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Aviation History
1961
1961 - 0820.PDF
830 FLIGHT, 15 Jur« ' a ise •is. de T,, ter I had to let down about 500ft at one point, and as theincreased to 120 m.p.h. the Bell became distinctly rougher ventilator intake began to make a considerable noise. Oth>.noise level was reasonable and there weie few vibration pe The instrument layout was clear and tidy and the deep,windscreen gave good forward view. Sideways and up and v the field was more restricted than in many machines. If the Bell is a straightforward, comfortable transport matthe Kaman Huskie which I next flew is a highly specialized heliu well endowed with curious features. Power is again a free tu. me(Lycoming T53-L1) from which 725 of the available 850 h.p. ,nay- be "pulled" by reference to the torque meter. The teetering, -vo'.blade rotors constant-speed and intermesh and are controller by servo-tabs which twist each blade about its fixed root. All torqueis cancelled out in the contra-rotating rotor system so that the rudder pedals, acting on aerodynamic rudders on two of the fourfins and on asymmetric cyclic-pitch control, need only be used for changing direction. This means that the machine can be taken fromfull-power climb to autorotation without, in theory, touching the These two pictures show the many singular and distinctive features of the Kaman H-43B Huskie rescue helicopter for the USAF A THREESOME OF CHOPPERS .. . for about ten occupants, with comfortable seating, carpets andsound-proofing. All access panels and tail shaft fairing were made of glass plastics: radio and instruments were all accessible througha single panel in the nose. Full dual control and blind-flying instrumentation were provided, together with a long console forradio equipment between the pilots' seats. A skid undercarriage was fitted. In flight, the 204B proved to be the smoothest, quietest and mostnearly hands-off machine of the three I flew. Irv Franklin, the Bell pilot, took me up with several other passengers and showed howthe 204B handled. The rotor was governed and turned almost constantly at between 290 and 310 r.p.m., with an output shaftspeed between 6,200 and 6,600 r.p.m. The governor regulated fuel input to the engine so that no throttle co-ordination was neededonce the transmission had been set at the required speed. Franklin said it was impossible to exceed the maximum j.p.t. by over-fuelling, even on a hot day. The main limiting factor as far as power was concerned was the maximum of 780 h.p. which the pilot wasallowed to take out of the engine. More was available and there was no gate or stop, because the full 780 h.p. had to be available upto what might be termed the full throttle height. The actual power being used at any given time was indicated by a torque meter red-lined at 3401 b/sq in. In the Widgeon there was a limiting boost, but one had to jugglethe boost and r.p.m., actually working to balance the one against the other, in order to derive some indication of the power marginremaining beyond hovering power, that is, the ability to continue the flight or not under any given circumstances. On the Bell 204B,the torque meter gave instant indication of power being consumed without any juggling to arrive at a correct assessment. In fact, thefull 780 h.p. allowed a l,000ft/min vertical climb at full load and the margin for all normal work was more than ample. Over-pitching was therefore also hardly a problem, especially in view of the constant-speeding of the rotor system. I do not know how theBell fares, but in the Hiller 12E there was even enough power to climb out of vortex ring conditions. A generous margin of powerand constant speeding therefore take most of the possible "corners'" out of normal operation. Having explained these points, Franklin launched out into thecountryside around Le Bourget and had a look round. We moved along at about 110 m.p.h. and Franklin trimmed the Bell to flyhands-off, which it did quite happily for a surprisingly long time. He even managed to get it to maintain a shallow angle of bank for afew seconds. About autorotation, Franklin said that he had on occasions cut the power and kept the collective lever at the cruisingsetting until r.p.m. dropped to 220 after 7 or 8sec. Then the collective was pushed fully down and the rotor r.p.m. went straightback to 300. The skid undercarriage was suitable for run-on land- ings at quite high speeds, so that the flare problem was muchreduced. After a few minutes Franklin made me take over at about100 m.p.h. The Bell felt light and surprisingly stable. The stabilizer bar is mounted above instead of below the rotor on this machineand stability has considerably improved. Cyclic-control response was also light and progressive, without the tricky feel of directpowered control on some other types. Directional control was very light and called for small pedal movements, but did not seem over-sensitive. The machine was certainly easy to fly in forward flight, and the slight loss in control response caused by the interpositionof the stabilizer bar between pilot and rotor was if anything a help. <*»<• "Flight" photograph rudder pedals. In fact, the Huskie is directionally relatively unstablein cruising flight and has to be positively held straight as it tries to wander into a yaw one way or another. But because the directionalcontrol is largely aerodynamic and not as sensitive as a tail rotor, it is quite easy to "nail the nose on course" with occasional applicationof a stout boot. Rotor disc area is large and the lift per engine horsepower large,so that the Huskie performs well at height. Blade stall has never been encountered, even during the record lift of l,OOOkg to25,000ft. Rotor speed is low, at 236 r.p.m. All this makes for a very good lifting helicopter, but at some sacrifice in forward speedcapability. The Huskie is red-lined at 105kt and normally flies at about 80kt, but a large part of the military acceptance tests weresuccessfully completed at 130kt. The Huskie has probably been seen with as many different finsas any aircraft, but the configuration shown above is final. It con- sists of four fins, two of them with rudders, mounted on a fully tiltingtailplane with liberal wire and rod bracing. The tailplane is freely hinged, but a large servo-tab is connected to the collective stick sothat tailplane angle is adjusted as a function of power. The object is to provide normal longitudinal stability in forward flight. Twospring tabs bracketing the geared tab act as blow-down tabs to provide further reaction to power changes. The tail-pipe of theturbine is also carried right back aft of the elevator and consider- ably turned down, presumably for similar reasons. An interestingfeature was that the main-rotor tabs could be trimmed ard the blades tracked in flight. I flew in the Huskie with Mr Newton, the Kaman test pi!-started the turbine by pressing one button and then releasr rotor brake and winding up into the constant-speed ran-Strong once-per-rev vibration set in and remained with u stantly through the flight. Newton remarked that the torquewas the best instrument ever given to the helicopter pilot ant. given torque setting would lift a given load anywhere. We ;•shakily out into countryside east of Le Bourget once more.: 75kt. Newton throttled back the engine, held the collect! \up and we just slid slowly down with the rotor r.p.m. se;> t. Heg the I A con- meter hat a ibled .king lever •d at
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