Editing Rolls-Royce Thrust Measuring Rig (section)

== Design ==
The Rolls-Royce Thrust Measuring Rig (TMR) was a VTOL aircraft developed to explore the practicality, characteristics, and requirements of such an aircraft.<ref name = "ill 2 3" /> It was widely known by its nickname of the ''Flying Bedstead'' due to its radically unconventional appearance for an aircraft, basically consisting of a rectangular tubular framework that was built around the engines, a platform being placed on top of which to accommodate a single pilot. It did not have any [[Aerodynamics|aerodynamic]] shape, lacking either wings or a tail; it instead generated all of its lift by directing the thrust of its engines directly downwards.<ref name = "ill 3 13">Illingworth 1961, pp. 3, 13.</ref> Due its small size, the TMR had a maximum flight endurance of only six minutes.<ref name = "fricker 25" />

It was powered by a pair of [[Rolls-Royce Nene|Nene]] [[turbojet]] engines, which were installed in a back-to-back configuration.<ref name = "ill 3" /> The output of the [[Jet engine|jets]] was directed towards the [[Center of mass#Center of gravity|centre of gravity]] of the rig; one jetpipe discharging downwards through a central nozzle while the other jet discharged downwards through two smaller nozzles on either side; this was so that, in the event of a single engine failing during flight, there would not be any sharp adverse movement as a result. Considerable precautions were taken to safely sustain such an engine failure; the four-leg [[landing gear|undercarriage]] was designed to support a vertical velocity of {{convert|34|ft/s}}, and to withstand a single-engine landing from any height below {{convert|50|ft|round=5}}.<ref name = "ill 3" /> The TMR possessed only marginal excess power, which complicated the act of flying the aircraft; this was further compounded by the slow response time of the engines to throttle changes. Accordingly, there was a considerable degree of anticipation in the use of engine power required to prevent overshooting of desired altitude, and to ensure a gentle touchdown when landing.<ref name = "ill 7 8">Illingworth 1961, pp. 7-8.</ref>

A total of four outrigger arms extended out from the rig, one on either side and one each at the front and rear, through which [[compressed air]] was released for control in [[Flight dynamics|roll]], [[Flight dynamics|pitch]] and [[Flight dynamics|yaw]] when in flight.<ref name = "ill 3 4">Illingworth 1961, pp. 3-4.</ref> While the controls for yaw and height were mechanically based, the pitch and roll controls were electrically signalled, without any provision for reverting to mechanical operation. Initially, key components for the electrical control system components were duplicated; however, in order to make the detection of faults infallible, a safer partial-triplex arrangement was adopted for the RAE's free flight testing phase.<ref name = "ill 4">Illingworth 1961, p. 4.</ref> As the TMR possessed no inherent [[Flight dynamics|stability]], it incorporated an experimental automatic stabiliser system.<ref name = "ill 12">Illingworth 1961, p. 12.</ref> During its numerous test flights, varying degrees of intervention by the stabiliser were performed, including a few in which no stabilisation was active at all.<ref name = "ill 9 10">Illingworth 1961, pp. 9-10.</ref>