While practicing an emergency descent during a dual training flight, the pilot receiving instruction entered the Lancair IV-P into a steep dive, which resulted in a 0.5-G load factor for about five seconds and a transient drop in engine oil pressure of about 15 psi.
As the descent continued, engine speed steadily increased beyond the maximum operating limit of 2,700 rpm.
While still in the dive, the pilot initiated a left turn with a 3-G load factor, during which the engine oversped to 3,390 rpm. The engine immediately began to run rough, and subsequently experienced a total loss of power.
The pilot executed a forced landing to a field near Shawano, Wisconsin, with the landing gear and flaps retracted. The plane hit a rock wall and tumbled.
Post-accident examination revealed that eight teeth on the left magneto distributor drive gear and 16 teeth on the right gear had fractured. No evidence of progressive damage or material anomaly was observed with the distributor drive gear teeth. The nylon gear teeth were most likely damaged by the abnormal shock loads on the gear train during the engine overspeed.
The damage to the gear teeth resulted in a dual magneto failure and subsequent loss of engine power.
The flight profile of a low-G pushover to a steep dive, which was accompanied by a drop in engine oil pressure, may have led to the propeller governor not supplying adequate oil pressure to the propeller, which subsequently contributed to the engine overspeed and the failure of the magnetos.
Probable cause: A total loss of engine power due to a dual magneto failure, as a result of exceeding the engine’s operating limitations while maneuvering.
NTSB Identification: CEN16LA043
This November 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
I would have expected the high time owner not to over limit any aircraft he operated unless he had a bogy at 6:00 high! Appears to be a show off to the CFI who was probably checking the owner out for insurance purposes. You know the 10 hours in type stuff.
According to NTSB documents the CFI only had 32 hours in make and model, 327 hours dual given, and just a tad more than 1400 hours total flight time. The PF (the owner of the aircraft) reported over 27,000 hours, including 4,000 hours in piston engine aircraft, and many ratings with experience in lots of aircraft. The NTSB Final report says the CFI admitted he was intimidated by the very high time and experience of his student. This misplaced awe prevented him from correcting errors in the PF emergency procedures, as well as assuming command of the aircraft after the engine failed. The NTSB report also states that the pilot and CFI never discussed who would be PIC should a ‘real’ emergency occur. Implied, but not mentioned in the report was a lack of system familiarity by both CFI and owner, and the lack of CRM exhibited during the emergency.
Nothing to see here. Pushing a plane past it’s placarded limits results in expected outcomes.