William J. Claxton - The Mastery of the Air
It is claimed for the "A. G." barograph that it is the most precise instrument of its kind. Its advantages are
that it is quite portable - it measures only 6 1/4 inches in length, 3 1/2 inches in width, and 2 1/2 inches in
depth, with a total weight of only 14 pounds - and that it is exceptionally accurate and strong. Some idea
of the labour involved in its construction may be gathered from the fact that this small and
insignificant-looking instrument, fitted in its aluminium case, costs over L8.
CHAPTER XLII. How an Airman finds his Way
In the early days of aviation we frequently heard of an aviator losing his way, and being compelled to
descend some miles from his required destination. There are on record various instances where airmen
have lost their way when flying over the sea, and have drifted so far from land that they have been
drowned. One of the most notable of such disasters was that which occurred to Mr. Hamel in 1914, when
he was trying to cross the English Channel. It is presumed that this unfortunate pilot lost his bearings in a
fog, and that an, accident to his machine, or a shortage of petrol, caused him to fall in the sea.
There are several reasons why air pilots go out of their course, even though they are supplied with most
efficient compasses. One cause of misdirection is the prevalence of a strong side wind. Suppose, for
example, an airman intended to fly from Harwich to Amsterdam. A glance at the map will show that the
latter place is almost due east of Harwich. We will assume that when the pilot leaves Earth at Harwich
the wind is blowing to the east; that is, behind his back.
Now, however strong a wind may be, and in whatever direction it blows, it always appears to be blowing
full in a pilot's face. Of course this is due to the fact that the rush of the machine through the air "makes a
wind", as we say. Much the same sort of thing is experienced on a bicycle; when out cycling we very
generally seem to have a "head" wind.
Suppose during his journey a very strong side wind sprang,up over the North Sea. The pilot would still
keep steering his craft due east, and it must be remembered that when well out at sea there would be no
familiar landmarks to guide him, so that he would have to rely solely on his compass. It is highly
probable that he would not feel the change of wind at all, but it is even more probable that when land was
ultimately reached he would be dozens of miles from his required landing-place.
Quite recently Mr. Alexander Gross, the well-known maker of aviation instruments, who is even more
famous for his excellent aviation maps, claims to have produced an anti-drift aero-compass, which has
been specially designed for use on aeroplanes. The chief advantages of this compass are that the dial is
absolutely steady; the needle is extremely sensitive and shows accurately the most minute change of
course; the anti-drift arrangement checks the slightest deviation from the straight course; and it is fitted
with a revolving sighting arrangement which is of great importance in the adjustment of the instrument.
Before the airman leaves Earth he sets his compass to the course to be steered, and during the flight he
has only to see that the two boldly-marked north points - on the dial and on the outer ring - coincide to
know that he is keeping his course. The north points are luminous, so that they are clearly visible at
night.
It is quite possible that if some of our early aviators had carried such a highly-efficient compass as this,
their lives might have been saved, for they would not have gone so far astray in their course. The
anti-drift compass has been adopted by various Governments, and it now forms part of the equipment of
the Austrian military aeroplane.
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