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Aviation History
1938
1938 - 0368.PDF
134 Commercial Aviation FLIGHT. FEBRUARY IO, 1938. readers to check (if they so desire) the accuracy of the instru-ment by plotting. Problem I. To find the true track, and ground speed, for a givenmagnetic course and airspeed. • Given: Mag. var. 120 \V.; wind S.W. 24 m.p.h., aircraft'scourse 134° magnetic; and airspeed 130 m.p.h. Procedure:—Pencil mark the magnetic variation 12° to theright of the True Heading Index. Turn knob A until the wind direction (S.W.) is set against the True Heading Index. Plot the wind (O-X Fig. 2) from the centre of, the transparentdisc straight down the centre line of the chart, to equal 24 miles according to the chart scale (actually a small mark issufficient). By turning knob B set the chart to read the air- speed (130 m.p.h.) at the dot in the centre of the disc. Setthe compass ring to read the machine's course (134° magnetic) against the pencil mark indicating the magnetic variation onthe drift and variation scale. Solution:—At the end of the wind arrow read the drift (10sto the left) and the ground speed 137 m.p.h. Opposite io° left on the drift and variation scale read the true track 112°. Note: Actually the above procedure takes far longer to writedown (or read) than it takes to do. Two pencil marks only are made: (1) The magnetic variation, and (2) the wind. Therest is done by turning two knobs. Problem II. To find the wind from drift observations (double drift). Given magnetic variation 10° W.; airspeed 130 knots; 1stcourse 6o° magnetic, drift 50 to port; and 2nd course 115° magnetic, drift 8° to port. Procedure:—Pencil mark the variation (Magnetic HeadingIndex) 10° W., on the drift and variation scale. Set the chart to read the airspeed (130 knots). Set the first course (6o° M.)at the Magnetic Heading Index. Trace with a pencil from the chart the track 5° to the left of the centre line. Set the second course (1150 M.) and make a mark where thesecond drift line (8° to port) crosses the first drift line. By means of knob A bring the wind point (the intersection of thetwo drift lines) vertically below the centre of the transparent disc. The wind direction 1860 is read at the True HeadingIndex, and the centre-line scale gives the wind speed as 18 knots. Problem 111. To intercept a ship:—Var. 140 W.; wind W.N.W. 30 knots- ship's velocity 1000 (T) at 20 knots,; airspeed 125 knots; and bearing to ship 2^3°. Distance 86# miles. To find the Magnetic course to steer to intercept the ship: — Kate of approach; ground speed; track; and time of inter- ception. • • . Procedure:—Pencil mark the mag. variation, 140 W. (MagHeading Index) and the wind'vector as in the previous ex- amples. Set the ship's course (ioo°) at the True HeadingIndex. By means of knob B adjust the upper edge of the square grid chart under the wind point (W.) and plot theship's speed (20 knots) down the vertical grid lines from the wind point. To mark the relative wind point (R), set theairspeed (125 knots) at the centre of the disc. Pencil mark on the compass ring the line of approach -to the ship (243°),and orient the transparent disc until the relative wind point (R) reads on the chart the same angle (50 left) as the line ofapproach (2430) makes on the drift and variation scale. Read the course to steer (2620 Magnetic) against the Mag-netic Heading Index. Read the rate of approach I2o| knots from the chart at R. Read the drift angle (n° to port) at W.If this is applied to the course, the track (2370 True) is obtained. One sentence in the instructions accompanying the instru-ment struck me very forcibly, i.e., "It should be remembered that the accuracy of dead reckoning navigation depends justas much upon the accurate calibration of the airspeed indicator and the proper application of its corrections, as upon theaccurate calibration of the compass." How true this is, and how often it is forgotten ! Now for my criticisms. (1) The cost—this is rather highat the moment, but I understand that this may be remedied in the near future when quantity production commences.