"The first and most striking thing about the Concorde supersonic transport is that it is being built", Dr.
"The first and most striking thing about the Concorde supersonic transport is that it is being built", Dr. W.J. Strang, Director and Chief Engineer of the Filton Division of British Aircraft Corporation, told members of the Aviation and Space Writers Association when he reviewed progress on the project at the Association's conference in New York today.
For the Engineering Department, Dr. Strang said, the most straightforward measure of progress was the drawings issued. "In June 1964 we - BAC only - programmed the drawings to be issued by April 1966 as 17,800: by the end of April 1966, we had issued 19,500 drawings - 110 per cent of target".
The structural test programme, he said, called for a major wing-body specimen, 27 ft.long and 44 ft. wide, to start testing in July, 1966. That specimen was on its way from the Sud-Aviation factory at Toulouse to the nearly test site on March 4th, 1966.
The programme also required the development of a novel fatigue testing technique that would enable them to apply heating, cooling and mechanical loading cycles to a complete airframe. The solution was a full-size, 15 ft. long fuselage specimen at Filton, which was already undergoing a full programme of combined thermal and applied loading cycling. The airframe was enclosed in a kind of giant wind tunnel in which alternate blasts of hot and cold gas produced the thermal cycling conditions.
The production plan called for nine major components into the Sub-Aviation assembly jig at Toulouse, France, for join-up into the cental structural element of the first prototype. They had done just that.
In September this year, front and rear fuselage, intake and engine bay components from BAC factories would be on their way to Toulouse.
The Bristol Siddeley Olympus 593 engine for the Concorde first ran on the 11th November, 1965, three weeks in advance of the target set when instructions to manufacture were given. The thrust guaranteed for first flight engines was soon exceeded and the engine had been run at full production take-off thrust and turbine-entry temperatures. It had also been run successfully with a heated intake giving Mach 2 inlet temperature. A flight clearance test with Concorde variable primary nozzle was successfully completed, and bench running hours were currently 100 hours ahead of schedule.
Setting out what he called "The general Concorde scene", Dr. Strang explained that the main effort at this time was devoted to the design and build of the two prototype aeroplanes and associated development programmes. Design and development were shared by Sud-Aviation in France and BAC in Britain, which had a combine work forces of 57,500 men.
The engine was the responsibility of the Bristol Siddeley Engines Limited in Britain and the jet pipe and nozzle assembly was being designed and developed by the SNECMA company of France. Their combined work force exceeded 40,000 men. The enterprise was additionally backed by the research establishments of both countries in a truly international enterprise on a 50/50 basis.
The first prototype was being assembled by Sud-Aviation at Toulouse and the second by BAC at Bristol. Both assembly lines drew components from Sud and BAC plants, with each component made at one place only.
These prototype aeroplanes could carry 120 passengers but they would never do so. Instead, they would be equipped as flying laboratories with hybrid digital-Analogue data-recording systems logging 3,000 transducers on each aeroplane.
Dr. Strang went on: "Of course, modern instrumentation systems can easily be geared up to produce as much information as the International Geophysical Year, and the real trick lies in mechanising the means of extracting the interesting bits. To do this, twin data-reducing systems are being installed at the two flight test centres at Bristol and Toulouse, with on-line computers and compatible interfaces with our big general-purpose digitals.
The next two aeroplanes were what they called the "pre-production" aircraft. They would be bigger than the prototypes, fully representative of production aircraft, but they too would have full flight test installations in addition to a representative passenger cabin section with standard seating.
The principal differences from the prototypes were:
Longer body#191 ft. instead of 184 1/2 ft.
Higher gross weight#350,000 lb. instead of 326,000 lb.
Extra tankage#185,000 lb. instead of 174,000 lb.
Higher payload capacity#28,000 lb. instead of 23,600 lb.
There were other differences as well - in window and door arrangement, for instance.
The first of these bigger aeroplanes was scheduled to fly from Bristol in September, 1969, and the second from Toulouse in November, 1969. Scheming had been going ahead for some time and engineering drawing issue for manufacture had begun.
