NTSB Factual Report

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 the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed at the time of the accident and no flight plan was filed. The planned local flight was originating at the time of the accident.

The pilot was not able to recall the events leading up to the accident due to his injuries.

The passenger reported that shortly after takeoff, and while turning crosswind to the north, the engine experienced a total loss of power. The passenger stated that at this time the pilot attempted to restart the engine but was unsuccessful. He then attempted to make a left 180° turn back to the airport, however, was unsuccessful as the airplane stalled and crashed into a fence and a tree. The passenger mentioned that at the time of the accident, the engine was completely off; "there was no power at all to the engine."

A witness to the accident, who was a student pilot at the time, reported that he was observing a small Grumman [airplane] take off from runway 25L at DVT. The witness stated that the airplane climbed to an altitude of about 200 to 300 ft above ground level, when he heard the engine slow to what sounded like half power. He further stated that a few seconds later the airplane leveled off and it veered about 30° to the right, and then began a steep 45° or more bank to the left. The witness opined that it appeared that the pilot was going to try to make it back to runway 7R, or at least land in the field near the end of the runway. However, during the left turn on an approximately southwest heading, the witness stated that the airplane stalled and banked sharply "…like a snap roll to the right and pitched nose down"; he did not witness the last few feet prior to impact.

According to the Federal Aviation Administration (FAA) inspector who responded to the accident site, several witnesses reported that after the airplane had taken off and was in its initial climb to the west, the wings started to rock back and forth. The airplane subsequently began to descend, struck the airport's western perimeter fence, and collided with a tree where it came to rest. Both wings and the engine had separated from the airplane due to impact forces.

An acquaintance of the pilot, a certificated flight instructor (CFI), reported that a few days prior to the accident the pilot contacted him and reported that on a recent flight the airplane's engine had run a bit rough for about 3 to 5 seconds. He asked the pilot what actions he took, and the pilot stated that he switched the electric boost pump on and switched fuel tanks, which resulted in the engine running smoothly. The CFI stated that he thought the pilot mentioned that he then switched the fuel selector back to the rough running side and it again ran smoothly but was not sure. The pilot did not indicate which side or tank had the issue. The CFI did not know if the pilot had a mechanic examine the engine prior to the accident flight, which occurred about 4 to 6 days after the rough running engine was reported to him. The CFI informed the airplane's owner of his conversation with the pilot relative to the engine issue when he met him at the hospital on the day of the accident. The CFI opined that the owner had no knowledge of the rough running engine issue, that he had taken all precautions to ensure that the airplane was safe, and that he had just spent $5,000 on an annual inspection.

During the investigation the passenger reported to the NTSB IIC that a few days prior to the accident the pilot was telling people and the CFI that he was having trouble with the fuel selector. When the IIC queried the CFI about the passenger's statement, the CFI stated that the pilot never mentioned anything about the fuel selector being an issue during any of their conversations.

PERSONNEL INFORMATION

The 18-year-old pilot held a private pilot certificate with a rating for airplane single-engine land. A friend of the pilot reported that the pilot had accumulated about 270 total flight hours, 207 hours as pilot-in-command, and 226 hours which were in the same make and model as the accident airplane. The pilot held an FAA first-class airman medical certificate, which was issued on April 23, 2015, with no limitations reported.

AIRCRAFT INFORMATION

The two-seat, low-wing airplane, serial number AA1B-0016, was manufactured in 1972. It was powered by a Lycoming model O-320-A3A, 150-horsepower engine, and equipped with a Sensinich two-blade propeller, model M74DM-0-58. A review of the maintenance logbook records revealed that during the 100-hour inspection that was performed on February 9, 2017, the number 3-cylinder was replaced with a new Millennium cylinder, part number SA 32006N-A21P, at a tach time of 432.4 hours. At the time of the inspection when the number 3-cylinder was checked for compression, it registered 36/80, which prompted the cylinder change. The most recent 100-hour inspection was performed on May 11, 2017, about 125 hours prior to the accident. At this time the number 3-cylinder exhaust gasket was replaced. In conjunction with the inspection, a subsequent ground run revealed no anomalies with the engine. A maintenance logbook entry revealed that all cylinders were inspected with a borescope. At the time of the accident the cylinder had accumulated 324.1 hours of operation since installation. (Refer to excerpts of maintenance records, which are appended to the docket for this accident.)

