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Aviation History
1947
1947 - 0085.PDF
JANUARY I6TH, 1947 FLIGHT 73 index scale on the fixed head. The small lever is pushed over to lock the dial in position and the projecting end of the wind-bar is moved round to set the centre-line at 330 deg (wind direc- tion) on the dial. The pivot-bar is then moved in relation to the base-bar to set 25 (wind velocity) on the wind- bar scale against 175 (T.A.S.) on the upper scale of the base-bar. The following can be read off: — Ground speed: 164 (on pivot-bar ,. 'L scale against red index arrow). •i Drift: 8 deg to port (-8 on drift scale where cut by pivot-bar). True Course : 31 deg (on circular dial read against — 8 on fixed head index scale). The knurled knob at the end of the base-bar is rotated to set the 60- minute arrow on the rubber scale against 164 (ground speed) on the rigid scale above, and the flying time is read off against 190 (distance). Flying time : 69J minutes. To obtain the track, if this is not known, the pivot-bar is first released from the base-bar by an upward pull on the knob. The wind-bar is set at " O" on the circular dial and the dial unlocked. The pivot-bar is placed along the track with the circu- lar head in the flying direction and the wind-bar moved to set " O " on the dial pointing north on the map, the wind-bar being parallel with meridians. With the dial locked in this position, the track is read off against the arrow on the fixed head-index scale. Inci- dentally, the dial is now placed for further operation to find ground speed and drift. The triple drift method can be used for finding the wind direction and velocity in the following manner. Given: — True course 60 deg. Drift 10 deg starboard. True course 120 deg. Drift 5 deg starboard. True course 180 deg. Drift 4 deg port. The true air speed, say 175, on pivot-bar scale is placed against the red arrow on square of plastic, and the true course, 60 deg on dial, is set against " O " on the fixed head-index scale. If 10 deg starboard is read off on the drift sight, then the pivot-bar (lower edge) is set against —10 on the drift scale and the circular dial is marked with a grease pencil exactly along the bottom edge of the upper scale on the base-bar. This procedure is repeated with 120 on the circular dial and — 5 on the drift scale, and with 180 on the dial and — 4 on drift scale, using, this time, the upper edge of the pivot-bar. The tri- angle thus made with the grease pencil is bisected by the wind-bar scale, the wind velocity being read in the centre of the triangle, and the wind direction read on the circular dial opposite the triangle. The flying time from " A" to "B," using topographical map (1 :500,000), can also be calculated. In order to find the flying time when using a mercator chart (1:2,000,000) the correction scale on the top edge of the rubber band is used. Using the appropriate scales on the back of the base-bar, the true air speed can be calculated, given indicated air- speed, altitude and temperature and statute miles can be converted to kilometres or nautical miles. The slot in the pivot-bar is used to plot radio bearings on the map, the central hole in the dial being placed over the radio station and the bear- ing set at the red mark "X." This computor, which has been de- veloped by Capt. Blom Bakke, is to be manufactured by E. R. Watts and Son, Ltd., of 123, Camberwell Road, S.E.5. Capt. Bakke, who joined the Royal Norwegian Air Force in 1935 an<i new with Transport and Bomber Commands during the war, is now flying with Norwegian Air Lines. So the device should be practical as well as ingenious. Cheaper Light Engines; A Proposed Two-stroke Design for Low Production and Running Costs IN answer to the demand for cheaperand more economical engines for light aircraft, two designers in America, Messrs. Oehrli and Jandasek, have sug- gested the opposed-piston two-stroke type. There is nothing very novel in their basic idea, various forms of two- stroke with opposed pistons, or with a common combustion chamber for pairs of cylinders^ having been proposed on many occasions in the past, particularly in France. However, the neat layout and simplicity of construction are note- worthy and certain features are unique. The layout of the proposed unit as •"..~4.mi.aA ;= cppn +n he three horizontal By comparison with four- stroke opposed engines, as- sembly and stripping-down are very simple in view of the absence not only of valve gear but of cylinder heads, holding-down studs and the like. A single wrench is said to be sufficient assembling the entire unit (except for sparking plugs), and simple through- bolts are used wherever possible, in spite of their slight weight penalty. Fuel consumption/* as indicated by single-cvlinder tespt compares well with•s for nders, showing the twin piston gement. The simple external layout of the Oehrli and Jandasek engine. more orthodox units, and the overall mechanical efficiency is good. Best running conditions from curves for the test unit would seem to fall between 80 and 85 per cent of rated power at 3,400 to 3,500 r.p.m. and with a consumption of about 0.45 to 0.47 lb/b.h.p./ hr. Peak engine speed is at 4,000 r.p.m. The sketches reproduced here -uggest that the Oehrli and Jandasek engine should be amenabie-to simple installation and clean cowling. There is a number of com- mendable features of this pro- posed unit, and it will be inter- esting to see if it will live up to its promise.
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