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Aviation History
1958
1958 - 0136.PDF
138 FLIGHT, 31 January 1958 British European Airways and VTOL What the Corporation would want: Points from a Requirements Study THOUGH B.E.A. has no immediate requirement for a VTOL aero-plane (notwithstanding its interest in the Fairey Rotodyne) it has thought a good deal about its requirements in this direction. Beloware selected points from a study by Mr. R. H. Whitby, of the Corpora- tion's project and development branch, in which some provisionalrequirements—including a cruising speed of not less than 350 m.p.h.— are set out See also page 160. IN the development of air transport the VTOL aircraft can giveimproved direct communications between many points nowserved by conventional aircraft by eliminating much of the surface travel to and from the airport; it can open up new routeswithout the need to build new airports or improve existing ones.; it can provide a convenient means of feeding major airports withtheir good frequency of aeroplane services, and in certain conurba- tions can supply a link between airports. Needless to say, thepracticability of such new and improved services depends on the safety, reliability and cost of the VTOL aircraft available to operatethem. It is essential that the level of external noise, blast and atmospheric contamination be acceptable for VTOL operationsinto and out of built-up areas. The basic factor affecting operational unit cost (cost per seatmile) is the transport capacity of the aircraft, i.e., seat-miles per hour, the product of capacity payload and block speed. Past andrecent experience in civil air transport operations shows that dur- ing the life of an aircraft type and development of traffic and theoperation of other factors are constantly pressing on unit aircraft capacity. This pressure is reflected in the steady increase, seenall over the world, in payload capacity of transport aircraft, for specific routes and route systems. Hence, the largest payload capa-city, and size of VTOL aircraft, which is generally agreed to be within the competence of existing design knowledge is specified. This line of approach leads to the broad definition of an initialdesign payload and "developed" payload. Thus, the design initial capacit should not be less than 40 seats over a 200 n.m. stagewith a standard seating arrangement. The ultimate development should be capable of accommodating at least 50 seats over a200 n.m. stage. The performance required under normal and one engine opera-tive conditions is given below. Unless otherwise stated, maximum take-off weight and ISA+10 deg C and 80 per cent relativehumidity conditions are to be assumed. All performance is out- side the ground cushion: — The payload should be made up of passengers and associatedbaggage at 200 lb per passenger, together with a passenger service allowance of 10 lb per passenger.The fuel load for any stage is to be calculated on the engine manufacturer's stated fuel consumption + 3 per cent at the poweroutput required on climb, descent and at cruise altitude at the average cruising speed denned below together with the followingreserves: (a) Fuel needed for an overshoot and climb to 1,000ft and second landing; (b) the fuel required at the minimum powerfor level flight for 60 min duration (n.b. this reserve is for hold-off and diversion). Tankage shall be provided for stages of up to 300 statute mileslength in a 40 kt head wind with reserves and allowances (a) and (b) above. The cruising speed should be not less than 300 kt with theengines operating at the manufacturer's recommended cruise power, and the aircraft at 95 per cent of the maximum take-offweight. Vertical rate of climb at sea level and maximum continuous (orone hour) rating of all engines shall not be less than 600ft/min, without ground effect, and at zero forward airspeed. Hoveringceiling without ground effect and with maximum continuous or one hour rating of all engines shall be at least 5,000ft. With thecritical engine or engines inoperative and the remaining engine(s) operating at the maximum continuous or one hour rating, the rateof climb at the best forward speed for climb shall be not less than 150ft/min at all altitudes between sea level and 5,000ft, and thegradient of climb not less than 2.5 per cent. The VTOL aircraft should be capable of operation out of andinto sites of limited dimensions closely surrounded by obstruc- " tip'ris. The characteristics of such a site may be taken as thosedescribed in the report of the second IATA Helicopter Meeting (Brussels, 1955). In the event of failure of the critical engine orengines at any stage of the take-off it shall be possible to return safely to the take-off area or continue flight and land elsewhere.It shall be possible without requiring exceptional pilot skill to approach and land in a crosswind at