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Aviation History
1957
1957 - 0840.PDF
846 FLIGHT, 21 June 1957 HELICOPTERS IN CONTRAST . . . the first time I had handled the type. Previous experience on thePiasecki HRP-1 and the Bristol 173 was, of course, helpful, and I soon picked up the new feel. Response to control in cruising flight was positive, and withthe hydraulics in operation there were no undesirable stick forces present. I was able to do a few gentle turns in both directionswhile following the course of the river into the centre of Paris. It might have been preferable, I thought, to have the controlcentering device coupled to provide some degree of artificial feel, but it was certainly not essential. The action of the hydraulicjacks was smooth; and, although the stick forces were light, one was still aware that one had seven tons of helicopter in one'shands. There was the characteristic difference in response, nor- mally associated with the tandem-rotor configuration, to lateraland fore-and-aft stick movements, but since I expected this it presented no problem. The rudder control was, I felt, inclinedto be a little over-sensitive and I tended to skid slightly at times. However, M. Schmitt did not appear to have the same trouble, soI would probably have become accustomed to its sensitivity. I was particularly impressed (and relieved) to find that thetwist-grip throttle was not too sensitive in its action, so that it was possible to maintain the correct r.p.m. accurately without"hunting." In some helicopters, adjustment of the throttle control is far too precise for comfort in making small changes of r.p.m.To digress for a moment, I was surprised to see, on flying a modern American helicopter again for the first time after anumber of years, that the U.S. engine and rotor r.p.m. indicators still have the engine speed as the primary indication on the dualtachometer. That is to say, the large needle is the engine-speed pointer, reading against marks around the outer periphery of thedial, while the rotor pointer is the smaller needle reading against a smaller inner scale. In the autorotation case the large needlefalls back, leaving only the little needle to give the pilot an indica- tion of rotor r.p.m. This design has apparently remainedunchanged since 1945. (For the benefit of those unfamiliar with helicopter practice, it may be explained that the two needles lieone above the other and work in unison during normal powered flight with the clutch fully engaged.) Having been originally responsible for introducing a change inthis layout, and one which for many years has been standardized in British helicopters, I was rather interested in this point. Inthe British instrument, the rotor needle is the large one and the pilot flies the helicopter on rotor revs, rather than engine revs.The smaller engine needle is read against the inner scale, which is quite adequate for starting procedures. In the autorotation case,the small needle falls back, leaving the pilot still with the large needle indicating rotor speed against the outside scale. This ismuch truer symbolism of what is happening physically and I was surprised that the American instrument manufacturers had notadopted a similar principle. The first instrument based on this principle was made in 1946 by the Fairey Aviation researchdepartment, which was then headed by an enthusiastic helicopter adherent, Geoffrey Hall, who is now chairman and managingdirector of the company. It was an adaptation of an American design and was fitted in a Sikorsky R.4 helicopter at Heston.Later the idea was adopted by British instrument manufacturers. I was tempted to take up the question with M. Schmitt, butthere were more important interests to occupy my attention. We arrived at Paris-Issy heliport after just over 15 minutes' flying andlet down into the approach, the captain taking over for the landing. Approach speed was 60 kt, reducing progressively as we nearedthe ground, and there was no sign of vibration in the slightly tail-down attitude. Serious vibration caused by rotor slipstreaminterference in this flight condition has been laboured by the "anti- tandem" school of thought as an insurmountable disadvantage ofthe tandem-rotor configuration. The original Piasecki HRP-1 which I had flown in die U.S.A. had certainly suffered from itand, with this in mind, I was anxious to see what improvements had been made in this more advanced machine. The improvement was, in fact, 100 per cent. On discussing the point afterwardswith Charles Schmitt, I learned that what remained of the fault (after design improvements had removed the major part of it)could be obviated by pilot technique. A slight yaw out of wind during the final approach phase, of between 20 and 30 deg, wassufficient to ensure that the two rotor, slipstreams did not interact, and it was barely perceptible to the occupants of the machine. After a quick turn-round at the heliport, where a Sabena S-58was taking on a load of passengers for Brussels, we left again for Le Bourget, now with only five passengers. The salon was thenclosing for the day, and most of the traffic was in the opposite direction.This time I took over the machine from hovering flight and climbed away to follow