The airframe and powerplant mechanic who performed the installation of the number 3-cylinder during a 100-hour inspection, stated that on July 29, 2017, three days prior to the accident, he and the accident pilot exchanged a series of text messages, in which the pilot stated that on a go-around/missed approach, the engine started shaking and shuttered for about 10 seconds, and then it was fine. When the mechanic replied that he wondered if it could have been carburetor ice, the pilot said he didn't think so. The mechanic also mentioned that he did not perform any work on the airplane after the initial report of the engine running rough.

AIRPORT INFORMATION

The airport is surrounded on the south, west and north by industrial and commercial buildings. The road which borders the airport on its west perimeter is a main north/south arterial road, as is the road which borders the south side of the airport, both of which have traffic throughout the day. The nearest open field is located about 1,500 ft northeast of the initial upwind departure leg.

METEOROLOGICAL INFORMATION

At 1253, the DVT weather reporting facility indicated wind from 180° at 4 knots, visibility 10 miles, sky clear, temperature 34° Celsius (C), dew point 16° C, and an altimeter setting of 29.93 inches of mercury.

WRECKAGE AND IMPACT INFORMATION

A FAA aviation safety inspector, who responded to the accident site shortly after the accident, reported that after impacting the ground the airplane skidded into a tree, then broke at mid-fuselage splitting the airplane body into two pieces, with the cockpit and the fuselage on each side of the tree. The inspector stated that the engine appeared to be producing power, based on observable propeller blade signatures. The blades exhibited chordwise striations across the cambered surface, torsional twisting and trailing edge "S" bending. Additionally, the engine had separated from the airplane and came to rest on the road that borders the airport to the west, about 90 ft south of the main wreckage site. Both the left and right wings had also separated from the fuselage, with the left wing having come to rest about 30 ft northwest of the main wreckage, and the right wing about 180 ft south of the main wreckage site.

During a postaccident examination of the fuel selector by the NTSB IIC and a Federal Aviation Administration inspector, the component functioned as designed through all positions. It was observed that a stop pin was sheared off inside of the selector that would have prevented the selector from traveling too far to the left. Photo documentation at the accident site showed that the fuel selector was selected to the left tank position.

The left fuel tank had been breached and showed evidence of fuel dispersion; the quantity of the fuel spill was estimated to be between 3 to 5 gallons. The inspector reported that the right wing did not show any evidence of a fuel spill and that no fuel remained in the wing.

The inspector opined that the Type Certificate Data Sheet for the AA-1B airplane states that there is 2 gallons of unusable fuel in each wing. The inspector's review of the fuel receipts for the accident airplane revealed that 7.8 gallons of fuel was purchased on July 31 at 2107, and that the accident flight was the first flight since the fuel was added.

Engine Examination

The engine remained attached to the engine mount and had been liberated from the firewall during the accident/impact sequence. The engine had sustained significant impact energy absorption to the right forward/lower area of the number two cylinder and exhaust system. The attached propeller and flywheel were bent. All engine accessories remained secure at their respective mountings. Visual examination of the engine revealed no external evidence of pre-impact catastrophic mechanical malfunction or fire.

The left and right magnetos remained securely clamped at their respective mounting pads. The ignition harness was secure at each magneto. Magneto to engine timing could not be ascertained, due to the flywheel impingement on the engine crankcase. The magnetos were removed for examination. Each magneto produced spark at the end of the respective spark plug lead, during hand rotation of the drive. The drives of each magneto remained intact and undamaged.

The propeller and flywheel were removed to facilitate the examination. The top spark plugs were removed, examined and photographed. The rocker covers of each cylinder were removed. The vacuum pump was removed, and the crankshaft was rotated by hand through the drive pad utilizing a drive tool. The crankshaft was free and easy to rotate in both directions. "Thumb" compression was observed in proper order on cylinders 1, 2 and 4. It was noted that the number 3-cylinder exhaust valve was not moving and stuck in the OPEN position. The complete valve train was observed to operate in proper order and appeared to be free of any pre-mishap mechanical malfunction. Normal "lift action" was observed at each rocker assembly and pushrod of the number 3 exhaust valve. Clean, uncontaminated oil was observed at all four rockerbox areas. Mechanical continuity was established throughout the rotating group, valve train and accessory section during hand rotation of the crankshaft. The bottom spark plugs were removed, examined and photographed. The spark plug electrodes remained mechanically undamaged, and according to the Champion Spark Plugs "Check-A-Plug" chart AV-27, the spark plug electrodes displayed coloration consistent with normal operation. The combustion chamber of each cylinder was examined through the spark plug holes utilizing a lighted borescope. The combustion chambers remained mechanically undamaged, and there was no evidence of foreign object ingestion or detonation. The valves were intact and undamaged. There was no evidence of valve to piston face contact observed. The gas path and combustion signatures observed at the spark plugs, combustion chambers and exhaust system components displayed coloration consistent with normal operation. There was no oil residue observed in the exhaust system gas path. The exhaust system was found free of obstructions.

