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Aviation History
1972
1972 - 1001.PDF
FLIGHT International, 27 April 1972 .%;;fiyrih'r:.::n CONCORDE ELECTRICS and elec-tronics were the subject of a discussion at a Royal Aero nautical Society/Institution of Elec trical Engineers meeting on April 13. The proceedings were opened by Mr H. Hill of the British Aircraft Corporation, who presented a brief resume of Concorde development. He outlined airframe and engine com mittee structures, the advisory con tributions made by the operators' Airline SST Committee, and the bipar tite Governmental cost supervision. The evolution of Concorde's elec trical-generation systems was de tailed, starting with the prototype's 4X40kVA twin sub-system supply (when the commercial load demand stood at 7kVA), and comparing this with the present basic 4X60kVA, four-parallel-channel system (com mercial load demands having crept up to 40kVA). Having left the audience in no doubt that comparable development had occurred in other areas, Mr Hill pointed out that, des pite such growth, the overall aircraft weight had crept up by a mere 2,0001b. Mr S. T. M. Reynolds, also of BAC, took a more detailed look at the elec trical-generation system. The original twin sub-system supply had resulted from weight controls imposed by the airframe committee. As electrical de mands grew, however, so did the attractiveness of the four-channel parallel system. As Mr Reynolds pointed out, certain generation faults may occur which cannot readily be tracked down in the earlier twin lay out, whereas the later parallel system provides greater safety and flexibility, and can lose one channel and still provide 75 per cent of output rather than only half. Two charts illustrated the electrical loadings imposed on the four-channel system. On the first chart, electrical loads were broken down by service demand. From this it could be seen that the highest sustained demand, at 40kVA, was from galley services. Well below this figure came the 16kVA air-conditioning demand, 8kVA for avionics and 5kVA for lighting. The highest single demand was the 68kVA de-icing load, but this was only required during subsonic climb in known icing conditions. The second chart broke down total electrical loads by flight mode, with the worst load, 169kVA, occurring By HUGH COWIN during subsonic cruise in icing condi tions. In supersonic cruise the total demand came out at 104kVA, rising to 128kVA during descent. There then followed a brief review of more recent developments, pro viding 115-200V three-phase 400Hz a.c. and 28V d.c. Starting with the four Sundstrand integrated-drive generators (60kVA continuous and 90kVA for 5min), Mr Reynolds des cribed the a.c. and d.c. systems and the associated protective devices. Control, isolation and system safe guards were touched upon, including the separation of essential services d.c. busbars (driven from Nos 1 and 4 engine channels) from main d.c. busbars (from Nos 2 and 3 engines). Other features mentioned in this con text were the separate bus employed for ground-supplied power, with its own control and isolation, and the engine-relight bus, supplied by the standby generator, and capable of continued operation even after all four main generation channels had been lost. The standby generator, providing 30kVA, is mounted in the tail-cone and is powered by a one- shot hydrazine-burning unit with an operating time of 20rnin. Finally, Mr Reynolds referred to the operational aspects of the elec trical-generation system, pointing out that the aircraft could operate with one channel out under no restriction, galley load-shedding and load-moni toring only being deleted in the two- channel-out case. M M. Le Bouar of Aerospatiale then discussed avionics. By virtue of its shape and heat-soak qualities, Concorde posed a number of problems, particularly in antenna design and positioning. Wherever possible, use had been made of sup pressed aerials. In certain cases, how ever, resulting from considerations of radiated power or coupling problems, external aerials were fitted and these had to impose minimum drag penal ties. The weather / collision - avoidance radar was a duplexed system, using a common antenna. Individual trans mitter/receiver channels were used, each with their own cathode-ray tube displays for pilot and co-pilot, time- shared through wave-guide switching. Antenna design had been complicated by the high nose temperature of 100°C and by the narrow-angle 595 radome. The system also required a droop-nose indicator and carried pilot and co-pilot proximity-warning flasher units, separate from the c.r.t.s, although the flashers may be deleted in production aircraft. The twin VHF installations are conventional, using common super sonic blade aerials, with the upper aerial mounted on top of the fuse lage aft of the forward passenger door, and the lower aerial beneath the over-wing emergency exit. The thin fin section necessitated external VOR/localiser aerials, and these are mounted on either side of the fin, close to the top leading edge. The positioning of the glideslope aerial was critical, owing to the 12-14° nose-up attitude adopted on approach, combined with the landing-gear posi tion. In practice, it was found that this aerial could not be mounted more than 19ft, 5-8m forward of the main landing gear for accurate glideslope information during final approach. The belly marker aerial, just forward of the lower VHF aerial, is a sup pressed "top-hat" type, feeding pilot and co-pilot marker indicators. The HF system employs two notch aerials, mounted in tandem just aft of the forward base of the fin. Only one of these aerials can be used for transmission at any given time, how ever, owing to power limitations. Selcal (selector coding) is incor porated into both HF and VHF. The ATC transponder equipment comprises two separate channels, each with its own suppressed top-hat aerial, belly-mounted in tandem aft of the cockpit. Each channel is connected to a separate 28V d.c. busbar. Two systems are again employed for ADF, using external aerials, chosen for their lightness. Though external, the aerial system has been neatly faired into the fuselage top, housed in the parallel long strakes (sensors) and shorter strake (loop) that lie between the over-wing exit and the front of the fin. At present, pilot and co-pilot ADF-control units are fitted, but production machines will use only one. The DME employs two suppressed top hats, one positioned aft of the nose radome on the fuselage under side and the other, also belly-mounted, forward of the marker aerial. The radio altimeter also uses two suppressed top hats, mounted side by side, aft of the lower VHF blade. Only the captain has an indicator, the system being used on finals below 250ft, 76m QFE. A conventional crew interphone system is installed. Concorde carries three inertial- navigation systems, one each for pilot and co-pilot, with the third acting as standby. It was of interest to note that at one time a moving-map display, quite separate from the other systems, had been contemplated. Primarily because of its high cost, however, little or no airline support could be found and the idea was dropped. • The generation game
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