What happened
During a flight training maneuver on the downwind leg, the instructor simulated a left engine failure by reducing the manifold pressure to 11 inches Hg. The instructor noted that the engine had been running rich and that the engine was not cleared during the visual approach.
As the aircraft reached short final approach, the instructor took control of the aircraft and applied full power to both engines to initiate a go-around. However, the left engine failed to accelerate, causing the aircraft to roll rapidly to the left. To stabilize the flight, the instructor reduced engine power, which allowed the aircraft to return to a level attitude. The aircraft subsequently touched down on the runway in a side slip, resulting in the collapsed landing gear.
The investigation
A postcrash examination of the left engine revealed that the spark plugs were fouled with combustion deposits. Additionally, investigators found that the fuel control was operating at a rich mixture within the idle range because of sand contamination.