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Aviation History
1957
1957 - 0071.PDF
FLIGHT, 71 18 January 1957 BRISTOL 192 ... Alternative layouts of the machine for (top) troop-carrying (18 seats plus despatcher) and ambulance roles. I \ I \ FUEL ACCESS TO \ FLIGHT DECK EMERGENCYEXIT FUEL MEDICAL STORES RADIO STOWAGE by springs, these stops are actuated by a stepped-cammechanism and engage with the blade links. Disengagement takes place at about 120 rotor r.p.m., and the stops engage againwhen the rotors slow down to 80 r.p.m. Controls. The basic flight-controls consist of the pilot'scyclic-pitch control column, the central collective-pitch control lever, and adjustable rudder pedals. The collective-pitch leveris linked to the engine throttle so that the rotor r.p.m. remain approximately constant as collective pitch is increased. Throttleadjustment can also be made by a twist-grip on the collective- pitch lever, and hand throttles are provided for independentcontrol of each engine. Secondary controls comprise an electrically operated pitchtrimmer to compensate for varying e.g. positions, and a rudder bias control to trim out pedal loads. Fore-and-aft control is obtained by the application of anequal amount of cyclic pitch to both rotors together with differential application of collective pitch. Thus in moving thecontrol stick forward both rotors are tilted forward and, simul- taneously, the front-rotor collective pitch is reduced and that ofthe rear rotor increased. This combined control is designed to give a satisfactory combination of linear and pitching acceleration. Yawing forces are obtained by movement of the rudder pedalswhich causes lateral tilting of each rotor by equal amounts but in opposite directions. Lateral control is provided by lateralmovement of the control stick, causing both rotors to tilt laterally by the same amount and in the same direction. Collective-pitchstick movement gives an equal change in the collective pitch of both rotors. Power assistance is provided by small servo motors in thefore-and-aft cyclic-pitch, yawing and collective-pitch control systems, and an automatic pilot can be fitted. By means of amaster switch on the collective-pitch lever, all servos and the autopilot (if fitted) can be disengaged simultaneously. Undercarriage. The landing gear, designed for vertical land-ing velocities of 8ft/sec (normal) and 12ft/sec (emergency), com- prises two units equally spaced fore and aft of the aircraft e.g.to give a wheelbase of 30ft and a track of 10ft. The configuration of each unit is conventional in that eachconsists of inclined oleo legs with radius rods in the form of torsion boxes. The inboard ends of each pair of torsion boxesare coupled together by means of a swinging link which in turn is attached to an air/oil strut operating as both a spring and adamper. Fully castoring wheels are incorporated in the front unit, the direction of the rear wheels being fixed.Electrics. Two 4kW, 28v D.C. generators are employed, one being driven from each engine, and provision is made on theintermediate gearbox for two alternators, each with an output of up to 9kW. The capacity and voltage of the alternators willdepend upon electrical requirements. Estimated Performance. Calculations of the performance ofthe 192 in the roles of troop-carrying, casualty evacuation, freighting, search and rescue, and parachuting and supply-dropping are given below. Two basic types of operation have been considered: in the first the cabin load is restricted to obtainmaximum range; in the second the maximum possible load is carried over short distances. Troop-carrying. As illustrated, the normal troop-carrying accommoda-tion provides for a pilot, co-pilot or navigator, and 18 passengers (long- range operations). For short-range operations, 22 troops each weighing250 lb, or 25 at 200 1b, could be carried. Passenger seats are of the folding deck-chair type with tubular framework and are removable. Under sea-level I.S.A. conditions, 18 troops could be carried for100 n.m. (cushion take-off to 20ft) or 14 troops for 190 n.m. (vertical climb outside ground cushion), allowing 10 gal of fuel for warm-up andtake-off. For short-range operation, 22 or 19 troops (depending on the same respective take-off techniques) could be carried over 25 n.m., withreserve fuel for 14 minutes' flying at economical cruise in addition to ,tne ten-gailon take-off reserve. (Casualty Evacuation. The ambulance version of the 192, illustratedabove, provides