Rayo destruye ASK 21 durante vuelo de entrenamiento cerca de Northall, Bedfordshire

El 17 de abril de 1999, un planeador Schleicher ASK 21 fue alcanzado por un rayo durante un vuelo de entrenamiento cerca de Northall, Bedfordshire. El planeador, que operaba desde un sitio en Dunstable, volaba a aproximadamente 2.500 pies cuando ocurrió el incidente. El impacto del rayo causó que la estructura se desintegrara, llevando a ambos ocupantes a saltar en paracaídas para ponerse a salvo. Tanto el instructor como el alumno sufrieron heridas leves, y el planeador fue destruido. El incidente fue presenciado por varias personas que informaron de un fuerte estruendo y posterior caída de escombros del cielo.

1. Aerotow — thermaling: The ASK 21 was aerotow-launched from Dunstable and spent about an hour soaring up to 4,000 feet between Leighton Buzzard and Bletchley before returning toward the airfield along the edge of an advancing cloud mass.
2. Thunderstorm nearby: A large area of bad weather with heavy rain and wet snow, including cumulonimbus with forecast lightning, was slowly advancing toward the local flying area, with the glider operating close to the cloud edge.
3. Non-conductive structure: The ASK 21’s largely glass-reinforced plastic, non-conductive structure and lack of designed-in lightning protection made it vulnerable to severe structural damage from a lightning strike.
4. Lightning strike: While turning away from the cloud at about 2,500 feet agl, roughly 800 yards from the cloud base and flying at about 80 kt, the glider was struck by a powerful lightning discharge that attached to the airframe.
5. In-flight breakup: The lightning strike caused large sections of the GRP airframe, including most of the right wing, outer left wing, and fuselage center section, to disintegrate and separate in flight.
6. Crew bailout: After an initial dazed period and communication difficulty, the student and then the instructor abandoned the disintegrating glider, with both parachutes inflating by about 1,800 feet agl.
7. Crash - minor injury: The wreckage descended near Northall and was destroyed while both occupants parachuted to the ground with minor injuries, including hearing damage and a broken ankle for the instructor.