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Aviation History
1960
1960 - 0622.PDF
622 HANOVER ROUND-UP The Sikorsky S-62 at Hanover, preparing to taxi. At right is a view of the cockpit, showing main instru- ments arranged for the first pilot. The floor-level window is not fitted here FLIGHT, 6 May 1960 peller actually gives negative thrust (although still in positivegeometric pitch). As airspeed increases during and after take-off, a constantgeometric pitch would give a steadily reducing aerodynamic pitch, and the automatic control would therefore progressively reducepower to prevent the r.p.m. increasing—or the pilot would have to keep pitch advancing (very accurately) to maintain maximumpower. Turbomeca have avoided this by providing a maximum- power governor working on j.p.t. To maintain both constantr.p.m. and constant maximum j.p.t. (and therefore power), it is simply necessary to press the "max" button beside the pitch lever.An amplifier in the j.p.t. circuit then automatically adjusts the electric propeller so that j.p.t. remain at 420°. Thereupon thepitch lever moves mysteriously forward throughout the take-off run and initial climb. Running at constant speed, the enginedevelops 80 per cent power from near-zero thrust in one second, and full power in between three and four seconds. Should thej.p.t. be exceeded, pitch is automatically reduced to 12° and automatic feathering may be provided. In case of engine failurein a twin, therefore, a button can simply be pressed to obtain virtually immediate and regulated full power from the otherengine. As an extension of this, Turbomeca are planning to providea similar automatic control for cruising power. So we can look forward to automatic full and cruising power, and automaticpower control for manoeuvring flight, approach and round-out, plus reverse thrust and airbrake effect or negative thrust for rapidspeed-reduction or dive-speed limiting. Reliability during the l,500hr of flying so far completed withtwo Astazous has been extremely good, and the engine has passed three 150hr French type-tests. It is to be available for sale thisyear and is in production. Turbomeca have really proved their genius with this system, but major credit is also due to SFERMAwho, with Beechcraft support, have converted the Twin Beeches, Holste 153, Nord 1110 and Travel Airs and have handled thetest-flying. CGTM have also done much development flying, particularly in proving the Bastan clip-on powerplant. SIKORSKY S-62 in the Air "LTELICOPTER representation at Hanover was not very wide,•"• but included one of the Sikorsky S-62 prototypes, an Agusta Bell Super Ranger and 47G and a Sud Alouette II demonstrator.I wanted to fly one of these and chose the S-62, partly because I had not yet flown a constant-speeding machine and partlybecause it was the biggest and newest. Weser Flugzeugbau, who represent Sikorsky in Germany, saythey are prepared to build the twin-engined S-61 under licence if a Government order is received. At Hanover many GermanAir Force officers flew the S-62; the machine, gorgeously furnished for nine passengers and a crew of two, looked like a very smoothS-58 replacement. Its powerplant is a General Electric T58 with hydro-mechanical fuel control which derates it from its normal1,050 h.p. to 900 h.p. Of this, 730 h.p. can be "pulled" in the S-62 for five minutes, and 670 h.p. continuously. The excesspower is available to maintain sea-leyel performance in hot or high situations. The T58 is a free-turbine engine and the rotor andturbine are governed between 170 and 215 rotor r.p.m. Power turbine r.p.m. are noted in per cent on a separate dial and usedin flight rather like the boost gauge of a piston-engined helicopter. Never-exceed limit is an indicated 95 per cent; but this is morethan sufficient for hovering, and the only time when "boost" must be watched is during the take-off transition when collective pitchmay be used to the limit. Otherwise the collective lever is purely an up and down demand control, without a twist-grip to worry about. This enormously simplifies flying and really takes the work-out of it altogether. When I leapt into the co-pilot's (left-hand) seat with Sikorskypilot Pete Blanchard, this was about all he had time to explain before we had taxied to the take-off point just outside the mainstatic park. From then on he was talking me through the standard power-on manoeuvres and I was trying to cope with a controlsensitivity which I have never before experienced. The Westland Widgeon on which I have been training has what I thought atfirst were virtually force-free, fully powered controls with very slight spring feel, but control movements can be quite consider-able and little time is needed co get used to the feel. Yet I could barely keep the sensitive S-62 straight and level, and I saw aGerman Sycamore pilot do some violent rolling when he insisted on making his first take-off unaided. Sensitivity for Ease of Control Blanchard said it takes about two hours to get used to thesensitivity, but after that the S-62 is very pleasant to fly. For an almost Unnoticeable force, full rate of roll or pitch resultedfrom what seemed to be between one and two inches of cyclic stick-displacement; but this meant that handling and manoeuvringrequired virtually no exertion. The collective lever is also extremely light, but not nearly so sensitive, and the rudder bar is light anddirectional response very good. I saw the S-62 make turns on .the spot in quite strong winds. I first took control during forward flight at 80kt—well belownormal cruising speed—and struggled for a while to keep level. The machine was exceptionally quiet and smooth, with only afaint once-per-rev vibration and little mechanical or airflow noise. With a very deep windscreen and floor-level windows visibilitywas excellent. Instrument arrangement and colour-marking were also very clear. We made a few turns and then returned to a small pool setsome 10ft below general ground level and surrounded by fences and bushes. Up to this Blanchard brought us; I following throughon the controls, and I then hovered and lowered the S-62 into the water. Attitude changes were fairly large when seen fromoutside but barely noticeable from the cockpit. We rose out again and made a circuit to the original pad, where I slowed to a hoverand made the landing. Transition was very easy from an approach at 60kt, because there was no boost to worry aboui and littledirectional reaction to power changes. The final surge of power to come to the hover was applied with a small collective lever move-ment and a slight yaw and could be done without any reference to engine instruments. By this time I was beginning to feel the machine and to becomefascinated by its simplicity and easy responsiveness, but I would have needed more time to get the knack of those sensitive controls.Incidentally, the seats are adjustable for height and reach, so that I could set mine to a height at which I could rest my arm on myknee to get steadier control. The stick was then about four inches from the seat, but movements were never large enough to foul it. One point which Blanchard explained was that lateral controlwas difficult at first because the pilots' eyes were on the roll axis of the fuselage. Lateral displacements were therefore much moredifficult to sense than if a roll movement actually caused the pilot's head to move perceptibly sideways, as it does in an S-55or other types. Engine starting on the S-62 is simple, involving an automaticcycle for starting the turbine, followed simply by movement of s hand throttle to obtain engine operating speed. The rotor brakeis then released and the rotor accelerates smoothly to governed r.p.m. There is no clutch to be engaged.
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