NTSB Factual Report

On June 23, 2011, about 2021 Pacific daylight time, a Cessna 172S, N222MF, sustained substantial damage during a forced landing near the Palo Alto Airport (PAO), Palo Alto, California. The airplane was registered to Aviolease LLC, Wilmington, Delaware, and operated by Advanced Flyers, Palo Alto, under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot and his two passengers were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the positioning flight. The cross-country flight originated from Concord, California, at 2000 with an intended destination of PAO.

In a written statement, the pilot reported that following an uneventful return flight to PAO, he entered the airport traffic pattern midfield for runway 31. The pilot said that the air traffic control tower (ATCT) controller advised him to follow another aircraft ahead of his position. Upon turning base to final for runway 31, the pilot applied 10 degrees of flaps, and as the airplane descended through about 700 feet above ground level (agl), he determined that the airplane was slightly low. The pilot partially advanced the throttle forward and noted that the airplane's descent rate continued. After the pilot applied full throttle and received no response from the engine, he realized that the engine had lost power. The pilot immediately began troubleshooting the loss of engine power and continued toward the runway, but due to the low sun on the horizon he could not completely see the runway; his attempt to restart the engine was unsuccessful. The pilot initiated a forced landing to an open marsh area south of PAO. During the landing roll, the nose wheel dug into terrain and the airplane nosed over.

Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the airplane came to rest within a muddy marsh field about one-half mile south of PAO. The fuselage was bent and buckled aft of the baggage compartment, and the vertical stabilizer and rudder were structurally damaged. The smell of fuel was present at the accident site. The wreckage was recovered approximately three weeks after the accident to a secure location for further examination. According to the FAA inspector, the area where the airplane came to rest was within the tidal area for the marsh land, which resulted in the airplane being partially submerged every few days.

Examination of the recovered engine revealed that it remained attached to the airframe via all of its mounts. All engine accessories remained attached to their respective mounts. The top spark plugs were removed from the engine and the engine crankshaft was rotated by hand. Thumb compression was obtained on all four cylinders. The spark plugs were reinstalled along with the ignition harness leads. An external fuel source was attached to the left wing root fuel inlet line in addition to an external power attached to the battery leads. Due to impact damage to the propeller, a replacement propeller was installed to facilitate the engine run.

The engine was started and ran throughout various power settings for about five minutes before being shut down utilizing the mixture control with no anomalies noted. During the engine run, a magneto check was performed and an approximate 100 rpm drop was noted for both the left and right magnetos. In addition, the throttle was advanced momentarily full forward and a peak rpm of about 2600 rpm was observed on the engine tachometer.

The reason for the loss of engine power was undetermined.

Review of the aircraft maintenance records revealed that the engine was overhauled on March 2, 2007, at an engine and airframe total time of 2,056 hours. The most recent annual inspection was completed on April 1, 2011, at a tachometer time of 1,565 hours. At the time of the accident, the engine had accumulated 1,639.9 hours since major overhaul.

NTSB Probable Cause

A total loss of engine power for undetermined reasons during the landing approach over unsuitable terrain.