The Concorde Olympus 593 Mk 610 engine, remain to this day the most efficient jet engine in the world at Mach 2, where thermal efficiency in concerned. But at lower speeds the engines consumes fuel at a massive rate.
Subjects included in this section are as follows-
Concorde engine Combustion Chamber/Turbines/Engine Control/Power Control/Mass Control/Fire Supression/Support Structure/Reheat
For Concorde to be economically viable, it needed to be able to fly reasonably long distances, and this therefore required high efficiency. For optimum supersonic flight, turbofan engines were considered, but then rejected, this was due to their large master cross-section which would cause excessive drag. Turbojets were found to be the best choice of engines for Concorde. The quieter high bypass turbofan engines such as those which are now used on the Boeing 747s could also not be used. The engine chosen was the twin spool Rolls-Royce Olympus 593, a version of this Olympus engine had originally been developed for the Vulcan bomber, and then developed into an afterburning supersonic engine for the BAC TSR-2 strike bomber and then in association with the French company Snecma Moteurs , this had been adapted for Concorde, with the final version fitted to the production aircraft known as the 593 mk610.
The Olympus 593 Mk 610 engines that were installed in all the production Concordes remain to this day, the most efficient jet engines in the world at Mach 2, as far as thermal efficiency is concerned. They may be efficient at Mach 2 and above, but at slower speeds it uses fuel in a most inefficient way, so this required a minimum amount of low flying speeds for Concorde.
The original design for the Concorde Olympus 593 reheat system was carried out by SNECMA, but due to them getting into all sorts of trouble during the project with the fuel injection system and the flame stabilisation, Rolls-Royce got involved and baled them out, and the re-heat system became a Rolls-Royce/ SNECMA design. (The core engine was a 100% Rolls Royce design, with no French input whatsoever. However some engine sub-assembles were manufactured by SNECMA).
THE CONCORDE 593 ENGINE VARIANTS
- 593 – Original version designed for Concorde
Thrust : 20,000 lbf (89 kN) dry / 30,610 lbf (136 kN) reheat
- 593-22R – Powerplant fitted to prototypes. Higher performance than original engine due to changes in aircraft specification.
Thrust : 34,650 lbf (154 kN) dry / 37,180 lbf (165 kN) reheat
- 593-610-14-28 – Final version fitted to production Concorde
Thrust : 32,000 lbf (142 kN) dry / 38,050 lbf (169 kN) reheat
Specifications (Olympus 593 Mk 610)
- Type: Turbojet
- Length: 4039 mm (159 in)
- Diameter: 1212 mm (47.75 in)
- Dry weight: 3175 kg (7,000 lb)
- Compressor: Axial flow, 7-stage low pressure, 7-stage high pressure
- Combustors: Nickel alloy construction annular chamber, 16 vaporising burners, each with twin outlets
- Turbine: High pressure single stage, low pressure single stage
- Fuel type: Jet A1
- Maximum Thrust: wet: 169.2 kN (38,050 lbf) dry: 139.4 kN (31,350 lbf)
- Overall pressure ratio: 15.5:1
- Specific fuel consumption: 1.195 (cruise), 1.39 (SL) lb/(h·lbf)
- Thrust-to-weight ratio: 5.4
- World’s first FADEC control system
- Straight pipe with pneumatically operated convergent nozzle
- Single ring afterburner
- ‘Eyelids’ which act as variable divergent nozzles/thrust reversers
DESIGN AND DEVELOPMENT
The Olympus 593 project was started in 1964, using the BAC TSR-2’s Olympus 320 as a basis for development. Bristol Siddeley of the UK and Snecma Moteurs of France were to share the project. Acquiring Bristol Siddeley in 1966, Rolls-Royce continued as the British partner. The early stages validated the basic design concept but many studies were required to achieve desired specifications, e.g.
- The critical factor – fuel consumption
- Pressure Ratio
- Turbine entry temperature
Initially, engineers studied using turbojets or turbofans, but the lower frontal cross-sectional area of turbojets in the end was shown to be a critical factor in achieving superior performance. The competing Russian Tu-144 initially used a turbofan, but quickly changed to a turbojet with considerable improvement in performance.
