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Aviation History
1956
1956 - 1007.PDF
27 July 1956 153 THE HERALD ADVANCES . . . ROUTE ANALYSIS Bringing the H.P. Airliner's Performance to Life H this page we reproduce an actual route analysis for the Herald. It was prepared for Aden Airways, a B.O.A.C. subsidiary at present equipped with DC-3s and Dragon Rapides, according to data supplied by the airline. All told, more than 40 such route studies have been made for potential Herald purchasers. The map shows the sectors under consideration, with their lengths, and the tables provide appropriate route and airfield data together with the payloads, block times and fuel required under ROUTE DATA SECTORS Stags Mukeiras—Aden Aden—Djibouti Djibouti—Diredawa Diredawa—Addis Ababa Safety height (ft) 8.000 1.500 5,000 8.000 Distance (njn.) 73 133 140 190 AIRFIELDS Aerodrome Mukeiras ... Aden Djibouti ... Diredawa ... Addis Ababa Elev. (ft) 6.60010 233.950 7.749 Max. amb. temp (degC) 38 39 35 30 27 Runway length (yd) 1.700 2.795 1,970 1,330 1,900 Alternate Aden Mukeiras Aden Awash Awash Diet. (n.m.) 73 73 133 113 82 both visual and instrument and flight rules. The version of the Herald under consideration is the 36-seater, of which the capacity payload is 10,100 lb. It will be seen that the maximum take-off weight of 37300 lb is, for reasons of runway length, limited at Mukeiras and Addis Ababa to respectively 34,000 lb and 36,300 Ib. The payloads quoted in the tables are related to the basic equipped weight of 25,780 lb. This results, on some of the stages, in the payload being greater than the capacity payload limited by minimum fuel and oil. In these instances take-off weight has to be reduced by the excess of payload above the capacity payload. Block time allows seven minutes for start, checks, taxi and take-off; five minutes for climb, cruise, descent, circuits and landing; and four minutes for taxi after landing. Fuel required includes 16.4 gal for the seven-minute item above; 9.8 gal for the five-minute item above; and 2.1 gal for the four- minute item above. Under I.F.R. conditions it is assumed that the flight to the alternate is made from the circuit height of the destination aerodrome. Cruising is at 50 per cent M.E.T.O. power, and a stand-off of 45 min at the alternate is included. Under V.F.R., an allowance of 45 min stand-off at 1,000ft is made at the destination aerodrome (stand-offs are made under cruising threshold speed conditions). Fuel allowances for con- tingencies are: 1.5 per cent en route and 5 per cent overall. Oil quantities are assessed proportionally to the fuel load with a four- gallon allowance for feathering. Performance conditions assumed are as follows: take-off and landing weights, still air, are assessed according to I.C.A.O. requirements with airfield elevation and temperature effects included. Take-off and landing weights, for example, are con- trolled by (1) rate of climb on three engines (Annex 8); (2) aero- drome runway length, elevation and temperature (Annex 6); (3) runway bearing strength; (4) maximum design take-off and landing weight (37,500 lb); and (5) volumetric capacity 10,100 lb. Over the shorter stages where this latter payload can be carried, the fuel load is such that maximum take-off weight may not be reached. The maximum zero fuel weight of 35,880 lb must of course not be exceeded. Take-off, approach and baulked landing net flight paths in accordance with I.C.A.O. Annex 8. For example, for take-off net flight path, the minimum three- engine rate of climb shall be the lesser of 0.35 V,,2 or 0.38 Vsi'"5 ft/min, where Vsi is the power-off stalling speed or mini- mum steady flight speed, m.p.h., in the following conditions (1) inoperative airscrew in auto-coarse pitch; (2) remaining engines operating within take-off power limitations; (3) landing gear retracted; (4) wing flaps in the appropriate take-off position corresponding with the flap control setting at the critical point; (5) cowl flaps and radiator shutters in the position relative for normal use during take-off; (6) aeroplane weight equal to maxi- mum take-off weight appropriate to the altitude; (7) air speed equal to the take-off safety speed. \ ADDIS \ o r 1 1L « •• »AWASHABABA V"I \ f\ 'DIREDAWA > MUKEIRAS GULF RCXJTi s —-••. ^ N A DEN Four sectors from the route-network of Aden Airways, an ultra-short- haul local-service operator in a region of mountainous terrain and hot, high airfields. It is the kind of territory which inspired the design of the Herald. ROUTE PERFORMANCE SPEEDS Stage Mukeiras—Aden Return Aden—Djibouti ... Return Djibouti—Diredawa Return Diredawa—Addis A baba Return Headwindkt 09 09 0 9 0 9 Block Time hr ntrn 0 43 0 47 10 10 11 13 1 29 31 Block Spaed kt 103.0 93.4 115.3 114.0 118.8115.4 127.6 125.7 PAYLOADS Stag* Mukeiras—Aden Return ... .:. Aden—Djibouti Return Dj ibouti—Di redawa Return Diredawa—Addis Ababa Return PayhxI.F.R. 6,535 10,008 9,576 9.853 9.270 9,408 9,282 8.051 id(lb) V.F.R. 7.140 10,100 9.965 10.100 10,015 10.100 9.800 8,750 Take-off w I.F.R. 34,000 37.500 37.500 37.500 37.500 37.500 37,500 36.300 eight (Ib) V.F.R. 34,000 37,252 37.130 37,309 37,500 37.353 37.500 36.300 FUEL Stage Mukeiras—Aden Return Aden—Djibouti Return Djibouti—Diredawa Return Diredawa—Addis Ababa Return Fuel (Ir I.F.R. 214.8 217.8 275.7 236.8 314.4 296.1 313.2 315.5 np. gal) V.F.R. 130.4 170.6 176.0 181.0 218.0 187.1 244.7 225.9 Block Fuel Consumption gal/hr 116.6 138.4 108.5 106.4 133.9 107.7 122.0 109.3
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