Un rayo desintegra un ASK 21 al borde de la tormenta
El instructor y el alumno de un ASK 21 resultaron con lesiones leves cuando un rayo desintegró el planeador en vuelo; ambos saltaron y estaban bajo paracaídas a 550 m AGL, planeador destruido. En un curso en Dunstable, el ASK 21 fue remolcado y voló cerca de una hora hasta 1.220 m MSL. Al avanzar mal tiempo, el instructor se apartó de la nube a 900 m AGL. A 30° del eje de la nube, a 760 m AGL y 80 kt en aire claro, una descarga positiva >80 kA alcanzó al planeador. Grandes secciones se desprendieron. El instructor se rompió un tobillo al aterrizar. Daños en el sistema de alerones — único camino conductor de la célula GRP.
- Training at Dunstable; storms forecast: An ASK 21 was on a training course out of Dunstable, with an instructor and student aboard, both wearing parachutes. A large storm system was advancing slowly from the north.
- Cruise along advancing cloud front: After a soaring flight up to ~1,220 m, the glider flew along the front edge of an advancing cloud before the instructor turned away to return ahead of the weather.
- Positive >80 kA strike at 17:08:57 LT: Lightning-detection data recorded a positive strike over 80 kA close to the accident site at the moment of impact — the discharge that struck the glider.
- Aileron rods crushed; ~1,000°C bolt: Most of the right wing, the outer left wing, and mid-fuselage detached in flight. Lightning current followed the aileron system, melting a bracket bolt and crushing a rod.
- Both bailed; parachutes open ~550 m AGL: The student bailed out first, followed by the instructor; both parachutes were open by ~550 m AGL. The student landed unhurt; the instructor broke an ankle.
- GRP gliders have no lightning protection: The ASK 21's GRP structure is non-conductive and has no built-in lightning protection. The strike's current followed the only metallic path — the aileron system.