Aftonmunicipal Airport
Aircraft Accident/Incident Report

Afton, Wyoming 83110
Monday, May 26, 2003 11:00 MDT

The pilot had three passengers and 50 gallons of fuel on board when he made the first scenic flight. The density altitude was reported to be 7,200 feet msl. On the second flight, he had another three passengers and 38 gallons of fuel. Density altitude had increased to 8,500 feet msl. The mixture was leaned. The pilot said "the plane did not develop the same amount of power as on the previous takeoff" and the takeoff roll was longer. "The plane rotated approximately 200 yards before the departure end of the runway, and did not accelerate beyond 70 knots." He lowered the nose to gain airspeed. Airspeed slowly increased and the airplane "was ascending at about the same rate as the terrain. Approximately eight seconds after take off, I felt a slight surge in power and lifted the nose." He then heard a "pop" and "felt a slight shudder." He concluded he had "grazed over the top of some object with the stinger at the rear of the plane." Concerned about possible damage to the airplane, the pilot radioed the airport manager and asked that he inspect the airplane when he made a low pass over the airport. He lowered the landing gear and flew over the runway. The airport manager advised him that "everything looked fine." The pilot then proceeded with the flight. As the passengers disembarked, they noticed the rear foot step had been knocked off. Further investigation revealed a gash under the right wing, 2 feet outboard from the fuselage, that extended from just aft of the leading edge to the flap. Based on a maximum gross weight of 3,600 pounds and a density altitude of 8,500 feet, it was computed that the airplane would require 2,100 feet for the takeoff roll and would climb approximately 600 feet per minute. According to the engine manufacturer, a full power setting is to be used for pre-takeoff leaning on all normally-aspirated reciprocating engines. This information is contained in the various engine handbooks. If the engine were to be leaned at a lower power setting, the mixture would become richer as power was increased beyond the setting used for leaning, and would result in lower rpm and reduced horsepower.

the pilot's failure to achieve an adequate climb rate, resulting in an inflight collision with the sign. Contributing factors were the pilot's improper mixture leaning procedure, the high density altitude, his failure to abort the takeoff in a timely manner, and the highway sign near the end of the runway.