What happened
During a multiengine check ride, an aircraft was being operated by an examinee, a certified flight instructor (CFI), and a private pilot passenger. Prior to departure, both the designated pilot examiner (DPE) and the examineer noted that the left engine was not producing sufficient power during the pre-takeoff engine check. After cycling the mixture settings, the crew completed a simulated engine failure and proceeded with a normal takeoff.
Near the end of the runway, the DPE observed a loss of climb performance and noted that the left engine's manifold pressure was between 21.5 and 22.0 inches. Although the crew initially considered an off-airport landing, they gained enough altitude to return to the airport. During the downwind leg of the landing pattern, the right engine oil temperature approached its upper limit, and the oil pressure decreased toward the lower limit. On final approach, the right engine oil pressure dropped near the lower redline limit.
Following the landing, a second run-up revealed that the left engine was still not developing power equal to the right engine. The crew discontinued the check ride and taxied to the ramp. After consulting with a mechanic, the decision was made to fly the aircraft back to its home base. During the subsequent takeoff roll, the aircraft yawed to the left three times but remained on the runway centerline. After a long ground roll, the aircraft lifted off and gained altitude very slowly. Shortly after takeoff, a loud shriek was heard over the UNICOM frequency, and local law enforcement later reported the aircraft had gone down.
The crash resulted in 3 fatalities. The impact occurred in desert terrain near a rural residential area, where a post-impact fire thermally destroyed the aircraft.
The investigation
An examination of the airframe revealed no discrepancies. Mechanical and valve train continuity were established for both engines. A differential compression check on the left engine revealed low pressure on cylinders number 2 and 4. While cylinder number 4 showed improved compression after being staked, cylinder number 2 remained unchanged; both cylinders were removed for inspection, but no internal discrepancies were found. Due to the extent of thermal destruction from the fire, meaningful tests of the fuel and ignition system components could not be performed. Ground scars and impact damage indicated the aircraft struck the ground in a steep left bank attitude and tumbled.