What happened
On June 30, 1995, a Piper PA-25 was conducting a flight conformance test to verify that modifications for a Supplemental Type Certificate (STC) had not altered aircraft performance. The aircraft had been modified with an extended canopy and a second seat in the hopper area. For this specific calibration flight, the aircraft was equipped with an external airspeed calibration device and loaded with 560 lbs of ballast to achieve maximum gross weight and the required forward center of gravity.
Weather conditions at the time were characterized by gusty winds and a temperature of 64 degrees Fahrenheit. After taking off from runway 21, the pilot maintained the best rate of climb speed and engine RPM between 2525 and 2550. The pilot then transitioned to the best angle of climb speed; however, the aircraft failed to climb. In an attempt to maneuver, the pilot turned downwind to return to the runway, but the aircraft collided with trees approximately 1/2 mile east of the airport. Witnesses observed that after liftoff, the aircraft began a left turn midway down the runway. The pilot stated this climbing turn was intended to increase clearance from obstacles at the south end of the airport. Following the turn, witnesses noted the aircraft turned north and remained at a low altitude and airspeed until the impact. The crash resulted in a fire that demolished the aircraft; there were no fatalities reported.
The investigation
An investigation into the accident revealed that the standard wing root and landing gear strut fairings had not been installed on the aircraft during the test flight. According to Piper, the absence of the wing root fairings would significantly reduce the wing's lifting capability and alter airflow over the horizontal tail, necessitating increased elevator deflection for maneuvering. Additionally, the lack of landing gear fairings was found to have slightly increased aerodynamic drag.