Rolls-Royce carried out the development of the original Bristol Siddeley Olympus and engine accessories, while Snecma was responsible for the variable engine inlet system, the exhaust nozzle/thrust reverser, the afterburner and the noise attenuation system. Britain was to have a larger share in production of the Olympus 593 as France had a larger share in fuselage production.
In June 1966 a complete Olympus 593 engine and variable geometry exhaust assembly was first run at Melun-Villaroche, Île-de-France, France. At Bristol, flight tests began using a RAF Vulcan bomber with the engine attached to its underside. Due to the Vulcan’s aerodynamic limitations the tests were limited to a speed of Mach 0.98 (1,200 km/h). During these tests the 593 achieved 35,190 lbf (157 kN) thrust, which exceeded the requirements of the engine.
In April 1967 the Olympus 593 ran for the first time in a high altitude chamber, at Saclay Île-de-France, France. In January 1968 the Vulcan flying test bed logged 100 flight hours, and the variable geometry exhaust assembly for the Olympus 593 engine was cleared at Melun-Villaroche for flight in the Concorde prototypes.
At 15:40 on the 2nd March 1969 Concorde prototype 001, captained by chief test pilot Andre Turcat, started its first take off run, with afterburners lit. The four Olympus 593 engines accelerated the aircraft, and after 4,700 feet (1.4 km) of runway and at a speed of 205 knots (380 km/h), captain Turcat lifted the aircraft off for the first time.
BASIC BACKGROUND TO THE OLYMPUS 593-610
The production airliner Concordes are propelled by four Olympus 593 Mk.610 engines and together they produce 152,200 lbs of thrust at take-off and 27,160lbs of thrust during the cruise at 60,000feet. With their air in-take, re-heat and exhaust systems they are among the most technically impressive features of Concorde, but there are very noisy…….
Designing the engines for a Mach 2 supersonic aircraft such as Concorde, involves a lot of compromises. The first necessity is that they must work successfully in the cruise. This would require them to be narrow in cross-section, to minimize drag, add to that, they would also require a high exhaust velocity, otherwise the exhaust itself would tend to slow the aircraft. All of this means that Concorde required an engine with low by-pass ratio, a pure jet.
The disadvantages of this type of engine compared to that of a high by-pass ratio type, used on subsonic aircraft, is that it moves a smaller mass of air faster, unlike a high by-pass ratio that is comparative quiet. As a major component of aircraft noise comes from the mixing of the exhaust with the static air outside, a sort of tearing effect, the disadvantages of this pure jet type of engine used for Concorde starts to become obvious, but there was no other choice.
The Rolls-Royce (originally Bristol Siddeley)/Snecma Olympus 593 Mk.610 engines that are fitted to Concorde were at first called the Olympus 593B (B for big) and are a highly developed version of the Bristol-Siddeley Olympus 593D (D for derivation) the original Concorde engine and the first civil Olympus. The 593D is, in turn , a development of the Olympus 320 for the TSR2, the successor to the 201 and 301 series engines used in the Vulcan bombers this generated 11,000lbs of thrust.
The reason for the changed from the 593D to 593B was that when the Concorde specifications were upgraded to improve the range, in 1963, the increased take-off weight demanded a 12 per cent increase in thrust. This could have been obtained by development of the 593D, but it was decided that it was too early in the engine’s life to make such a large redesigned in its long term development potential. Therefore the engine was redesigned as the 593B, with new compressors and turbines. . Rolls-Royce provided the development of the Olympus engines while SNECMA developed the exhaust and re-heat system. On the prototypes this powerplant system was upgraded to generate 33,000Lbs of thrust and by the time it was fitted to the production aircraft, 38,050Lbs were available.
The Olympus engines used on the prototype Concorde’s,were an axial flow twin spool engine with a can-annular combustion chamber. But one problem with this engine was the exhaust smoke; the Prototype Concorde’s exhaust smoke was horrendous. This therefore required a change from the can-annular combustion chamber to an annular, vaporising type. This cured the smoke, but the vaporisers kept falling off with regular monotony.
