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Engine Test Facilities

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Engine installation in Cell 3.

Pyestock is located near Farnborough, Hampshire, South-East England, 35 miles South-West of London. The 250 acre site contains the most comprehensive range or aero engine altitude test facilities in Europe. It originated in 1946 when the Engine Department of R.A.E. Farnborough merged with the Whittle Power Jets team to form The National Gas Turbine Establishment. In 1983 Pyestock became part of the R.A.E., the major air system research establishment of the Ministry of Defence Procurement Executive.

There are five altitude test cells which between then can cover tests ranging from sea-level to 70,000 feet altitude and forward speeds up to Mach 3.5. The cells are provided with air by a centrally situated air processing plant capable of delivering up to 1200 lb per second of air and absorbing up to 120 MW of electrical power. Large diameter pipes deliver air from the generating compressors to the test cells and also duct the exhaust gases from the cells back to atmosphere through exhausting machinery.

Military engines which can be tested range from small missile power plants of 60 lb thurst to military combat aircraft engines in full reheat, delivering 20,000lb thrust. Civil engines can also be tested up to 65,000lb thrust.

With an engine rigged in the connected test mode, steady state engine performance can be measured anywhere within the typical test envelope illustrated below. The engine can also be acclerated and decelerated in response to throttle movement to explore its dynamic behaviour. Test conditions of altitude and Mach number can be changed rapidly during a test (although not in aircraft mission real time) enabling many flight conditions to be simulated during a half-day testing session.

Cell 3 is mainly used for miltary engine testing. The engine is lowered into the test cell through an access lid on the top and the lid is then bolted down to form a pressure vessel. The cell is 20ft internal diameter and the working section is 56ft in length.

Test requirements that can be met include:

  • Steady state performance measurement
  • Control system evaluation
  • Relight at altitude
  • Limits of combustion stablity
  • Evaluation of behaviour in severe icing conditions
  • Tolerance to distorted inlet flows

Air House Machinery

The Air House contains eight electrically driven compressor/exhauster sets which can be used to supply high pressure air to the inlet of military engines to simulate high forward speed at low altitude. These machines can also extract the engine exhaust gases and lower the cell pressure so producing the required altitude conditions. There are two other compressor sets on site that can be used for exhaust duties only. A typical miltary combat engine test might need two machines compressing at a pressure ratio of 9:1 for air delivery and three operating as exhausters at a pressure ratio of 3:1. In constrast, a large civil fan engine drawing its inlet air from atmosphere might need nine of the available 10 machines on site for the exhaust extraction duty.

Exhaust/air suction mains

Air House control room
Cell 3 West has an internal diameter of 25ft and the working section is 30ft in length. It is mainly used for civil fan engine testings and unlike Cell 3 has an atmospheric inlet. Air is drawn through an inlet cooler through which refrigerated ammonia is circulated at temperatures down to -50°C. The air temperature can be reduced to -40°C which is appropiate to a civil aircraft crusing at an altitude of 40,000ft. Cell 3 West is capable of the same type of tests as Cell 3.

Engine installation in Cell 3 West

Each test cell has a control room dedicated to it in which the test control team set up test conditions and control the test.

Cell 3 test control room

The test cells are all linked with a central computer controlled data gathering system which enables the tests to be monitored on-line using graphical displays on video units. Pyestock Engineers can use this system to check that the test plant is set up correctly and producing the right flight conditions whilst the customers' engineers can evaluate the engine or rig performance during the course of the tests.

Test cells 1 and 2

Other test cells on the site include:
  • Cell 2 - which is similar in many respects to Cell 3 but does not have a cold air inlet and has a restricted test envelope.
  • Cell 1 - is very similar to Cell 2.
  • Cell 4 - is a supersonic free jet test facility used for engine intake compatibility testing but not in current use.

The instrumentation capabilities are very broad and vary from cell to cell. The following tabulation gives a summary of the numbers of parameters which can be recorded in the three active test cells.

Non aero-engine work can also be undertaken in the Pyestock facilities. With cells rigged in the free-jet test mode, icing tests on full scale helicopter and engine intakes are examples of such use.

A full scale model helicopter fuselage positioned in Cell 3 West for engine intake icing trials

V.2500 engine and intake assembly rigged for free jet icing tests in Cell 3 West

For further information on the capabilities of the altitude test cells at Pyestock enquires should be addressed to Head of Propulsion Department, RAE Pyestock, Farnborough, Hants. GU14 OLS.