IATION

In a previous chapter the various methods of signalling between the
ground and the airman aloft have been described. Seeing that wireless
telegraphy has made such enormous strides and has advanced to such a
degree of perfection, one naturally would conclude that it constitutes
an ideal system of communication under such conditions in military
operations.

But this is not the case. Wireless is utilised only to a very limited
extent. This is due to two causes. The one is of a technical, the other
of a strategical character.

The uninitiated, bearing in mind the comparative ease with which
wireless installations may be established at a relatively small expense,
would not unreasonably think that no serious difficulties of a technical
character could arise: at least none which would defy solution. But
these difficulties exist in two or three different fields, each of which
is peculiarly complex and demands individual treatment.

In the first place, there is the weight of the necessary installation.
In the case of the dirigible this may be a secondary consideration,
but with the aeroplane it is a matter of primary and vital importance.
Again, under present conditions, the noise of the motor is apt to render
the intelligent deciphering of messages while aloft a matter of extreme
difficulty, especially as these are communicated in code. The engine
noise might be effectively overcome by the use of a muffler such as,
is used with automobiles, but then there is the further difficulty of
vibration.

This problem is being attacked in an ingenious manner. It is proposed to
substitute for audible signals visual interpretations, by the aid of an
electric lamp, the fluctuations in which would correspond to the dots
and dashes of the Morse code. Thus the airman would read his messages by
sight instead of by sound.

This method, however, is quite in its infancy, and although attractive
in theory and fascinating as a laboratory experiment or when conducted
under experimental conditions, it has not proved reliable or effective
in aeronautical operations. But at the same time it indicates a
promising line of research and development.

Then there are the problems of weight and the aerial. So far as present
knowledge goes, the most satisfactory form of aerial yet exploited is
that known as the trailing wire. From 300 to 700 feet of wire are coiled
upon a reel, and when aloft this wire is paid out so that it hangs below
the aer