N1835UCessna 172S · 2005

On April 16, 2011, about 0900 mountain standard time, a Cessna 172S, N1835U, was substantially damaged when it impacted terrain following a touch-and-go landing at Payson Airport (PAN), Payson, Arizona. The certificated private pilot and his passenger were not injured. The instructional flight was operated under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed.

According to information provided by the pilot and his flight school, he was enrolled in an ab-initio flight training program at Deer Valley Airport (DVT), Phoenix, Arizona. He obtained his private pilot certificate in March 2011, and had accumulated about 110 hours of total flight experience. The pilot had planned the 50-mile flight from DVT to PAN as a means to build time towards meeting the requirements for his instrument rating. Before departure, the airplane was topped off with fuel. During the descent for landing at PAN, the pilot enriched the mixture from its cruise setting, and entered the traffic pattern for a touch-and-go on runway 24. He used 30 degrees of flaps for the landing. After the touchdown, he retracted the flaps to 0 degrees, added power, and lifted off.

The pilot stated that the airplane was under performing on the climbout, so he enriched the mixture. That did not rectify the problem, and he heard the engine make "popping" sounds. He observed that despite the application of full throttle, the airspeed was lower than normal, and the tachometer indicated about 1,800 rpm, instead of the target value of about 2,300 rpm. The pilot began a right turn back towards the airport, and lowered the nose to increase the airspeed, but stated that the airplane did not seem to accelerate. He also stated that he heard the stall warning horn during the attempted turn back. The airplane impacted terrain about 3,500 feet from the runway.

The pilot reported that he held a private pilot certificate, and that he had approximately 109 total hours of flight experience, all of which were in the accident airplane make and model. The pilot was enrolled in the flight training program at Westwind School of Aeronautics, an FAR Part 141 flight training organization based at DVT. His most recent flight review was completed in March 2011. His first-class Federal Aviation Administration (FAA) medical certificate was issued in December 2010.

The airplane was manufactured in 1995, and was equipped with a Lycoming IO-360 series piston engine. The airplane was registered to a corporation, and operated and maintained by Westwind School of Aeronautics. Examination of the maintenance records revealed that the most recent annual inspection was completed on February 11, 2011, when the airplane had a total time (as recorded by the tachometer) of 2,721.5 hours, and that the most recent 100-hour inspection was completed on March 30, 2011, when the tachometer registered 2,819.0 hours. Although discrepancies in the recorded times provided by the flight school and those observed in the maintenance records could not be explained, examination of the maintenance records did not reveal any items or discrepancies which warranted further investigation or examination.

The PAN 0855 automated weather observation included calm winds; visibility 10 miles, clear skies; temperature 18 degrees C; dew point 16 degrees C; and an altimeter setting of 30.08 inches of mercury.

According to a representative of Lockheed Martin Flight Service (LMFS), the pilot telephoned the Prescott Arizona LMFS facility and was provided with a weather briefing for the flight from DVT to PAN.

DVT was the pilot's primary flight training airport, and the departure airport for the flight. The elevation of DVT was 1,478 feet above mean sea level (msl).

The elevation of PAN, the destination airport, was 5,157 feet msl. PAN was a non-towered airport, and the runway 24 dimensions were reported as 5,500 by 75 feet. The traffic pattern altitude was specified as 6,200 feet msl. Based on the reported meteorological conditions, the PAN density altitude was calculated to be approximately 6,200 feet.

On-Scene Examination

According to information provided by first responders and the FAA inspector who also responded to the accident scene, the airplane impacted trees and terrain about 3,500 feet northwest of the departure end of runway 24, and came to rest upright. There was no debris or ground-scar path, and nearly all trees and vegetation surrounding the airplane were undisturbed. The right wing was rotated about 90 degrees tip-forward, and the left wing was bent tip-down about 15 degrees. The fuselage, engine cowling, and both wings were deformed by crush damage. The spinner was crushed, and the two-blade metal propeller exhibited tip curling, with some chordwise gouges and scoring. The cockpit hour meter registered 3,477.1 hours after the accident. First responders reported that the right fuel tank appeared nearly empty, but the fuel line had been breached. They reported that the left tank was about 1/2 full. There was no post-accident fire.

