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Aviation History
1940
1940 - 0070.PDF
JANUARY II, 1940 AIRSCREW EFFECTS A Subject of Increasing Importance FOR his Wright Brothers Lecture, not to be confusedwith the Wilbur Wright Memorial Lecture, Dr. ClarkB. Millikan had chosen the subject of " The Influence of Running Propellers on Airplane Characteristics." The lecture, which was the third in the series, was held on Saturday, December 16, this being the week day nearest to the date of the event which these lectures are intended to commemorate, the first power-driven flight by the Wright brothers'at KiU Devil Hill, North" Carolina, on December 17, 1903. The first of these lectures was given in 1937 by Professor B. Melvill Jones, of Cambridge Uni- versity, England, and dealt with flight experiments on the boundary layer. The second, on turbulence and the boundary layer, was given in 1938 by Dr. Hugh L. Dryden, of the National Bureau of Standards. Dr. Millikan is a distinguished scientist and a fellow and past-president of the Institute of the Aeronautical Sciences, the American equivalent of our Royal Aeronautical Society. He is Associate Professor of Aeronautics at the California Institute of Technology at Pasadena. His many investigations there, dealing particularly with, wind tunnel testing, wing theory, and aeroplane design, have resulted in notable contributions to the science of aviation. In his lecture Dr. Millikan described the experimental and theoretical investigations undertaken at the California Institute of Technology during the past few years. He stated that it was early realised that running airscrews might have effects on aeroplane characteristics other than drag, such as on stability, control, flying qualities, etc. Results o'f scattered investigations of such questions began to appear at a relatively early date, but until fairly recently these secondary effects were generally of a minor character, so that the power-on characteristics could be estimated from the power-off or gliding characteristics by applying rough empirical correction factors. In recent years, Dr. Millikan pointed out, this procedure had become increasingly unsatisfactory. Engine powers had increased, with corresponding decrease in power load- ing. Wing loading had increased spectacularly, and four- engined installations had'become more widely used. The result was that a greater percentage of wing area was affected by the slipstream, and the velocity of the slip- stream itself had greatly increased. The effect of slipstream, or, in other words, the difference between power-on and power-off flight, might often require serious modification in the overall proportions of an aircraft. Dr. Millikan's lecture gave the results of a two-year investigation at the Guggenheim Aeronautical Laboratory, undertaken to ascertain the nature and magnitude of power-on effects. To mention but a few of the effects dis- covered : Stability was decreased; elevator effectiveness was increased ; directional control depended upon the direc- tion of the turn ; the effect of one engine stopped on multi- engined performance was also studied. The lecturer described the equipment used at the Guggenheim Aeronautical Laboratory. Models of about 7ft. span were generally used. They were equipped with small electric motors, capable of running up to speeds of 18,000 r.p.m., placed inside nacelles and driving model airscrews. A theoretical analysis was given of the effect of power- on. This analysis had for its object to make available a systematic framework in terms of which the results may be viewed so that the data obtained will be of use in increasing our general knowledge of the phenomena involved; and also to give the aircraft designer some method of obtaining a rough preliminary estimate of the power-on characteristics of a new machine. Various para- meters were defined which must be evaluated by wind tunnel tests. In conclusion Dr. Millikan expressed the view that this particular field of research was one of the most important in contemporary design and wou!d in the near future be the subject of intensive and widespread investigation. Squadron Leader W. N. Camming SQI.ADRON LEADER W. N. CUMMING, D.F.C.,F.R.Met.Soc., A.F.R.Ae.S., has now taken over command of No. 5 A.O.N.S. (Air Observer Navigation School) at Weston-super-Mare. The school is operated by Straight Aviation Training, Ltd., on behalf of the Air Ministry. Sqn. Ldr. Cumming formerly served with the company in the capacity of Director ot Training; prior to this he was with Imperial Airways foi some time, and is the holder of a First Class Navigator's licence and a Master Pilot's Certificate for both land and sea aircraft. American Barrel Engine AN engine of unorthodox type has been designed by AircraftDevelopment, Inc., of Boston, U.S.A., and is receiving assistance from the Civil Aeronautics Authority who have recently issued a report on a two-hour test done on it. Known as the Alfaro, the engine is a two-stroke utilising the well- known but seldom-adopted principle of the swash plate. The four cylinders (bore 2^in., stroke 3fin. per piston) are arranged round the driving shaft with axes parrallel to it, and each cylinder has two opposed pistons like the successful Junkers Jumo 205 compression-ignition. The Alfaro is, how- ever, a spark ignition engine with fuel injection. The two swash plates are machined integral with the driving shaft, ;uid piston thrust is transmitted to them through roller bearings. Ports are holes in the cylinder walls, exhaust covered by one piston, intake by the other. Fuel injection is by Bosch pump at 2,000 lb./sq. in. and scavenging air (at a pressure of 6.5m. of mercury) is supplied by a centrifugal blower running at ten times crankshaft speed. Compression ratio is 9.5. On 87-octane fuel, the engine developed 113 b.h.p. at 2,030 r.p.m., which corresponds to 132 lb./sq. in. b.m.e.p. The specific consumption of 0.59 lb./h.p.-hr. is not low. Dry weight is 2.34 lb./h.p to which the weight of the cooling system must be added. (This is not at all promising; better engines are already in existence, though maybe some weight refinements can be made on the engine tested.) Frontal dia- meter is low at I5jin., but radiator resistance must also be considered. The engine layout docs not appear to be adaptable to air-cooling as the swash plates seem to prevent all chance of the air being led down the centre. Death of Airship Pioneer IT is with the most profound regret that Flight records thedeath in a nursing home at Winchester on January 3 of Capt. F. L. M. Boothby, R.N. Born at St. Andrews, Fifeshire, Frederick Lewis Maitland Boothby entered the Royal Navy at the usual tender age. When airship work began in 1910 or 1911 he became a member of the experimental crew. In 1913 he was put in command of naval airship No. 4. Shortly after the outbreak of war in 1914 he was sent to Somaliland to report on the feasibility of air operations against the Mullah. For a time after his return he served in the armoured car section of the Royal Naval Air Service, and afterwards he specialised on airship work, serving at such airship stations as Barrow, Howden and Pulham. Capt. Boothby became, and remained to the end, an airship enthusiast. He firmly believed in the value of airships, and it hurt him bitterly when first the Admiralty and afterwards the Air Ministry abandoned airship work. He regarded this an a calamity, and even the Hindenburg disaster did not shake his faith in the ultimate success of airships. We on Flight had the good fortune- to come into contact with Capt. Boothby on very many occasions, and even when we did not see eye to eye with him we uhvnvs n-sju-cted his specialised knowledge and his almost boyish enthusiasm. He had a smile which was the most disarming we have ever known. The passing of Capt. Boothby robs us of a valued friend, and to his widow, sons and daughter we extend our very sincere sympathy in their sad loss.
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