Accident Details
On June 3, 2015, about 1718 central daylight time, a Gulfstream-Schweizer A/C Corp. Gulfstream AM G-164B airplane, registration N8402K, was substantially damaged during an in-flight collision with terrain after takeoff from a private airstrip near Delaplaine, Arkansas. The pilot sustained minor injuries. The airplane was registered to and operated by Wilson Flying Service, Inc. under 14 Code of Federal Regulations Part 137 for agricultural application. Visual meteorological conditions prevailed, and the local flight was not operated on a flight plan.
The gravel runway was approximately 2,300 feet long and oriented northeast-southwest. The departure was to the southwest.
Pilot Account
The pilot reported that the gravel runway was shorter than he normally used and the thicker gravel may have extended his takeoff rolls. He had been flying since about noon, accumulating about 5 hours of flight time before the accident. The airplane was refueled before the preceding 15-minute flight, which was completed without incident. The fertilizer load on the accident flight was approximately the same as on the previous flight.
The pilot noted that the accident takeoff ground roll was longer than for previous takeoffs, which had been about 1,700 feet. After recognizing the extended ground roll, the airplane had already passed his pre-determined takeoff commitment point. The airplane became airborne but did not climb. The tailwheel subsequently impacted a rice levee, causing the airplane to settle into the field. The pilot stated he never lost control. He did not perceive any airframe or engine issues during the takeoff. Engine torque indication was normal at the beginning of the roll, but he did not check it again due to focus on flying.
Aircraft Examination
The airplane came to rest inverted in an open field. The nose and forward fuselage sustained minor damage. The aft fuselage and empennage were deformed and separated from the remainder of the fuselage. The wings were deformed and dislocated, with the upper right wing section separated from the upper center wing section; the separated section was located adjacent to the airplane at the accident site.
A postaccident examination was conducted after recovery. The wings had been removed for recovery. The engine and propeller remained attached. The upper and right side gearbox mounts were bent but attached; the left side mount separated from the airframe. The rear mounting bolt was fractured; separations appeared consistent with overstress failures. Propeller blades remained attached to the hub; all three blades were bent aft, and tips of two blades were separated. At examination, blades appeared in low-pitch position.
Initial engine examination revealed a discontinuity between the propeller and third-stage turbine. Deposits consistent with compressor shroud metal spray were on the aft sides of third-stage turbine blades. The main fuel line was disconnected from the fuel pump inlet; fluid consistent with jet fuel was observed in the line. Engine control continuity was confirmed except for the propeller feather valve, where no linkage was connected or observed. The engine was removed for teardown examination.
Engine and Component Testing
Teardown examination of the Honeywell/AiResearch TPE331-1-151A turboprop engine (serial number P-92108) showed earthen debris throughout compressor, combustion, and turbine sections. Rotational scoring was observed in compressor and turbine sections. One first-stage compressor impeller vane was bent opposite rotation at the leading edge outer diameter, consistent with foreign object damage. The combustion section was unremarkable except for debris. Turbine section stator vanes and rotor blades had suction-side metal spray deposits consistent with operation at impact. The torsion shaft was sheared immediately forward of aft splines; metallurgical examination indicated torsional overload. The shouldered shaft was intact. No evidence of loss of engine oil. The fuel filter element was intact and free of debris.
A fuel sample from the fuel filter assembly was consistent with Jet A aviation fuel but contained small-particle debris of undetermined origin. The amount and size of debris appeared inconsistent with a loss of engine power.
The fuel control unit was tested; standard acceleration schedule fuel flows exceeded specification by about 9% high-side at three start-range points and were out of specification by about 1% low-side at one high-power point. Other acceleration points were within limits. Underspeed and overspeed fuel flows were lean (low) compared to specification; input drive speeds were adjusted by 0.4% (underspeed) and up to 1.6% (overspeed). The main metering valve TT2 and PT2 correction schedules showed high-side deviations at maximum power settings up to 13% and 20%, respectively, but TT2 correction under standard day maximum power was within specification; PT2 correction exceeded specification high-side by about 3.6%. The component manufacturer noted this setting is commonly adjusted by the operator.
The fuel pump flow rates and discharge pressure were within specification when tested at high speed (100% power) and low speed (starting). Flow rate at high speed was 1,720 lbs/hr (minimum required 1,400); at low speed, 148 lbs/hr (minimum 120). Discharge pressure was 1,340 psi (maximum 1,375).
The propeller governor was tested; maximum and minimum speeds exceeded new production component specifications. Maximum speed measured 3,858 rpm (specification 3,754 +/-10); a reduction of 14 degrees in input lever angle (from 139 to 125 degrees) was necessary to obtain specified maximum speed. Minimum speed measured 3,665 rpm (specification 2,815 +/-10); a reduction of 26 degrees (from 88 to 62 degrees) was necessary. Relief valve pressure measured 11 psi below the minimum specification of 445 psi. Pump case pressure remained within limits. The component manufacturer noted that maximum and minimum speed parameters are subject to in-service adjustment by the operator.
Aircraft History
The accident airplane, Gulfstream-Schweizer G-164B serial number 687B, received its airworthiness certificate in April 1982. NTSB records show five prior accidents, the most recent on August 22, 2013, in Walnut Ridge, Arkansas (CEN13LA504). A maintenance record entry dated July 9, 2014, indicated the airplane was disassembled and reassembled using a repaired fuselage; total airframe time then was 12,381.6 hours. The most recent annual inspection was completed on February 2, 2015, at 12,381.6 hours; operator reported total time as 12,489.5 hours.
The engine total time was approximately 11,981.0 hours; most recent annual inspection on February 2, 2015, at 11,873.1 hours; most recent hot section inspection on May 9, 2014, at 11,873.1 hours. Airframe and engine maintenance records showed no history of recurring or unresolved issues.
Environmental Conditions
Prevailing winds were from the northeast at 4 or 5 knots, providing a light tailwind during the takeoff. Elevated air temperatures increased density altitude to about 1,680 feet compared to runway elevation of approximately 265 feet.