in which the commission proposed updating the Operation Manual of the PA-28R-200 with a warning about the potential for ice formation in the fuel injector unit along with instructions on icing prevention, akin to later versions of the Operation Manuals for the same aircraft type.

B1/2010L Report (pdf, 3.85 Mt)