History of Flight
On February 18, 2014, about 1638 central standard time, a Hawker Sea Fury ISS-25 single-engine, single-seat airplane, N13HP, was destroyed after impacting terrain during climb at Stephens County Airport (BKD), Breckenridge, Texas. The pilot was fatally injured. The airplane was registered to Breckenridge Aviation Museum and was in the process of changing registration to J R Consulting NV, LLC. It was operated by a private individual. Visual meteorological conditions prevailed, and no flight plan was filed for the 14 CFR Part 91 instructional flight.
The accident pilot had completed one previous flight earlier that morning, lasting about 20 minutes, and was making only his second takeoff in a Hawker Sea Fury. Several witnesses near the runway at mid-field reported hearing abnormal engine and propeller sounds and observed a slower-than-normal vertical climb speed. One witness, with pilot experience in the Hawker Sea Fury, reported hearing the engine "screaming" and recognized a propeller overspeed.
The flight instructor, flying a second single-seat Hawker Sea Fury in formation trail behind the accident airplane, reported maximum takeoff power for the type was about 2,900 rpm at about 50 inches of manifold pressure. After his takeoff, he joined on the right side of the accident airplane and heard the pilot transmit that his "rpm was at 3,500." No further transmissions were heard. Both airplanes climbed to about 1,000 feet agl. About one mile from the runway, the accident airplane began a slow left turn. The instructor transmitted instructions to lower the nose and reduce throttle.
The accident airplane almost completed a left turn to downwind, descended to about 500 feet agl, slowed, and was nose-up. The instructor saw the airplane stall and suddenly roll right, then enter a vertical nose-down dive and impact terrain. An immediate explosion and postimpact fire followed.
Personnel Information
The pilot, age 38, held a private pilot certificate issued December 4, 2012, with a rating in airplane single engine land, and a third-class medical certificate issued August 6, 2012. His personal logbooks were unavailable. Based on partial records and statements, his total flight experience on February 1, 2014, was estimated at 527 hours, including about 100 hours in a P-51 Mustang and no previous time in a Hawker Sea Fury.
Aircraft Information
The low-wing, retractable conventional landing gear, single-seat airplane, serial number 37536, was built in 1956 by Hawker Aircraft Limited. Originally powered by a 2,480 hp Bristol Centaurus 18-cylinder radial engine, it had a maximum takeoff weight of 14,650 pounds and a listed maximum speed of 400 knots. After import to the United States in 1976, it was extensively modified and issued an FAA experimental exhibition airworthiness certificate in 1989.
At the time of the accident, it was powered by a 2,800 hp Wright R-3350-26WD "Duplex Cyclone" 18-cylinder engine with a displacement of 3,350 cubic inches. The geared nose case had an output gear ratio of 0.4375:1, providing propeller rpm of 1,225 at engine rpm 2,800. The engine drove a 13-foot 6-inch diameter Aero Products A642–G805 four-blade propeller with a blade angle range of 40 degrees. The hollow steel propeller blades were controlled by a hydraulic propeller regulator unit mounted aft of the propeller hub.
Aircraft maintenance logbooks could not be located and were likely consumed in the postimpact fire. An annual condition inspection was completed on February 7, 2014, with estimated total time of 2,102.2 hours and engine/propeller time of 902.2 hours.
Meteorological Information
At 1630, the Automated Surface Observation System at BKD reported wind from 260 degrees at 10 knots gusting to 18 knots, visibility 7 miles, clear skies, temperature 30°C, dew point 7°C, and altimeter 29.83 inches of mercury. At accident time, sun altitude was about 20 degrees above horizon with azimuth 241 degrees; apparent sunset at 1824.
Wreckage and Impact Information
The wreckage was located on dirt and rocky terrain at an estimated elevation of 1,250 feet msl about 1 mile southeast of BKD. The airplane impacted in a nearly vertical nose-down attitude. A postimpact fire thermally damaged vegetation within a diameter over 100 feet. The initial impact crater was about 1 foot deep and 5 feet in diameter. The front section of the engine separated and was found upright on the southeast crater edge. The propeller hub remained attached to the engine shaft; two blades remained attached, two were separated. Blades showed leading edge impact damage and chordwise smearing. Broken tree limbs overhead had corresponding damage.
The engine oil filter showed no preaccident contamination. The outer portion of the right wing separated and was located 20 feet north-northwest from the crater. The separated wing section, including spars, right flap, both flap actuators, main landing gear, and left aileron, was found 45 feet east. Flap actuators were in the up position; main landing gear were retracted. Fuel caps were intact and latched.
Magnesium structure in the separated wing was mostly consumed by fire, leaving fine white ash. The empennage was separated and located 70 feet east-northeast, oriented 210 degrees, with horizontal stabilizer, elevator, vertical stabilizer, and rudder attached. Flight control continuity was confirmed from elevator and rudder to separations at the empennage front. The cockpit fuselage upper section was mostly consumed. The instrument panel separated, and portions were scattered. The canopy frame and rail were separated. The cockpit seat frame separated.
The rear engine section, including supercharger and accessory gearbox, was 95 feet east of the crater. All portions of the airplane were accounted for. Impact and thermal damage prevented examination of ignition or induction systems and complete flight control continuity assessment. No evidence of preimpact mechanical malfunctions or failures was found.
Additional Information
The Hawker Sea Fury Emergency Checklist for "Runaway Propeller" (page 36) states: Reduced throttle (2,900 RPM), propeller to DECREASE, airspeed 140 knots, raise nose to lose speed, then level flight. If rpm cannot be kept within limits, expect engine to quit or seize.
The Department of Energy Handbook notes magnesium ignition temperature near 1,202°F, with some alloys igniting as low as 800°F; once ignited, magnesium burns intensely and is difficult to extinguish.
Tests and Research
The propeller regulator and associated parts were examined at the NTSB Materials Laboratory. The broken control input connecting rod showed fracture from bending overstress. The drive gear had deformation consistent with twisting and bending; gear teeth had smear marks on aft faces. The hydraulic gear pump was still attached to the fractured propeller housing; fracture surfaces were consistent with overstress. The pump assembly had darkening and soot from fire. The pump was disassembled; internal surfaces had dried hydraulic fluid and ferrous corrosion product confined to gear recess corners, consistent with postaccident water pooling. No excessive wear or smearing on interior surfaces; hydraulic fluid channels were clear. Gear teeth had rotational wear marks typical of service. The laboratory examination revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation.
Probable Cause
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