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Aviation History
1949
1949 - 1905.PDF
FLIGHT, 24 November 1949 6/3 AERODYNAMIC CLEANNESS Increasing Importance of Detail Design . Mr. E. J. Richards' R.Ae.S. Lecture IN his paper to be given before the Royal AeronauticalSociety this evening (November 24th), Mr. E. J.Richards, M.A., B.Sc., A.F.R.Ae.S., is to review the subject of aerodynamic cleanness. The lecture is to begiven at Bristol. Mr. Richards, who is assistant chief designer (aero-dynamics) to Vickers-Armstrongs Aircraft Section, will show how, in the past, aerodynamic cleanness has resultedfirst from a basic change in design conception (e.g., from biplane to monoplane) and, secondly, by progressive im-provement in detail design. At to-day's speeds detail design is of the greatest import-ance and can make or mar the efficiency of a jet airliner. Laminar flow gives by far the greatest potential gain ofany individual item, though an appreciable loss of payload can occur if the wrong type of laminar-flow aerofoil sectionis chosen for the achieved transition position. Severe losses arise from high induced-drag factors arisingfrom poor nacelles, poorly designed boundary-layer fences or high sweepback, while leakage and discontinuities inprofile on controls can give rise to severe drag penalties which must be taken into account when assessing therelative merits of manual and power-operated controls. The lecturer will show that designing for good internalairflow is as important as good external design and that, «for this reason, great attention should be given to intakedesign. With well designed intakes, ram efficiencies of over 95 per cent are attainable, a marked improvementon the 80 to 85 per cent now existing on side-intake air- craft. Cabin pressurization air, engine cooling air andother smaller items cause considerable losses in payload; thus good '' inner cleanliness '' on an aircraft is as importantto achieve as good external characteristics. For example, unnecessary generosity in the air supply to the passengerscan cause a loss of payload which is a substantial propor- tion of the whole. Laminar flow on a production scale can give an extremelyhandsome bonus on conventional types of aircraft. Pre- senting one example, Mr. Richards will show that attain-ment of laminar flow over 50 per cent of the chord allows the payload to be practically doubled for the design range.Acceptance of the flying-wing layout increases this gain by a further 50 per cent. This advantage, however, is closelyassociated with far-back transition, and vanishes if leading- edge transition is assumed. Thin Griffith wings show no advantage over normalwings, while thick suction-winged aircraft of orthodox lay- out present little if any advantages over normal pushertypes with far-back transition. The thick suction wing principle must, therefore, be associated essentially withflying-wing layouts. With transition at the slot on the flying-wing suction aircraft examined by the lecturer, theavailable payload is quadrupled over the orthodox type, while the range for the design payload is increased from4,000 nautical miles to over 10,500 nautical miles. There is a case for the use of 30 or 40 per cent thickwings with auxiliary suction on the assumption that transi- tion, in practice, will always be near the leading edge. While there is every possibility that individual sheetscan be made sufficiently smooth to allow laminar flow to persist, the problem of eliminating steps and waviness atjoints is insurmountable at the moment and it is therefore best, in the lecturer's opinion, to aim at single-sheet transi-tion. This means that a good degree of laminar flow can be obtained on V.C.4 types, but that the maximum limiton large tailless types is probably about 20-30 per cent chord. If transition cannot be kept to the slot, but onlyto 40 per cent of the chord, there is little advantage in using the suction principle. It follows that a practical suctionwing must have auxiliary slots or a porous nose to eliminate the crippling effect of early transition in emergency cases. Forward slots can eliminate the adverse effects of flies,mud or rain and for this reason must be considered in con- junction with laminar flow and suction wings. A sensibleporous wing construction to achieve this aim can be pro- duced and should not carry any great penalty in weight. CROP-DUSTING in SOUTH AFRICA /"^ROP-DUSTING is quite a paying proposition in Southv-' Africa. Before and immediately after the war (writes a Pietermaritzburg correspondent) most of the Union's dustingwas carried out by Rapides of the Aircraft Operating Co., one of the Hunting Group. During the 1947 season, a Natalcompany received the contract for dusting the thousands of acres of wattle-plantations in Natal and the southern Trans-vaal. An aviation engineer, Harry Back, using expensive American-designed equipment as a basis on which to work,constructed an efficient dusting outfit at a small cost, and, having fitted it to a standard Piper Cub, the company set towork. At a cost of between 10s and 15s an acre, this offered the farmer an economical proposition and, since then, Cubshave been without opposition where commercial crop-dusting is concerned. Although Ansons, later replaced by a Sikorski helicopter, were used against the tsetse fly in Swaziland, theywere operated entirely by the Air Force, and cannot be con- sidered as offering the Cubs any competition. The equipment can be installed or removed in five or sixhours. The 2oolb-capacity hopper is bolted-in in place of the rear seat; an agitator, rotated by a slipstream-driven wind-mill outside the fuselage, occupies the bottom of the hopper, the outlet being via a venturi directly beneath the cabin. With two pilots working in relays, work usually starts at thecrack of dawn, and proceeds until about midday; after this, air currents tend to disperse the dust too widely. Supplies of"dust" are conveyed by lorry to the nearest small clearing, where the aircraft refuels every five or ten minutes. Demonstration by one of the dusting Cubs. Nov. Nov. Nov. Nov. Dec. Dec. 1950 Jan. 24 26 , 26 . 29 IS. 21. 7. Jan. 20. Jan. 24. Jan. ten. 28. 28. FORTHCOMING EVENTS R.Ae.S. ; " Aerodynamic Cleanness," by E. J. Richards, M.A., B.Sc, A.F.R.Ae.S. (at Bristol). Helicopter Association ; " Aero-elastic problems of Rotary Systems," by Prof. A. R. Collar, M.A., D.Sc, F.R.Ae.S. Society of Licensed Aircraft Engineers : " Electrical Remote Indication," by C. Williams, A.R.Ae.S., M.S.L.A.E. Society of Instrument Technology : " Instrumentation on the Martin Open-hearth Furnace " ByG. Husson and P. Rodtcq. R.Ae.S. : " Navigational Systems and Instrument Aids." by Dr. D. E. Adams, B.Sc.. A.inst.P., and Dr. A. N. Uttley B.Sc., Ph.D. R.Ae.S. (Weybridge) : " Round the World in 90 days," film by W. Courtenay, M.M. British Interplanetary Society : " The Circum-lunar Rocket," by K. W. Gattand and A. E. Oixon. London Aeroplane Club : Annual Dinner Dance. R.Ae.S. (Belfast) : " Recent Development in Aircraft Production Engineering," by Pro.. Connolly, B.E., F.R.Ae.S. t Helicopter Association : " Pest Control and the Helicopter, by Dr. W. E. Ripper. F.R.E.S. Society of Licensed Aircraft Engineers : " Dowty Electro- hydraulic Systems," by Neville J. Home. 8 It
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