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Aviation History
1918
1918 - 0127.PDF
JA1TOARY 31, 1918. The inertia torque for the whole blade, that is, ~ ": Q - 2 K * ) R = I « (13) Where I is the axial moment of inertia, equals the engine torque less the air resistance to rotation. If the screw runs at full speed, first at no throttle, then at full throttle, the opposing blade torque changes from a small negative to full positive value. Gyroscopic loads.*—To express the gyroscopic resistance to pitching and yawing, assume fixed centroidal axes X, Y and Z, through the air-screw parallel to the conventional axes of the air-plane, X being the longitudinal axis of the latter ; and let a and fl be the angular speeds of rotation and of yaw without pitching. Then any particle m at xyz has parallel to X the linear speed y fl, and the linear accelera- tion z w fl, as shown graphically in Fig. 13. Multiplying this acceleration by m gives the force / = vazuin. (14) which varies at quadrant intervals through the values of m, r w Q, o, and — m r u> n. This force exerts about Y and Z respectively the torques qy •= mz^mCL (15) q? — — myzu>a . (16) which also vary cyclically, as illustrated in Fig. 14, and, together With their resultant, in Fig. 15. Similar effects ensue front pitching without yaw. The above expressions and the figures illustrating them, show that for yaw without pitch the gyroscopic force on m is • For a fuller treatment see the writer's Periodic Stresses in Gyroscopic Bodieswith Application to Airscrews, Report of National Advisory Committee for Aeronautics, 1917. W (S5S25 always parallel to X, and reverses twice each revolution ; that its torque about Y is always positive and fluctuates from zero to a maximum m r* a fl, twice each revolution; that its torque about Z oscillates from m r2 w fl/2 to —mna fl/2 twice each revolution ; that the resultant torque is a maxi- mum, m r2 o> fl, when the particle is crossing the XZ plane. Similar conclusions are obvious for pitch without yaw. The entire gyroscopic force on any blade segment is parallel to X, and, when at its maximum value, is very closely F = 2 mrwnt = MrwQ (17) in which M is the mass of the segment, r the radial distance of its centroid. This force is at a distance r\ •= r\'jr from X where r-2 is the radius of inertia of the segment referred to X. The maximum gyroscopic torque about Y for yawing without pitch is, for any blade segment, 2 m z2 <•» n, inte- grated throughout the segment ; and for a whole screw is Q =7«.fl (18) in which I is the moment of inertia referred to X of the entire screw. The gyroscopic torque of the whole screw or any segment is found for any position « , Fig. 13, by multiplying the maximum by sin2oc . Since the entire gyroscopic force on a blade fluctuates like that of a particle, the moment about Y ranges from zero to I <« fl, about Z from / w fij-z to —/ os 0./2, twice each revolution. The equivalent gyroscopic stress may therefore be computed as for a repetitive load ranging many times per second from zero to I w fl. t Owing to the width and thickness of the blade this expression is in slight error—less than one part in 5,000 for ordinary blades. Fatal Accidents. ^Probation. Flight Officer W. E. Floyd, R.N.A.S., was killed on January 22nd as the result of his machine catching fire whilst flying at an Essex aerodrome. WHILE flying near Rugby on the afternoon of January 22nd, 2nd Lieut. H. G. Nelson was killed through falling from his machine at a height of 3,000 ft. He Was flying alone, and it is supposed that in some inexplicable way the belt attaching him to the machine came unfastened, The aeroplane con- tinued its flight and came down a few fields away. Lieut. Brendel, while flying over the Mersey on January 27th, fell into the river and was drowned. Revised Rates of Pay for R.F.C. Officers. IN the Royal Warrant setting forth the pay of officers and allowances for children, issued on January 26th, it is stated that the regimental pay of officers in the R.F.C. remain as at present except that the pay of a Flight Com- mander commences at 19s. a day. It is stated that the full allowance of £2 a month in respect of each child, up to a maximum of four, will be issuable to Equipment Officers, 3rd Class, and half rate of £1 a month for each child, up to a maximum of four, Will be issuable to Flying or Balloon Officers, Observers and Equipment Officeis, 1st and 2nd Class R.F.C. U.S. Nary Air Service Expanding. ONE item in the proposed increase of the U.S navy per- sonnel from 80,000 to 180,000 is the increase of the U.S. naval air service from 350 to 10,000. U.S. Naval Aviators' Badge. 1 THE U.S. naval authorities have now approved of a dis- tinguishing badge for qualified aviators in the U.S. Navy and Marine Corps. It consists of a winged foul anchor, with the letters U.S. in gold and silver metal. It will be worn on the left breast. Air Work in Palestine. In the despatch from General Allenby describing the operations in Palestine from the end of June last year up to the capture of Jerusalem, there are several incidental references to the work of the Royal Flying Corps. Thus it is mentioned that on November 6th airmen noticed movements on the roads north of Gaza enabling the heavy artillery to get to work. During the 8th, " it soon became obvious from the reports of the Royal Flying Corps, who throughout the 7th and 8th attacked the retreating columns with bombs and machine-gun fire, and from other evidence, that the enemy was retiring in considerable disorganisation, and could offer no very serious resistance if pressed with determination. In the operations on November 10th, " R.F.C. reports indicated the total hostile forces opposed to us on this line [on the Wadi Sukereir] at about 15,000." After the occupation of Jafia on November 16th, " reports from the K.F.C. indicated that it was the probable intention of the enemy to evacuate Jerusalem and withdraw to organise on this line [Tul Keram-Nablus]. "Among the booty taken at Ludd were five destroyed aeroplanes, and in the operations from October 31st to December 9th more than twenty aeroplanes were destroyed by our airmen or burnt by the enemy to avoid capture." The Attack on the "Goeben." THE following announcement was made by the Admiralty on January 24th :— " In continuation of the former communiques, Royal Naval Air Service machines have made several day and night attacks on the ' Goeben ' and have secured two hits With heavy bomb. They have also bombed one of the tugs which were secured alongside the ' Goeben.' In every case heavy anti-aircraft gunfire was encountered, but all our machines have returned safely. These attacks are continuing." An Admiralty announcement issued on January 25th said :— " Since issuing the last communique, aerial attacks on the ' Goeben' have been carried on ceaselessly both by the Royal Naval Air Service and the Royal Flying Corps, and during the last 48 hours some seven tons of bombs Were dropped on and around the ship, and on the aerodrome at Galata, several direct hits being observed, and results have been confirmed by photographic reconnaissances. The Turkish cruiser which was near the ' Goeben ' has left and proceeded up the Straits, and a steamer which was apparently engaged in lightening the ' Goeben ' was forced to desist. The anti-aircraft fire has been very severe, but the only casualty as yet reported is one Greek officer [Whose name is unofficially given as Hambas], whose machine was shot down. The operation is continuing." The Admiralty issued the following announcement on January 28th :— " Since the last communique bad Weather has hampered operations against the ' Goeben.' Nevertheless several raids have been carried out and some bombs have been dropped on her, and on gun positions at Gaba Tepe. At noon yester- day (the 27th) the position of the ship was unchanged." A Turkish report issued in Constantinople on January 24th said :— " In the Dardanelles there was lively aircraft activity. Flight Lieutenant Meinicke brought down an enemy aero- plane, which was burnt, the pilot being killed. A second enemy machine Was damaged by Lieutenant Groners in an aerial engagement." The following was issued in Constantinople on January 28th :— " The Turkish cruiser ' Sultan Selim' (' Goeben ") entered on January 27th. She is quite fit for service. The numerous enemy air attacks inflicted only unimportant damage to the funnel and the armoured plating, occasioned by two small bomb hits." 123
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