Aircraft and Modifications
The accident aircraft was a Piper PA-25 that had been modified for the purpose of developing a Supplemental Type Certificate (STC). The modifications included the installation of a second seat in the area normally used for the hopper and an extension of the canopy forward. The operator had reported to the Federal Aviation Administration (FAA) that flight conformance testing up to that point had shown no change in aircraft performance compared to the original configuration.
Test Flight Details
On June 30, 1995, the aircraft was being flown for an airspeed calibration test. It was equipped with an external airspeed calibration device. To meet the maximum gross weight and forward center of gravity requirements for STC testing, the aircraft was loaded with 560 pounds of ballast. Weather conditions included gusty winds and a temperature of 64 degrees Fahrenheit, which was about 30 degrees warmer than the day of the previous test flight.
Accident Sequence
According to the pilot, after taking off from runway 21, he maintained the best rate of climb speed and engine rpm between 2525 and 2550. He then attempted best angle of climb speed, but the aircraft would not climb. He turned downwind and attempted to return to the same runway, but the aircraft collided with trees and crashed approximately half a mile east of the airport.
A witness reported that during takeoff, the aircraft lifted off and then began a left turn about halfway down the runway. The pilot indicated that a climbing turn was made to provide more clearance from obstacles at the south end of the airport. Other witnesses stated that the aircraft then turned north and remained at low altitude and low airspeed until it struck trees and crashed. A fire erupted, and the aircraft was destroyed.
Investigation Results
The subsequent investigation found that the standard (original) wing root fairings and landing gear (strut) fairings were not installed on the aircraft. Piper stated that the removal of wing root fairings would significantly reduce the wing's lifting capability and change the airflow over the horizontal tail, requiring more elevator deflection for maneuvering. The absence of landing gear fairings would have slightly increased drag.