Gnome Engine Test Laboratory (GETL)

The Gnome Engine Test Laboratory is operated by S & C Thermofluids on behalf of the Defence Science and Technology Laboratory (Dstl), an agency of the Ministry of Defence.

The laboratory offers a low cost propulsion research capability.

The Gnome engines used in the laboratory were manufactured by Rolls-Royce. The Gnome is a turboshaft propulsion unit. Three main variants of the engine have been produced - 1000, 1200 and 1400. The 1400 variant is used to power the Sea King helicopter.

The engine comprises a free power turbine and independent gas generator.

  • Mass flow - 5.63kg/s
  • Ten stage axial compressor with variable incidence inlet guide vanes (1st four stages)
  • 8.3:1 compression ratio
  • Straight through annular combustion chamber with sixteen fuel injectors
  • Fuel type - Kerosene - JP-4
  • Exhaust temperature up to 685 ºC
  • Fuel consumption - approx. 5 litres/min at max continuous rating
  • Dry weight without gearbox 125kg
  • Electric start - two HT ignitors

S & C Thermofluids have converted the engines to create the following versatile rigs.


To provide a means for simulating typical thrust engine environments, two of the GETL engine rigs use a Gnome with the power turbine removed.

The 3rd stage nozzle guide vanes which support the rear bearing have been cut back to reduce swirl and an additional vane set has been provided to reduce swirl still further.

The gas generator can then be run as a turbojet engine generating some 3kN of thrust.

The turbojet rigs allow new nozzle designs to be demonstrated and evaluated. Parameters such as mass flow, thrust, temperature, pressure, fuel flowrate, noise and vibration can be measured.

The thrust can be measured in two axes. Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV) can be used to obtain detailed information about the engine flows.

The turbojet rigs provide from small scale up to full scale testing of nozzles depending upon the application (0.16m diameter).


The GETL also has three turboshaft rigs which use the Gnome engine in its conventional format - i.e. with the power turbine. These rigs provide a full scale test capability for helicopter nozzles and their associated installation.

One turboshaft engine is loaded through a Wessex helicopter gearbox using the compressor from another Gnome engine. The other two turboshaft rigs have a bespoke gearbox which means the engine can be fully loaded to 1235SHP.

This in turn provides compressed air which can be used to carry out a number of functions:

  • Downwash for helicopter studies (via a bank of small ejectors).
  • Provision of bypass flow for the turbojet rig to allow the simulation of turbofan nozzle systems.
  • Simulation of high pressure ratio nozzle systems at small scale.


Flight stream

S & C has two flight stream rigs, utilising the compressed air from the turboshaft rigs passed through an ejector. The first is high velocity, small scale:

  • Flight simulation up to M=0.5, sea level
  • Hot exhaust flow NPR=1.3, T=400ºC
  • Option for NPR=1.9, T=600ºC
  • Two axis thrust measurement
  • Typical scale 1:6 (for missile systems)

The second rig is much larger scale and can accommodate the combustor rig within the plenum space.

  • Flight simulation up to M=0.3, sea level
  • Hot exhaust flow NPR= 5:1, T= 750ºC
  • Two axis thrust measurement
  • Typical scale 1:5 (for fixed wing aircraft)

Combustor rig
  • Utilises a Gnome Combustion Can
  • Up to 4kg/s at max NPR of 5:1 (turboshaft 1200 loading compressor)
  • Kerosene fuel
  • Temperature variable nominal 750ºC
  • Pressure and temperature are decoupled and can be controlled independently from one another
  • Multiple valve system including automated dump valve keeps compressor on running line
  • Axial and pitch thrust (or yaw if nozzle turned through 90 degrees)
  • Detuner and noise shields available

© S & C Thermofluids Ltd 2014

S & C Thermofluids Ltd

The Old Tannery, Kelston, Bath, BA1 9AN
Tel: 0117 932 7378 Fax: 0117 932 9652

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