FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1935
1935 - 0462.PDF
14 bUPPLEMEXT TO FLIGHT 226ft THE AIRCRAFT ENGINEER FEBRUARY 28. i93. case ot landing on one wheel (Case 2 (i) (c) (2) in A.P. 1208, A.L. 33 is a single vertical ground reaction of 1.5 W on the one wheel making contact. Equation (7) shows that this must actually be accom panied by a side-load of ah 1. o Wjr ** or the total resultant ground reaction is at an angle to the vertical of which the tangent is ah/(h2 -f- k2). The nature of the coefficient shows that, given the weight ol the machine and the vertical ground reaction, the side reaction is greater for a wider track, higher centre of gravity or greater concentration of masses. A relationship is also given between the deceleration of the fall of the aircraft (or upward acceleration of the centre of gravity) fg, and the vertical ground reaction. Since the centre of rotation is the tyre contact point, we may substitute for 8 the value (/„ —/„)/«, given for equation (6). /.-/, _ Rag 1 a _ W A» + k2 or l <» J» w5 W6 A2 + *2 •• (8) Shock absorbers on aircraft by the strength requir ments of the Air Ministry (Cases 2 (i) (a), etc., A.P j2!o A.L. 33) are required to withstand an ultimate load equal to at least 2 W on each wheel, which means the liniitin actual load must be about 1.75 W. If the absorber I being used for as much load in one wheel as in ordinary landing R/W in (8) is 1.75. ' The difference between the acceleration at the wheel and that of the centre of gravity will, therefore, be approxi mately :— i-75 X 32 = 56- ft. h* + kz D h* + &2sec.2 When the shock absorber has ceased working and conse quently fw = o, equation (8) shows the centre of gravity to have a downward acceleration of R a2 \\8 h* + k* It is understood that the Air Ministry has under con sideration new regulations to cover the combined upward and side loads. TECHNICAL LITERATURE Summaries of Aeronautical Research Committee Reports REPORTS published by His Majesty's Stationery Office, London, which may be purchased directly from H.M. Stationery Office at the following addresses: Adastral House, Kingsway, W.C.2; 126, George Street, Edinburgh; York Street, Manchester; 1, St. Andrew's Crescent, Cardiff; 15, Donegal! Square West, Belfast; or through any ordinary bookseller. INTERFERENCE BETWEEN BODIES AND AIRSCREWS. PART III. By C. X. H. Lock, M.A., and H. Bateman, B.Sc. R. & M. No. 1522. (27 pages and 3 diagrams.) August 13, 1932. Price is. 6d. net. During the last few years a large amount of experimental data has been amassed on airscrew body interference, but no attempt has been made to co-ordinate the results so as to ascertain the general effect of changes of body or airscrew. By the use of the semi-empmcal methcvdjdcvelopcd in R.& M. 1445*, it is possible to analyse all this data and the results are given in the present report. To obtain further evidence, chiefly with regard to the effect of excrescences, some additional experi ments were made on the 3 : 1 fineness ratio body of R. & M. 1380s, and these results are given in this report. All results are consistent with the conclusions that the direct spoiling drag is- largely a suction at the tail produced by rotation of the slipstream, and that the presence of an airscrew fairly near excrescences reduces the drag associated with their turbulent wake. A strip theory analysis, based on the total head measurements, was made of the extreme pusher position. It was found that the power required to drive the airscrew, as calculated by strip theory, was in excellent agreement with the experimental results, thus proving that there is no appreciable direct loss of energy associated with the central sections of the airscrew blades even when these are situated in the turbulent wake of the body and annular excrescences. It should be possible with the aid of the curves deduced to calculate the performance of a screw situated in any position in the short ellipsoidal body. ' R. & M. 1445. Analysis of experiments on the interference between bodies and tractor and pusher airscrews.