Accident Overview
On May 29, 2012, about 0930 mountain standard time, a Piper PA-28R-201, registration N963WW, operated by Westwind Aviation, was substantially damaged following a forced landing due to a loss of engine power at the Pleasant Valley Airport (P48), Peoria, Arizona. The aircraft was occupied by a certified private pilot receiving his commercial pilot checkride in the left seat and a Federal Aviation Administration (FAA) Designated Pilot Examiner (DPE) in the right seat. Neither pilot was injured. Visual meteorological conditions prevailed during the local check flight, which departed Deer Valley Airport (DVT), Phoenix, Arizona, about 0830.
Pilot Reports
The pilot under examination reported that prior to performing a steep spiral from about 8,400 feet mean sea level (msl), he turned on the fuel pump, extended the landing gear, and pulled the throttle back to idle; he did not indicate the position of the mixture control before the maneuver. During the spiral descent, he cleared the engine every 180 degrees of turn. After the fourth spiral, he attempted a simulated emergency landing to runway 05 at P48. When he observed he was high, he put the airplane into a slip to lose altitude. He then verified his checklist: FUEL PUMP ON, MIXTURE RICH, PROP FULL FORWARD, GEAR DOWN. When he advanced the throttle full forward to go around, there was no response from the engine, and he decided a forced landing was his best option. On approach, the airplane floated further than anticipated, and after touching down and bouncing, it rolled hundreds of feet off the paved runway onto a dirt surface before coming to rest upright. The right wing skin was wrinkled in multiple places, the right landing gear was damaged, and one wing rib was bent.
The DPE reported that the left-seat pilot performed the steep spirals maneuver from 8,500 feet, clearing the engine after every turn. After the maneuver, the pilot continued to a simulated emergency approach and landing to P48. On final approach from 700 feet above ground level, the DPE instructed a go-around. When the pilot advanced the throttle, the engine failed to power up. The pilot then performed a power-off landing, touching down on the paved portion of the runway and continuing onto the unpaved portion. The DPE did not state the mixture control position before the spiral.
Post-Accident Examination
An FAA airworthiness inspector examined the airplane and interviewed the pilots on the day of the accident. The inspector observed wrinkling on the left hand skin outboard of the landing gear. The engine was started and run at low power (the aircraft was on dirt/gravel), and no anomalies were observed that would have precluded normal operation.
Engine and Mixture Considerations
The FAA inspector discussed leaning procedures with the flight school's chief flight instructor, who stated that the best guidance from Lycoming was to set FULL RICH below 5,000 feet. The chief instructor later disseminated a policy update advising that when leaned at altitude, students and instructors should gradually enrichen the mixture throughout the descent, reaching full rich by 4,000 feet.
A senior air safety investigator for Lycoming Engines reported that the mixture position during a low power descent is not a concern; it only needs adjustment when power is required for takeoff, climb, and cruise. He stated that if the pilot had set the mixture to full rich and descended, the engine should have been fine, and leaving it lean might cause issues when applying power.
Textron Lycoming SERVICE INSTRUCTION No. 1094D (March 25, 1994) notes that for density altitudes of 5,000 feet and above, or high ambient temperatures, roughness or power reduction may occur at full rich mixture.
Conclusion
The reason for the loss of engine power was not determined. The airplane was returned to service on August 30, 2012.