Each spool carries seven compressor stages and one turbine, the low pressure shaft running inside the high pressure shaft. The low pressure spool is carried in three bearings: a roller bearing mounted in the boss of the in-take casing, a twin-row ball thrust bearing in the intermediate casing which connects the two compressor casings and a roller bearing at the rear of the low pressure turbine. The high pressure spool is carried in a second twin-row ball thrust bearing in the intermediate casing and a roller bearing in the compressor inlet guide vanes, mounted in the intake casing, are of fixed incidence and tangential layout.
The blades and discs of the low pressure compressor and of the first stages of the high pressure compressor are made of titanium, to withstand the high temperatures to which they will be subjected during supersonic cruising and possible damage from any foreign objects; in the rear stages of the high pressure compressor, Nimonic 90 was used because of the even higher temperatures. At Mach 2 cursing the low pressure inlet temperature would be 127C. Both compressor casing are steel.
The high pressure turbine rotor and stator blades are vacuum cast. They are air cooled on all engines and on the production engine the low pressure turbine rotor and stator blades were cooled also; the latter are forged and vacuum cast respectively. At supersonic speeds when the air approaches the combustion chamber is very hot due to the high level of compression of 80:1.
Nimonic 90 – Nickel-Chromium-Cobalt Alloy
Nimonic 90 is a Nickel-Chromium-Cobalt alloy being precipitation hardenable, having high stress-rupture strength and creep resistance at high temperatures up to about 950°C (1740°F). It is widely used and a well proven alloy in high temperature conditions.
The oil tank is mounted on the portside of the low pressure compressor casing and supplies The combustion chamber contains eight flame tubes which are mounted between the compressors delivery casing and the first stage high pressure stator ring. The latter, which has to withstand temperatures of up to 1148C, is cooled by Air trapped from the high pressure compressor at up to 560C and allowed to escape into the gas stream through slots machined in the trailing edge of the blades
Fuel is injected through a Simplex air-spray burner in the head of each flame tube and there are two igniters. Fuel flow is looked after by the electro-mechanical engine control system, the Ultra electronic throttle and fuel control system. This incorporates a 6A00 electric throttle, acceleration control, engine speed control, turbine entry temperature limiter and a magnetic computer unit. There is an over-speed governor for each fuel pump, but these only come into operation if a fault in the electrical system allows the turbine speed to rise above predetermined limits. The control system is analogue and control of it by the pilot is very straightforward, although, due to automation, detailed examination indicates a very complicated arrangement. The pilot has the ability to select the mode in which the engine operates by a single switch per engine –take-off, climb and cruise.
the pressure pump, which in turn feeds the main bearing through calibrated orifices. Sumps under the intermediate casing collect the oil by gravity drainage and the scavenge pump returns it to the tank through the fuel-cooled oil cooler.
On each of the four engines, are mounted two gearboxes, one for airframe accessories and one for engine accessories, both driven from the high pressure compressor drive shaft through the intermediate casing. Each of the former drives one or two hydraulic pumps (this is according to engine position) and a constant speed unit which drives a constant frequency a.c. main generator. Each of the latter drives a variable stroke high pressure fuel pump, a centrifugal low pressure pump and oil pumps.
THE COMBUSTION CHAMBER
Air flows directly from the HP compressor to the combustion chamber where the big challenge is to separate-off exactly the right amount of air to provide the correct mixture strength for complete and efficient combustion, and to slow down that portion of the air so that it doesn’t keep blowing the flame out. The rest of the air, and it is a substantial amount, is a cooling medium, carefully channelled to protect the walls of the chamber from the direct heat of combustion. It is the oxygen content of this airflow that enables reheat fuel to burn in the jet pipe.
It will be recalled that Concorde prototypes generally displayed a bit of a smoky exhaust. Which was down to incomplete combustion and was a waste of potential thrust, but the Olympus was derived from a military engine, where the function may have overridden friendliness.
