NTSB Factual Report

On August 19, 2010, about 1200 mountain standard time, a Grumman G-164B, N6607Q, collided with terrain during takeoff from a dirt strip near Buckeye, Arizona. Crawford Aviation Services was operating the airplane under the provisions of 14 Code of Federal Regulations (CFR) Part 137. The commercial pilot sustained serious injuries. The airplane sustained substantial damage from impact forces and a post-crash fire. The local aerial application flight was departing. Visual meteorological conditions prevailed, and no flight plan had been filed.

The pilot reported that he had flown the airplane about 4.2 hours on the date of the accident. The airplane was loaded with approximately 200 gallons (maximum capacity 315 gallons) of water and insecticide in the hopper, and 50 gallons of fuel (maximum 80 gallons). He detected no discrepancies during taxi or during the run up. He initiated takeoff on runway 16, and noted normal acceleration, engine indications, and tail liftoff.

After completing 2/3 of the takeoff roll, the revolutions per minute (rpm) increased to 2,600-2,700 (maximum allowable 2,550). The pilot felt a moderate to severe vibration, and immediately initiated aborted takeoff procedures. He retarded the throttle to idle, applied maximum braking, and held the control stick full aft. As the airplane slowed to 20-30 knots, he elected to steer the airplane away from a fence made of railroad ties at the end of the runway onto hard packed desert adjoining the west edge of the runway. After rolling a short distance, the left main landing gear went into a depression and sheared off. The airplane settled onto the left wing, and was almost immediately engulfed in fire. The pilot egressed through the left window hatch with serious injuries.

A National Transportation Safety Board investigator examined the wreckage. The report is in the public docket for this accident, and pertinent excerpts follow.

The engine sustained fire damage to the aft section, which exposed the gears in the accessory section. Fire consumed all accessories, including both magnetos. The crankshaft rotated freely with manual rotation of the propeller; the magneto drive gears rotated. The investigator removed the spark plugs. Seven of the nine plugs had dark brown/black deposits, and the center electrodes were oval shaped. Two spark plugs were oil soaked.

The investigator examined the cylinder bores with a lighted borescope. All piston crowns exhibited light brown deposits with no indication of piston to valve contact or catastrophic failure. The valves in the lower cylinders were oil soaked.

The engine controls remained attached at their respective control quadrants. The governor control remained attached at the engine. The burnt remnants of the mixture and throttle control assemblies were located within the firewall with their connections still attached to the control cables. Outer cables were intact and continuous; fire damage and bends prevented continuity of internal linkage to the cabin.

Fire consumed the airframe surfaces from the empennage to the firewall; both upper and lower wings were consumed from mid-wing span inboard. All ailerons were attached at their hinges. All empennage control surfaces were attached at their respective hinges. Fire consumed control surfaces in the cabin and inboard wing areas.

NTSB Probable Cause

An increase in engine rpm and vibration, which resulted in an aborted takeoff and runway excursion. The reason for the increased engine rpm and vibration could not be determined because of postaccident fire damage.