Peoria, AZ, USA
N963WW
PIPER PA28R
At 8,500 feet, the designated pilot examiner instructed the commercial pilot to demonstrate steep spirals. The pilot configured the airplane by placing the mixture control to the FULL RICH position, entered the spiral maneuver, and cleared the engine every 180 degrees while in the turn. After the fourth spiral, the pilot attempted to make a simulated emergency landing, but when he observed that he was high, he put the airplane into a slip to lose altitude. When the examiner instructed the pilot to go around, the pilot advanced the throttle, but the engine did not respond. The pilot subsequently landed the airplane long, and it ran off the end of the runway. During the postaccident examination, the engine was run with no anomalies noted. The inspector subsequently discussed with the flight school’s chief flight instructor the procedure for setting the mixture control to the FULL RICH position at altitude before initiating a maneuver such as steep spirals. The chief instructor alluded to information provided by the engine manufacturer that the recommended procedure is to set the mixture to FULL RICH below 5,000 feet. After the accident, the chief instructor issued a company policy statement which read, “When leaned at altitude for flight, students and instructors should gradually enrichen the mixture throughout the descent, reaching full rich mixture while descending through 4,000 feet.” According to Service Instruction No. 1094D, issued by the engine manufacturer on March 25, 1994, relative to fuel mixture leaning procedures for all of the manufacturer's Opposed Series Engines, “For 5,000 feet density altitude and above or high ambient temperatures, roughness or reduction of power may occur at full rich mixture.” A representative for the engine manufacturer stated that the mixture setting during a low-power descent is not really a concern and that the mixture only needs to be adjusted when the engine power is required during takeoff, climb, and cruise. The engine representative added that if the pilot had put the mixture to full rich and descended, the engine would have been fine and should not quit. Therefore, while it may have been possible that the placement of the mixture to the FULL RICH position at altitude could have resulted in the power interruption at the lower altitude, there is no definitive evidence to support this position. The reason for the reported loss of engine power could not be determined.
On May 29, 2012, about 0930 mountain standard time, a Piper PA-28R-201, N963WW, was substantially damaged following a forced landing due to a loss of engine power at the Pleasant Valley Airport (P48), Peoria, Arizona. The airplane is owned and operated by Westwind Aviation, Phoenix, Arizona. The certified private pilot, who was receiving his commercial pilot checkride, occupied the left pilot seat, and a Federal Aviation Administration (FAA) Designated Pilot Examiner (DPE), occupied the right pilot seat. Neither pilot was injured. Visual meteorological conditions prevailed during the check flight, which was being conducted in accordance with 14 Code of Federal Regulations (CFR) Part 91, and a flight plan was not filed. The local flight departed Deer Valley Airport (DVT), Phoenix, Arizona, about 0830. In a report submitted to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot receiving his commercial checkride 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; the pilot did not indicate the position of the mixture control prior to the start of the maneuver. The pilot further reported that during the spiral descent he cleared the engine every 180 degrees of turn; after the fourth spiral, he attempted to make a simulated emergency landing to runway 05 at P48. The pilot stated that when he observed that 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. The pilot reported that when he advanced the throttle full forward to go around there was no response from the engine, and that [he felt at this time] a forced landing was his best option. The pilot stated that when he was on approach to runway 05 he noticed that the airplane was floating further than anticipated and that he was going to land long. The pilot added that after touching down and bouncing a few times, the airplane rolled hundreds of feet off of the paved end of the runway [onto a dirt surface] before it came to rest upright. The pilot stated that a section of the right wing skin was wrinkled in multiple places, the right landing gear was damaged, and that one wing rib was bent. According to a report the DPE submitted to the IIC, the left-seat pilot being examined performed the required steep spirals maneuver from 8,500 feet, and cleared the engine after every turn. After this maneuver was performed satisfactorily, the pilot continued the steep spirals to a simulated emergency approach and landing to P48. The DPE stated that the pilot cleared the engine on downwind and base, and on final approach the DPE instructed the pilot to go around from 700 feet above ground level. When the pilot initiated the go-around by advancing the throttle, the engine failed to power up. The pilot then proceeded to do a power-off landing, which resulted in the airplane touching down on the paved portion of the runway and then continued on to the unpaved portion of the runway. The DPE did not state what position the mixture control was in prior to the start of the spiral maneuver. A FAA airworthiness inspector traveled to P48 on the day of the accident to examine the airplane and interview the pilots. The inspector reported that during the examination he observed some wrinkling on the left hand skin outboard of the landing gear. The inspector further reported that the engine was started and an engine run performed. However, the engine was not run above low power, as the airplane was positioned on the dirt/gravel portion of the runway. The inspector stated that there were no anomalies observed with the engine that would have precluded normal operation. The FAA inspector revealed that in subsequent discussions with the flight school’s chief flight instructor about procedures for leaning the engine, he discussed the practice of going to the FULL RICH position with the mixture when entering these maneuvers. The school’s chief flight instructor stated that for leaning procedures, the best guidance he had from Lycoming was to follow their recommended procedures by setting FULL RICH below 5,000 feet. In further response to this concern, the chief flight instructor, in preface to a policy update to staff instructors stated, “During the flight, the student and DPE were evaluating the steep spiral into an emergency descent. They were leaned for altitude and as they started the maneuver at 9000 ft then they went ‘full rich’ prior to the decent.” The chief instructor subsequently disseminated a policy update, which stated, “When leaned at altitude for flight, students and instructors should gradually enrichen the mixture throughout the descent, reaching full rich mixture while descending through 4,000 feet.” A senior air safety investigator for Lycoming Engines reported to the IIC that the mixture position during a low power descent is really not a concern, and that it only needs to be adjusted when the engine is required to make power during takeoff, climb and cruise. The engine representative further reported that if the pilot had put the mixture to full rich and descended, the engine would have been fine and should not quit. He added that the pilot could have left the mixture at the lean setting he had and may have had an issue if he applied power for the pattern and never returned it to rich. According to Textron Lycoming SERVICE INSTRUCTION No. 1094D, dated March 25, 1994, relative to fuel mixture leaning procedures for all Textron Lycoming Opposed Series Engines, “For 5,000 feet density altitude and above or high ambient temperatures, roughness or reduction of power may occur at full rich mixture.” The reason for the loss of engine power was not determined. The airplane was returned to service on August 30, 2012.
A loss of engine power for reasons that could not be determined because postaccident examination did not reveal any anomalies that would have precluded normal operation.
Source: NTSB Aviation Accident Database
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