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Aviation History
1957
1957 - 0404.PDF
406 FLIGHT, 29 March 1957 Fig. 2. Schematic diagram of Mr. Reid's suggested instrument layout, with Decca Flight Log, described in detail below. HELICOPTER BLIND FLYING ... altimeter that could be used in conjunction with stabilized hover- ing devices was also desirable. The time had come for a new approach to the problem of instrument presentation for helicopters and his own proposal (Fig. 2) included two dial instruments and four ribbon instruments in place of the ten dials on existing panels. The upper dial, which gave the pilot his most important forward-looking information, was a combination of pitch-roll attitude and flight-director indi- cator. It also incorporated the turn-and-bank needle turned forward 90 deg so that only its down-turned tip was seen. The lower dial was the gyro-magnetic compass. To the right of the dials were the altimeter and vertical-speed indicator, while to the left were the airspeed and rotor-speed indicators. A red Perspex screen on the altimeter, activated by the radio altimeter, indicated terrain clearance. Elevation in relation to an I.L.S. glide-path was shown on a small indicator at the left of the artificial horizon, while the Decca Flight Log was immediately below the gyro compass. Because of the very precise flying required in restricted areas, a modified flight-director system coupled to the automatic pilot was most desirable, and work was scheduled to begin on this project as soon as equipment was available. Mr. Reid concluded his lecture with a mention of night-flying problems—which, fortunately, were few. After much experimen- tation, the "Cross of Lorraine" lighting pattern had been accepted as providing the maximum attitude information on the approach and whilst hovering prior to touchdown. For smooth landings a good deal of ground illumination was helpful, as also was the readily adjustable landing light which, on one helicopter type, was controlled from the top of the cyclic-pitch stick. THE DISCUSSION W/C. R. A. C. BRIE, the chairman, opened the discussion by thankingthe lecturers for two excellent papers. Their most significant aspect was that these results were all based on factual experience. No fancifultheorizing was involved and only existing equipment had been referred to. The objective was known and all that was required to attain it wasfurther development of known techniques. It was interesting to recall that, nearly ten years before, B.E.A. had operated such a successfulscheduled night mail service in the Norwich-Peterborough area, an achievement that had been a "first" in helicopter activities. MR. K. REED (Saunders-Roe) thought that helicopter manufacturersand operators were faced with a tremendous task in the near future. Within three years larger machines would be available, and unlessimmediate steps were taken to enable preparatory development to be pursued energetically at the present time, ancillary equipment wouldnot be ready soon enough to allow the larger machines to be used to their greatest potential. Action at a very high level was called for. Hewould like to see more aerodynamic stability introduced into helicopter design and he wondered if better instrument flying results could not beachieved by using rotor-plane sensing through the flapping hinges, instead of fuselage-attitude sensing, as the basis on which instrumentindications were presented. Among the important problems requiring much attention were de-icing of rotor blades, position error of airspeedindicators and instrumentation development. He was attracted by Mr. Reid's proposals for a new instrument-panel layout but he would like to goeven further and incorporate all the necessary instrument pointers on one large dial immediately in front of the pilot. MR. D. A. WILKINSON (A. and A.E.E., Boscombe Down) said that hisEstablishment had carried out a good deal of night and instrument flying experimentation from the military point of view. Their experienceconfirmed many of the results described, although some aspects were different when seen from the Service angle. Their lighting patternhad to be capable of improvisation with torches or flares, but a similar design had been evolved. He stressed the value of parachute flares foremergency night landings in single-engined helicopters. Boscombe Down was interested in low-airspeed measurement and had underdevelopment for this purpose an instrument which was showing great promise. MR. R. SWALES (Decca Navigator) said that the accuracy problemsreferred to by the lecturers were caused by static and had been resolved as far as installations in fixed-wing aircraft were concerned. Thesolutions would soon be applied to helicopters. In reference to Mr. Reid's proposed new panel layout, he asked whether B.E.A. weresatisfied with the size and shape of the Flight Log presentation. CDR. N. FULLER (Royal Navy) wanted less stress placed