Probe into 2024 Aviation Accident in Räyskälä: Even Training and Experience may not Safeguard against Accidents

The airplane had recently been sold to a new owner.

The engine failure occurred during initial climb about 100 m above ground level. The pilot initiated a steep right-hand turn in an attempt to return to the airfield for landing, but the airplane impacted ground after about one minute from the commencement of takeoff.

Knowledge of Old-time Technology and Quirks of Vintage Aircraft Is Essential

“Investigation determined that the engine failure resulted from fuel flow restriction. The airplane was likely fitted with an original factory-installed fuel tank selector valve with a cork seal that had apparently degraded over the years and therefore did not allow unrestricted fuel flow to the engine during takeoff. This, combined with considerable backlash in the operating linkage between the selector and valve, which resulted in the seal being in an incorrect position, led to a falling fuel level in the carburetor and engine stoppage,” explains investigator-in-charge Janne Kotiranta.

”Although SNJ-3 selector valve problems were known among the recreational aviation community, it is possible that all silent knowledge related to airplane operation was not transferred to the accident pilot during ownership changes, ” he adds.

“The airplane had experienced engine roughness during the evening preceding the accident flight, but troubleshooting had focused on propeller governor operation. Since the anomaly appeared randomly, it was not assumed to be related to fuel supply. Even though the pilot had a wealth of experience of airline and recreational flying, he was rather unfamiliar with the SNJ-3. In that respect, the situation was akin to those encountered with old automobiles - insight into their workings and quirks is essential, ” Kotiranta says.

Pilot’s Training and Experience may not Safeguard against Accidents

“The pilot’s decision to turn back after the engine failure was not compliant with the flight manual procedure. In this case, successful completion of a steep turn to the runway at a low altitude was practically impossible, also taking into account the fact that the pilot had less than ten seconds available for decision-making, ” Kotiranta continues.

​Link to photos (Flickr)Avautuu uuteen välilehteen​

Process of Elimination Led to Identification of Probable Cause

“I’d like to give special credit to our subject matter experts for their outstanding work. During the investigation we had to dismantle the wreckage to the last nut and bolt and conduct thorough examination of airplane components. That done, we were left with only ‘either-or’ options, but finding the smoking gun required, once again, a great many sit-down meetings, ” Kotiranta concludes.

The SIAF recommends that the Federal Aviation Administration (FAA) of the United States informs the owners and operators of the airplane type of risks related to the wear and aging of the fuel selector valve and its operating mechanism and of relevant risk management practices.

The FAA had released a non-mandatory modification in order to eliminate the need of in-flight fuel tank switchover, but the modification had not been performed on the accident airplane.

​Link to investigation report and summary​

Further information:

Investigator-in-Charge Janne Kotiranta, tel. +358 2951 50703