There was always right from the start the plan to supply a totally new combustion chamber, but this did not arrive until 1970, and was the penultimate evolution of the Olympus engine, the 593-602. Prior to the change, fuel/air mixing had taken place in eight separate but interlinked chambers. Post-modification, there was but one large annulus, a cylinder within a cylinder, if you like, and inside sixteen twin-armed vaporisers spraying upstream against the gas flow. Rather than simply providing a highly atomised spray, the vaporisers sat far enough into the combustion chamber to be raised in temperature sufficiently to vaporise the fuel, providing highly efficient, smoke-free combustion, but extremely vulnerable to erosion, burning and cracking, alleviated to some extent by a changer from fabricated to cast vaporisers.
The annular combustion chamber was initially a great success, achieving all that was expected of it, but as engine operating hours built up after Concorde’s entry into airline service, the extreme conditions within the chamber took their toll. Splits, tears, burning and erosion of the chamber walls and fractures of the fuel vaporisers were detected by borescope inspections and in-flight analysis. During this period, maintenance engineers honed their pit-stop skills to the point where a complete engine change plus the attendant ground-run test could be wrapped-up in one eight-hour shift.
Development, however, never stands still: a revised annular chamber featuring anti-corrosion ceramic plating, better cooling and more efficient combustion appeared in 1981; it was good enough to see Concorde through its 27 years of airline service.
The turbines and the major controlling parameter – Turbine Entry Temperature TET has always been dependent upon metallurgy. Only the very best of super-alloys can withstand the continuous battering from the 1,000C plus, sonic velocity gas stream. Strength, heat resistance and immunity to exotic forms of corrosion are prerequisites. The HP turbine and its ring guide vanes bear the brunt of this onslaught. HP turbine blades have eighteen cooling holes drilled top and bottom, this is a technique developed to provide cooling passages for guild vanes and blades alike, using air bled from HP compressor fifth stages as the cooling medium – if 1,450C air can ever be termed a cooling medium! By this means TET was raised to 1,450C.
Turbine cooling air temperature, as a measure of turbine health, is sensed at two points between the HP and LP turbine and indicated on instruments at the flight engineer’s position on the flight deck. Normal super-cruise value would be around 550C, with a warning triggered at 640C requiring an engine shut down to prevent further deterioration. Exhaust Gas Temperature (EGT) and a jet-pipe pressure (P7) are both measured at position downstream to the turbines and displayed at the forward engine instrument panel and the flight engineer’s position respectively.
The Olympus engine combustion chamber is made from the material called Nimonic 263, which is described as nickel (47%), chromium (20%) and cobalt (20%) alloy. It has in the mix varying percentages of carbon, silicon, manganese, sulphur, aluminium, titanium, boron, copper, iron and lead with a dash of silver (0.0005%) and a hint of bismuth at 0.0001%; each element making its contribution to life in the ‘hot lane’
OILS & BEARINGS
The two main rotating assemblies are supported by five bearings – roller, ball, roller, roller – front to rear. The LP spool has a roller bearing in front of the compressor and the thrust bearing (ball) behind, with a roller bearing to support the turbine end, whereas the shorter HP spool runs on a thrust bearing in front of the compressor and a roller in front of the turbine.
The five main bearings, together with all accessory gears and drive bearings are lubricated by a single oil pressure pump set at 26psi. Five scavenge pumps direct return oil. Through fuel-cooled oil cooler, back to an external tank attached to the LP compressor casing, LH-side.
