History of Flight
On August 1, 2017, about 1300 mountain standard time, an American AA-1B airplane, N6216L, was substantially damaged following a partial loss of engine power and subsequent loss of control during takeoff initial climb at the Deer Valley Airport (DVT), Phoenix, Arizona. The private pilot and pilot rated passenger were seriously injured. The airplane was registered to a private individual and operated by the pilot under Part 91. Visual meteorological conditions prevailed; no flight plan was filed. The local flight was originating at the time.
The pilot could not recall the events due to injuries. The passenger reported that shortly after takeoff, while turning crosswind north, the engine experienced a total loss of power. The pilot attempted to restart but was unsuccessful, then attempted a left 180° turn back to the airport, but the airplane stalled and crashed into a fence and a tree. The passenger stated the engine was completely off at impact.
A witness, a student pilot, observed the airplane take off from runway 25L. He reported the airplane climbed to about 200-300 ft agl when the engine slowed to half power. The airplane leveled, veered right 30°, then banked left steeply 45° or more. The witness believed the pilot aimed for runway 7R or a field, but during the left turn the airplane stalled and banked sharply right, pitching nose down. He did not see the final impact.
The FAA inspector reported multiple witnesses saw wings rocking after takeoff, then the airplane descended, struck the western perimeter fence, and collided with a tree. Both wings and the engine separated due to impact forces.
An acquaintance (CFI) reported the pilot mentioned a few days prior that the engine ran rough for 3-5 seconds; the pilot switched on the electric boost pump and fuel tanks, and the engine smoothed. The pilot did not indicate which tank had the issue. The CFI did not know if a mechanic examined the engine before the accident flight. The owner was unaware of the rough running issue.
The passenger later reported the pilot had trouble with the fuel selector a few days prior, but the CFI stated the pilot never mentioned such an issue.
Personnel Information
The 18-year-old pilot held a private pilot certificate with single-engine land rating. A friend reported about 270 total flight hours, 207 as pilot-in-command, 226 in the accident make/model. The pilot held a first-class medical certificate issued April 23, 2015, with no limitations.
Aircraft Information
The two-seat, low-wing airplane, serial number AA1B-0016, was manufactured in 1972. It was powered by a Lycoming O-320-A3A, 150-horsepower engine, and a Sensinich two-blade propeller. Maintenance records showed a 100-hour inspection on February 9, 2017 replaced the number 3-cylinder (compression 36/80) with a new Millennium cylinder. The most recent 100-hour inspection was May 11, 2017 (about 125 hours prior), when the number 3-cylinder exhaust gasket was replaced; ground run showed no anomalies. The cylinder had 324.1 hours since installation at the accident.
The mechanic who installed the cylinder exchanged texts with the pilot on July 29, 2017. The pilot reported a go-around where the engine shook and shuttered for about 10 seconds. The mechanic suggested carburetor ice; the pilot disagreed. No work was performed after that report.
Meteorological Information
At 1253, DVT reported wind 180° at 4 knots, visibility 10 miles, sky clear, temperature 34°C, dew point 16°C, altimeter 29.93 inHg.
Wreckage and Impact Information
The FAA inspector reported the airplane skidded into a tree after ground impact, breaking the fuselage into two pieces. The engine appeared to have been producing power based on propeller blade signatures (chordwise striations, torsional twisting, trailing edge S-bending). The engine separated and came to rest on a road about 90 ft south of the main wreckage; both wings separated. The left wing was 30 ft northwest, right wing 180 ft south.
Postaccident examination of the fuel selector showed it functioned as designed through all positions. A stop pin was sheared off; the selector was found in the left tank position.
The left fuel tank was breached with an estimated 3-5 gallons spilled. The right wing showed no fuel spill and had no fuel remaining. The inspector noted the Type Certificate Data Sheet indicates 2 gallons of unusable fuel per wing. Fuel receipts showed 7.8 gallons purchased on July 31 at 2107; the accident flight was the first since then.
Engine Examination
The engine remained attached to the mount, liberated from the firewall. Impact damage was noted to the right forward/lower area of the number 2 cylinder and exhaust. The propeller and flywheel were bent. No external evidence of pre-impact catastrophic mechanical failure or fire was found.
Magnetos produced spark during hand rotation. The crankshaft rotated freely; thumb compression was observed on cylinders 1, 2, and 4. The number 3-cylinder exhaust valve was stuck in the open position. The valve train operated properly on other cylinders. Clean oil was observed. Mechanical continuity was established. Spark plugs showed normal operation per Champion Check-A-Plug chart. Combustion chambers were undamaged, no foreign object ingestion or detonation. The exhaust system was unobstructed.
The number 3-cylinder was removed. The cylinder assembly was properly secured and free of significant impact damage. The intake and exhaust rocker assemblies were undamaged and properly lubricated. The piston and rings showed normal wear; no valve-to-piston contact. The cylinder barrel bore was undamaged.
Examination at Superior Air Parts found the exhaust valve stuck in the open position with the spring nearly fully depressed. Heavy combustion deposits were on the valve stem and guide. After removing deposits per Lycoming Service Instruction 1425A, the guide measured an average of 0.0017 inches of deposit buildup. No metallic material was found. The NTSB investigator concluded no preaccident deficiencies were found with the cylinder; the stuck valve was consistent with combustion deposit buildup in the guide.
Lycoming Service Instruction 1425A notes that exhaust valve sticking occurs more frequently in hot conditions due to lead deposits from fuel. Service Bulletin SB-388C requires 400-hour exhaust valve and guide inspections; the engine had 324.1 hours since last mandatory inspection, so compliance was not due. Service Bulletin SB-480E requires 25-hour oil changes for engines with pressure screens; the last oil change was at tach 702.1 hours and the accident tach was 756.5, which was 54.4 hours later, exceeding the 25-hour interval. However, FAA Order 8620.2A states such manufacturer data is not mandatory unless mandated by regulation.
Maintenance records showed no evidence of compliance with Service Instruction 1425A or Service Bulletins SB-388C and SB-480E.
Probable Cause
null