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Aviation History
1953
1953 - 0828.PDF
822 FLIGHT A NEW CIVIL HILLER NOW that military requirements are being met to schedule, Hiller Helicopters have resumed work on production for the civil market. For the last two years orders for the U.S. Army and Navy machines, the H-23B and HTE-2 respec tively, have absorbed almost the entire production capacity of the Palo Alto factory. The new commercial machine, designated UH-12B, has been developed from the H-23B and incorporates many improvements in comparison with its predecessor, the Type 360. The 360's original 178 b.h.p. Franklin engine has been developed to give 200 b.h.p. at maximum power, and its installa tion in the new machine is similar to that in the H-23B. Also similar is the control layout, which includes a conventional floor- mounted control column to operate cyclic pitch (as opposed to the earlier hanging stick) and a new twist-grip throttle on the collec tive-pitch lever. The improved rotor head incorporates a redesigned collective ballast-weight system to reduce the load on the collective-pitch lever at various settings. This ensures that the lever needs no force to shift it, and an adjustable friction nut allows it to be set for any flight condition and then disregarded. The other new device in the control system is fitted to the cyclic-pitch linkage behind the canopy to prevent cyclic vibra tions from being transmitted to the control column. The two sprung weights, one applied to fore-and-aft control and the other to lateral, are tuned to the rotor frequency and vibrate themselves when any cyclic oscillations come back from the rotor head. The Hiller machines have always been reasonably smooth to fly and this further refinement must indeed eliminate all stick-shake completely. The skid landing gear has been subjected to stringent tests on more than one helicopter type. It is much preferred by pilots, even for—one might say especially for—autorotative landings. Two jockey wheels are fitted just behind the helicopter's centre of gravity to facilitate ground handling. They are lowered manually when required. It is significant to note, in parenthesis, that metal skids were first used experimentally by the U.S. Coastguard in 1945, and the inclusion of this type of landing-gear as standard equipment seems to mark the permanent acceptance of a new helicopter design- trend. Among the advantages they offer are greater stability on the ground and a saving of weight in relation to the conventional wheel undercarriage. On larger machines, no doubt, it would be necessary to employ some system of screw jacks, or power-assisted jacks, to lower the jockey wheels, four of which would be needed. For civil helicopters which are intended to operate over long stretches of water, skid-type landing-gear lends itself well to the carriage of emergency pontoon flotation-gear, which can be The 200 h.p. Franklin engine installation and rotor-head assembly (with redesigned collective ballast-weight system) of the new UH-MB. In spite of their small overall dimensions, the exhaust silencers are claimed to reduce the noise-level to 85 decibels at a distance of 100ft. inflated, if necessary, by CO2 bottles. The helicopter's known ditching characteristics make it seem likely that some form of flotation gear will be a necessary safety precaution when carrying passengers over such routes, even though twin-engined machines may be in use. The Hiller organization has always held ease of maintenance to be a most important feature of helicopter design. The opera tional experience, both civil and military, which has been gained during the last few years has been put to good use in the UH-12B. Throughout the whole machine there is evidence of many refine ments to this end. Certain engine accessories, such as fuel pumps and oil cooler, have been re-located where necessary to provide easy accessibility. Quick-release fasteners permit inspection below the floor, and the whole instrument-panel hinges at the pedestal for rapid instrument maintenance. To achieve longer service-life of moving parts the transmission lubrication system has been completely revised. The tail-rotor Left) The neat new instrument-panel does not include blind-flying instruments, but they can be fitted if required. The pilot sits centrally, with one root on either side of the pedestal. (Right) This view of the original Hiller 360 rotor-head affords a comparison with the new assembly illustrated above.
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