P.SATRE J.AIRCRAFT 00C VORTICES (d] 10 CL PREDICTED +38 IN FLIGHT.BETWEEN M O AND M.0.8 Fig.6 Anticipated improvements. lieve this would be by far preferable to imposing statutory reserves not strictly necessary for safety,for,like the empty weight,the fuel weight must be determined even more pre- cisely than on subsonic aireraft beeause of its economic (d implications. 10 15 OF ATAC In short,the performance problem with SSTs is a genuine one but let us not add to it through excessive conservation Fig.8 Concorde lift curve and lift increase due to vortices. on reserves based on a misconception.Presently,when I go on to examine operating problems,I shall show why ean be reduced.3)It must possess excellent flying qual- ities throughout the flight envelope. it is no exaggeration to speak of excessive conservation, especially when reserves equal to or greater than those on Now although the third requirement can be met by making subsonic aireraft are being contemplated even through the the necessary refinements,the first two are in direct conflict. contingencies likely to be met on the journey are far fewer. The subsonic regime is of considerable importance in the And while we are on the subjeet of performance,let me turn over-all economies of the SST,as portrayed diagramatically right away to another misconception. in Table 5. The takeoff and landing speeds associated with delta You will observe that the requirements imposed for holdings wing aircraft are higher than with other aircraft.Some and diversions have a determining effect.This being so,the have inferred from this that landings in particular would attractions of variable geometry as a means of resolving present difficulties.At no time was this view shared by this contradiction are manifest,and I am not surprised that the chief pilots of our customer Airlines,who from the outset Boeing attempted a breakthrough along these lines.Their has posed the problem in stark and simple fashion:speed design study,the only one to have been taken far enough. is important,but less important than flving qualities.The was necessary to establish that the variable geometry solution CONCORDE's flight tests have shown how right they were: is not yet ripe.This is not to say that we shall not see back thanks to excellent flying qualities,landings at 160 kt can with us some day.But so far the 3 SST design projects be controlled without any trouble,and you will find confir- feature near-fixed geometry,I say "near"because the droop mation of this in Table 4. nose and the air intakes do feature variable geometry,which This leads me straight on to the origin of these relatively makes my task simpler.I shall simplify it still further by high takeoff and landing speeds,namely the aerodynamic confining myself to what I know well:the solutions adopted for the CONCORDE. compromise between high and low speeds Starting with a pure delta wing with 63.5 of sweepback, we set about looking for improvemnents,with special emphasis High-Speed/Low-Speed Aerodynamic on low-speed qualitics. Compromise A sharply swept apex (about 76),as shown in Fig.7, produced a triple advantage:1)a reduction in the thick- There are at least three requirements to be met in de- ness ratio at the wing root,plus an arrow planform,both signing an SST:1)The airplane must be configured for favorable factors for supersonic flight,2)a forward supersonic cruise fight.2)It must adapt readily to shift in aerodynamic center location,which in turn shifted subsonie fight,notably for takeoff,for landing,and also, for holdings prior to lauding until such time these holdings Table 4 Concorde 001--first fandings Touch down WING TIP:55 Approach Air Vertical Bank No.of speed, speed, speed, angle BASIC DELTA:63,5 fight kt kt m/sec 167 T60 1 0.9 APEX:76 2 171 165 0. 0.6 3 175 165 0.6 0.7 4 171 166 0.4 5 179 171 0.2 6 175 16 0.5 0 7 176 0.s 0 174 16S 0.8 0.4 165 10 0.2 Mean values 172 165 0.7 0.4 Fig.7 Wing plan form. Cinetheodolite failureP. SATRE J. AIRCRAFT 100 CL Fig. 6 Anticipated improvements. lieve this would be by far preferable to imposing statutory reserves not strictly necessary for safety, for, like the empty weight, the fuel weight must be determined even more pre￾cisely than on subsonic aircraft because of its economic implications. In short, the performance problem with SSTs is a genuine one but let us not add to it through excessive conservation on reserves based on a misconception. Presently, when I go on to examine operating problems, I shall show why it is no exaggeration to speak of excessive conservation, especially when reserves equal to or greater than those on subsonic aircraft are being contemplated even through the contingencies likely to be met on the journey are far fewer. And while we are on the subject of performance, let me turn right away to another misconception. The takeoff and landing speeds associated with delta wing aircraft are higher than with other aircraft. Some have inferred from this that landings in particular would present difficulties. At no time was this view shared by the chief pilots of our customer Airlines, who from the outset has posed the problem in stark and simple fashion: speed is important, but less important than flying qualities. The CONCORDE'S flight tests have shown how right they were: thanks to excellent flying qualities, landings at 160 kt can be controlled without any trouble; and you will find confir￾mation of this in Table 4. This leads me straight on to the origin of these relatively high takeoff and landing speeds, namely the aerodynamic compromise between high and low speeds. High- Speed/Low- Speed Aerodynamic Compromise There are at least three requirements to be met in de￾signing an SST: 1) The airplane must be configured for supersonic cruise flight. 2) It must adapt readily to subsonic flight, notably for takeoff, for landing, and also, for holdings prior to landing until such time these holdings WING TIP:55° ACL DUE TO VORTICES (X (d*} i PREDICTED IN FLIGHT,BETWEEN M=OANDM = 0.8 <X (d") Fig. 8 Concorde lift curve and lift increase due to vortices. can be reduced. 3) It must possess excellent flying qual￾ities throughout the flight envelope. Now although the third requirement can be met by making the necessary refinements, the first two are in direct conflict. The subsonic regime is of considerable importance in the over-all economics of the SST, as portrayed diagramaticallv in Table 5. You will observe that the requirements imposed for holdings and diversions have a determining effect. This being so, the attractions of variable geometry as a means of resolving this contradiction are manifest, and I am not surprised that Boeing attempted a breakthrough along these lines. Their design study, the only one to have been taken far enough, was necessary to establish that the variable geometry solution is not yet ripe. This is not to say that we shall not see back with us some day. But so far the 3 SST design projects feature near-fixed geometry, I say "near" because the droop nose and the air intakes do feature variable geometry, which makes my task simpler. I shall simplify it still further by confining myself to what I know well: the solutions adopted for the CONCORDE. Starting with a pure delta wing with 63.5° of sweepback, we set about looking for improvements, with special emphasis on lowr -speed qualities. A sharply swept apex (about 76°), as shown in Fig. 7, produced a triple advantage: 1) a reduction in the thick￾ness ratio at the wing root, plus an arrow planform, both favorable factors for supersonic flight, 2) a forward shift in aerodynamic center location, which in turn shifted Table 4 Concorde 001—first landings Touch down Fig. 7 Wing plan form. No. of flight 1 2 3 4 5 6 7 8 9 Mean values Approach speed, kt 167 171 175 171 179 175 176 174 165 172 Aii￾speed, kt 160 168 165 166 171 169 172 168 150 165 Vertical speed, m/sec 1.1 0.5 0.6 . . . a a 0.5 0.8 0.8 . . . a 0.7 Bank angle d° 0.9 0.6 0.7 0.4 0.2 0 0 0.4 0.2 0.4 1 Cinetheodolite failure