On March 26, 2004, a Piper PA-18A-150 (registration EC-ALK) was involved in an aviation accident near Aeródromo de Casarrubios (Toledo), ES. This summary draws on records from the Spanish Civil Aviation Accident and Incident Investigation Commission (CIAIAC).
On 26 March 2004, Piper PA-18-150 EC-ALK overturned during a training takeoff at Casarrubios del Monte, Spain. Two occupants escaped unharmed; the aircraft sustained major damage.
Overview and flight details On Friday, 26 March 2004, a Piper PA-18-150 with registration EC-ALK was conducting a general-aviation instruction flight with dual command at the aerodrome of Casarrubios del Monte in Toledo, Spain. The aircraft was powered by one Lycoming O-320-A2B engine. The flight began at 14:00 local time with an instructor and a student aboard. The planned duration was about one hour, and the objective was to practice takeoffs and landings in a tail-dragger aircraft. The pilot in command was 26 years old, held a commercial pilot license for airplanes, and had 1,353 total flight hours, including more than 800 hours on the type. ## Sequence of events After five takeoff-and-landing exercises, the crew began a final maneuver on runway 08 at 14:50. During the landing roll, the crew reported a vibration in the tail when the tailwheel touched down. The vibration recurred when the tail was raised and lowered again, then disappeared after another touchdown. The aircraft then taxied a short distance before the crew initiated a takeoff. According to the instructor’s account, the aircraft suddenly yawed about 60 degrees to the left. The crew attempted to steer it back onto the runway using rudder and the right brake. While the aircraft was off the runway and skidding at about 50 degrees to the runway axis, the crew decided to take off. The tail was raised, but the aircraft decelerated on the terrain and the main landing gear struck the ground. The crew cut the engine power and lowered the tail. The left gear entered a depression in the terrain, causing a left yaw and the aircraft overturned. Both occupants left the aircraft under their own power. ## Damage and ground evidence The aircraft sustained major damage. The propeller had one bent blade and notches on the other. The engine was probably damaged because it stopped at idle against mud. The left wing had deformations at its tip. The cockpit had broken front and upper windows. The left landing gear was completely destroyed. The vertical stabilizer had minor damage. The fuselage had significant structural deformations. Ground marks showed that the aircraft left the runway within 25 meters. The right gear mark had the longest run on the runway and began near the runway centerline. The tailwheel mark showed signs of vibration. The aircraft was skidding, and the skid angle had decreased when it left the runway. The path off the left side of the runway formed a 45-degree angle with the runway axis. After leaving the runway, the aircraft traveled 55.6 meters and came to rest 38.5 meters from the runway edge. ## Aircraft and aerodrome information The Piper PA-18-150 used a tailwheel steering system in which the rudder and tailwheel were mechanically linked. In normal operation, the tailwheel could be turned up to ±15 degrees relative to the aircraft’s longitudinal axis. The design also allowed the wheel plane to rotate 180 degrees relative to its attachment point, a feature intended to permit sharp ground turns when used with asymmetric main-gear braking. Casarrubios del Monte is a private aerodrome classified A1 under ICAO Annex 14. Its runway 08-26 is asphalt, 23 meters wide, with the runway 08 threshold displaced 295 meters. The runway strip extended 30 meters from the runway centerline. At the time of the accident, the left side of the runway where the aircraft departed had a 4- to 5-meter-wide compacted area adjacent to the runway, with disturbed ground beyond. Ruts and vehicle marks of varying depths were observed along the aircraft’s path. ## Analysis The investigation found that the aircraft’s abrupt departure from the runway was consistent with the tailwheel not being aligned with the aircraft’s longitudinal axis when power was applied for takeoff. The crew’s reported vibrations during the landing roll were probably caused by tailwheel oscillations, possibly induced by a runway surface irregularity or by the tailwheel not being firmly on the ground. Post-accident inspection of the tailwheel assembly found no damage or functional anomalies, and its configuration was normal. The investigation considered it unlikely that landing loads had forced the tailwheel outside its normal ±15-degree operating sector. The direction of the tailwheel would have corresponded to the position of the rudder pedals and rudder, as no control failure was found. Increased speed from applying engine power contributed to the aircraft becoming uncontrollable, preventing correction of the runway path. The short distance over which the aircraft left the runway was considered consistent with the described situation. The sinusoidal marks left by the tailwheel on the asphalt indicated an oscillatory movement compatible with the aircraft skidding at significant speed.