accommodation for pilot, co-pilot or navigator, medical attendant and eight stretcher cases. The vertical distance betweenI stretchers in this arrangement is 28in. By reducing this separation, the stretchers could be mounted in tiers of three, increasing the number to • . addition, accommodation for three "sitting wounded" cases ca 27 Freighting. The maximum distributed load that could be carried inthe cabin is 6,000 lb, and the maximum concentrated load is 5,250 lb (with a limit load factor of 2g) or 4,000 lb (with a limit load factor of 3g).Maximum floor loading is 75 lb/sq ft, and lashing-down points arc fitted to the cabin floor, which is level throughout. Crew accommodation isprovided for a freight operator in addition to the pilot and co-pilot or navigator. Freight can be loaded and unloaded through the main entrance door,50in wide x 54in high, and the escape hatch at the port after end of the cabin, 28|in wide x 36in high. By substituting a door carrying a winch(as in the search-and-rescue role) in place of the normal canvas door, freight up to 600 lb per hoist could be raised and stowed, or lowered,with the aircraft hovering. Awkward loads which cannot be carried in the cabin could be slung externally from a strong-point under thefuselage, pilot-operated electrical and mechanical release mechanisms being incorporated, up to the same maximum as for concentrated loadsin the cabin. Long-range performance figures under sea-level I.S.A. conditionsinclude 3,500 lb load for 300 n.m. (cushion take-off) or 210 n.m. (vertical climb outside ground cushion). Short-range performance under theseconditions comprises 5,745 lb or 5,045 Ib respectively, over 25 n.m. Search and Rescue. The main innovation for the role of search andrescue is that the canvas entrance door is replaced by a metal door carrying an electrically operated winch capable of hoisting a 600 lbload at 3ft/sec, and also carrying a searchlight. The door is spring- balanced and can be opened and closed in flight. The operation of thewinch is controlled either by the pilot, by means of a switch on the cyclic control column, or by the aircrewman by means of a switch locatednear the door. Ten persons could be rescued at a radius of action of 210 n.m., undersea-level I.S.A. conditions and at a take-off weight of 16,200 lb. This assumes reserves of 20 per cent of total fuel carried on take-off, and20 minutes at maximum power while hovering. At shorter ranges more than ten could be rescued, but fuel would have to be jettisoned asnecessary to bring the gross weight down to that at which the machine could hover without ground effect. Paratrooping and Supply-dropping. For the parachuting of personnelor supplies, a static line is secured to the strong points near the main door, and a non-skid mat is used. Despatching lights are located abovethe entrance door. Under sea-level I.S.A. conditions, 12 paratroops could be carried for250 n.m. (cushion take-off) or 170 n.m. (vertical climb outside ground cushion); under the same respective conditions 17 or 15 could becarried over 25 n.m. Bristol 192 (2 Alvis Leonides Major): Leading Data General: Maximum gross weight, 17,200 Ib; disc loading, 4.57 Ib/sq ft; nominal power loading, 10 Ib/b.h.p. Major dimensions: Overall length (blades folded), 54ft 4in (max 89ft 9in); distance between rotor centres, 41ft 1in; maximum height (blades folded), 17ft; undercarriage track, 10ft; undercarriage wheel base, 30ft; main cabin length, 24ft 1in; main cabin height, 4ft 11 in; main cabin width, 5ft 3in. Rotors: Diameter. 48ft Bin; aerofoil section, NACA 64,-012; chord, 15Jin; disc area per rotor, 1,860 sq ft; gear ratio (engine to rotor), 12:1; maximum rotor r.p.m., 270; maximum tip speed. 687ft/sec. Napier Gazelle version 'two NG.2s, each of 1,650 s.h.p.): gross weight, 18,000 Ib; cruising speed, 115 m.p.h.; ceiling, 14,000ft; range, 450 miles. 6OO (A) TAKE-OFF WEIGHT- 17,200 Ib (B) TAKE-OFF WEIGHT- laSCO Ib (A) TAKE- OFFWEIGHT - (4,860 Ib 13POO Icould be provided on troop seats, giving a total of 15.I Under I.S.A. sea-level conditions, 12 stretcher cases and three sitting icasualties could be carried over ranges of 360 n.m. (cushion take-off) andIZ/5 n.m. (vertical climb outside ground cushion). HOOO GROSS WEIGHT LESS FUEL (Ib) ispoo Range-payload characteristics under I.S.A. conditions using (A) ground- cushion take-off and (B) vertical-climb take-off outside ground cushion, at 80 kt cruising speed. u
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