History of Flight
On April 22, 2010, at 0917 mountain standard time, a Grumman-Schweizer G-164B, registration N48455, collided with a gate during an attempted takeoff near Buckeye, Arizona. Crawford Aviation Services was operating the airplane under 14 CFR Part 137 as an aerial application flight. The certificated airline transport pilot sustained minor injuries; the airplane sustained substantial damage to the fuselage and both wings. The flight departed from a private dirt airstrip. Visual meteorological conditions prevailed, and no flight plan was filed.
The pilot reported that the 335-gallon hopper was loaded with 250 gallons of liquid herbicide mixture, and the fuel tanks contained about 36 gallons of fuel, approximately half capacity. Prior to takeoff, the pilot performed an uneventful preflight inspection and engine run-up. During the takeoff roll to the south in quartering headwind conditions, about two-thirds of the way down the 2,500-foot runway, the pilot heard the engine pitch change. Engine speed was about 2,080 rpm, lower than the expected 2,250 rpm. The propeller control was full forward, and manifold pressure was just below 36 inches. Increasing throttle did not increase engine speed, which dropped to 2,040 rpm. The airplane had not yet become airborne, and airspeed stagnated. The pilot attempted to force the airplane airborne with control inputs, and it struck a fence at the end of the runway, then nosed over. The pilot did not release the herbicide load during the ground roll due to concern about low airspeed and potential uncontrolled pitch-up.
Aircraft Information
The fixed-gear, tailwheel-equipped biplane, serial number 28B, was manufactured in 1976. At the last annual inspection on September 18, 2009, the airplane had accrued 15,268.06 total flight hours, with a tachometer time of 1,395.45 hours. The tachometer at the accident site indicated 1,452.09 hours.
The airplane was powered by a Pratt and Whitney R-1340-AN-1, nine-cylinder air-cooled radial engine, serial number 11075, equipped with a Hamilton Standard three-bladed constant speed propeller. The engine was overhauled in September 2008 by Covington Aircraft. At that time, estimated engine total time was 8,750 hours; since overhaul, the engine had accrued 195.22 hours according to the airframe tachometer. The last maintenance was an oil and filter change on February 22, 2010, 37.92 flight hours before the accident.
Examination
An FAA inspector examined the engine and airframe at the accident site. The airplane came to rest inverted about 200 feet beyond the departure end of the runway. The vertical stabilizer sustained impact damage and was folded against the horizontal stabilizer. Both upper and lower wings had leading edge crush damage and spar twist. All three propeller blades had chordwise abrasions and leading edge gouges; one blade exhibited a 90-degree aft bend midspan; the remaining blade tips had separated, revealing jagged tear features. Propeller balance weights were firmly attached.
The engine remained attached to its mounts with no obvious holes in the case. Damage included a bend in the number six cylinder pushrod cover, a damaged number eight forward spark plug lead, and a gouge in the number three intake cowling support lug, consistent with impact.
The airplane was subsequently examined by the NTSB investigator-in-charge and the FAA inspector. Fuel lines from the shutoff valve to the gascolator were intact, and the fuel filter was clear. Throttle, carburetor heat, mixture, and propeller controls in the cabin achieved full travel at respective engine control arms. No obstructions were in the air induction system. No cracks or holes were present in the engine case or cylinder heads. Exhaust pipes had tan deposits, with no oil residue or sooting. No mechanical anomalies were identified in the airframe.
The engine was transported to Covington Aircraft for further examination. Spark plugs had dark grey electrodes with slight ovaling, consistent with normal wear. Hand rotation of the crankshaft was smooth; thumb compression was attained for all cylinders. Rocker covers revealed oil-wetted surfaces; valve assemblies had no excess play or binding; full valve travel achieved. Governor filter screen was clear; drive-train continuity was confirmed through to the blower, magnetos, starter, alternator gears, and governor spline. Magneto timing was 23.5 and 23 degrees before top dead center; magnetos produced sparks at 2,000 rpm. Valve timing clearance matched the data plate. Nose case gears were intact and oil-wetted; oil screen had about 1/4 teaspoon of fibrous lint debris and dark deposits. Lower impeller had no gouges or distress; oil seal was oil-wetted without damage. Carburetor showed no damage; fuel idle mixture jets were about one notch short of maximum rich; fuel inlet screen clear. The carburetor was tested on an exemplar engine from 500 to 2,250 rpm; magneto drop was acceptable (80-90 rpm). No mechanical anomalies were identified.
The pilot sustained minor injuries.