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Aviation History
1968
1968 - 0080.PDF
82 FUGHT International, 18 January AIR TRANSPORT. More Than Two-and-a-Half Problems So THAT WE COULD PRINT a qualified second opinion on theproposal, long sponsored by Mr R. A. Twomey, for theuse of a combined APU/booster third engine (see "'Why Two-and-a-Half?" in the issue of January 11, page 50), we asked for the views of Mr J. P. Smith, chief engineer for the European Airbus at Hawker Siddeley Aviation, Hatfield. He says that the proposal, so far as the Airbus is concerned, should really be split into two parts. "First," Mr Smith asks, "is it feasible and economical to provide an APU /booster, and, second, is there a case, which must be primarily an economic one, for providing a boost engine on the Airbus? I can make a number of comments on the first, but the second question requires a detailed study of the Airbus operation over the airlines' route networks, and an assessment, of the economic benefits of fitting a boost engine, by the airlines. "We have made two previous attempts at fitting a combined APU/booster. The first was several years ago in the early days of the Trident, when an investigation was made of the possibility of using a lift engine for this purpose, and it was reconsidered using the RB.162 in the Trident 3B. "The fundamental problem is that the noise and fuel con- sumption of current engines, of a size suitable for the booster application, prevent their use as an APU in the conventional manner. There is an added problem in the Airbus size of aircraft, since, whereas the smaller sizes of boost engine can be started electrically from aircraft batteries, the size of engine, perhaps an uprated Spey, required for the Airbus puts this out of court on weight/economic grounds. One of the purposes of having an APU is to eliminate power supplies for starting the main engines. "Approximate figures for noise and fuel consumption, under ISA +15°C conditions, are as follows: — Spey, at r.p.m. to supply air for cabin conditioning on the Trident: 127 PNdb at 30ft; fuel consumption, 130 gal per hour. APU to supply air for cabin conditioning on the Trident: 107 PNdb at 30ft; fuel consumption, 45 gal per hour. Typical lightweight boost engine supplying air for cabin conditioningon the Trident; 136 PNdb at 30ft; fuel consumption, 720 gal per hour. Spey at r.p.m. to supply air conditioning on the Airbus: 137 PNdb at 30ft; fuel consumption, 340 gal per hour. APU to supply air for conditioning on the Airbus: 107 PNdb at 30ft; fuel consumption, 125 gal per hour. "It can be seen that the noise and fuel consumption of typical engine such as the Spey are far higher than those of; APU doing the same job. Airport authorities are pressing f. APU noise levels to be reduced below the currently accept figure of 105 PNdb at 30ft, and it is difficult enough to achie this on current types of APU using a deflected jet, silenciu etc. The increased size of boost engine required for the Aarb: makes this even more difficult. The lightweight boost engine derived from a lift engine—has a prohibitive fuel consumptit as well as a prohibitive noise level. "The above noise levels are produced when the engine is n at the r.p.m. necessary to deliver the air required for cab conditioning, the air being tapped from the engine cot pressor, as is normal practice. They can be reduced by drivii a separate compressor from the engine, at idling r.p.m., bi the Spey noise level at idling is 115 PNdb at 30ft. The noi could possibly be reduced to an acceptable level by fitting variable nozzle to reduce the jet velocity, when used as < APU, and by providing special silencing in intake and jetpip "When the engine is being used for its APU duty it mu have automatic speed regulation to provide constant-frequem AC power; alternatively a constant-speed drive (CSD) must i provided, which is not required on the conventional API The compressor delivery pressure of a Spey at idling r.p.m. well below that required to start the RB.207, so it must t brought up to higher r.p.m. for this purpose, and hence CSD is required to maintain the AC power. Self-containt starting of an engine such as the Spey could be provided I fitting a gas-turbine starter, which in turn would be start from a small electric starter from the aircraft batteries. "Thus, to provide full APU facilities, using an engine sue as the Spey, one has to add additional silencing, a large con pressor, a jet turbine starter, which is in fact a 'mini-APU,' an a constant-speed drive. The alternative is to fit an APU at a separate boost engine. "Bearing in mind that the combined unit would be speci; to the Airbus, at least initially, and would cost several millio pounds to develop—whereas one can buy a suitable APU o the shelf, which will also be used in large quantities on othi aircraft—it looks as if the separate APU and booster woul win on economic grounds. "Perhaps, however, the engine company can come up wil an engine which makes sense on technical and econom grounds." ; Hundredth One-Eleven Delivery The 12th of Mohawk Air- lines' 14 BAC One-Eleven on order was handed over for ferrying from Hum on December 30. It was the 100th One- Eleven to be delivered.. 737 Price Rise After February 15 the price of all models of the Boeing 737 will rise by up to 11 per cent. The basic 737-100 was previously priced at around $3.5 million (£1.46 million) and this will now be some $3.9 million (£1.63 million). Coming on top of devaluation, this means an effective price increase of no less than 30 per cent to operators such as Britannia Airways who will in all probability wish to re-order at some time—but not just yet. Preparing for the 1970s A £9 million programme to prepare BOAC's London Heathrow engineering base for the Boeing 747s and SSTs has been approved by the airline's board. The first stage will be a £1 million multi-storey car park in the maintenance area on which work will start in February. The second stage will be a maintenance hangar for 747s and the third will involve administrative buildings. Handling the 747 Invitations to design mobile grow equipment for BOAC's Boeing 747 jet fleet have been accept* by 14 British, four American and one Belgian company. Tl invitations were extended in September at a design confereiK held at London Heathrow to discuss the ground handlit problems which the high-capacity jets will bring in the 1970 The various ideas—such as aero bridges, moving pavement lifts, elevating passenger coaches—are now being studied t BOAC's ground-handling committee. The next stage will ' to invite tenders. BO AC up (a little), BUA down In 1967 BO AC recorded 2.3 per cent increase in passengers carried (to 1.48 million) a" a 17.3 per cent increase in cargo (to 51,839 tons). The aveiaj overall load factor was 51.6 per cent and the passenger facto was 58 per cent. The British United group recorded a 5 per ce! reduction in their passenger total, though this topped the 2 mi lion mark for the second year in succession. The reductiot were, BUA say, the result of the cut-back in British Air Ferris operations and in Government trooping. BUA themselvi handled more than a million passengers at London Gatwick.
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