Accident Overview
A Piper PA-25 aircraft, performing a local banner-tow operation, completed its mission and released the banner. While maneuvering for landing, the airplane entered a stall at low altitude. The subsequent impact with flat terrain on airport property resulted in substantial damage to the aircraft. The certificated commercial pilot aboard sustained serious injuries.
Aircraft Information
The accident aircraft was a Piper PA-25. It was equipped with a stall warning system consisting of a vane-activated switch on the wing and a cockpit warning light. The airspeed indicator was a standard instrument for the aircraft type.
Investigation Findings
Post-accident examination of the stall warning system revealed that the internal contacts of the vane-activated switch were fused. This condition prevented the switch from functioning as designed. Additionally, the Safety Board's Materials Laboratory analyzed the stall warning light and determined that it was not illuminated at the time of impact.
The airspeed indicator was subjected to calibration testing. The tests showed that the indicator erroneously read approximately 8 mph too high at speeds up to at least 90 mph.
Pilot Experience
The pilot held a commercial certificate and had accumulated approximately 450 total hours of flight experience, including about 130 hours in the accident airplane.
Meteorological Conditions
Visual meteorological conditions prevailed at the time of the accident. The reported wind was 9 knots.