N950TBStol UC-1 · 1980

**This report was modified on December 2, 2015. Please see the docket for this accident to view the original report.**

On October 25, 2014, about 1500 central daylight time, a Stol UC-1 airplane, N950TB, impacted rough terrain during a forced landing following a loss of engine power near Jacksonville, Texas. The commercial pilot and one passenger sustained minor injuries and the two other passengers were uninjured. The airplane sustained substantial wing damage during the forced landing. The airplane was registered to and operated by Yellow Peril Aero LLC under the provisions of 14 Code of Federal Regulations Part 91 as personal flight. Day visual meteorological conditions prevailed for the flight, which did not operate on a flight plan. The flight originated about 1430 from Flying M Ranch Airport (7TA7), near Reklaw, Texas, and was destined for Covey Trails Airport (X09), near Fulshear, Texas.

The pilot reported that he flew the airplane cross country to 7TA7 and a landed there about 1030. During the return flight, the pilot intended to fly the airplane in cruise flight at 4,500 feet above mean sea level (msl). During the climb to about 2,200 feet msl, the right engine "quit." The pilot performed the engine out procedures checklist tasks and the right engine power was restored for about two minutes. The right engine subsequently lost power a second time. The pilot checked the engine's right magneto again and he reported that the engine did not restart. He feathered and secured the right engine. The pilot diverted towards the nearest airport, which was about 11 miles away. The pilot said, "The airplane would not maintain altitude, and we were forced to land in a field short of the airport." The terrain in the area was "hilly" with pine trees. During the forced landing, the airplane touched down and "slid" up a terraced field, where its left landing gear separated, its empennage was damaged, and its right wing strut was broken. The airplane continued for about 60 yards when it came to stop.

The 60-year old pilot held a commercial pilot certificate, with airplane single-engine land, multi engine land and sea, and instrument ratings. The pilot's most recent Federal Aviation Administration (FAA) second-class medical certificate was issued on April 16, 2013, with a limitation for corrective lenses and a waiver for color vision. The pilot reported that he had accumulated 2,924 hours of total fight time and 73 hours of total flight time in the same make and model as the accident airplane.

N950TB was a twin-engine amphibian airplane, equipped with tailwheel landing gear, and was manufactured in 1980. According to the airplane's type certificate data sheet, the five-place airplane's fuel system was equipped with an 85-gallon main fuel tank and a 16-gallon auxiliary fuel tank. Both engines were fed fuel from the main tank. The pilot reported that the airplane's last annual inspection was accomplished on March 5, 2014. The airplane accumulated a total time of 1,040 hours at the time of that inspection. The airplane was powered by two Lycoming IO-360-B1D engines mounted on the wings. The left and right engine serial numbers were L-16451-51A and L-16452-51A respectively. The pilot reported that each engine accumulated 1,050 hours of total time and accumulated 10 hours of time since the last inspection.

At 1415, the recorded weather at the Cherokee County Airport, near Jacksonville, Texas, was: Wind 270 degrees at 5 knots; visibility 10 statute miles; sky condition clear; temperature 27 degrees C; dew point 15 degrees C; altimeter 30.15 inches of mercury.

FAA inspectors examined the wreckage and confirmed that the airplane sustained substantial airframe damage. The right engine could not be run on the airframe to verify its systems integrity due to damage of the right wing structure. The airplane's fuel strainers were removed and they contained no debris. The airplane's digital flow unit indicator and JPI engine monitor were removed and shipped to the National Transportation Safety Board (NTSB) Recorder Laboratory for downloading.

An NTSB recorder specialist was able to apply power to the engine monitor, downloaded its data, and produced a spreadsheet and plots of the data. The downloaded engine data plot from the prior flight showed that towards the end of that flight's recorded data, there was a drop in cylinder head temperature and exhaust gas temperature (egt) consistent with a reduction of power on the right engine.

The engine data from the accident flight showed that about 8 minutes into the flight the right engine's egt dropped from about 1,400 degrees F to about 375 degrees F during the next 30 seconds. The data showed that the egt then increased to about 1,400 degrees F for the next 30 seconds before it dropped again to 375 degrees F before decreasing to about 75 degrees F for the duration of the recording. A safety representative at Lycoming was consulted and the cause of the right engine's power interruption could not be determined based on the review of the data.

When powered up, the engine monitor's display showed that 49 gallons of fuel remained and 36 gallons of fuel was used, of which the left engine used 19.3 gallons and the right engine used 16.7 gallons.

An NTSB air safety investigator subsequently examined the recovered wreckage. Shop air was applied to the fuel lines and no debris was present in the lines. A liquid consistent with fuel was present in the right engine's fuel lines leading to its fuel servo. The cap of its flow divider was removed and no liquid was observed there. The right engine's fuel servo was shipped for further examination, during which the right engine's fuel servo was mounted to a test stand and it met flow bench test specifications.