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Aviation History
1945
1945 - 2106.PDF
OCTOBER 25TH, 1945 FLIGHT 443 AIRSPEED AMBASSADOR (AS-57) the cabin unobstructed, aileron operation being by means of rods and bell cranks inside the column. It is probable that the cut-spectacle type of wheel control seen in the mock-up will be replaced by a form of half-wheel. An entirely original "black-lighting" form of cockpit illumination is planned. In addition to more normal '' bright'' lighting from hidden lamps, each of the two control columns carries a small lamp directing its light towards the instrument panel. Each lamp is fitted with a screen which cuts off all but the ultra-violet rays, which are duly reflected by the fluorescent instrument dials. In practice, when these lights are on, all the instrument read- ings can be clearly seen with a light emanation rather greater than that obtainable in the case of unassisted luminous paint. After a long period in darkness it is prob- able that the crew will be able to see not only the instru- ments but a sufficiently faint outline of all essential controls. Certainly, in a blacked-out mock-up, there was no sign of reflection from either the two-piece flat screen or from the movable side panels. In Flight of February 22nd this year the estimated cost figures, for the Ambassador were given in an article which showed that, contrary to previously .accepted opinion, a high cruising speed can be combined with economy in operation. The direct operating costs, excluding over- heads, work out at £34.14 per hour. This figure is made up primarily of fuel and oil * (£14.50), with airframe and engine • maintenance at £5.76, flight crew Estimated ciimbi costs at £3.45, '' passenger service " Height Rate of Climb (including insurance and stewards' <ft> '^aso"' pay) at £2, airframe and engine 3Ooo 2! 100 depreoiation at £5.51, aircraft in- ^.000 1,950 surance at £1.88, and interest on is|ooo 1725 investment at £0.88. So many factors need to be con- sidered in assessing commercial —— efficiency that it is impossible to include them in a reliable formula. The figures given have been based on recognised principles, but there are addi- tional factors, in the case of all aircraft, which cannot be gauged without operating experience. For instance, the degree of "utilisation" depends on the reliability, and statistical evidence points to the fact that power plants and their components are more liable to be the subject of minor trouble than any other part of an aircraft. In theory, therefore, a twin-engined aircraft should, overall, be more efficient, for instance, than a four-engined aircraft. ( The cost figures have been worked for a cruising speed of " 240 m.p.h. at 20,000ft.; and it should be noted that the Ambassador, at this speed, is using only 37 per cent, of its take-off power. With such low power output it is reason- able to suppose that the maintenance costs will be lower still. Fare Estimates As fai as direct operating costs are concerned, and treat- ing the aircraft as being fully loaded on all trips, the figure works out at o.gid. per passenger-mile. With an average of 60 per cent, filling, and provided that the overhead charges are not more than half the direct operating costs, the fare would need to be 2.28d. per passenger-mile for uoperation without loss or profit. "Utilisation" is, of"course, the most important factor in air transport economy. In the cost figures it has been assumed that the aircraft would put in 2,000 miles a year. The reserve of available power, as previously out- lined, should Payload and Passengers in Relation to Still-Air Range at 240 m.p.h. and 20,000ft. Range Payload No. (miles) (Ib.) Passengers 2,000 6,000 25 1,600 7,000 30 1,200 8,200 36 950 9,000 40 600 11.000 — give the Ambas- sador a very wide range of permis- sible cruising i speeds, as well as an exceptional single-engined performance. In the matter of cruising speeds, a variation of 0.30 to 0.50 of available power permits the pilot to modify his cruising speeds (be- tween 10,000 to 20,000ft.) from 200 to 285 miles per hour, and the consequent consumption from 93 to 160 gal./hr. Naturally, such wide variations will enable the develop- ment and operational departments of an airline to produce cruising-control graphs to cover all possible conditions of wind and stage-length. Single-engined Performance Taking the cruising figure of 240 m.p.h. at 20,000ft., and with a maximum disposable load of 14,245 lb., the still-air range, allowing for climb, is 1,000 miles with 40 passengers and a crew of four. In the same conditions, but with 24 passengers and a crew of five, the maximum range is 2,000 miles. In each case luggage and freight, to the extent of 60 lb. and 50 1b. respectively for each passenger, has been included, as well as all necessary "passenger service." It follows that the combination of an ample reserve of * power and low span loading provides an unusually good single-engined performance—which is, in fact, 20 per cent, better than the official requirements. The de- signers considered that the aircraft should be capable of taking off with a moderate rate of climb even when, in -case of extreme emer- gency, the pilot was not able to retract the undercarriage or feather the airscrew, so, in addition to a cleaning-up of the aircraft in this condition, special attention was paid to rudder control. Not only aie there three rudders of narrow chord and with sealed nose balances, but these are assisted by a spring servo-tab. It is usual for the remaining engine of a twin flying at full load to be running in continuous rich mixture con- ditions. The A.S.57 still shows a wide speed-range and a ceiling of 18,oooft. at full ioad with the one engine at its weak mixture cruising settings. An accompanying graph (on the previous page) shows the aircraft's perform- ances in these conditions. In normal conditions the initial climb in weak mixture is 1,200 ft. /min., while the distance taken to reach a height of 50ft. is only 750 yd. at take-off power, and the continuous rate of climb is 1,580 ft./min. Altogether. Mr. A. E. Hagg, the Airspeed Technical Director and Chief Designer, his assistant, Mr. A. E. Ellison, and their staff can be congratulated on a really outstanding, design. It is early yet to give possible dates of production, but work on test sections and jigs is already proceeding, and the firm expects the prototype to be in the air some twelve months from' now. Weak Height (ft.) 0 3,000 5,000 10.00015,000 20,000 25,000 30,000 Mixture Power Rate of Climb (ft./min.) 1,150 1,200 1,225 1,1251,025 900 600 225 Weights, Dimensions and Loadings Structure Services and Equipment Tare weight (40-seater) Tare weight (24-seater) Volume as a freighter Span Length Height Wing loading (45,000 Ib.) Span Loading (45,000 Ib.) Power loading 16,570 Ib. 2,020 Ib. 30,755 Ib. 30,715 Ib. 2,590 cu. ft. 115ft. 80.25ft. 18.8ft. 37.5 Ib./sq. ft. 3.4 Ib./sq. ft. 8.7 Ib./b.h.p. MAIL RATE ANOMALYT O our perhaps mathematically feeble way of thinking, the present Empire mail rate of is. 3d. for every half-ounce seems to be a remarkably high one. Before the war the charge for all first-class Empire air mail was ijd. per half-ounce. The present figure is equivalent to ^4,480 for the carriage of a ton—which represents about 28s. per ton /mile or 2s. 6d. per passenger/mile. The pre-war rate was equivalent to £448 per ton. The present charge is therefore ten times higher than it was. In those days the average cost of carriage throughout the Empire was about 3d. per half-ounce, the mail being subsidised for the remainder. Whatever may be the additional costs in- curred nowadays, it certainly seems that someone is profiting to the extent of 9c!. or more every half-ounce of mail carried.
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