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Aviation History
1963
1963 - 0995.PDF
964 FLIGHT International, 20 June 196: I N THE PARIS AIR... governed at 400 all the time (they may "droop" to 390 in flight) but there is a "beeper" switch beside the captain's collective-lever to allow r.r.p.m. to be recovered for maximum performance. All these figures may seem to load the pilot with a built-in headache, but in fact the power margin under all normal conditions is so good that he can forget the power system entirely, cast only an occasional eye at the torque gauge and concentrate entirely on flying—a delightful and revealing experience for anyone accustomed to the baleful art of twist-grip twiddling. Starting has also been simplified. The master switch is operated, and radio, alternator, fuel pumps, starting-cycle and other buttons pressed, h-p cock opened and starter switch moved, and the engine bursts into life all by itself. At the ground idle setting of 45 per cent c.r.p.m. the free turbine causes the rotor to spin up to about 155 r.p.m. with the rotor brake released. The twist-grip is then advanced to bring the system into the governed range and need thereafter be regarded only as "not to be closed." The Scout really performs most impressively. At a gross weight of 5,0001b in ISA at sea level it will come to the hover at only 65 per cent torque and can easily reach 115kt in level flight. This, the present cleared maximum, represents only the maximum set by the Army as a customer rather than by the capability of the aircraft. The 115kt is a good 10kt below the blade-stall area. Normal cruising speed can be 106kt. At the book climb speed of 50kt, the Scout will reach 12,000ft in 6£min and will still achieve more than l,000ft/min at that height. Again, the Army specified ceiling is 12,000ft, but the aircraft can go higher. Speed and manoeuvre limits, of course, decrease in the normal way with height. The Scout I flew was a dual-control aircraft with an extra set of blind-flying instruments at the instructor's seat to port. The pale grey panels and integrally lit centre console gave an unusually neat and tidy impression. The "greenhouse" roofing seemed slightly over-strutted for good visibility, but was certainly adequate for accurate hovering; and it was fitted with very welcome sun- blinds to cover all top windows. At a relatively early stage in development Saunders-Roe—who originally produced the Scout—fitted Widgeon-type powered controls and saved much painful development of acceptable manual handling. Thus there is full power, with l,0001b/sq in hydraulic pressure, in a 3,0001b/sq in system, plus manual reversion —though the powered system has never been known to fail. Man ual forces are high, though not impossibly so at reduced forward speeds and certainly better than those of the Widgeon. The full- power system has no feed-back and a trimmable spring centring is applied to the cyclic stick. The rudder pedals are unboosted. For the flight I took the left seat and Mathews the right, while a passenger sat on the rear bench. Mathews started up, contacted the heliport control tower on VHF and got airborne. With about half the normal 155 Imp gal of fuel and three occupants, in a fresh wind, 60 per cent torque got us into air, 70 per cent gave a l,500ft/min climb and 55 per cent 500ft/min. We held 80kt in 'Flight International" photograph Cof/ect/ve-fw'tc/i and rotor r.p.m. gauge are high on the left and the torque gauge at the top left corner of the blind- flying panel. Switches and radio controls are on the in tegrally lit centre console. Pale grey background colour ing is much better than the traditional black level flight on only 48 per cent. Noise-level was surprisingly low, with only a distant hiss from the engine. Vibration was virtually nil at medium speeds and built up very slightly on this particular Scout at above lOOkt. On taking control in forward flight I was immediately impressed by the fact that stick forces and displacements corresponded per fectly naturally with aircraft response, giving quite the best control feel I have yet met in a helicopter. We were restricted to a left-handed circuit close to Le Bourgefs western side, but had plenty of room to make a few turns and to change speed between 50kt and HOkt. Because engine and rotor r.p.m. took care of themselves, speed changes involved completely natural co-ordination of cyclic and collective levers as pure aero dynamic controls, and very little rudder co-ordination or trim- changes were needed. I managed to go from 80kt to UOkt and back below 80kt over what seemed like 1J miles of ground. Torque remained a long way below 100 per cent. Though not autostabilized, the Scout did not wander much from a set attitude. WESTLAND SCOUT AH.I (One Bristol Siddeley Nimbus transmission-limited to 685 s.h.p.) Rotor diameter. 32ft 3tn; fuselage length, 30ft 7^in; empty weight, 3,0841b; normal gross weight, 5,3O0lb; fuel capacity, 155 Imp gal; max seating capacity, pilot and five passengers. Performance Max speed, 132 m.p.h.; max cruising speed, 122 m.p.h.; climb at 58 m.p.h,, l,660ft/min; vertical climb, 730ft/min; hovering ceiling, i.g.e. 15,600ft. o.g.e. 10,200ft; service ceiling, 17,700ft; manoeuvre ceiling, 13,500ft; max range, with 5min hovering and I5min reserve cruise, 316 miles; max endurance, 3.2hr. I came down to the landing area at 50kt, finding less difficulty in reducing speed and height together than with any helicopter I had previously flown. I slowed down gently and came to the hover at about 30ft. There was a slight peak of vibration as I applied higher power, but only a little left rudder was needed. In the hover, the well-matched cyclic forces and responses made flying comfortable and the collective proved extremely responsive. I made turns on the spot and nosed round the triangular "H" marker without difficulty. At 30ft one is clear of most of the ground effect, and Mathews told me that rudder sensitivity considerably increased lower down; but when I tried a landing I did not find this characteristic obtrusive. Higher weight would have made it more noticeable. The Scout hovers slightly left-skid-low, but sits down firmly with no apparent tendency to doddle. The lift-off requires no left stick or quick rudder application. The smallness of the cyclic-trim changes can be judged from the fact that it did not occur to me to ask where the trimmer was until after a complete circuit, hover and landing. Jim Mathews made a vertical climb at 100 per cent torque and maintained l,800ft/min up to 1,000ft—really going like a high-speed lift. He also showed the Scout's run-on capabilities by sliding over the grass on the skids at 40kt. In this apparently brutal manoeuvre the rudder must be treated with care, but otherwise gives a remark ably smooth ride. Rudder is extremely powerful, and turns at several times the "book" limit of 40°/sec can be made at the hover. I found that the Scout was slow to settle into a hovering turn, but wound up into it after about 60° and then sailed round. The machine is responsive enough to require only a fraction of the available cyclic stick-travel for all usual manoeuvres, so that most of the travel is available for dealing with the very wide permissible-c.g. range —5in forward, 5£in rearward, 3in port and 5Jin starboard of rotor centre of lift, the last allowing for offset loads on the hoist. There was no chance to try autorotation, because of restricted operating area and pretty dense and random movements of other aircraft in the immediate vicinity. I gather that rate of descent in autorotation can be held to l,500ft/min at maximum gross weight at the best speed of 50kt—roughly average for modern high-loaded rotor discs—and that such a rotor system requires a properly judged flare and touch-down. Absolute minimum rotor r.p.m. are 280 and the aircraft must be down by then; but run-on landings certainly present no problems. If the twist-grip is turned back to ground idle, an autorotative landing can be made without switching the engine off—a useful training point—but some seconds must be allowed if autorotation is to be abandoned and power reapplied. With its full standard blind-flying panel and lighting the Scout can be flown at night and is pleasant to fly in cloud at speeds down to 50kt. It has been hovered in cloud, but special instruments are really necessary at below minimum-power speed. Altogether, I found the Scout the pleasantest helicopter I had yet flown. c. M. L.
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