Of the aerodynamic, structural and system development programmes, he could select only a few items. Maintaining a comfortable passenger environment was one of the more obvious requirements to be tackled with a supersonic transport and a fullscale Concorde fuselage section, 20 ft. long, was used to prove the insulation and air distribution design. This system went on test at Yeovil, England, in August, 1964, and successfully completed all tests by July, 1965. Many of these tests were carried out with full loads of "live occupants", including airline personnel. In August, 1965, with all design objectives achieved, the specimen was shipped to Toulouse and was now built into the integrated air conditioning rig at the Sud-Aviation factory.
The structural development programmes comprised a wide range of specimens built up through major component tests like those to which he had already referred, culminating in full-scale static strength and fatigue tests of Toulouse, and Farnborough, on two complete aircraft.
The required test facilities were under construction and the fatigue rig at Farnborough was especially impressive. Employing the gas heating and cooling system in pioneer use at Bristol, it would consume liquid nitrogen at a rate of 100 tons a day. Ground and flight loads would be combined with thermal cycling in the most compressive simulation of flight conditions ever attempted on an aeroplane structure.
In mid-1970, development flying would be reinforced by the first production aeroplanes, leading to a planned total of over 4,000 hours' flying time by certification date, April, 1971. That was more than twice the flying hours customary on subsonic aeroplanes and reflected the determination of Concorde management to ensure that Concordes would be safe and fully-working tools of the airlines by the time they were delivered.
Dealing with the characteristics of these production aeroplanes, Dr. Strang reminded his audience that any long-range aeroplane was a sensitive device at the design stage and that quite small differences in design estimates could escalate into large changes in gross weight. Supersonic long range aircraft were exception, and 1 per cent of drag meant a ton of fuel for Concorde on a trans-Atlantic mission with full airline reserves.
In those circumstances, he said, they had set themselves a minimum acceptable performance level, which was to carry 26,000 lb payload non-stop Paris-New York, with a hot day take-off and other adverse factors.
He went on: "We not only have to convince ourselves of this; we have to convince two governments as well. Naturally, we expect to do a lot better and the most probable performance has to be a lot better for the approach to be valid at all. It is a policy aimed at making sure that the world's first supersonic transport will not fail, and it makes a fine springboard for future development." There had been misunderstandings in the past about Concorde range, he said, but perhaps it would make it quite clear if he stated that their minimum performance level gave a range of over 4,000 statute miles, with FAA reserves.
The configuration was usually described as 136 seats, which meant 4-abreast seating at 34 inches' pitch, no triples. It was a very comfortable standard, and they had a 32" pitch arrangement with special seats in the mock-up that most people thought was 34" until they measure it for them. If the airlines chose that, he did not think anyone would complain when Atlantic crossings were three hours, and transcontinental flights two hours.
Turning finally to Concorde economics, he stressed that they depended, as usual, on how fare structures were arranged.
Dr Strang went on to set out the best, second-best and worst cases which could be foreseen.
In the best case, withe no fare differential, the Concorde would automatically operate at extremely high load factors, certainly up at the maximum bookable level of around 85 per cent. Even if subsonics maintained 55 per cent load factor in those conditions, the 30 per cent difference in load factor represented an extra profit of 60 per cent of turnover, and an immensely superior return on investment for operators, compared with subsonics. The supersonic aircraft would dominate the long-haul market as fast as the manufacturers could build them.
In the second-best case - ie, with a 10 per cent fare differential - their calculations led them to believe that the SST load factors would be reduced to about 65-70 per cent, compared with the subsonics' 50-55 per cent. In this case, the combination of differential fare and load factor gave the SST an extra profit of 35 per cent on turn over. Whether the fare differential was produced by a supersonic surcharge or a subsonic discount, this was still true. Protecting subsonics in this way would slow down SST dominance of the long-haul market, but not for long.
The worst possible economic situation for the SST was to postulate a fare differential of such magnitude that the SST's load factors would drop to parity with subsonic aircraft. It had been estimated that a fare differential of about 30 per cent would be required to bring this about. The SST would show a better profitability than subsonics, but SST penetration would be relatively slow.