John,
The AIB report is available to view in the Kew archives.
5(a): "That the accident was due to fire in the air caused by the escape of petrol through the unscrewed cover of the bottom carburetter and subsequent ignition by the exhaust gases."
5(B): "That the pilot succeeded in subduing or putting out the flames but was unable to properly control the aeroplane when landing owing to physical disability caused by burns and spinal hemorrhage."
Ciarain.