The oil tank contains 16 US quarts; total system content is 26 US quarts. Replenishment access is via a small hinged panel at the forward end of the main engine door. A special hand pump gun or dispenser must be used; a ‘fill’ connection and overflow connection are located at the tank base. There is no gravity top-up facility. For a complete oil change, oil may be drained through the ‘fill’ connector. The only oils/lubricants that could be used for the Olympus 593-610 were:
LUBRICANT – ‘A’ / SPECIFICATION – D.E.R.D.2497 – Iss.3
Mobil RM 193A-3
Shell ASTO 555
( Shell ASTO 555 USA blended must me marked D.E.R.D.2497 on the container)
Royco Turbine oil 555
LUBRICANT – ‘B’ / SPECIFICATION – D.T.D.806B
AeroShell grease 8
Rocol Aerospec 305
LUBRICANT – ‘C’ / SPECIFICATION – MSRR4008
LUBRICANT – ‘E’ / SPECIFICATION – MSRR4008
LUBRICANT – ‘E’ / SPECIFICATION – MSRR9295
LUBRICANT – ‘G’ / SPECIFICATION – D.T.D.900/4980
Rocol G576 (Formerly Foliac G576)
LUBRICANT – ‘L’ - Never-seez aerosol spray NSN-16A
LUBRICANT – ‘M’ - Molycote G
LUBRICANT – ‘R’ - Rocket W.D.40
LUBRICANT – ‘S’ / SPECIFICATION – AIR 4247 (D.T.D.392B)
AeroShell compound 08
LUBRICANT – ‘T’ – Guardian Chain Lubricant 1
But the different oils could not be mixed in the same tank. Engine oil pressure, temperature and contents are displayed at the flight engineer’s position
The engine is controlled by a duplicated analogue electronic system; Main and Alternate, used turn and turn about. Each system can be divided into two parts: (1) the conventional fuel injection control that responds to throttle lever input to set the required fuel flow; (2) the networks that vary the primary nozzle area to control jet-pipe pressure, thus matching N1 to N2
Concorde has two engine nacelles; each one accommodates two engines and is divided into two structurally independent parts, consisting of air-intakes and engine bays. There is an extension of the engine bay which incorporates the secondary nozzles. The intakes and engine bays are attached to the wing by flexible joints which ensure the complete sealing and continuity of form.
At the simplest level, the throttle lever sets power: its position is signalled electrically to each Engine Control Unit (ECU). The ECU mixes throttle lever position with engine and atmospheric data to output a drive to the fuel throttle valve. Additional circuits control engine acceleration and prevent exceeding maximum and minimum limits
MASS FLOW CONTROL
Also contained within each ECU is a set of ‘schedules’, basically electronic graphs that output a drive signal to the primary nozzle to facilitate matching of LP and HP rpm to deliver maximum air mass flow, whilst keeping clear of surge, at all conditions. There are four ‘schedules’, selected either manually or automatically, according to phase of flight.
Being the first of a new generation of aircraft, the constructors have spared no effort to prove the integrity of each individual system and component on the aircraft, thus ensuring that the Concorde is the most thoroughly tested aircraft ever to enter airline service. This minute attention to detail is reflected in the design of the main powerplant fire protection systems.
In each engine bay there is a two-shot fire extinguisher and optical fire detector. If an extinguisher is used, the secondary air cut-off valve, the engine bay ventilation door and the tertiary air doors are closed. At the same time the heat exchanger inlet door, normally open either to atmosphere or to secondary air, splits under the action of a spring thus cutting off both air flows.
The closing of the secondary air cut-off valve causes the four fire doors to close also, because they are lightly spring loaded in the closing sense and are kept open only by the pressure of the secondary air flow. When closed they blank off triangular spaces between the compressor casing and the corners of the rectangular nacelle, completing a fire wall.
Two electrically separate fire wire loops, co-sited in a performed steel conduct, are located in the nacelle doors and around the engine, in normal operation both loops are in a circuit and both must detect a fire signal a warning. If only one loop is unserviceable, the good loop may be selected for single channel operation.
There are four engine suspension points on Concorde: two front suspension links attached to the top of the low pressure compressor casing and two main points, one on each side of compressor delivery casing. The front links are free to swing to allow for axial and radial expansion of the engine forward of the main points. The main points, which are conventional trunnion fixings, are connected to the wing structure by pin jointed vertical links and by engine thrust struts running forward and upwards. They take engine thrust loads, transverse and vertical loads and gyroscopic couples. One trunnion is fixed; the other is not restrained laterally to allow for the lateral expansion. There are four large non-structural access doors beneath each nacelle. All electronic connections are brought to a single panel above the compressor delivery casing.
