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Cell 4 (635)

Built: 1965
Decommissioned: 1980

Cell 4 was an integral part of the massive supersonic-testing expansion of Pyestock, as the need to test engines in close association with their air intake systems was an urgent requirement for this new generation of aircraft. This could only be achieved by full-scale free-jet testing and Cell 4 was designed to provide that capability. Therefore the cell could provide a means of observing on the ground the interaction of the intake and engine combination at changing altitudes, Mach number and incidence.

The cell was constructed in 1965 for £6.5 million in the north-western corner of the site, in close proximity to the newly built Air House where it was directly delivered air from the GEC compressor sets and indirectly via the Ceca air dryer.

Cell 4, south east aspect, as seen from the elevated section of Weir Road.
05|05|07 © Simon Cornwell 2007

The cell was the largest testing cell built at Pyestock. Its total length of 400 feet included many specialised sections: there was the 30ft-diameter 36ft-long inlet plenum chamber with its supersonic blowing nozzle, a 10.5ftĖlong working section, a 10ft-diameter 16ft long engine chamber, a 55ft-long exhaust diffuser, 160ft-long first and second stage coolers and finally 105ft of ducting at the rear to accommodate seven GEC exhauster connections.

This was all housed in a huge brick and steel shed which was designed and constructed by the Ministry of Public Buildings and Works (MPBW). The partly basemented building included the cell in one massive room along with offices and control facilities in the brick wing on the south side of the main shed.

South-westerly elevated view across Cell 4.
24|03|07 © Simon Cornwell 2007

The fuel system was teed off the complimentary Cell 3, so both cells could not be run simultaneously. 100 gallons per minute of fuel could be pumped to the engine under test whilst 200 gallons per minute were available for the reheat systems if desired.

Flight speed was simulated by two different supersonic blowing nozzles which had adjustable throats and wall contours to provide variable Mach number operations. The total weight of the nozzle and moving chamber assembly was 75 tons. One measured 25 square feet whilst the other was 20 square feet. They would be positioned in the plenum chamber during testing.

Cross-section of Cell 4 test plant

The heat exchanger to cool the engine exhaust was a major design consideration and plant item. The cooler had two stages. The first stage cooler had six flame torches to ignite any unburned fuel in the engine exhaust. The exhaust gases were at 1700°C at this stage where they would enter the first cooler where they were cooled to 1000°C by a gas-over-tube-matrix which required a water flow of 620,000 gallons per hour. In the second stage cooler, the gases passed through tubes in the conventional manner, and the temperature of the gases was reduced to 150°C, which again required a similar amount of water. Water sprays were used in the final section to reduce the gas temperature to 50°C which was the maximum allowable to return to the GEC exhausters. Excess water drained into a 40ft deep barometric well.

The main control room was located in the ground floor of the brick built extension. All test results were fed to the SDS 9300 computer with its PDP7 in support. Back-up photographic recording equipment was also available. Instrumentation permitted 300 pressure and 200 temperature points to be measured during steady-state processing. Twenty-eight channels of magnetic tape, thirty-six channels of U.V. recording and digital counters for engine speed and fuel flow were available for transient conditions.

Back section of Cell 4 including the diffusers, coolers and flame traps.
24|06|06 © Simon Cornwell 2006

Shortly after its construction, the cell was modified to enable it to fly the Rolls-Royce Olympus 593 which was being developed for Concorde. The cellís abilities were enhanced to be able to fly at Concordeís cruise parameters of Mach 2 at 61,000 feet. To enable this, further exhaust capacity was installed as Number 9 Machine; and extra spill diffusers, mounted above and below the intake, were used to obtain the altitude conditions in the working section. Extra ductwork was added to accommodate the "ramp bleed" and "dump floor" flows which were an essential feature of the Concorde aircraft power plant.

After the successful Concorde trials, the cell was used for general free jet testing in supersonic mode and for subsonic free jet testing of the engine and intake. However, the cell was limited to investigations of aerodynamic compatibility of the intake/engine combination and was never used to test performance (unlike the complimentary Cell 3). With the decline of supersonic projects and its specialised, power-hungry needs, Cell 4 was surplus to requirements and was mothballed in the 1980s.

Cell 4 Walkthrough...

The western flank of Number 9 Exhauster (in light yellow steel cladding) and the adjoining Cell 4 (in grey steel cladding). The south-west corner of Cell 4 as seen from the exhaust pipe array. Looking north-east at the corner and southern side of Cell 4. Elevated view of the south-west corner of Cell 4. Looking north across Cell 3 to the southern flank for Cell 4. Looking north-west from the elevated section of Weir Road towards Cell 4. The south-east and eastern sides of Cell 4. The eastern and southern sections of Cell 4 seen in context by Weir Road. The eastern flank of Cell 4 as seen from the Computer Building. Cell 4 looking west.
Inside the pressure main looking north. Climbing up the sloped section of the pressure main, looking down. The interior of the air pressure main leading eastwards. The northern end of the air pressure main before it turns west into the main building. General view of Cell 4 and the eastern end of the plenum chamber. Looking across Cell 4 from the north-eastern corner. South-westerly elevated view across Cell 4. Looking north-west across the plenum chamber of Cell 4. Film-set dressing added to the south-west and eastern parts of the cell. Stairway on the north-east side of the cell leading up to the working section.
Northern door which leads into the working section. Interior of the working section looking east into the plenum chamber. Interior of the working section looking south towards the opposite door. Interior of the working section looking west into the engine exhaust diffuser duct. The interior of the plenum chamber looking east. Southern-side working section bleed flow leading down to the lower spill diffuser duct. Looking up the southern-side working section bleed flow towards the top of the plenum chamber. View north across the southern working section door, through the working section, to the other side. Looking south towards the working section from the elevated southern walkway. View westwards alongside the southern exhaust ducts.
View from the ground floor looking east along the southern flank of the cell. Looking west towards the diffuser ducts at the rear of the cell building on the ground floor. Looking west towards the diffuser ducts at the rear of the cell building on the elevated walkway. General view of Cell 4 looking east. Back section of Cell 4 including the diffusers, coolers and flame traps. Looking west along the elevated walkway along the northern flank of the cell. Doorway into the northern side of the working section. General view of the northern side of the plenum chamber. Discarded scrap metal from the Sahara set in the northern part of the building. Walkway over the top of the cell looking south.
Walkway on the top of the cell looking west. View from the central walkway along the top of the cell looking west. Sign on a door leading into the adjoining offices. Ground floor office in the south-eastern corner of the office area. Ground floor corridor leading to the workshops. Looking west. Phone booth in the workshop area. The ground floor workshop and store area looking east. The ground floor stairs looking south. The first floor office spine corridor looking west. Western view across a first floor office.
Looking west across the open-plan offices on the first floor. View east across the open-plan offices on the first floor. Looking south across the doorways at either end of Brianís Bridge. The office beyond Brianís Bridge looking south-west. The second office after Brianís Bridge looking south-west. The second floor stairs looking south. Piping in the concrete cage on the roof of the office block looking south-east. View south through the concrete cage towards the Air House.

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