Accident Overview
On July 9, 2012, at about 1700 eastern daylight time, a Cessna 172S, registration N680MA, was substantially damaged when it departed the runway during a touch-and-go landing at Allentown Queen City Municipal Airport (XLL), Allentown, Pennsylvania. The airplane was being operated by Gateway Aviation under 14 CFR Part 91 as a local instructional flight. Visual meteorological conditions prevailed, and no flight plan was filed.
Event Details
According to the pilots, they were practicing touch-and-go landings. After touchdown, around the time of power application, the airplane veered off the left side of the runway. A Federal Aviation Administration inspector reported that the airplane exited the runway into the adjacent grass, crossed a taxiway and an intersecting runway, struck an airport sign, and came to rest near a berm. Three distinct tire marks were observed in the grass from the point where the airplane first left the runway edge to a location past the impacted sign, ending at a hole in the ground described as a "gopher hole."
Damage and Findings
The airplane sustained substantial damage to the airframe and the horizontal stabilizer. The left main landing gear axle was impact-separated, and the associated tire was located about two weeks after the accident, inflated, in a ditch approximately 300 feet from the airplane's final position. Examination of the left main landing gear axle and associated parts at the NTSB Materials Laboratory revealed that the fractures were consistent with overstress from a single loading event.
Weather and Maintenance
At 1655, the recorded weather observation at XLL included wind from 240 degrees at 4 knots, visibility 10 miles, temperature 29°C, dew point 12°C, and barometric altimeter 29.94 inches of mercury. According to maintenance personnel, the airplane had been examined several times in the preceding two weeks for an unusual vibration originating from the left main landing gear.
Reference Material
The FAA Airplane Flying Handbook (FAA-H-8083-3A, Chapter 5) notes that during takeoffs, the throttle should be advanced smoothly and continuously to takeoff power, as an abrupt application of power may cause the airplane to yaw sharply to the left due to torque effects of the engine and propeller.