AFTERBURNERS OR REHEAT
Afterburners are simply a method of making use of the hot exhaust gases once they have passed through the turbines. Fuel is spayed into a ring in the exhaust pipe and burned to increase thrust when it is required, such as on take-off and during acceleration through Mach 1. These are the two most power-demanding periods of the flight. An engine powerful enough to cope with them would be too powerful for the cruise, and probably too heavier as well. Concorde’s afterburners increase thrust on take-off by about 20%, but they do make heavy demands on fuel, causing nearly a ton of fuel to be burned between the start of a heavy-weight take-off and 1000 feet on the climb.
The ORIGINAL design for the reheat was done by SNECMA, but due to them getting into all sorts of trouble with the fuel injection system and flame stabilisation, Rolls-Royce baled them out, and it became a Rolls-Royce/ SNECMA design. (The core engine was a 100% Rolls design, with no French input whatsoever. However some engine sub-assembles was manufactured by SNECMA).
The basic way the afterburner worked was by spraying the fuel FORWARDS initially at high pressure, against the jet stram about one inch, until it hit the anvil. . As the fuel strikes the anvil it is blown back by the jet stram and atomises, passing over the spray ring and the over the flame holder. The ignition operated by passing 15KV across a dual cylindrical tube, the resulting arc was ’swirlied’ into the fuel stream by blowing engine 5th stage HP compressor air into the tube (there were 7 stages in all).
The key to successful ignition was a healthy spark, a good supply of air to the ignitor and accurate scheduling of fuel flow. (This was scheduled against dry engine flow as a function of total temperature). The other important factor (as with any afterburner) was correct and rapid operation of the exhaust nozzle. Fortunately, Concorde used it’s primary nozzle for control of engine N1 anyway, so adapting this to operate as an afterburning nozzle also was a relative walk in the park, and it operated superbly.
During the light up phase of 3.5 seconds, the fuel ratio is a fixed 0.45 (ie. reheat fuel is 45% of dry fuel). After the light up phase the full scheduling commenced. As far as the FLIGHT RATING figures go (not take-off) the ratios were 0.6 at a TAT of 54 deg’s C, falling linearly to 0.3 at 107 deg’s C and above. (Remember that Concorde used afterburning really sparingly, just for take-off and then transonic acceleration; cut off at Mach 1.7 altogether.
The system is connected to the engine fuel supply, it comprises of a single spray ring and flame holder mounted on the tail cone behind the turbines. Fuel, metered electronically in proportion to the engine fuel flow, is switched from the flight deck. When the system is activated, fuel flows to the ring, is sprayed upstream into the gas flow and is lit by a timed run of a single igniter plug. The flame then stabilizes on the flame holder, some 8 inches behind the ring. Utilising residual oxygen in the gas flow, its effect is to further increase jet velocity, adding approximately 22% of thrust at take-off and 30% at climb power for transonic acceleration. Its performance is monitored on the flight deck, first by noting rise in fuel flow at initiation, followed by indication of primary nozzle areas running fully open on light-up.
Reheat is used on every take-off, its light-up sequence taking place on the roll as the engines accelerates up to full power – it needs the mass flow associated with an N1 of 81% or more to function. It is switched off at 500ft on a standard flight or at noise abatement cut-back where needed. For the transonic acceleration it is switched on at climb power at M0.95, then off again at M1.7 – a run of between 10 and 15 minutes dependent upon aircraft weight and outside air temperature
In the end, there were 67 Rolls-Royce/Snecma Olympus 593 Mk.610 engines, that were manufactured for the aircraft.
Plans were drawn up by the two companies for a quieter and more powerful version of the engine, this would have had an extra turbine section and a larger-diameter air compressor that would have eschewed the reheat system and added sound-deadening to the aircraft. This new engine would have had improved efficiency across the board and permitted rather greater range for Concorde and therefore opened up new routes, particularly across the Pacific as well as transcontinental across America. However, the poor sales of Concorde meant that this plan for a Concorde ‘B’ was never put into practice, which is a shame as the next airframe to be build after 216 G-BOAF, would have been the newer version fitted with the newly designed Olympus engines.
Today years after Concorde made its last flight, versions of the Rolls-Royce Olympus engine are still in use powering everything form large passenger ships such as the Queen Mary 2 and navy ships to power stations.