The number 3-cylinder was removed to facilitate further examination. The cylinder assembly was properly secured to the crankcase and appeared free of significant impact energy damage. The intake, exhaust rockers and valve train components within the rockerbox area appeared properly lubricated and free of mechanical damage. The intake and exhaust pushrods remained straight and free of damage. The intake pushrod shroud had sustained superficial impact damage. The intake rocker assembly remained undamaged and exhibited no evidence of lubrication depravation. There was no intake rocker pin oil hole. The exhaust rocker assembly remained undamaged and exhibited no evidence of lubrication depravation. The exhaust rocker pin oil hole remained free of obstruction.

The number 3-piston was removed from the connecting rod. The piston pin was undamaged and free of heat distress. The piston pin bushing remained secure and exhibited no unusual wear signatures. The number 3-piston exhibited no evidence of valve to piston face contact. The piston skirt exhibited no unusual wear signatures. The ring assemblies at each piston were intact and free to rotate within their respective ring land. The cylinder barrel bore remained free of damage and was absent of any significant heat distress signatures. There was no evidence of foreign object ingestion or detonation. The valves remained intact and undamaged. There was no further disassembly or examination of the subject cylinder. The valve was not moved from the original position it was found in during this examination.

TESTS AND RESEARCH

An examination of the number 3-cylinder was performed at the facilities of Superior Air Parts, Coppell, Texas. The results of the examination revealed the following:

There were no valve strike marks or impact damage exhibited on the piston. The piston rings were free in the ring lands and there was no damage to the sides of the piston. There was no evidence of scuffing, scoring or overheating. The piston part number could not be observed on the top due to heavy combustion deposits. Piston overall height was measured to be 3.177", which included the build-up of carbon deposits on top. The measurement was consistent with a low compression piston correct for the engine model. The piston pin was removed easily to facilitate inspection of the back side of the piston. The forging number on the underside of the piston was 13020, and manufactured by ECI. With the exception of heavy combustion deposits, the piston exhibited normal operational signatures.

The intake and exhaust valves exhibited combustion deposits on the stems close to the rear of the valve face. The exhaust valve was found stuck in the open position with the valve spring nearly depressed fully. The valve was tapped on the combustion side with a rubber mallet to close the valve to facilitate removal of the valve keepers and removal of the valve for inspection. With the valve keepers removed, the intake valve was removed with little effort. The exhaust valve required tapping with a rubber mallet and brass drift to remove it from the valve guide. The valve was tested using a Rockwell hardness tester and found to be within specifications.

The exhaust valve stem and guide exhibited heavy combustion deposits. The valve guide diameters were measured with the deposits present. The deposits were then removed using a .4995" ream in accordance with Lycoming Service Instruction 1425A, titled "Suggested Maintenance Procedures to Reduce the Possibility of Valve Sticking." The guides were re-measured after reaming and found to have an average of .0017" build-up of combustion deposits. The deposits were collected into a filter and sealed with the cylinder. All material removed during reaming was combustion deposits and no metallic material was found. (For additional information relative to the before and after ream dimensions, refer to the Summary Airframe and Engine Examination report, which is appended to the docket for this accident.)

The NTSB investigator who observed the examination commented in conclusion, that there were no observable preaccident deficiencies found with the cylinder. The stuck valve was consistent with

NTSB Probable Cause

The partial loss of engine power during initial climb due to the No. 3 cylinder exhaust valve becoming stuck open due to deposit buildup in the exhaust valve stem and guide and the pilot’s exceedance of the airplane’s critical angle of attack while attempting to turn back to the airport, which resulted in an aerodynamic stall.