National Gas Turbine Establishment

The Air House (1961) was a modernistic structure. Its eastern side is sheet glass; 8 large blue exhaust pipes rise the full length of the building, for the 8 compressor/exhauster sets inside. The pipes transported the fast moving air to/from the test cells.

The Air House had two functions: blowing or sucking air, at up to 2,000 mph (for Cell 4). There were eight identical GEC compressor/exhauster sets which aggregated to 352,000 horsepower, then the largest installation of its kind in the western world.

This is the final design for the compressor/exhauster sets from the late 1950s. They are made up of an in-line arrangement (from left to right) of an 8,000 horsepower steam turbine, then two low-pressure compressors, a high-pressure exhauster, a 27 MW 11 kV synchronous motor that provided 36,000 horsepower, and finally the barring gear and the exciter (a small generator that provides a current needed to start the main motor).

The 8,000 horsepower steam turbine, which was powered by the site's boiler house, gave the compressor sets a kick start before it was synced with the grid. They could also be used whilst they were being run but this was expensive and only used on the supersonic tests.

Cell 3 was mostly underground and was a supersonic replacement of Cell 2, allowing for higher speeds and a greater engine temperature range. There was a fairly large building above ground. But that was just to allow engines to be lowered into the test chamber from a huge crane. The test chamber itself was almost entirely underground.

Cell 3 West was a comparatively small building, with a large blue and white round opening on the front of the test chamber. It was the last altitude test cell built on site. It was one of the largest cells internally, allowing icing tests (testing to see how ice affects a turbine's performance) to be carried out on engines and helicopter rotors. The engine or turbine was suspended from the roof of the cell.

The largest test cell on site, Cell 4 was built in 1965, at a cost of £6.5 million, as part of the Concorde programme but also to test other supersonic jet engines. The test cell, unique in the world, takes up most of the steel clad structure with its mass of pipes, blast doors and electronics. It is connected to the Air House by blue pipes and was designed to simulate Concorde's flying conditions - Mach 2 (1522 mph) at 61,000 feet, but could test Concorde's engines at a maximum wind speed of 2,000 mph.

The amount of energy required to run the air house (see below) at the speed needed was too great for the site's own power station, so electricity had to be taken from the National Grid. By the early 1970s, Pyestock had to negotiate with the Central Electricity Generating Board (CEGB) to have enough electricity generated. So as not to strain the grid, Cell 4 could only be powered up at night.

Pyestock's designers built the Air House on a large scale, thinking it could supply adequate suction for the supersonic test cells. But they could not have anticipated the phenomenal force required by Cell 4 - even with all eight exhausters running the suction was insufficient. The solution was to build another exhauster set directly next to Cell 4. As there are eight in the Air House, this one was named number 9.

It is a Parsons "multi-stage axial-flow exhauster". It was used mainly by Cell 4 but also occasionally by Cell 3 and Cell 3 West. It was driven by a 36,000 horsepower synchronous motor, with power being taken first from the site's power station, and then when 3,000 rpm was reached it was synchronised with the National Grid.