Click on the links below to read more concerning the following main parts of the Concorde Powerplant
A personal story regarding the Concorde/Olympus Development 1956-1969
By Malcolm Knight
The earliest Concorde related item I can find in my father’s old notes is a press release dated 1956 detailing the installation of an engine test facility at the National Gas Turbine Establishment (N.G.T.E.) at Pyestock, Hampshire for a Super Sonic Transport (SST). I don’t recall him making any further comment about any such project until a couple of years later when Conservative defence minister Duncan Sandys came to the conclusion that manned military aircraft had no future and work on a projected Mach 3 bomber was abandoned. I always imagined that that was probably the beginning of the Concorde idea as so much development work had taken place that some use ought to be made of it. One of my earliest Concorde specific memories is that the first designs had no windows as befits a bomber and of course their absence made the aeroplane much stronger and able to resist the high skin temperatures encountered at supersonic speeds. However BOAC (British Overseas Airways Corporation), the UK’s international airline of the time made it amply clear that although little could be seen from 60,000 feet a windowless airliner was unsaleable.
By the early sixties Dad was the engineer-in-charge of the engine test facility at Pyestock and he took me to see it a few times. It consisted of a Parsons steam turbine which used to spin eight electric motors up to mains synchronous speed and all nine then powered air compressors which pushed enormous quantities of air at up to 2,000 miles per hour into the Olympus engine wind tunnel. The total power was a little short of half a million horsepower. The steam was generated by a boiler taken from an old Battle class destroyer (hence the name Battle House for the boiler room) and the electricity was taken from the national grid but only when the Central Electricity Generating Board’s (CEGB) headquarters at East Grinstead said there was sufficient spare capacity. In practice this meant that Concorde’s engine could only be tested at night. Dad made several trips to East Grinstead presumably to liaise and negotiate with the CEGB. I suspect it was no coincidence that some areas within several miles of N.G.T.E. had gas street lighting until the early 1970s. We always knew when Dad had got to work and switched on his electric motors because the home television picture would shrink and a moment later we would hear the roar of the engines starting up even though the test facility was about two miles away from home.
My recollection of the test facility known as the Air House is that it was of course enormous and looked like a cross between a power station and a ship’s engine room. The motor/compressor units were laid out in lines and were of considerable length, 50 or 60 feet each I would think and they were surrounded by those cast iron see-through walkways of the type to be seen in TV documentaries set in old fashioned factories or prisons. In one corner of the room at a vantage point looking down on the machinery was the control gallery. Quite what was in it I do not know apart from the main on/off switches. These were the days before computer control and telemetry and in fact machine readings were taken by hand by people who walked around the complex noting down individual gauge readings and reporting back to the control desk at half-hourly intervals. The object of the exercise was to develop the Olympus engine (which started life at 10,000 pounds of thrust and which was giving twice that by the late fifties) to give sufficient power to get Concorde across the Atlantic economically (for its day) and with range to spare. My recollection is that the aim was to get 42,000 pounds of thrust from the engine but as Concorde is said to have only 38,000 pounds per engine either my recollection is at fault or the ideal target was never met. The economic standards for airliners of the day were set by the Boeing 707 and de Havilland Comet and the aim was to ensure that Concorde achieved a similar fuel consumption. In this it succeeded but what no one seemed to account for was the development of more efficient by-pass and three-spool engines. See below.
I have two particular memories from the time that Dad ran those engine tests. Firstly that the air flow was very difficult to turn off. It suffered the equivalent of ‘water hammer’, the same as if you close off the flow at your basin tap by suddenly capping it with your hand, or similar, the shock wave will make the pipes go bang. Shutting off air flowing at twice the speed of sound quickly tended to break the compressors. Apparently the engineers at various companies including Rolls Royce had supplied equipment designed to do the job but all were unsatisfactory. Dad designed a system mounted in a Dexion rack the size of a small wardrobe full of (as I recall) pipes and aneroid barometers which did the trick at a cost under £100. Dad always did say a good engineer was someone who could make for a penny what any damned fool could make for a shilling!