least equal to the minimumlevel flight speed of the aircraft with the critical engine or engines inoperative and the remaining engines(s) delivering maximum oremergency power. Experience in helicopter operations to the present time hasemphasized the need for greatly improved handling characteristics in instrument flight, which will be a regular feature of scheduledoperations. The essential need when using restricted sites for steep flight paths at low forward speed in landing and take-offis for good flying qualities under these conditions, both under full power and in the event of engine failure. Further, operation intosmall sites closely surrounded by obstructions will, in gusty conditions, demand good co-ordination of control and crispresponse. C.A.R. (Sections 6.120 to 6.123) and B.C.A.R. (Section G,paras. 2-6 to 2-10) lay down minimum requirements to be met by rotor-craft, and should where appropriate be fulfilled byVTOL aircraft. An integrated autopilot flight system shall be installed. In addi-tion, it shall be demonstrated that the information offered by the instrument panel is sufficient for a normally skilful pilot to main-tain control of the aircraft while forward speed is increased from zero to the minimum for steady forward flight without auto-stabilization and while power is increased to the maximum con- tinuous or one hour rating.A weight provision of 500 lb for communications and navigation equipment shall be allowed, together with appropriate spaceprovision. The undercarriage shall be so designed that the aircraft can bemanoeuvred into any desired position with no point of the aircraft passing outside an area 400ft x 200ft. It shall be possible to movethe aircraft with a single tractor which is rigidly connected to the aircraft and the manoeuvring required shall not be excessivelyprotracted. A means of rapidly stopping the rotors which does not requireheavy maintenance shall be provided. Means shall be provided to prevent "blade-sailing" while starting or stopping the rotor insteady or gusty winds up to 50 kt. When required by the operator, it shall be possible to provide means for rapidly folding any fixedsurfaces to facilitate parking in confined spaces. The time from tanker in position to tanker away, employingthe normal means of refuelling, shall not exceed five minutes when the tanks are completely filled, while in off-loading fuel the timetaken to remove 10 per cent of the fuel capacity shall not exceed three minutes. Pressure refuelling is required together with alter-native means of "gravity" refuelling not requiring special equip- ment. The pressure refuelling point shall be directly accessiblefrom the ground. Improved accuracy fuel gauges are required. Doors (other than servicing doors) should be on the port sideof the aircraft. Simultaneous loading or unloading of passengers and baggage/freight shall be possible (i.e., baggage/freight shallnot have to be loaded through the passenger door). Doors shall be so positioned that this will still be possible when a mixed loadof passengers and freight is carried. The principal passenger door shall not be less than 2ft 6in x 5ft 6in high. Airstairs are required.The baggage/freight and secondary passenger door shall be at the opposite end of the cabin to the principal passenger door andso designed that a truck can approach the opening without obstruc- tion. This door should be large enough to admit a spare engineof the type installed in the aircraft and, in any case, not less than 4ft Oin x 5ft 6in high. Emergency exits, other than doors, shallopen inwards. Pressurization is required so that cabin altitude does not exceed8,000ft and rates of change of cabin altitude do not exceed 300ft/min. At least 2 lb/min of fresh air per seat is required forpassengers and crew at all heights. At a distance of 200ft the overall noise level during landingor take-off should not exceed 90 db above 2 dynes/sq cm. The cabin width at 25in from floor level should permit theinstallation of seats of the following dimensions: (1) width between arm-rests, 16^in; (2) width of arm rest, 2in; with a mini-mum gangway of 15in. Seat pitch should be 34in minimum, and a headroom in the gangway should be 6ft minimum. A luxuriousseat is not needed, the standard of comfort required being that for a two-hour journey. Seats shall be mounted on rails. Total volume provided for stowage of baggage, registered andunregistered, shall assume a density of 9 lb/cu ft of usable gross volume. In addition to space in the registered baggage compart-ment stowage shall be provided for unregistered medium sized suitcases carried by the passengers themselves in racks near thepassenger entrance door. The registered baggage compartment shall be so laid out that the flight attendant can sort registeredbaggage in the air. Continued on page 160.)
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