Part 5 (1/2)
”Very good,” said the Pilot; and then turning to the Observer, ”Before we start you had better have a look at the course I have mapped out (see p 40)
”A is where we stand and we have to reach B, a hundred and fifty e that, at the altitude we shall fly, there will be an East wind, for although it is not quite East on the ground it is probably about twenty degrees different aloft, the wind usuallyround clockways to about that extent I think that it is blowing at the rate of about fifty miles an hour, and I therefore take a line on the map to C, fifty miles due West of A The Aeroplane's speed is a hundred miles an hour, and so I take a line of one hundred miles from C to D
Our compass course will then be in the direction A--E, which is always a line parallel to C--D That is, to be exact, it will be fourteen degrees off the C--D course, as, in this part of the globe, there is that much difference between the North and South lines on the netic North to which the compass needle points If the corees, that, too, must be taken into account, and the deviation or error curve on the dashboard will indicate it
[Illustration: A--B, 150 miles, A--C, 50 miles; direction and miles per hour of wind
C--D, 100 miles; airspeed of aeroplane
A--D, Distance covered by aeroplane in one hour
A--E, Compass course]
”The Aeroplane will then always be pointing in a direction parallel to A--E, but, owing to the side wind, it will be actually travelling over the course A--B, though in a rather sideways attitude to that course
”The distance we shall travel over the A--B course in one hour is A--D
That is nearly eighty-seven ht to accomplish our journey of a hundred and fifty miles in about one and three-quarter hours
”I hope that's quite clear to you It's a very si the compass course, and I always do it like that”
”Yes, that's plain enough You have drafted what engineers call 'a parallelogram of forces'; but suppose you have miscalculated the velocity of the wind, or that it should change in velocity or direction?”
”Well, that of course will more or less alter ood landmarks such as lakes, rivers, towns, and railway lines They will help to keep us on the right course, and the co far astray when between them”
”Well, we'd better be off, old chap Hop aboard” This from the Observer as he cliood view over the lower plane; and the Pilot takes his place in the rear seat, and, afterhis safety belt, andfreely, he gives the signal to the Engine Fitter to turn the propeller and so start the engine
Round buzzes the Propeller, and the Pilot, giving the official signal, the Aeroplane is released and rolls swiftly over the ground in the teeth of the gusty wind
In less than fifty yards it takes to the air and begins to climb rapidly upwards, but how different are the conditions to the cal of yesterday! If the air were visible it would be seen to be acting in theand dropping, gusts viciously colliding--a oria of forces!
Wickedly it seizes and shakes the Aeroplane; then tries to turn it over sideways; then instantly changes its mind and in a second drops it into a hole a hundred feet deep; and if it were not for his safety belt the Pilotaway from beneath him
Gusts strike the front of the craft like so many slaps in the face; and others, with the motion of mountainous waves, so to see it plunge over the suoes on, but the Pilot, perfectly at one with his htestperhaps fifty rasping the ”joy-stick” which controls the Elevator hinged to the tail, and also the Ailerons or little wings hinged to the wing-tips; and the latterthe Rudder control-bar
[Illustration: The Pilot's cock-pit]
A strain on the Pilot? Not a bit of it, for this is his Work which he loves and excels in; and given a cool head, alert eye, and a sensitive touch for the controls, what sport can co battles of the air?
The Aeroplane has all this tireat wide circles, and is now some three thousand feet above the Aerodros belo seeround, and the whole country below, cut up into di been lately tidied and thoroughly spring-cleaned! A doll's country it looks, with tiny horses and cows orna the fields and little modelaway across country like ribbons accidentally dropped
At three thousand feet altitude the Pilot is satisfied that he is now sufficiently high to secure, in the event of engine failure, a long enough glide to earth to enable hi furtherine, he decides to climb nothe co the Elevator, he gives his craft its le of incidence at which it will just ht and secure its hts he has now for the changing panorama of country, cloud, and colour Ever present in his reat 'cross-country queries ”Around within gliding distance?” And ”How is the Engine running?”
Keenly both he and the Observer compare their maps with the country below The roads, khaki-coloured ribbons, are easily seen but are not of much use, for there are so many of them and they all look alike from such an altitude
Nohere can that lake be which the map shows so plainly? He feels that surely he should see it by now, and has an unco too far West What pilot is there indeed who has not s in the air can create greater anxiety Wisely, however, he sticks to his coht of the lake, though indeed he now sees that the direction of his travel will not take hi over the shortest route to his destination He htly miscalculated the velocity or direction of the side-wind
”About ten degrees off,” he ly