—Lock and Bateman. ' R. & M. 1380. Pressure and force measurements on airscrew body combinations. —Bateman and Johansen-. THE EFFECT OF A CONTRACTION ON THE TURBULENCE IN A FLUID STREAM. By A. Fage, A.R.C.Sc. R. & M. No. 1584. (8 pages and 3 diagrams.) November 21, 1932. November 24, 1933. Price 6d. net. Experience has shown that a large contraction has a steadying influence on a turbulent fluidlstream. It is for this reason that modern wind tunnels are often designed with convergent intakes. The present experiments have been undertaken to measure the changes in the disturbed velocities in both water and air streams flowing through a contraction of the same type as that used in wind tunnel design. The stream flowing into the contraction was made thoroughly turbulent by means of a grid placed in the inlet. Measurements made on the axis showed that the maximum longitudinal velocity disturbances (Uj) were not greatly changed by the contraction, and that the maxi mum lateral velocity disturbances (vt) were reduced roughly in the ratio of the outlet diameter to the inlet diameter. In other words, the values of U] /U and Vj/U in the outlet were about 1/m and 1/m3/2 respectively of the values in the inlet, where m is the ratio of the outlet velocity to the inlet velocity, and U is the local mean velocity. This result differs from that which would be expected from a theoretical consideration of the behaviour of a single vortex passing through a contraction. WIND TUNNEL TESTS ON—(1) FRISE AILERON WITH RAISED NOSE, (2) HARTSHORN AILERONS WITH TWISTED NOSE. By A. S. Hartshorn, B.Sc, and F. B. Bradfield, Math, and Nat. Sci. Triposes. Com municated by the Director of Scientific Research, Air Ministry. R. & M. No. 1587. (13 pages and 8 diagrams.) February, 1934. Price 9d. net. The ailerons tested are an attempt to provide a closely balanced aileron which Of be used to large angles and which is not sensitive to differences in rigging. Rolling and yawing moments and hinge moments have been measured on a Frist aileron with raised nose and on two " Hartshorn " ailerons having a Frise section at the outer tip, the nose being raised progressively from the outer to the inner tip. The corresponding moments for a Frise aileron of the same overall dimensions were measured for comparison. The modified Frise aileron with raised nose is an improvement on the Frise, giving a lighter control with less danger of overbalance. The twisted nose ailerons give a more linear hinge moment curve than the Frise with raised nose and are lighter for large aileron angles. PRESSURE EXPLORATION OVER AN AEROFOIL THAT COMPLETELY SP«S A WIND TUNNEL. By W. L. Cowley, A.R.C.Sc., and G. A. MCMILLAN, M.Eng. R. & M. No. 1597. (13 pages and 3 diagrams.) October, 1933. Price gd. net. A series of pressure explorations has been made to determine how closely the flow over an aerofoil which completely spans the wind tunnel approximates to two-dimensional flow. A 26 in. chord aerofoU of Gottingen 387 sectiou was ts* It had equal numbers of exploration tubes fitted in both upper and lower surtaco parallel to and at the same chordal distances from the leading edge. ^ The present tests were made in connection with the development oi the (ions of a four-engined aircraft. A large model aerofoil was constructed for «Penm|L on body-wing interference. The'aerofoil completely spanned the Duplex tup and measurements of the pressure distribution were taken on the aeroioii a ; It was intended to measure the change due to adding the body. The PurPfL]v the present report is to show that the flow over the aerofoil approximatea cm*. to two-dimensional flow as for infinite aspect ratio. _ ,, „ Tests were made at a wind speed of 75 ft. /sec. and angles of incidence m * |f 0 deg., 4 deg. and 8 deg. The pressures were measured on the aerofoil »m ^ ends were 6 in. from the walls, and when the gaps between the ends and tu were filled in with end pieces of the same aerofoil section. Speed and Drag " Th£ A few misprints occurred in last month's article on ^ Speed and Drag of Commercial Aeroplanes," by Mr•. ' ft Manning. Most readers will probably have realised the mi • "' but for the benefit of those who wish to correct "^"SjJ the amendments are as follow : Near the bottom of *!* Jg hand column of p. 4 the sentence " R is obviously — ~'__0» for D substitute O, and again further on "as then kn^ (not D). Again, from the line beginning " W^1 en, in,n;eCOnd d should be substituted everywhere for «, the third ana lines from the -5 = 0, dh bottom then reading when „ - shorf" KW - 2K*L = O." Finally, the last equation, on p- > W* read R = K —-4*
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
