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Aviation History
1964
1964 - 0669.PDF
392 LETTERS... cant, with an angle of bank not in excess of 5 degrees. Vmc shall not exceed 1.2 Vs with: (1) Engines operating at the maximum available take- off thrust and/or power; (2) Maximum sea-level take-off weight or such lesser weight as might be necessary to demonstrate Vmc; (3) The airplane in the most critical take-off configura- tion existing along the flight path after the airplane be- comes airborne, except that the landing gear is retracted; (4) The airplane trimmed for take-off; (5) The airplane airborne and the ground effect negli- gible; (6) The centre of gravity in the most unfavourable position; (d) In demonstrating the minimum speed specified in paragraph (c) of this section, the rudder force required to maintain control shall not exceed 1801b and it shall not be necessary to reduce the power and/or thrust of the opera- tive engine(s). (e) During recovery from the manoeuvre specified in paragraph (c) of this section, the airplane shall not assume any dangerous attitude, nor shall it require exceptional skill, strength, or alertness on the part of the pilot to pre- vent a change of heading in excess of 20 degrees before recovery is complete." BCAR D2.8 says almost exactly the same thing, except that there is one little obscurity which may have a bearing on Mr White's contention:— "4.1.1 ... From the time at which the power-unit becomes inoperative until the aeroplane is once more settled in straight steady flight at the initial airspeed, a rudder pedal force of 1801b shall not be exceeded, nor shall exceptional skill be required to prevent: loss of height other than that, if any, which is implicit in the loss of performance)." The parenthesis at the end of the extract [my italics] looks as if it might include a VTOL aircraft which can descend at a speed lower than the stall. More probably, however, it seems to me that it may be intended to let in a Vmca lower than Vs where slipstream or efflux effects during the mini- mum control manoeuvre (which is a max power with one- engine-out condition) lower the effective stall to a value substantially below Vs (which is a power-off measurement). On this basis I would be prepared to meet Mr White halfway, at point X, as shown on the diagram. But I do not at present feel inclined to venture further to the right into a flight regime which cannot really exist. RIGHT International. 12 March 1964 WEIGHT " An easy compromise would, of course, be to omit in the definition all reference to the stall. However, the pilot has good reason to connect Vs and Vmca. If he loses an engine just after lift-off, he is very interested to know that he is likely to come up against a directional control problem before the aircraft stalls on him—the stall of the jet at take- off power being practically the same as Vs (power off). If possible, the connection should be shown in the definition and I therefore currently favour something like this:— Definition The Minimum Control Speed in the Air (Vmca) is a speed selected at maximum power such that, on loss of an engine, it is possible, by aerodynamic means alone (nor- mally rudder and/or aileron), but without exceeding 5 degrees of bank, to keep within 20 degrees of original heading and then to recover control so as to maintain the new heading. Vmca is normally greater than the power- on stalling speed but must not exceed 1.2 Vs. Note: The power-on stalling speed is the speed Vs reduced by the aerodynamic effects of slipstream or jet efflux. Perhaps I may add that, in this definition and in any of the others, I am most grateful to receive comments and pro- pose to take these fully into account in the final version to be given as a one-page summary at the end of the series. Meantime, it may not be possible to comment in these columns on all the points raised. c. c. J. Aspects of Camouflage SIR,—In your issues of August 2, 1962 (page 178), December 19, 1963 (page 1013) and February 6 (page 224) you pub- lished photographs of groups of British military aircraft in identical camouflage schemes. Now camouflage is a science and I don't pretend to know much about it. However, it does look to me as if a civil servant has produced a specification that in error is being too rigidly interpreted. Camouflage is a thing of the past, but why give a sniper a pattern to follow? It is interesting to note from the photograph of US Army helicopters in Viet- nam on page 156 in the January 30 issue that they are all camouflaged differently. Robert R. Rodwell, in his excellent article "The Steel in the Blue" (Flight International, February 13), refers to Victors being painted up as of old. I wonder how much the temperature of a high-speed aircraft is affected by paint variations ? Will the Victor on page 242 be hot on top and cold underneath? London SW19 CHRISTOPHER R. ELLIOTT FORTHCOMING EVENT8 Mar 12 Mar 12 Mar 12 Mar 12 Mar 13 Mar 13 Mar 13 Mar 13 Mar 16 Mar 17 Mar Mar Mar Mar Mar Mar MarMar Mar Mar Mar 17 17 17 18 18 18 18 18 18 19 19 RAeS: 17th Louis Bleriot Lecture, in Paris: "Power for Supersonic Flight," by S. G. Hooker and M. M. Gamier. RAeS Luton Branch: "Systems, Design and Main- tenance," by E. C. Bezant; and "Air Traffic Control" by R. Easterbrook. RAeS Prestwick Branch: Historical lecture. RAeS Yeovil Branch: a.g.m. and film show. RAeS Man-powered Aircraft Group: "Propeller Design far Man-powered Aircraft" by A. Lassiere. Institute of Navigation- "Meteorology and Supersank Transport," by S. Serebreny. Institute of Transport, Northern Section: "Develop- ment of the North East Airport," by J. H. Denyer. RAeS Coventry Branch: Annual dinner dance. RAeS Reading Branch: "Man in Space," by T. E. Gabb. RAeS Joint Discussion with the I.E.E., "Electrical Aspects in the Integration of Systems in Aircraft," to be opened by Dr C. S. Hudson. RAeS Leicester Branch: a.g.m., N. E. Rowe competi- tion lectures and films. RAeS Luton Branch: "Future of Air Warfare," by R. Cochrane, and film "Nature of Plastics." RAeS Preston Branch: "The Belfast Freighter," by C. D. Hatton. RAeS Gloucester and Cheltenham Branch: Main lecture: " Vectored Thrust for Single and Multi- engined Aircraft," by T. P. Frost and R. A. Bishop. RAeS Air Law Group: "Development of Legislation for Hovercraft," by A. R. Barrowclough. RAeS Coventry Branch: "Air Navigation" by R. H. C. Burwell. RAeS Hatfield Branch: "Bird Flight," by J. L. Nayler. RAeS Southampton Branch: " Weapons System Management" by P. A. Norman. RAeS Weybridge Branch: "The Flight Development of the VC10," by E. B. Trubshaw. RAeS: "Electronic Controls for Gas Turbine Engines," by A. Sadler. RAeS Halton Branch: "Man-powered Aircraft," by B. S. Shenstone.
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