Recovery Facility Examination

A joint NTSB and FAA examination of the recovered airframe and engine was conducted on January 4, 2012, at Air Transport, Phoenix, Arizona. All observed damage was consistent with the airplane impacting the ground in a left spin. The damage was consistent with the engine operating at a low power setting. The engine was examined, and several components were removed and disassembled for detailed examination. No evidence of preimpact mechanical malfunction that would have precluded normal operation and continued flight was noted during the examination of the recovered airframe and engine. Detailed documentation of the examination results is contained in the public docket for this accident.

The flight school's ab-initio training consisted of three primary segments: private, instrument, and commercial. Ab-initio students cycle through the segments and curricula in groups/classes. Subsequent to the accident, the school implemented a 1-week stand-down for all actual flying for all members of the accident pilot's class.

The school's instructors are not used to conduct the students' check rides. The school had a set of standard operating procedures in electronic format for use by students and instructors, but the guidance was not contained in a single electronic document/file.

The school had a "dispatch" department, but their responsibility was limited to airplane scheduling, release, and verification that pilots comply with the school's requirements for flight, including having filed a flight plan. The department did not share in flight preparation, duties, or decisions, exclusive of the functions enumerated.

High density altitude (DA) operations were covered in the primary and commercial classroom segments of the ab-initio training curriculum. Prior to the accident, the school did not have any specific or explicit requirements for actual practice/experience with operations at high DA airports. The pilot was not required to obtain, and did not obtain, specific/explicit approval to fly to a high DA airport, or to conduct touch and go operations there.

Subsequent to the accident, the school implemented a prohibition on all solo operations at high DA airports for all members of the accident pilot's class, until they each received actual training at a high DA airport with an instructor. In addition, the school revised its training requirements to ensure that all future students obtain actual training at a high DA airport with an instructor prior to being permitted to conduct solo operations at high DA airports.

Pilot's Operating Handbook (POH) Information

Section 4 (Normal Procedures) of the airplane manufacturer's Pilot's Operating Handbook (POH) contained both checklist-style and amplified procedures for operating the airplane.

Step 2 of the "DESCENT" section of the checklist-style normal procedures was "Mixture – ADJUST if necessary to make the engine run smoothly." Step 4 of the "BEFORE LANDING" checklist section was "Mixture Control – RICH." The amplified procedures did not contain any additional information on the descent or landing procedures.

The "BALKED LANDING" section of the checklist procedures did not contain any references to the mixture setting. However, in contrast, the "BALKED LANDING" section of the amplified procedures contained the statement "Above 3000 feet pressure altitude, lean the mixture to obtain maximum RPM."

Step 4 of the "NORMAL TAKEOFF" section of the checklist procedures was "Mixture Control – RICH (Above 3000 feet pressure altitude, lean for maximum RPM)." The amplified procedures contained the same guidance.

Flight Instructor Allegations

Several months after the accident, a flight instructor who previously instructed at WSA contacted the NTSB, and alleged that one or more other WSA airplanes had experienced some partial-power events similar to that encountered by the accident pilot. The CFI reported that two of the events had occurred to her during stall demonstrations with students. She did not specify the altitudes of her events, or the altitudes or other salient details for the other cases. The CFI reported that no individual or systemic causes were identified for the events, and that the flight school did not disseminate information about the events to the instructors or students.

The maintenance technician cited by the CFI was contacted by the NTSB for information about the events. He reported that some WSA airplanes were referred to maintenance for the partial power events, but that no systemic issues were found, and in most cases, the alleged problems could not be duplicated. He reported that in all cases, airplanes that were referred to maintenance for these problems were satisfactorily test-flown before they were returned to service.

The chief pilot for the flight school reported that the CFI-cited airplane was referred to the maintenance provider for examination, testing, and inspection, and that no relevant abnormalities were detected. He further stated that all airplanes with maintenance or operational discrepancies were referred to the maintenance provider for disposition and/or corrective actions, and that no systemic issues regarding the partial power events were ever noted. In addition, the FAA principal maintenance inspector for the flight school reported that she had not heard of these events prior to the CFI allegations, but neither would she necessarily expect to.