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Aviation History
1962
1962 - 0154.PDF
156 FLIGHT International, 1 February 7&51 WORLD NEWS . Army Autogyros In May the British Army are to take delivery of three Beagle- Wallis WA.116 single-seat autogyros. The first of the three has been bought by the Army, the other two are being loaned by Beagle. It is understood that the aircraft are to be subjected to a 500hr evaluation programme, including participation in Army exercises both in the UK and Europe. The WA.116, designed and built as a personal private venture by Wg Cdr K. H. Wallis, RAF, is the subject of a Beagle development programme with the object of production at Shoreham. Jigs have been erected and work has started on the first batch. Application has been made for a special category C of A and a programme of rotor-system strain-gauging agreed with the ARB. No Demand for Beryllium? Technical difficulties have caused the UK Atomic Energy Authority to postpone the use of beryllium as a fuel canning material, and this threatens the run-down of the special plant opened early in 1960 at Whitley by Whitworth Gloster Aircraft. The company met all AEA specifications and schedules; they feel this work has proved to be too much in advance of present European in dustrial requirements, but are convinced their knowledge and experience will one day prove of great value and are endeavour ing to keep the plant operating. Allison Increase T56 Power Norma: rated at 3,755 s.h.p., the modified power section of an Allison T56 turboprop has been run over periods up to 5hr at a peak output of 6,770 s.h.p. Mass flow has been increased by raising the diameter of com pressor and turbine (within the same en velope), and air-cooled blades permit a peak turbine entry temperature of 2,060 F (1,127°C). The latter figure is remarkable, and calls to mind the company's collabora tion with Rolls-Royce. Bristol Siddeley Lift/Thrust Engines "*F"HE curves below yield important addi- • tional information on the character istics of turbofan engines equipped with rotating exhaust nozzles to provide any combination of lift and thrust. Bristol Siddeley Engines Ltd relate these curves specifically to the BS.53 Pegasus, although there is no reason to suppose that figures for the larger BS.100 (Flight, December 14, 1961) will be fundamentally dissimilar. Precise performance data for these engines are classified, but the Pegasus is described as "suitable for single-engined aircraft in the 15,000/20,0001b weight class" and the BS.100 was last year proclaimed suitable for "supersonic single-engined aircraft in the 30,0001b weight class." In the first diagram the company make the point that a single vectored-thrust engine will, for a given total installed thrust, always result in substantially in creased take-off performance in comparison with any combination of separate lift and propulsion engines with essentially fixed thrust axes. The central sketch emphasizes the vastly improved T/W in supersonic flight at altitude of a lift/thrust engine with PCB in comparison with a conventional turbo jet with afterburner. PCB, or plenum- chamber burning, is the combustion of additional fuel in the forward fan ducts, raising their temperature to that of the rear jets. Not only does PCB greatly increase thrust available for supersonic flight but it also enables the engine performance to be matched to aircraft cruising require ments (which is not normally possible in VTOL aircraft with a single lift/thrust engine), and enables more fuel to be carried over and above that needed for PCB in order to increase the radius of operation. Bristol Siddeley point out that the low airflow temperature enables augmentation of the order of 30 per cent at take-off and almost treble the non-PCB thrust at M2 to be achieved with only a modest increase in specific consumption. With conventional afterburning the reheat fuel has to be in jected into very hot exhaust gas and the attainable thermodynamic efficiency is substantially lower. Actual figures for the two types of engine are given in the third diagram. Like the previous sketch, this is plotted for i.s.a. conditions at the tropopause, for an ideal two-shock intake and a practical nozzle. The third sketch is drawn for flight at M2, and over T/W ratios for supersonic military aircraft it can be seen that there is a con siderable difference in specific fuel con sumption. Among other advantages claimed for single lift/thrust engines are the simplicity of powerplant maintenance, the fact that intake momentum drag acts in line with engine thrust in cruising flight and that the pilot need have only conventional instru ments and one additional control—the propelling-nozzle position selector. Engine life and reliability are expected to be con siderable, since the powerplant is throttled well back in cruising flight; although proponents of the composite arrange ment would point out that this also results in increased specific consumption and reduced range. Finally, Bristol Siddeley have shown how thrust can be boosted by water injection into the combustion chambers and utilizing a "TRR" or thrust-restoration rating. Augmentation can be pre-selected to come into operation at a given nozzle deflection, and the combination of water injection and the TRR can maintain full take-off thrust at temperatures up to 40CC at airfields up to 1,350ft altitude. These Bristol Siddeley diagrams are discussed above: from left, take-off performance, thrust atl36,0O0ft and s.f.c. at 36,000ft at M2 0.4 0.6 O.S 1.0 1.2 1.4 1.6 1.B 2.0 TOTAL INSTALLED THRUST C.6S 0.60 0.55 C.5C Q 45 0 40 0.35 i F. _. .,., ._._. PCB TO TOOO'X /r OFF THRUST = |.2 * AIRCRAFT WEIGHT / / // 7 : C £ / Y TURBOJET '•/ FULL REHEAT TO JOOO'K / TAKE-OFF THRUST = 0.7 * AIRCRAFT WEIGHT 1.0 1.2 l.« 1.6 1.8 2.0 2.2 MACH NUMBER 1 r o H 1.7 fl. 1 ALL-UP WEIGHT 1.3 0. TURBOJET WITH RE ! 1 1500'K-X 1 HEAT 1/ j 1000"K 2Q0 0°< 1400"K^t / ?^~r 1 TURBOFAN WITH PLENU . CHAMBER BURNING ; 1 i 2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 THRUST AIRCRAFT ALL-UP WEIGHT
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