What happened
On April 13, 2001, a Mudry CAP-10-B, registration EC-FVK, was completing a local pleasure flight at Zaragoza Airport. After a two-hour flight, the pilot landed on runway 30L. Following the landing, the pilot executed a 180-degree turn to head toward taxiway C-1.
As the aircraft approached the threshold of runway 30L, the pilot attempted to turn left onto the taxiway. During this maneuver, the aircraft began turning much more sharply than intended. In an attempt to correct the trajectory, the pilot applied the right brake pedal, but found that the pedal depressed fully to the floor without providing any braking force. Unable to control the direction of the aircraft, the pilot continued the turn, causing the aircraft to exit the taxiway. Although the pilot shut down the engine, the aircraft's propeller struck an airport information sign, causing the aircraft to come to a halt. Both the pilot and the passenger were uninjured.
The investigation
The investigation focused on the mechanical failure of the braking system and the environmental conditions at the time of the incident. Investigators examined the aircraft's brake assembly and reviewed meteorological reports from the period surrounding the event.
Meteorological data indicated that winds were blowing from 300° at speeds between 21 and 23 knots. Investigators also inspected the brake system components to determine why the pedal failed to respond to pilot input.
Findings
- The investigation established that the sharp left turn was exacerbated by wind conditions. As the aircraft turned left, the vertical stabilizer became more perpendicular to the wind, increasing the aerodynamic pressure on the vertical surfaces and driving the aircraft into a more aggressive turn.
- The primary cause of the inability to correct the turn was a hydraulic fluid leak at the connection between a hose and the brake system pump.
- This leak was caused by an insufficiently tightened union nut, which resulted in a total loss of braking effectiveness when the pilot attempted to use the right brake.