FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1932
1932 - 0070.PDF
FLIGHT, JANUARY 22, 1932 Ground Speed and Course Correction W i E have received from Mr. A. W. Berry, of the Meteorological Otiice at Lympne Airport, Kent, a set of tables from which a pilot can, knowing his true course from the map, and the wind direction, work out the course to steer and the ground speed. As it is thought that the tables will prove useful to private owners on cross-country flights, we have repro duced them below. Mr. Berry has compiled his tables on the assumption that the pilot of the aircraft knows his air speed, and that this is 90 m.p.h., 100 m.p.h., 110 m.p.h., or 120 m.p.h. Obviously for machines with still-air cruising speeds which fall between any two of these figures the pilot will have to " guess " at his corrections and ground speed. That is a drawback of all tables of this sort. Intermediate figures have to be estimated whereas on a set of curves they could be read off direct. However, in many ways tables are preferable to curves for use on board an aircraft, and with a little practice it should not be very difficult for a pilot to make a fairly accurate estimate even if his air speed, is not exactly that shown on one of the four tables. In this connection it might, perhaps, be pointed out that the tables can be used for fractions and multiples of the given air speeds. For example, for an air speed of 200 m.p.h. (there are not very large numbers of private owners' machines cruising at that speed yet—ED.) and a wind velocity of 40 m.p.h., the appropriate figures would be given in the table for air speed 100 m.p.h. under wind velocity 20 m.p.h. Mr. Berry calls the angle which the wind direction makes with the map course " Wind Deviation." This angle is, of course, obtained by subtracting the map course AIR SPEED 90 MJ>.H. Wind ,.„.. Speed.j l°m-P-h- Wind Devia tion. 15 30 45 60 75 90 105 120 135 150 165 180 195 G.S. 81 82 83 85 87 89 92 95 97 98 99 100 99 210 98 225 240 255 270 97 CtoC Deg. + 2 4 5 6 7 7 7 6 5 4 2 0 - 2 4 5 95 e 92 j 7 20 m.p.h. 30 m.p.h. 40 m.p.h. G.S. 71 73 75 78 83 88 93 98 CtoC Deg. + 4 7 9 11 13 14 13 G.S. 61 63 67 71 78 85 CtoC Deg. + 5 10 14 17 19 20 93 19 11 j 101 j 17 104 ] 9 j 109 14 107 109 110 109 107 7 j 115 | 10 4 | 118 0 j 120 - 4 118 7 115 104 \ 9 98 i 11 93 13 89 J 7 | 88 j 14 285 87 7 83 : 13 ! 300 85 3(5 330 345 360 83 82 81 80 fi 78 11 5 75 4 | 73 2 0 71 70 9 7 4 0 109 101 93 85 78 71 67 63 61 60 G.S. 51 53 58 63 72 81 91 103 114 122 5 127 0 - 5 10 14 17 19 20 19 17 130 127 122 CtoC Deg. + 7 13 18 23 25 27 25 23 18 13 7 0 - 7 13 114 i 18 103 91 81 72 63 14 58 10 53 5 j 51 0 50 23 25 27 25 23 18 13 7 0 50 m.p.h. G.S. 41 43 48 54 63 75 88 104 118 129 137 140 137 129 118 104 88 75 63 54 48 43 41 40 CtoC Deg. + 8 16 23 29 33 34 33 29 23 16 8 0 - 8 16 23 29 33 34 33 29 23 16 8 0 EXPLANATION : In the Tables pub lished below, " Wind Deviation " is map course (in degrees) subtracted from wind direction. When wind direction is less than angle of course, add 360 degrees to wind direction. G.S. is ground speed in m.p.h. C. to C. (Correction to Course) is the angle (positive or negative) which must be applied to the course angle in order to obtain the course to steer under the conditions obtaining (in degrees) from the wind direction. // the wind direc tion (in degrees) should be smaller than the map course (also in degrees), 360 degrees must be added to the wind direction. In the tables, in the columns headed " C to C " (Correction to Course), all negative figures are shown in bold type to make them distinct and avoid confusion and errors. Examples: An aircraft with a still-air cruising speed of 90 m.p.h. is flying to a destination the map course to which is 120 deg. The wind direction is 240 deg., and the wind speed 30 m.p.h. Then " Wind Deviation = 240 deg. — 120 deg. = 120 deg. From the table corresponding to air speed 90 m.p.h. the ground speed (G.S.) is then found to be 101 m.p.h., and the C. to C. (Correction to Course) 17 deg. The course to steer is therefore 120 deg. + 17 deg. = 137 deg. To this must be added the magnetic variation. Another case, in which the wind direction is smaller than the map course, and in which, therefore, 360 deg. must be added to the wind direction: Air speed, 100 m.p.h. ; course from map, 245 deg. ; AIR SPEED 100 M.P.H. Wind Speed. Wind Devia tion. Deg. 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 315 330 345 360 10 m.p.h. 20 m.p.h. 30 m.p.h. G.S. 91 92 93 95 97 99 102 105 107 108 109 no 109 108 107 105 102 99 97 95 93 92 91 90 CtoC Deg. 4- 1 3 4 5 6 6 6 5 4 3 1 0 - 1 3 4 5 6 6 6 5 4 8 1 0 G.S. 81 83 85 89 93 98 103 109 113 11 6 118 120 118 116 CtoC Deg. + 3 6 8 10 11 11 11 10 8 6 3 0 - 3 6 113 j 8 109 103 98 93 89 86 83 81 80 10 11 11 11 10 8 6 3 0 G.S. 71 73 77 82 CtoC Deg. + 5 9 12 15 89 i 17 95 103 112 119 125 128 130 128 125 119 112 103 95 89 82 77 73 71 70 17 17 15 12 9 5 0 - 5 9 12 15 17 17 17 15 12 9 5 0 40 m.p.h. G.S. 61 64 68 74 82 92 102 114 124 132 138 140 138 132 124 114 102 92 82 74 68 64 61 60 CtoC Deg. + 6 12 17 20 23 24 24 20 17 12 6 0 - 6 12 17 20 24 24 23 20 17 12 6 O 50 m.p.h. G.S. 52 54 59 65 75 87 99 115 129 140 147 150 147 140 129 115 99 87 75 65 59 54 52 50 CtoC Deg. + 7 15 21 25 29 30 29 26 21 15 7 0 - 7 15 21 26 29 30 29 25 21 15 7 0 70
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
