FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1960
1960 - 0594.PDF
594 PIA's Boeing 707 Services . . . PIA's managing director, some hitherto unpublished facts aboutthe PIA-PAA lease agreement. Until June of this year either aide can withdraw from the agreement but after that the agreementholds until June 1962, after which either side can terminate the agreement with one year's notice. This means that the lease mustcontinue to June 1963 and I gained the impression that it is PIA's desire to continue the arrangement into 1964. t The air commodore feels that 1964 is about the right time forPIA to begin operation of its own fleet of second-generation jet aircraft. This timing should place British aircraft in a particularlyhopeful situation—a fact that has not been lost on at least one British manufacturer. Air Cdre Nur Khan confirmed that the total operating costto PIA for each Boeing round trip is in the region of £16,000, including fuel and handling. Based aS the 44 first-class and 69tourist-class configuration used, a 100 per cent passenger load- factor flying London - Karachi and return at present fares wouldbring in approximately £32,335. This means that without allow- ance for freight and mail the break even load-factor is just under50 per cent. PIA's future plans for the Boeing are not yet finalized but it isalmost certain that from October three flights a week will be operated over the Karachi - London route. One would probablyfollow the existing route, with a second operating via Teheran, Istanbul and Frankfurt. If there is sufficient promise of end-to-endtraffic the third service might be operated non-stop. Some public statements made in Pakistan, but not emanatingfrom the airline, have rather embarrassed PIA over the question of providing the Karachi - Dacca link with Boeings. PIA isanxious to do this but airport limitations would at this stage FLIGHT, 29 April I960 reduce the Boeing's payload to considerably less than that of theL.1049s now being used. Looking further ahead, PIA is studying the possibility ofextending its routes to the Far East and/or New York. Imple- mentation of such plans would necessitate the lease of a secondBoeing. I asked Air Cdre Nur Khan for his views on pooling and alsowhether he considered the BOAC/ Air-India/Qantas pool a serious threat to PIA's business. He said that the tripartite pool wouldaffect interline business but did not think it would seriouslv affect PIA's end-to-end traffic. He foresees improved relations between India and Pakistan andthe possibility of closer working between PIA and Air-India There is nothing in the PIA-PAA lease agreement to preventPIA going into pool with PAA or any other airline and he feels that at some stage PIA must enter a pool. This could be withPAA [US anti-trust laws?—Ed.] or with a European carrier such as KLM or SAS. Looking five or ten years ahead, the air com-modore thinks there is scope for a much bigger combine—perhaps a Commonwealth group, using common equipment, training andother facilities. I suggested that the high numbers of frequencies granted tosome foreign operators serving Karachi seemed to be unfair to PIA. Air Cdre Nur Khan agreed that other airline capacity wastoo great and said that PIA might recommend a review of various bilateral agreements.In mid-May PIA's own crews will begin to take over operation of the Boeings and there is evidence that the airline will providesome very stiff competition over the Karachi - London route in spite of its fairly limited resources. PIA is insistent that PAAhas given every assistance and been more than fair in helping the Pakistani airline to begin jet operation. It seems a pity that Britainhad not been more willing to help a member of the Commonwealth. The First Supersonic Turbojet GE's HUGE J53 OF 1950 NOW REVEALED BY 1950 a number of engine companies in this country andAmerica had turned their attention to powerplants forsupersonic aircraft. In Britain the de Havilland Gyron Senior was in the early design stages, and it first ran in January1953. In the USA the General Electric XJ53 was in a slightly more advanced state, since it ran in March 1951. Information onthe Gyron has been released for some years, but only recently have the Americans permitted a description of the XJ53 to bepublished. Before commenting on this engine, it is worth casting one'smind back to recollect the state of the art in 1950. Though it was known that