History of Flight
On November 17, 2016, at 1740 eastern standard time, an experimental, amateur-built Curtiss JN4D, registration N1662, collided with terrain shortly after takeoff from Peach State Airport (GA2) in Williamson, Georgia. The airline transport pilot and a pilot-rated passenger were on board. The airplane was destroyed by impact forces and fire. The flight was conducted under 14 CFR Part 91, and no flight plan was filed. Dusk visual meteorological conditions prevailed. The flight was local and personal, originating at the time of the accident.
According to a witness, the airplane departed runway 31 and appeared to enter a normal climb with the engine sounding as usual. When the airplane passed the runway end markers at an altitude of about 110–120 ft, the witness heard a loud backfire followed by two smaller pops. The airplane hesitated momentarily, then fell silent. The witness observed a left turn; after about 90° of turn, a flame appeared from the forward left side of the fuselage, quickly escalating into a large fire that streamed over the top and left side of the fuselage, extending about half the airplane's length. The fire persisted as the airplane disappeared behind trees and crashed.
Another witness, who had flown the airplane immediately before the accident flight, reported an uneventful flight with normal engine performance and no fuel smell. After landing, he exited and the other pilot climbed into the front cockpit and strapped in. He observed the takeoff, then turned away and heard someone shout "fire." When he looked back, the forward fuselage was engulfed in flames and the engine had stopped. The airplane turned south, the fire spread to the wings, and it descended rapidly into trees.
Personnel Information
The pilot in the aft cockpit held an airline transport pilot certificate with ratings for single- and multiengine airplanes and glider, plus flight instructor and mechanic certificates. He reported 25,200 hours of flight experience on his most recent FAA second-class medical certificate dated June 29, 2016.
The pilot-rated passenger in the front cockpit held an airline transport pilot certificate with ratings for single- and multiengine land and sea, plus flight and ground instructor certificates. He reported 13,862 hours on his most recent FAA second-class medical certificate dated May 12, 2016.
Aircraft Information
The single-engine, bi-wing, fabric-covered airplane had tandem open cockpits, two main wheels, and a tail skid. It was powered by a Hispano-Suiza E-2, 8-cylinder, water-cooled, reciprocating engine rated at 200 horsepower, driving a St. Croix wood laminate fixed-pitch propeller. A total restoration of the airframe and engine was completed in 2013 using mostly new materials, but with some vintage parts including the radiator, engine, and fuel tank. A condition inspection on June 20, 2016, recorded a total time of 58.6 hours, with about 10.5 hours accrued since then.
Meteorological Information
Weather at Griffin-Spalding County Airport (6A2), about 6 miles northeast, at 1815 reported calm wind, visibility 10 statute miles, clear sky, temperature 17°C, dew point 9°C, and altimeter setting 30.12 inches of mercury.
Wreckage and Impact Information
The accident site was about 1,060 ft southwest of the departure end of runway 31. The airplane came to rest upright in a grass field at the edge of a wooded area. No lateral wreckage path or crater was evident. Fire consumed the entire airframe except the aft fuselage and empennage. Flight control cable continuity was established from the ailerons, elevator, and rudder to the dual cockpit controls. A coating of residue consistent with engine oil was found on the lower surfaces of the horizontal stabilizer and elevator.
All components were accounted for except a 45-inch-long section of one propeller blade, later found about 380 ft southwest of the runway end and 670 ft from the main wreckage.
The engine suffered fire and heat damage. It was rigidly mounted to wooden bearers with no vibration isolators. Magnetos, carburetor, oil pump, and fuel pump showed no anomalies but could not be functionally tested due to damage. Spark plugs exhibited normal wear. Engine continuity was confirmed, compression and suction were present on all cylinders, and valve action was correct. The oil screen was clean. The copper line from the engine to the oil pressure gauge was separated and burned.
The steel fuel tank (original Curtiss component) was ruptured by impact with the engine bearers. No internal contamination was found; the tank was dry. The fuel shutoff valve, controlled from the aft cockpit, was separated and found loose. The aluminum plumbing between the valve and gascolator was partially consumed by fire. A fuel wobble pump was fire-damaged and loose. The gascolator was dry and clean.
The aft cockpit had a four-point harness, the front a lap belt; all buckles were attached but webbing consumed by fire. No emergency locator transmitter was installed.
Medical and Pathological Information
Autopsies were performed by the Georgia Bureau of Investigation. The pilot's cause of death was exposure to aircraft fire with extensive thermal injuries. Toxicology tests were negative for ethanol and carbon monoxide; alfuzosin and rosuvastatin were detected but are not generally considered impairing.
The pilot-rated passenger's cause of death was blunt impact injuries of the head and torso. Toxicology tests were negative for ethanol and carbon monoxide; amlodipine was detected but is not generally considered impairing.
Tests and Research
The propeller pieces were examined by the NTSB Materials Laboratory. The propeller was a two-bladed, fixed-pitch, wood laminate with formed copper sheets and lead/tin filler on the tips and leading edges. The separated blade (blade A) showed a transverse fracture in the leading edge strip, with underlying wood fractured spanwise. Fracture features included transgranular fractures with curving crack arrest lines consistent with fatigue, originating at a filled depression associated with a rivet. Fatigue striations counted in selected areas ranged from 20,250 to 79,320 per inch. Aluminum oxide deposits were found on fracture surfaces.
According to the airplane's primary caretaker and restorer, a crack was observed in the propeller's leading edge strip near the tip in July 2015. A photograph of the crack before repair was taken. The propeller was sent to St. Croix Propeller, where it was repaired. An October 2015 email from the manufacturer noted a "fatigue cracked rivet exactly halfway down inside the wood." The repair involved doubling up the rivets in the area. The propeller was reinstalled in November 2015.
Comparison of the pre-repair photograph with postaccident fractures showed that the fatigue fracture intersected both the original rivet and the adjacent repair rivet closer to the hub. The underlying wood fracture intersected an original rivet hole and the repair rivet closer to the blade tip.
An online blog detailing the airplane's restoration included entries about the propeller and engine. On May 6, 2013, the builder noted that the propeller was designed for the Hispano-Suiza E engine, and when fitted to the E2 engine, it was about 1/2 inch too thin for the hub length. A new hub was acquired. According to type certificate data, the Wright Hispano E engine was rated 180 hp at 1,800 rpm; the builder noted the E2 produced 200 hp.
A blog entry from April 23, 2014, noted that the engine had been running rough with hesitation and backfires when accelerating, corrected by adjusting idle speed from 350 to 480 rpm. A November 9, 2014, entry mentioned an oil leak leading to an engine overhaul. The propeller was polished on at least one occasion (April 23, 2014, entry), but the polish type was unspecified (metal polishes can contain aluminum or silicon oxides). FAA Advisory Circular 20-37E notes that propellers are highly stressed components.