What happened
On November 11, 2022, a student pilot and an instructor were performing a series of circuit flights at Amendoeira aerodrome using a PZL-Swidnik PW-6U glider, registration D-5159. The operation utilized an aerotow method with a Morane-Saulnier MS.893A Rallye aircraft, registration D-EMZO.
During the second flight of the session, the glider took off from runway 21. Shortly after crossing the N114 road at an altitude of approximately 25 meters, the tow rope detached from the towing aircraft. The student pilot, occupying the forward seat, observed the separation and felt a sudden, significant rightward bank. The student pilot reported that they attempted to communicate with the instructor in the rear seat twice but received no response. The instructor later recalled taking control of the aircraft and attempting a 180-degree turn to return to the runway, but the maneuver could not be completed.
The glider entered a steep right-hand turn with a bank angle approaching 90 degrees, causing the right wingtip to strike the ground. The aircraft transitioned into a descending, rotational motion, dragging the wing along the ground before the fuselage struck the earth violently in a nose-down attitude. The accident resulted in two minor injuries to the crew.
The investigation
The GPIAAF investigation examined the aircraft, the tow rope, and the equipment used during the operation. Investigators found that the 50-meter tow rope had failed at the weak link during the ground collision, while the end attached to the towing aircraft remained intact with the weak link and attachment ring undamaged. Tests confirmed that the Tost system release hook on the glider functioned correctly. The investigation also focused on the condition of the towing hook on the Morane-Saulnier MS.893A Rallye, noting an unairworthy condition that contributed to the rope's premature release.
Findings
- The inadvertent and premature release of the tow rope from the towing aircraft was the primary cause of the accident.
- The towing hook installed on the D-EMZO aircraft was in an unairworthy condition.
- There was a lack of clear protocols regarding the handover of flight controls between instructors and students during flight, leading to communication ambiguity during the emergency.
- The glider sustained substantial structural damage, including a broken tail boom, a fractured wing spar, and a separated canopy.