NTSB Factual Report

On June 4, 2010, about 1000 mountain daylight time, a Piper PA-28-140 airplane, N3922K, sustained substantial damage following a partial loss of engine power and subsequent forced landing near the Richfield Municipal Airport (RIF), Richfield, Utah. The private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed at the time of the accident, and a flight plan was not filed. The local flight, which was being operated in accordance with 14 Code of Federal Regulations (CFR) Part 91, had just departed RIF when the accident occurred.

According to the Pilot/Operator Aircraft Accident/Incident Report (NTSB Form 6120.1) submitted to the Safety Board investigator-in-charge (IIC), the pilot reported that prior to taking off the magnetos "checked good" during the engine run up. The pilot stated that after taking off and "gaining altitude nicely," the engine began to "lose engine rpms" but [was] still running smoothly, not missing and not backfiring. The pilot reported that he pushed the mixture in all the way, but "it did not help the engine rpms or power." The pilot stated that about this time the engine rpms were down to about 1,700 and he was losing altitude, which prompted him to land in a field. During the forced landing the airplane impacted a berm, which resulted in substantial damage to the left wing. The airplane subsequently slid between 60 feet to 75 feet before coming to rest in an upright position.

A Federal Aviation Administration (FAA) Aviation Safety Inspector, with the assistance of a local airframe and powerplant mechanic, conducted a post accident examination of the airplane. The inspector reported that there was fuel from both wing tanks to the carburetor and that all of the engine controls exhibited control continuity and were properly rigged. Valve train continutiy was confirmed on all cylinders. The inspector further reported that a cylinder compression check revealed the following: #1 cylinder – 0/80; #2 cylinder – 66/80; #3 cylinder 75/80 and #4 cylinder 40/80. The inspector stated that the propeller "turned smoothly," and that one of the bottom spark plugs was oil fouled. The inspector also noted that the engine had been sitting in a nose low attitude for nearly two weeks before the aircraft was recovered. The inspector reported that the timing on the magnetos was correct and that all of the [spark] plugs were firing. An engine run was not possible due to the condition of the engine. The inspector stated, "It appears the low compression on the cylinders may been the cause of the lack of power during takeoff. Because the two worst compressions were on cylinders on opposite sides of the engine, it may have run fairly smoothly but at a reduced power output."

In an interview with the local FAA certified airframe and powerplant mechanic located on the airport, a second FAA inspector reported that the mechanic revealed to him that the pilot asked him to check the airplane out "…because it had sat for a couple of weeks and [it] might be having some problems." The mechanic stated that he advised the pilot to "fly it around the patch and then bring it back" and he would do a compression check. After being advised by the inspector that the airplane was out of annual inspection, the mechanic stated that if he had known that he would have never recommended that the pilot fly it. The inspector stated, "I think a combination of low compression on two of the cylinders and a high density altitude when he was taking off contributed to the airplane not having enough power to achieve a stable rate of climb." The inspector added "…his first report to us was that he said his RPM was approximately 1,800 RPM. Then he changed that when we questioned him about it to approximately 2,200 RPM. His first report might have been correct."

A review of the airplane's maintenance records revealed that the airplane's most recent annual inspection had been conducted on May 3, 2009, at a total time of 3,569 hours on the airframe and engine. The engine had accumulated 220.3 hours since its most recent major overhaul.

At 1004, the RIF Automated Surface Observing System (ASOS), reported wind west-northwest at 2 knots, temperature 83 degrees Fahrenheit (F), dew point 39 degrees F, and an altimeter setting of 28.50 inches of Mercury. Using the reported weather conditions and airport elevation, the density altitude was calculated by the IIC to be about 9,723 feet.

A review of the FAA Carburetor Icing Probability Chart revealed "Icing – Glide and Cruise Power" for a temperature of 80 degrees Fahrenheit and a dew point of 40 degrees Fahrenheit.

NTSB Probable Cause

The pilot’s decision to operate the unairworthy airplane with suspected performance deficiencies in a high density altitude and the subsequent partial loss of engine power due to low compression.