NTSB Factual Report

On July 9, 2015, about 1050 eastern daylight time, N524SL, an Ayres Corporation S2R T34, was substantially damaged during a forced landing immediately after takeoff from a private airstrip near Climax, Georgia. The commercial pilot was not injured. The airplane was registered to and operated by a private company. Visual meteorological conditions prevailed and no flight plan was filed for the aerial application flight that was being conducted under the provisions of 14 Code of Federal Regulations Part 137.

The pilot stated that the accident flight was his third flight of the day and the two previous flights were uneventful. The wind was calm and he taxied to the west end of the 1,900 foot-long grass runway for a departure to the east. As the pilot prepared to takeoff, he brought the power up and checked the engine gauges. He said everything was normal and he proceeded to depart. When the airplane became airborne it "quickly settled to the ground as if the prop quit pulling." The pilot said there were no unusual engine noises or vibrations and the engine stayed running, but the propeller stopped producing thrust "like it was wind milling." The airplane struck a wire fence and came to rest in a cornfield at the end of the runway. The pilot said that his hand was on the power-lever the entire flight and he never moved the propeller control, which was full forward. He said the engine continued to run at takeoff power for about 30-to 45 seconds before he was able to shut it down.

An initial postaccident examination of the airplane and engine by a Federal Aviation Administration (FAA) inspector and Pratt &Whitney Field Service Representative revealed the left and right wing spars were substantially damaged. The propeller, firewall, landing gear, and lower fuselage were also damaged. The engine's power section was seized and would not rotate, but the gas generator compressor would turn through the AGB starter pad. The main engine oil filter was removed and no debris was noted. The power section chip detector and strainer were removed and no debris was noted. The PY and P3 sense lines were visually inspected and found to be in good condition. Positive torque was applied to all "B" nuts for the PY and P3 sense lines and all nuts were secure. The left exhaust stack was removed for power turbine blade inspection and found to be intact and in good condition. The power section rotor could not rotate. The airframe fuel filter was removed and the bowl was full of fuel and absent of debris and water.

The turbo-prop engine (Model PT6A-34, S/N 56452) was sent to Pratt & Whitney Canada where an examination and engine test-run were conducted under the supervision of the Canadian Transportation Safety Board (TSB). The engine power section displayed contact signatures consistent with the engine being near a high power setting at the time of impact. The engine was test-run using a slave power section, the original propeller governor assembly and a slave P3 filter and housing. The first attempt to start the engine resulted in a hung start. All pneumatic lines were checked and the P3 filter was checked with no anomalies found. The second start attempt again resulted in a hung start. Installation of a slave fuel control unit resulted in a normal start and test-run of the engine. Bench testing of the fuel control showed normal operation, and disassembly and detail inspection showed all the internal components to be in normal condition. The cause of the hung starts could not be determined.

The engine's last 100-hour inspection was conducted on June 18, 2015, and it had accrued 27,561 hours since new and 6,119.9 hours since overhaul. No pre-mishap mechanical discrepancies were noted with the engine or its components that would have precluded normal engine operation prior to impact.

The three-blade propeller (Model HC-B3TN-3D, S/N BUA32424) was examined on August 6, 2015 at the operator's facility, and additional examination of the propeller's cylinder assembly was conducted at Hartzell Propeller Inc. on October 5, 2015, under the supervision of the FAA. The propeller assembly remained attached to the engine and all three blades were uniformly twisted and bent aft toward low pitch. The cylinder, piston, feathering spring assembly and guide collar had separated from the hub unit but remained attached to the propeller assembly by the link arms and beta rods. The propeller assembly was removed and the interior of the piston was examined. An impact mark was observed about 2-inches from the bottom edge of the piston near the No. 2 blade. According to Hartzell, this equated to a blade angle about 12 degrees (toward flight idle) and that the piston was extended toward low pitch during the impact sequence. The piston also exhibited impact marks from the propeller's counterweight arms/slugs. The guide collar was fractured and marks were observed near each of the propeller blade's respective link arms. All three of the link arms were bent but remained secure to their respective attachment point. The No. 2 link arm was fractured. The cylinder, which had separated during the impact sequence, exhibited damage to the attachment threads. To determine if the cylinder may have separated due to a material anomaly with the thread, it was sent to Hartzell for additional testing. The testing revealed no material anomalies.

The propeller's last 100-hour inspection was conducted on June 18, 2015, and it had accrued 591.1 hours since overhaul.

The pilot held a commercial pilot certificate with a rating for airplane single-engine land. He reported a total of 6,986.8 hours; of which, 2,000 hours were in the same make/model as the accident airplane. His last FAA second class medical certificate was issued on April 22, 2015.

Weather reported at Camilla-Mitchell County Airport, Camilla, Georgia, about 12 miles northeast of the accident site, at 1000, included variable wind from 4 knots gusting to 6 knots, visibility 10 miles, clear skies and temperature of 90 degrees F.

NTSB Probable Cause

A loss of thrust on takeoff for reasons that could not be determined, because postaccident examination of the engine and propeller assembly did not reveal any mechanical anomalies that would have precluded normal operation.