Rolls-Royce Thrust Measuring Rig (TMR) XK426 at Hucknall during a tethered test. The TMR or 'Flying Bedstead' was used to test the principles of jet powered vertical flight. It was stabilised with small thrusters. Most of the 'flights' were tethered. Two were built, both suffered minor accidents but the lessons learned allowed progression to the Short SC1 and eventually the Harrier jump jet.
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