(2) It would be an advantage if provision were made at the side of the instrument to hold a pencil and eraser. (3) Whenstrapped to my knee the cover hinges back against my some- what corpulent figure, and I am sure the same would occurwith a less corpulent figure when wearing a flying suit. It would be an easy matter to arrange the cover to open sideways.The computer is to be made by Henry Hughes and Son, Ltd., whose sales are handled by Smith's Aircraft Instruments,London, N.W.2. C. W. M. IN EIRE LAST YEAR Commercial and Club Flying Reviewed : Planning for the Future COMMERCIAL aviation began to find its feet in Ireland—or Eire—in 1937, and there was a considerable increasein the traffic on the. cross-Channel routes. Mails,whicn Lad not previously been airborne from the Free State area, were carried on the Dublin-Isle of Man service during July and August, and the Minister for Posts and Tele- graphs announced that discussions had taken place with the British Post Office with a view to the establishment of an air mail service between Dublin and London. The numbei of passengers cleared at Baldonnel aerodrome, County Dublin, during the first nine months of the year, was well over ioa per cent, greater than in the previous year. The comparative figures were : 1937, inwards 1,687, outwards 1,724 ; 193ft inwards 589, outwards 663. The development of Irish Sea Airways (the organisation operated by Aer Lingus Teoranta and Blackpool and West Coast Airwavsi, was largely responsible for this increase. The services operated by this organisation were increased to two machines a day in each direction between London and Dublin and, for the peak period of the holiday season, three machines a day in each direction between Dublin and the Isle of Man. Northern and Scottish Airways and Railway Air Services operated five machines in and out of Ards during the summer. The number of passengers who passed through this airport between October 1, 1936, and September 30, 1937, was 7,116. During August 1,322 passengers were handled. This airport was extended during the year, the longest run being now 1,007 yards The North of Ireland Flying Club, which operates at Ards, had trained twenty-two "A" licence pilots by the end of November. Despite the pi ogress of air transport in the Free State area, private flying received little support. The Irish Aero Club, after being in existence for nine years, went into voluntary liquidation in December. The demise of this club reacted un- favourably on the Irish Junior Aviation Club, which had been reorganised and was working a flying training arrangement with the senior body. Some flying instruction was carried out at Kildonan aerodrome by Dublin Air Ferries and a new organisation, the Tramway Aero Club (composed of members of the Dublin tram and omnibus company staff). The number of aircraft registrations valid in the Free State at the end of September was 14, compared with 12 on the corresponding date of 1936. The number of " B " licences increased from five to six, but the number of "A" licences decreased by three to thirty. In order to permit Eire to take its place in the joint British-Canadian-Irish organisation which is to operate the transatlantic airway, a new company, Aer-Rianta Teoranta, was formed under the Air Navigation and Transport Act, 1936. This company will carry out all commercial flying, with sub- sidiary companies, in the former Free State area. Tests of the Shannon base by the Empire flying-boat Cambria early in the year proved successful and, in July, Caledonia and the Pan-American Clipper III made the first survey flights between Foynes and Port Botwood. Between July and the end of September, seven crossings wer.e made in each direction. All proved satisfactory and conferences to consider the results were held in London and Dublin. In November Mr. T. J. O'Driscoll, who was in charge of the Shannon airport during the transatlantic tests, sailed for America with Mr. R. W. O'Sullivan, the chief aeronautical engineer of the Army Air Corps, for further discussions and to study the working of the U.S. Bureau of Air Commerce. Considerable progress was made with the construction of the land airport at Rynanna, County Clare, for the Shannon air base. At the Dublin Municipal Airport (Collinstown) the site was sufficiently developed to permit the preparation of a mile-long runway for the transatlantic tests of the D.H. Albatross. Collinstown will cover about 500 acres, and the airport at Rynanna about 700 acres. While Rynanna is being financed entirely by the Government, the Dublin Corporation is providing ,£58,000 towards the cost of Collinstown. Mean- while, the Cork Airport Committee has selected a site in the Midleton-Carrigtwohill area for its aerodrome. The Govern- ment will bear half the cost, the local authorities sharing the balance. In Northern Ireland a licence was granted to the Belfast Harbour Commissioners for their aerodrome at Sydenham.
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