Accident Sequence
The accident occurred during a go-around after a balked landing. The instructor took over the controls and initiated the go-around following a student landing in an improper attitude. Engines number 1 and 2 failed to respond when the throttles were advanced; both engines decelerated. Airspeed decreased during the go-around. The flaps were retracted, causing a reduction in hydraulic pressure. The instructor was unable to maintain VMC speed and subsequently lost control of the aircraft. The aircraft crashed in a steep left turn and was destroyed by a postcrash fire. The airfield perimeter fence was damaged.
Aircraft and Engines
The aircraft was equipped with two engines. Maintenance records revealed a history of recent engine and propeller oil leaks. There was no record of engine washes after the leaks, although such washes were required by maintenance procedures.
Post-Accident Examination
Teardown and testing of engines number 1 and 2 revealed a heavy accumulation of oil and tar residues on the bleed valves and throughout the compressors. This residue limited the ability of the engines to respond to throttle movement.