Rolls-Royce Thrust Measuring Rig
|Thrust Measuring Rig|
|On display in the Science Museum|
|Role||Experimental vertical take-off|
|National origin||United Kingdom|
|First flight||3 August 1954 (free)|
The Rolls-Royce Thrust Measuring Rig (TMR) was a pioneering vertical take-off and landing aircraft developed by Rolls-Royce in the 1950s. The TMR used two Nene turbojet engines mounted back-to-back horizontally within a steel framework, raised upon four legs with castors for wheels. The TMR had no lifting surfaces (wings, blades, etc.) and was understandably nicknamed the Flying Bedstead.
Design and development 
The man largely responsible for the development of the TMR was Dr Alan Arnold Griffith who had worked on gas turbine design at the Royal Aircraft Establishment in the 1920s and was a pioneer of jet lift technology. Griffith was employed by Rolls-Royce in 1939.
Two Thrust Measuring Rigs were built with the first taking to the air on 3 July 1953 at Hucknall Aerodrome, Nottinghamshire, England, though it remained tethered to the ground while airborne. The first free flight by the TMR was made on 3 August 1954 with R.T. Shepherd, Rolls-Royce's chief test pilot, at the controls. The TMR had only marginal excess power and flying was tricky due to this, combined with the slow throttle response of the engines, and a considerably degree of anticipation in the use of engine power was required in order to prevent overshooting of desired altitude, and to ensure a gentle touchdown when landing.
As the TMR possessed no inherent stability, it incorporated an automatic stabiliser system. The output of the jets was directed towards the centre of the rig with one jetpipe discharging downwards through a central nozzle while the other jet discharged downwards through two smaller nozzles on either side. 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 roll, pitch and yaw when in flight. The purpose of the rig was, as the name suggests, to test turbojet engines for lifting purposes and to develop techniques for controlling such an aircraft.
Following successful trials of the TMR, Rolls-Royce began development of the Rolls-Royce RB.108 direct-lift turbojet, five of which were used to power the first true British VTOL aircraft, the Short SC.1.
Aircraft on display 
Specifications (Thrust Measuring Rig) 
- Crew: one, pilot
- Length: 28 ft (8.53 m)
- Wingspan: 14 ft (4.26 m)
- Height: 12 ft 8 in (excluding pylon) (3.86 m)
- Empty weight: 6,000 lb (2,720 kg)
- Loaded weight: 7,500 lb (3,400 kg)
- Powerplant: 2 × Rolls-Royce Nene , 4,050 lbf (18 kN) each
- Thrust/weight: 1.08:1
See also 
- Comparable aircraft
Flying the Bedstead – Part 2 – Aeroplane Monthly – April 1985
- Pictures of the Thrust Measuring Rig (with text in Russian)
- A Science Museum picture of XJ314
-  Flying Bedstead’ after its (Low Fuel) accident, Hucknall, Nottinghamshire, 1957. With Air Commodore Larsen
- Pathe News – Flying Bedstead