"Rolls-Royce Thrust Measuring Rig ('Flying Bedstead')
The TMR was a rig only, made of tubular steel and comprising two opposed Nene 101 engines with most of the thrust directed immediately downwards with 9% of the power being bled off to puffer pipes projecting fore and aft. The first of two rigs, without serial but later XJ314, flew on 9 July 1953 tethered and on 3 August 1954 free and 224 tethered and 16 free flights had been completed by December 1954. It went to the RAE where it eventually crashed on 16 September 1957. The second rig, XK426, flew on 12 November 1956 but it crashed on 27 November 1957 on a tethered flight after hitting the gantry and killing the pilot, Wg Cdr H G F Larson. The TMR had a design thrust to weight ratio of 1.25:1 but the actual figure was slightly less with fuel for about 15 minutes 'flight'. "
http://www.scienceandsociety.co.uk/results.asp?txtkeys1=Flying+Bedstead - more incident photos
http://www.youtube.com/watch?v=f8W2SI4c93s