the river route from the city centre. Whenwe settled down to cruising flight I found, with the lighter load, that we could maintain 90 kt pulling only 35in manifold pressurewith 2,400 engine r.p.m. There was no need on that occasion to make use of the longitudinal stick positioner.The return journey was uneventful and, as I followed the river out to Le Bourget, a number of general thoughts on the subjectof large transport helicopters passed through my mind. Sitting in the co-pilo.t's seat on the left-hand side of the machine, I wasreminded of my earlier fixed-wing flying and began to wonder whether this big helicopter had not grown up enough to warrantfitting it with a wheel for lateral control in common with con- ventional airliner practice. In a single-rotor helicopter wherethe stick is displaced laterally at higher forward speeds, there may be some disadvantage in this, in that the wheel would notbe level in cruising flight. In the tandem rotor helicopter, how- ever, the stick remains central throughout the speed range anda wheel might offer certain advantages. Another point that it occurred to me to question was whetherit was necessary or desirable in the civil version of this machine to perpetuate the principle of placing the captain on the right-handside of the cockpit. In the military H-21C, this is done to give him a good view of the hydraulic winch operation when onrescue duties; the winch is located on the starboard side forward and its loads are taken into the machine through the starboarddoor just abaft the cockpit. In the civil version this need does not arise and, since the captain of every other airliner sits on theleft-hand side to give him a better view of the landing ground when doing the standard left-hand circuit, why not in a helicopter?Further soliloquy along these lines was interrupted by our arrival and landing at Le Bourget and, as another full load ofpassengers were waiting to return to Paris, I was unable to pursue the matter further. Notwithstanding these minor comments, themachine is most impressive to fly and my brief introduction to its characteristics was extremely enjoyable.In the face of the Vertol 44's performance, it would indeed be a courageous single-rotor partisan who engaged in argumentagainst the tandem-rotor configuration. Personally, I believe that both types have their appropriate applications and advantages,and there is no doubt that the Vertol Corporation have gained considerable prestige from the Paris Show shuttle service. British planners, instead of playing their private little gameof ostriches "waiting until suitable helicopters are available in 1960 for inter-city services," might do well to think hard aboutthis machine—especially in view of the fact that two twin turbine- engined versions of the type are due to fly in the U.S.A. withinthe next two months. (One will have two General Electric T58 turbines of 1,000 h.p. each and the other will have two LycomingT53s, also of 1,000 h.p. each. The current single-engined version is so designed that its powerplant can be replaced by the twin-engine "package" with only minor modification.) B.H.A. Vertol 44 Leading Data.—Weight empty (with standard equipment), 8,655 Ib; useful load, 5,345 1b; gross weight, 14,0001b (useful load of military version is 1,000 ib in excess of above figures). Maximum speed (at 14,000 Ib), 110 kt; cruising speed (14,0001b), 88 kt; maximum sea-level rate of climb (14,0001b). 1,050ft/min; hovering ceiling (in ground effect, at 14,0001b), 5,000ft; hovering ceiling (out of ground effect, at 14,0001b), 3,500ft; service ceiling (at U.000 Ib), 10,600ft; fuel capacity (standard), 250 Imp gal; fuel consumption, 62 Imp gal/hr; range (with normal reserves), 315 n. m. FORTHCOMING EVENTS June June JuneJune June 21-24. 23. 24.26. 27 July 1 June 29-30. July July July July July July 5. 5-8. 6-7. 6-8. 9-14. 10. Palermo Aero Club: 9th International Aerial Tour of Sicily. Palermo. Northern Heights Model Aero Club: Gala, R.A.F. Halton. F.A.I. Annual Conference, Palermo. Kronteld Club: "The R.A.F. Formation Squadron," by S/L. Topp. British Institution of Radio Engineers: "Electronics in Automation" Convention, Cambridge. Invitation Rally, La Baule. Tiger Club: Aerobatic Contest, Sywell. Swiss Aero Club: International Rally, Bienne. Aero-Club de I'Ouest: International Rally, Angers. Invitation Rally, Deauville. Pescara Aero Club: International Air Week. Kronfeld Club: Film Show. July 12-13. Royal Aero Club: National Air Races, King's Cup, and Lockheed Aerobatic Trophy, Baginton. July 14. Northamptonshire Aero Club: At Home. July 14. Wolverhampton Aero Club: Invitation Rally. July 14. Yorkshire Aeroplane Club: At Home, Sherburn-in-Elmet. July 17. Kronfeld Club: "Meteorology for the National Champion- ships," by Wally Wallington. July 18-20. R.Ae.S., British Interplanetary Society, College of Aero- nautics Symposium, Cranfield. Born holm Flying Club: International Rally, Denmark.July 20-21. July 27- Aug. 5. Aug. 5-10. Aug. Sept. 7.2-8. National Gliding Championships, Lasham. Institute of the Aeronautical Sciences: National Naval Aviation Meeting, San Diego. Kronfeld Club: "Testing the Comet," by S/L. Topp. SB.AC. Show, Farnborough.
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