A Tale of Three Engine Failures

In May 2022, a Cessna 172 taxied out at the Show Low Regional Airport (KSOW) in Arizona. It was watched by several people, pilots, and other personnel at the firefighting airbase. One person said the engine was “spitting and sputtering” and “didn’t sound healthy.” Another described the first takeoff attempt by saying the Cessna was “bogging down the runway,” the nose coming up and then back down. The pilot “locked up the brakes and the airplane skidded sideways,” almost going off the end of the runway. After this, the pilot and passenger taxied back to try again.

One witness told the NTSB the engine “sounded bad.” They were seen doing a run-up and then attempted a second takeoff. A witness said the pilot “milked it off, set it back down, and then milked it off again and stayed airborne.” He said the engine appeared to be “running rich, bogged down.” A different observer said the engine sputtered during the takeoff.

The Cessna climbed out, made a left turn, then seemed to sink behind a ridge, now out of sight of the airport witnesses. It continued to descend, crashing 1 mile from the departure end of the runway at the edge of a stream in an open field. Pilot and passenger both died.

After the accident, the No. 4 cylinder exhaust valve was found to be stuck because of a buildup of material that enlarged the overall diameter of its stem. NTSB examination of the valve stem deposits showed “indications of an organic compound that was consistent with deposits of unburned fuel. The stuck valve led to a partial loss of power during the accident takeoffs.” There was a history here. In 2021, the No. 2 cylinder had been removed due to a stuck exhaust valve. In 2022, the engine exhibited signs of valve issues. Something was gumming up the exhaust valves.

The accident pilot told a friend he “never leaned the engine” and that you don’t need to lean an engine below 3,000 feet. It seemed to the friend he had “little or no training on leaning the engine.” At the time of the crash, the temperature was 77 degrees. Show Low Airport sits at an altitude of 6,415 feet. I calculated the density altitude that day to be 8,800 feet.

The NTSB concluded the probable cause of the accident to be “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.”

About two weeks later, there was an issue with a Piper Arrow that departed Northwest Florida Beaches International Airport (KECP), in Panama City. It was a sunny chamber of commerce afternoon. The airplane initially climbed straight out, reaching 1,200 feet, then the pilot declared an emergency to air traffic control (ATC), stating something about a fire, and turned back to the airport. Approximately 1.7 miles short of the runway threshold, it crashed into trees. The pilot and a passenger were killed.

Postaccident examination found an oil pressure line had fractured, leaking oil into the engine compartment and onto the outside of the airplane. About three flight hours earlier, a new avionics system sensor had been installed by a maintenance station. Unfortunately, a rigid oil line was used, not the flexible line specified by the installation manual that included the caveat: “Always mount the sensor to the airframe structure, and connect it with flexible hose to minimize vibration effects. Mounting the sensor directly to the engine may cause sensor failure/leakage and possibly fire.”

The warnings were prescient. The line suffered a high-cycle fatigue failure, starving the engine of oil and causing it to fail. As pilots, we’re not responsible for knowing the mechanical details of every engine modification when preflighting. Often, problems are impossible for us to identify. But sometimes there are clues.

A fresh oil spill marked the ramp parking spot where the Piper had sat for a few hours. In addition, a trail of oil led from that spot to the runway. The break had happened before the accident flight, maybe when the plane flew into KECP that morning. So why didn’t the pilot notice the low engine oil level during the preflight inspection?

Airport security camera video captured the pilot’s arrival on the ramp. He opened the baggage compartment, entered and exited the cockpit several times, walked around the front of the airplane, and stopped in front of each wing. The NTSB noted that during these 11 minutes, “he did not appear to spend any appreciable time inspecting the airplane’s engine or the ground below it.” The airplane then taxied to the runway.

The NTSB determined that contributing to the accident was the “pilot’s failure to perform an adequate preflight inspection of the airplane.”

The third crash was in November 2021 after a Cessna T210R had diverted into the Clarion County Airport (KAXQ) in Shippenville, Pennsylvania, with a reported oil pressure issue.

One airport witness, a helicopter mechanic, said there was oil “all over the airplane, wings, and tail.” The airplane’s pilot and the pilot-rated mechanic passenger said they thought the reason for losing oil pressure was because the dipstick wasn’t seated properly. They got some rags and cleaned up the exterior of the Cessna. They purchased 6 quarts of oil and put it all into the engine. The T210R has a total oil capacity of 12 quarts, with 10 usable. With no other inspection of the engine, they started up and left without doing an engine run-up. Another mechanic told the NTSB that the engine was making “abnormal cracking and popping noises. The airplane was still making the noises when they took off.”

The engine ran for about 15 minutes before quitting. Gliding down from 4,500 feet, the pilot accepted ATC vectors to a nearby airport but didn’t make it. The airplane impacted trees and steep terrain. Both occupants died in the crash. 

Accident investigators found the oil filler cap was securely installed. But forensic examination of the crankshaft revealed the main journal bearings had “evidence of polishing and metal-to-metal contact.” On the flight before, running the engine with very low oil quantity and oil pressure had inflicted significant internal damage—more damage than just adding 6 quarts of oil on the ground could fix.

The NTSB determined the accident’s probable cause to be catastrophic engine failure. But the sudden engine failure wasn’t entirely unexpected. It stated the “pilots’ decision to depart…without further examining the engine for signs of damage or conducting an engine run-up contributed to the accident.”

I’ve felt the beguiling power of “get-home-itis,” that psychological pull to just keep going. However, in these three accidents, the blind faith placed on one engine seems nearly delusional. Despite all the warning signs, no one was ready to handle an engine failure. Flying is magical. But it’s no place for magical thinking.

This story originally appeared in the March 2024 issue of Plane & Pilot magazine.