controlled supersonic flight was possible, there weremany difficulties. Nobody was sure how much thrust would be required, but it was certain that existing engines were too small.However, reheat or afterburning was coming into use, and from a given engine configuration (with no increase in frontal area ormass flow) offered increases in thrust which could vary from 40 per cent at sea-level static to over 200 per cent at high forwardspeeds. On the political front it was realized that there was a militaryneed for the supersonic aeroplane and that the way was clear for such an aeroplane to be produced within a reasonable period.Accordingly, the USAF initiated a project with the General Electric Company of America in January 1947. The objective wasto design an engine of high enough thrust for it to be capable of full development before aircraft could be produced which wouldrequire it. The design philosophy was aimed toward an engine that could be utilized in aircraft either designed for subsoniccruise and M.95 dash performance near sea level, or designed to cruise supersonically but requiring short life, as in a missile. Thebasic design requirements stipulated were a minimum specific fuel consumption and specific weight and the highest thrust per unitfrontal area consistent with a mechanical design suitable for mass production at a reasonable cost. Design maximum flight Machnumbers at 100 per cent r.p.m. are shown in Table 1. From a profusion of studies the XJ53 emerged, and a com-parison of its performance with other engines in current produc- tion in 1950 is given in Table 2. By mid-1950, as requirementsfirmed-up and the possibilities of the engine emerged, General Electric proposed the XJ53-GE-X10 for intercepter duties. Itwas reheated, but a limitation of 490 °F was imposed on com- pressor discharge temperature and lOOlb/sq in abs on compressordischarge pressure. These limitations allowed a very substantial decrease in engine weight—from 7,000 to 4,5001b—but still pro-vided adequate thrust for the proposed missions (24,9001b at * Chief Engineer, Gas Turbines, de Havilland Engine Co Ltd. ; •:; v. By John L. Edwards, BSc, AMIMechE, FRAeS* 93 per cent r.p.m., sea-level static). On the other hand, the turbineentry temperature was raised from 1,195 to 1,25O°K—a most ambitious target in 1950. The low hub/tip ratio (approximately 0.23:1) of the 13-stagecompressor gave a high specific airflow, a pressure ratio of 7.7 :1 and a high efficiency. Though today a pressure ratio of 7.7 canbe obtained with fewer than 13 stages, in 1950 this implied high blade loading. Compressor discharge temperatures approaching400 °C would occur in high-speed flight, and this necessitated a compressor casing manufactured in two parts, up to stage 6 beingof aluminium and the rear part being steel. On the -X10 engine the steel was to be replaced by titanium, to save weight. The useof this untried material was undoubtedly venturesome; but sub- sequent events have vindicated this decision. The engine incorporated variable inlet guide vanes, since it wasknown that these would be required by a high-performance com- pressor of single-spool design. In 1950 there was little experienceof such devices, but now they are standard practice, and several stators may be ganged together and positioned according to enginespeed. Today it is usual to modulate the r.p.m. signal by an air temperature control, to accommodate variation in non-dimensionalcompressor speed with changes in flight Mach number. A cannular design of combustion chamber was chosen. In 1950there were considerable doubts regarding the practicability of a fully annular flame tube under the high gas loadings which wouldbe met at supersonic flight speeds. Only one or two companies were making fully annular chambers, and even these had not been TABLE I: DESIGN FLIGHT MACH NUMBERS Sea-level 0°F ambient Sea-level NACA standard conditions 1S,000fc .. „ „ 30.000ft „ „ ,. XJ53-1 0.95 1.00 1.40 1.70 XJ53-3 0.70 0.80 1.20 1.70 TABLE 2: GE TURBOJETS, 1950 Military thrust (Ib) ... Corresponding s.f.c. Thrust at min s.f.c. ... Corresponding s.f.c. Thrust with reheat (Ib) Max cont thrust (Ib) XJ53-1 (Aircraft) 17,500 0.86 12,800 0.790 24,300 XJ53-3 (Missile) 20,000 0.965 11,750 0.870 27,200 18,700 Advanced J47 (became J73) 9,100 0.905 5,870 0.823 TG-190 X-2 6,090 1.005 4,630 0.938 J47 C-series 5,340 1.114 3,820 1.017
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