on the needfor artificial stabilization and more on the desirability of improved aerodynamic stability. It had been achieved to a certain extent on somemachines (e.g., the Westland Widgeon, Fairey Ultra-light and Bell 47 J), so why was it not possible with others? He thought that the combinedflight director/attitude indicator was too complicated and would like to see an instrument with just two-cross pointers which gave the pilotall the information he required. F/L. A. SHARPLES (Lee-on-Solent) asked for more co-operation between civil and military helicopter users. He thought the weather limits could be lower for Service flying. A typical Service pupil on a course was able to cope with break-outs at 200ft after an instrument let-down through cloud. MR. J. S. SHAPIRO (consultant) was of the opinion that while improvedaerodynamic stability was desirable for small helicopters it was a waste of time trying to achieve it for large transport machines. They wouldstill be affected by instability of the atmosphere itself, and artificial stabilization was the better approach. MAJOR R. I. WALTON (E.T.P.S., Farnborough) gave a brief descriptionof the rotor blade de-icing trials with a Bristol Sycamore in Canada. To test the de-icing equipment the helicopter had been hovered in anartificial cloud. The trials had shown great promise. MR. M. C. CURTIES (R.A.E., Farnborough) questioned whether Mr. Reid's proposed new instrument panel would in fact save space in the long run. The ribbon-type instruments he specified depended on trans- mission through servo links, which introduced an element of unreliability into the system. MR. J. W. LEACH (A. and A.E.E., Boscombe Down) was disappointedthat more had not been said about engineering features in basic design. There were still many problems to be solved before helicopters wouldbe suitable for all-weather transport operation. Not the least of these was noise, and crew comfort in relation to noise and vibration fatigue.The development of suitable restrainers to prevent blade sailing when starting and stopping rotors in high winds was also essential. MR. TWINNEY (R.A.E., Farnborough) said it appeared that, by thetime large transport helicopters were available, TACAN would probably have reached a stage where it could be used as a favourablealternative for the Decca system. He asked whether any consideration had been given to its possible utilization. MR. HEARNE, replying to the discussion, said he fully agreed withthe desirability for improving aerodynamic stability quite apart from artificial stabilization requirements. He thought Gustafson's work inthis respect was of great importance. Rotor-plane sensing as an alternative to fuselage-attitude sensing for attitude indicators had beentried in the U.S.A. and it had been found that there was no appreciable difference in the ability of a pilot to control the helicopter using eithermethod. Position-error was a serious problem with airspeed indication and a ground speed indicator might well be desirable. The most recent information he had from the U.S.A. regarding pilots'opinions of the combined flight director/attitude indicator was that although conflicting opinions did still exist, the school of thought thathad originally opposed its introduction was now becoming inclined to revise its views. B.E.A. did their best to ensure that Service operators were informedas to their activities through the medium of the Ministry of Supply. (A number of other speakers from various Service units confirmedthat liaison arrangements were entirely satisfactory.) Consideration was being given to the use of TACAN as asecondary navigation aid but it was not expected that a station would be available for use on this side of the Atlantic for some time. He had beensurprised by the fact that some manufacturers appeared quite unaware of the necessity to make provision for many of the navigational facilities,and closer liaison between manufacturers and operator was needed to avoid mistakes that had been made in the past. MR. REID, also in reply to the discussion, did not agree with thequestioner who thought his proposed new panel layout was more complicated. Its purpose was to provide more space for better visionforward when breaking out of cloud. He realized there were problems associated with ribbon-type instrument presentation, but there was agood deal of development work in progress in the U.S.A. to meet certain fixed wing requirements, and he hoped the results might be useful forthe helicopter application. The size of the Decca Flight Log had been the subject of much discussion and they felt that probably it could bemore square in shape and slightly smaller to advantage. With existing instruments, the airspeed indicator was unreliable below 40 kt and amore constant glide-path could be maintained by concentrating on the attitude indications during an approach at slow forward speed.
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