Accident Details
On June 4, 2010, at about 1000 mountain daylight time, a Piper PA-28-140 airplane, registration N3922K, sustained substantial damage following a partial loss of engine power and subsequent forced landing near the Richfield Municipal Airport (RIF) in Richfield, Utah. The private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The local flight, conducted under 14 CFR Part 91, had just departed RIF when the accident occurred.
According to the pilot's report submitted to the NTSB, the magnetos "checked good" during the pre-takeoff engine run-up. After takeoff and while gaining altitude, the engine began to lose RPMs but ran smoothly without missing or backfiring. The pilot pushed the mixture control fully in, but it did not restore RPMs or power. As engine RPM dropped to about 1,700 and altitude was lost, the pilot elected to land in a field. During the forced landing, the airplane struck a berm, causing substantial damage to the left wing. The airplane then slid 60 to 75 feet before coming to rest upright.
Post-Accident Examination
A Federal Aviation Administration (FAA) Aviation Safety Inspector, assisted by a local airframe and powerplant mechanic, examined the airplane. Fuel was present from both wing tanks to the carburetor, and all engine controls exhibited continuity and correct rigging. Valve train continuity was confirmed on all cylinders. Cylinder compression checks showed: #1 cylinder – 0/80; #2 cylinder – 66/80; #3 cylinder – 75/80; #4 cylinder – 40/80. The propeller turned smoothly, and one bottom spark plug was oil-fouled. The engine had been in a nose-low attitude for nearly two weeks before recovery. Magnetos timing was correct, and all spark plugs fired. An engine run was not possible due to its condition. The inspector noted that low compression on cylinders #1 and #4, which are on opposite sides of the engine, might explain the smooth but reduced power output.
A second FAA inspector learned from the local mechanic that the pilot had asked him to check the airplane because it had sat for a couple of weeks and might have issues. The mechanic advised the pilot to fly it locally and return for a compression check. Later, the inspector determined the airplane was out of its annual inspection; the mechanic stated he would not have recommended the flight had he known. The second inspector opined that a combination of low compression on two cylinders and high density altitude contributed to insufficient power for a stable climb, and noted the pilot initially reported RPM as approximately 1,800 before changing it to 2,200.
Maintenance History
Review of maintenance records showed the most recent annual inspection was conducted on May 3, 2009, at a total airframe and engine time of 3,569 hours. The engine had 220.3 hours since its last major overhaul.
Weather and Density Altitude
At 1004, the RIF ASOS reported wind west-northwest at 2 knots, temperature 83°F, dew point 39°F, and altimeter setting 28.50 inHg. The density altitude was calculated to be about 9,723 feet. The FAA Carburetor Icing Probability Chart indicated "Icing – Glide and Cruise Power" for a temperature of 80°F and dew point of 40°F.