On the morning of the accident, the pilot flew the Cessna 172 from Ak-Chin Regional Airport (A39) in Maricopa, Arizona to Falcon Field Airport (KFFZ), in Mesa, Arizona to pick up the passenger and then departed for Show Low Regional Airport (KSOW).
The flight arrived at KSOW about 9 a.m., and the pilot and passenger spent most of the day away from the airport. A witness, who told investigators the pilot and passenger returned to the airport in the late afternoon, assisted them with refueling the airplane at the self-service fuel pump. He stated that both wing tanks were filled to the bottom of the filler neck.
Witnesses at KSOW observed the airplane attempt to take off from Runway 25 about 5:45 p.m. The airplane became airborne two or three times during the first attempted takeoff, but did not climb very high.
One witness stated that the airplane touched down, “got squirrely,” and almost departed the end of the runway.
Another witness stated that the airplane slid sideways and that the engine “did not sound healthy.”
Another witness stated that the engine was “sputtering.”
The pilot then taxied the airplane back to the approach end of Runway 25 and performed a run-up. A witness stated the engine “sounded bad” when the airplane was taxiing.
The pilot then attempted a second takeoff. According to a witness who was also a pilot, the accident pilot “milked it off the runway, set it back down, and then milked it off the runway again.”
The witness added the engine was “running rich, bogged down” during the second takeoff.
The airplane remained at a low altitude, began a left turn toward the downwind pattern, and then “sank.”
Another witness stated that, during the left turn, the airplane descended out of sight behind a ridge line.
The airplane hit terrain in an open field about one mile southwest of the departure end of Runway 25. The airplane crashed near the edge of a stream in an open field.
Both the pilot and passenger were killed in the crash.
The accident site and debris field were confined to the initial impact point. Forward of the empennage, the fuselage was bent downward. All flight control surfaces were attached to the airplane, and flight control continuity was established to the cockpit controls.
The engine was pushed aft, and it protruded into the cockpit. The engine remained attached to the airframe. Engine control continuity was not established due to impact damage.
The carburetor was impact separated from the engine. The mixture control at the carburetor was observed in the lean position.
Valve train continuity and thumb compression/suction were obtained on all cylinders except for cylinder No. 4. Cylinder No. 4 was removed, and the exhaust valve was observed to be stuck in the open position.
The magneto leads for the bottom spark plugs of cylinders Nos. 2, 4, and 6 exhibited impact damage. Both magnetos were removed, and the magneto leads were cut near the housing. The removed magnetos were rotated by hand, and spark was observed on all the leads. The bottom spark plug of cylinder No. 4 exhibited carbon buildup and the cylinder contained debris.
The No. 4 cylinder was disassembled, and the exhaust valve stem was mostly covered in carbon buildup. The cylinder and associated exhaust valve components were sent to the National Transportation Safety Board (NTSB) Materials Laboratory for further examination.
Visual examination of the exhaust valve stem found that the 0.6 to 0.7 inches of the exhaust valve stem (from the seat) exhibited deposits and that the deposits that were 0.5 inches from the seat exhibited a dark brown color with a dull luster. The other 0.1 to 0.2 inches of deposits exhibited a black color that was more reflective. Dark brown and orange-yellow deposits were present over the exhaust valve head. The deposits exhibited a flaky layered morphology that increased the overall diameter of the stem.
The deposits on the exhaust valve stem and valve seat surface were further examined. They showed indications of a single-chained polymer-like organic compound, consistent with deposits of unburned fuel.
According to the NTSB’s investigation, the engine was overhauled on April 29, 2016, and six new Continental cylinders were installed. On Oct. 28, 2020, the pilot purchased the airplane.
On April 26, 2021, the No. 2 cylinder was removed due to a stuck exhaust valve. The work order for the cylinder repair did not specify a reason for the stuck valve. The valve was repaired and the cylinder was reinstalled four days later. At that time, the engine had accumulated 169.32 hours of tachometer time.
The engine logbook contained entries for an annual inspection on Sept. 29, 2021, and an oil change on Feb. 19, 2022. The tachometer displayed 276.79 hours at the time of the accident.
The pilot’s supervisor, who was also a pilot and had flown with the accident pilot, thought an exhaust valve also became stuck sometime between Jan. 16 and Feb. 27, 2022, and that the pilot had difficulty finding a mechanic to fix the stuck valve.
The supervisor further stated that he explained to the pilot the procedure for resolving the stuck valve, but he did not know if the pilot attempted that procedure himself or found a mechanic to perform the work.
The pilot’s supervisor also stated that, during one flight with the accident pilot, the supervisor was leaning the engine when the pilot stated that he “never leaned the engine” and “didn’t need to lean the engine below 3,000 feet.”
The pilot added that he had “little or no training” on leaning the engine.
Probable Cause: The pilot’s improper leaning of the engine during an extended period of time, which caused an exhaust valve to become stuck and led to the partial loss of engine power during the accident flight. Contributing to the accident was the pilot’s decision to attempt a second takeoff without having the engine further examined.
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This May 2022 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
So sad. Another unnecessary statistic.
Stupid is as stupid does! RIP.
Leaded fuel kills. While better leaning would have helped prevent a stuck valve, the fact is, all the lead run through this engine is the root cause of the stuck valve and this accident. This has been a chronic problem for 50 years since we did away with 80/87 fuel and the government had this bright idea that 100LL would be a wonderful drop-in replacement. How many of us have dealt with stuck valves in the last 50 years? How accidents have been contributed to poor engine performance due to stuck valves? Meanwhile, the government and FAA bureaucrats continue their foot dragging routine to force us to keep burning leaded fuel for as long as possible. Mogas has been a good alternative, but is now contaminated with so much other junk that it can be damaging to aircraft fuel system components. Come on guys, get the lead out!
It is tragic that the lack of experience can be so harmful. An old guy myself, with considerable experience operating and maintaining aircraft engines including the O-200 and O-300 Continentals I can’t understate the importance of understanding the effects of 100LL on these engines. As a flight instructor and A&P/IA I have performed the “rope trick” numerous times. I taught my students the science of proper leaning resulting in the elimination of lead fouling in the low compression engines we operated. In the early days when 80 octane was no longer available, I turned to autogas. At a point, my commercial insurance company prohibited the use of autogas in my rental aircraft. Mandated to use 100LL in the low compression engines required disciplined leaning procedures. The lead/carbon/goo abrasive paste formed by rich running can be eliminated by proper leaning.
Ignorance is bliss. How often do we try to give helpful advice to people who ignore it at their peril. I know guys who cover the Check Engine light in their trucks with masking tape to make it go away. RIP both men.
Regards/J
There’s more to this story than in the NTSB reports.
This guy had a ‘student pilot cert.’ issued in 2004, per the FAA registry….so not a pilot.
It’s amazing to see the huge deposits on the valves, mostly lead/ lead-bromide.
He had a stuck valve prior to this one, and never learned, or considered the cause- using full rich all the time.
Lycoming SB-388c, and SI-1425A require 300-400 hr inspection of the exhaust valves for sticking. I had a stuck exhaust valve on my GO-300 and I lean at all times other than climb.
So, these instructions should apply to Continental engines as well.
The last departure attempts were at KSOW, at 6,400 ft, at 77 degF, which had the air density at 9,500 ft. An old C172 with the O-300 would barely be able to climb under those conditions.
So, sad that this guy killed someone else in the crash….
There is noting stopping anyone from buying an aircraft and trying to fly it….no FAA police, orther than some random ramp check.