NTSB Factual Report

On July 25, 2015, about 1630 Pacific daylight time, a Stinson 108-3 airplane, N6152M, was substantially damaged during a forced landing near North Las Vegas Airport (VGT), Las Vegas, Nevada. The airplane was registered to Arizona Land Holding LLC, and was operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The private pilot, sole occupant of the airplane, was not injured. The airplane sustained substantial damage to the rudder. Visual meteorological conditions prevailed and no flight plan was filed for the personal, cross country flight, which was destined for Triangle Airpark (AZ50), White Hills, Arizona, and was originating at the time of the accident.

According to the pilot, he did not observe any anomalies with the airplane or engine during his preflight inspection and engine runup. Prior to departure, the tower controller issued instructions to the pilot to depart runway 12R and to make "left traffic." The pilot departed the runway and maintained about 80 miles per hour (mph) during the climbout. He started a left turn near the departure end of the runway at about 800 feet above ground level but the airplane "quit climbing" and started to shake. He lowered the nose to gain airspeed and some power returned. The pilot initially continued his turn to attempt a landing on runway 30R, but when the airplane began to "sink", he decided to land straight ahead on a paved parking area. He used a slip maneuver to descend quickly and touched down about "halfway down" the tarmac. The pilot deployed flaps and maneuvered to avoid obstacles, but was unable to slow the airplane down before it departed the tarmac, struck a fence, and nosed over. The pilot reported no preimpact mechanical malfunctions or anomalies related to the airframe and stated that he could have stopped the airplane with an additional "50 feet" of distance.

Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed substantial damage to the rudder.

The pilot/owner held a private pilot certificate with a rating for airplane single-engine land that was issued on July 16, 2014. His most recent FAA third-class medical certificate was issued on September 30, 2010 without limitations. According to the pilot's logbook, he accumulated 98 hours of total flight experience, 48 of which were in the accident airplane make and model. The pilot had not flown in the three calendar months that preceded the accident.

According to FAA airworthiness records, the airplane was manufactured in 1948, and registered to the pilot/owner on July 16, 2014, under Arizona Land Holdings, LLC. Review of the airplane's maintenance logbooks revealed that its most recent annual inspection was completed on June 12, 2014, at a recorded tachometer time of "2,835.8 hours." The pilot/owner remarked that the logbook tachometer times had been erroneously recorded in the logbooks by the mechanic and should have been documented as "283.58." During a follow-up telephone conversation, the pilot/owner stated that the tachometer had been replaced about 20 years ago, which was reflected in the tachometer time in the airframe logbook; however, there was no record of a tachometer installation during that time.

At the time of the accident, the airplane had accumulated approximately 44.6 flight hours since its most recent inspection. Based on the airplane's maintenance records, it had accumulated about 2,868 flight hours of total time in service.

The airplane was equipped with a Franklin 6A4-165-B3, 165 horsepower engine. The engine's most recent annual inspection, which was also completed on June 12, 2014, included the following cylinder compression record: #1 - 74 psi, #2 – 73 psi, #3 – 71 psi, #4 – 73 psi, #5 – 71 psi, and #6 – 71 psi. The last recorded engine overhaul could not be determined as the corresponding engine logbook was not provided.

An air traffic controller reported the winds as 180 degrees at 5 knots gusting to 14 knots a few minutes before the airplane departed on the accident flight.

According to the National Oceanic and Atmospheric Administration, the density altitude at the time of the accident was 5,538 feet.

The airplane came to rest inverted on a southerly heading beyond an airport perimeter fence. The landing area was a parking tarmac located on the east side of the airport and measured about 1,000 feet long by 600 feet wide. An airport perimeter fence bordered the north end of the landing site. The airplane's landing path was composed of several obstacles including two concrete drums and two light posts, which were located approximately 50 feet from the accident site. Further, several airplanes were parked along the airport perimeter fence and one was located in the accident airplane's landing path about 60 feet from where the airplane came to rest.

An airport employee stated that he observed "a lot of fuel" drain from the airplane during the recovery process.

An examination of the engine was completed by a certified airframe and powerplant mechanic under the supervision of NTSB and FAA investigators on August 26, 2015, at an aircraft storage facility in Las Vegas, Nevada.

Initial examination of the engine revealed that the right side engine mount was fractured. The crankshaft was rotated by hand and valve-train continuity and thumb compression were observed on all cylinders. The propeller remained attached to the engine. One blade exhibited leading edge damage and the propeller faceplate displayed bending.

The cylinders were examined with a borescope. Each cylinder exhibited normal operating signatures with the exception of the number 1 cylinder, which contained a large volume of carbon deposits. The number 1 cylinder also recorded a compression value of 20/80 psi when tested. A subsequent pressure test revealed a leak in the exhaust valve that directed airflow through the exhaust pipe. A follow-up borescope inspection revealed degradation on one side of the exhaust valve seal, which prevented the valve from seating properly.

Both the top and bottom engine spark plugs were removed and examined. The top spark plugs exhibited wear consistent with normal operation. Each spark plug gap measured about 0.032 inches; however, according to the engine manual the prescribed gap tolerance range for the spark plugs was 0.014 – 0.018 inches.

Both magnetos remained attached to the engine; testing revealed that the number 6 cylinder top magneto primary lead did not produce spark during propeller rotation or when tested with a high tension lead tester.

NTSB Probable Cause

The partial loss of engine power due to a degraded cylinder exhaust valve seal, which resulted in low cylinder compression.