The other episode was somewhat more dramatic. One evening, I forget just when, Dad came home late at night looking grey and unwell. I remember Mum being most concerned and I think she for a moment thought he must have stopped for a beer or two on the way home even though that is something I don’t think he ever did. When he’d calmed down a bit he told us what had happened. Apparently one of the men taking 30 minute interval meter readings from the air compressors thought one of them should be reported sooner rather than later and as a result Dad had rushed to the machine to see for himself. He put his ear to the engine casing (no wonder he went deaf!) and decided that the main thrust bearing was in serious trouble. He ordered everyone to run while he went back to the control room to close the system down. However he was too late and the main compressor shaft broke free from its casing and hurtled across the building wrecking most of the other compressors as it went. Fortunately because of the quick thinking of the meter reader and the instant diagnosis of the fault everyone had time to get out of the way and no one was hurt. When I saw the scene later it was one of complete devastation and it set the engine tests back six months.
At a later phase of Concorde’s development Dad used to spend alternate weeks in France. He would fly to Paris in the evening and get the overnight sleeper train to Toulouse. I think it would be true to say that Dad didn’t have the highest opinion of the French aviation industry’s abilities. He would complain that it could take up to six months to translate the various technical reports sent from Toulouse and neither was he very surprised that various key components that the French were supposed to build were delivered marked ‘Made in U.S.A.’. One of the lasting legacies of the commuting to France is the supply of duty free whisky and brandy that still resides in my drinks cabinet, neither father nor son being much of a spirits drinker.
Dad was not I believe heavily involved in flight testing however one of my memories is of him telling me just how strong Concorde was. He said that in the period when we were trying to sell the plane to foreign airlines a Pan-American crew was invited to loop Concorde over the Atlantic. Their response was to the effect that that would be silly as an airliner would break up during such a manoeuvre but they were persuaded that Concorde was an exception. Over the years I began to doubt this story and wondered if perhaps Concorde had been rolled rather than looped, rolling being a fairly easy accomplishment compared to a loop. I was therefore pleased to read newspaper commemorative articles during the final week of Concorde’s commercial life, evidence that I had not imagined it after all.
I managed to get inside Concorde myself just once, a quick end-to-end walk-through on the ground. I did however see it flying many times, once with full reheat on only a few feet above my own house roof in Connaught Road, Fleet. That would be in 1970 or 1971. I think it was in 1969 that I went to the flying display at Farnborough and the weather was absolutely filthy with driving rain and poor visibility. Concorde was due to fly in from Filton and it was doubtful whether it could make it. However it managed to make a couple of touch-and-go passes before disappearing into the low clouds. When I got home I discovered that conditions were so poor back at Filton that Concorde could not land there and the only runway within range that was both long enough and had the requisite blind landing equipment was Heathrow. As you may imagine it was the front page news in all the papers next day.
Concorde was undoubtedly a magnificent achievement and all the more so when so much of the design work was done by practical experiment and slide-rules. I cannot finish this set of recollections without mentioning Dad’s great friend Eric Lewis with whom he started his career on jet engine development in the late 1940s. Eric’s expertise led him in other directions doing a great deal of work on TSR2 and pursuing his ideas to make quieter jet engines. This culminated in the Rolls Royce RB211 ‘three-spool’ engine. This new type of jet engine became the norm for all current jet airliners. Despite his work on that project at the very same time that Concorde was being prepared for service, Eric was, if I remember correctly, appointed to be the Director of Production for Concorde when the expectation was that it would be mass produced. I recall Dad saying about Eric’s predecessor in that role that “he couldn’t manage a match box factory”. Fortunately that fact was recognised and equally fortunately I cannot remember his name – so I am probably out of reach of the libel laws. Eric still lives in Farnborough in the same house that he bought in 1958.
Disclaimer: Everything above is taken from memory of conversations around the family meal table and occasional visits to the Concorde test facilities. Whilst most of it is known to be true the forty intervening years may have had some effect on the precision of the detail. Two and a half years after recording the above notes I made a belated visit to Farnborough’s AirSciences museum which attempts to preserve the memory and artefacts of the N.G.T.E. and R.A.E.’s pioneering work on and research into aviation.