WILDERODER GREAT LAKES 2TIA — Lillian, AL

What happened

The pilot of the experimental, amateur-built airplane completed one 15-minute local flight with a passenger onboard. During a second 15-minute local flight with a different passenger, two witnesses near the accident site observed the airplane flying about 500 ft above ground level. They did not notice anything unusual about the flight and diverted their attention. The airplane was subsequently reported overdue and located about 6 hours later.

The airplane impacted wooded swampy terrain in a level attitude on a heading consistent with the closest airport. A strong smell of fuel at the accident site indicated the presence of fuel at impact. There was no evidence of pilot incapacitation. Examination of the wreckage did not reveal any preimpact mechanical malfunctions with the exception of the left magneto, which would not produce spark. Although records indicated the magnetos were overhauled within 2 years of the accident, laboratory examination of the left magneto revealed that its internal components were worn and near their life limit, which was not consistent with an overhaul during the previous 2 years. The points also did not make contact when closed. The investigation was unable to determine if the pilot performed a preflight check of the magnetos before departing on the accident flight or the preceding flight.

Additionally, the mechanic who maintained the airplane stated that about 6 months before the accident, the left exhaust manifold was sent out for repair due to cracking. To prevent further cracking, the repair facility installed ball joints; however, the carburetor heat shroud had to be reduced by about half-size to facilitate the modification. The reduced carburetor heat shroud would have resulted in a corresponding reduction in carburetor heat capability. A review of a carburetor icing chart revealed that, for the given temperature and dew point, atmospheric conditions were conducive to the formation of "serious icing" at engine glide power settings. The previous passenger reported that part of the scenic flight included a reduction in engine power to idle and a gliding descent. The carburetor heat control was found in the "ON" position. It was likely that an inoperative magneto and possible carburetor ice accumulated while gliding that the carburetor heat system was unable to melt resulted in a loss of engine power and forced landing into the swamp.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.