NOTES ON THE WAR

Hauraki Plains Gazette, Volume 52, Issue 3273, 9 June 1943, Page 8

NOTES ON THE WAR

HELICOPTERS TO BE USED DIRECT LIFT AIRCRAFT VALUE OF LIQUID AIR BOMBS While aeroplanes of all kinds fill the skies—and the news—with their” operations, to the eclipse, for the moment, of land and sea warfare, a newcomer in aircraft —the helicopter—is to be enrolled in active service. The announcement that helicopters are being adopted for anti-submarine work and also by the American Army, is of interest as an example of the way wartime use can be found' for things which have had no favour in peace. • The helicopter must not be confused with the autogiro, Cierva’s much-discussed invention, for though they are very similar in appearance, their principles are. in direct opposition. The autogiro is supported by wings which rotate of themselves as the machine is propelled by an air screw in the normal way, and if the propeller is stopped the machine descends.

In the helicopter, the revolving wings are power-driven and provide the lift, so that the machine can rise vertically if desired, and can be held

stationary in the air. By adjusting the “trim” of the aircraft so that the lift is not vertical, the helicopter travels at any speed from its maximum to “zero m-p-h.” Prose and Cons This facility of slow motion makes it unique as a sea-scout; its only possible rival is the gas-supported airship, such as the “ blimp,” some of which are understood to be in the American naval service. The helicopter has the additional advantage that it needs no extended or even prepared flying ground; it can land on or take off from any space big enough to hold it. Against these advantages there are serious defects. One is that for its lifting capacity •it needs a much greater engine-power than a normal aeroplane, high speeds are not possible; and constructional difficulties set a limit to the size that can be reached. The older generation of fiction readers will remember Jules Verne’s adventure novel, “The Clipper of the Clouds,” a great air-liner lifted by screws set upon masts, devised by the ingenious French author long before the day of aeroplanes. It was a helicopter on a grand and unachievable scale.

The helicopter’s greed for enginepower can be simply explained. Assuming that the machine weighs a ton, the revolving wings must pull upwards with that force. Any horizontal speed requires additional power’ to be used. A normal aeroplane will fly horizontally with a propeller pull of approximately one-eighth of its weight (the fraction depends upon its design) and the balance of the available power can be used to attain increased speed. “Liquid Air Bombs ” I Another “ discarded ” invention which has returned into the news is

the “liquid air” bomb, which is alleged to have been used with great effect in some of the latest German air raids on the south of England. This bomb is said to be filled with an explosive consisting of some combustible (the favoured material has been some form of carbon) saturated with liquid oxygen.

This explosive is not new; indeed, it has a respectable antiquity, having been devised almost as soon as liquid oxygen was made. It has been used for quarry blasting, but experiments in using it for war purposes have hitherto not resulted in its adoption. For one thing, liquid oxygen, the temperature of which is about 300 degrees "below zero, is very awkward stuff to handle in quantity, and cannot be kept in a closed vessel.

It is not impossible, however, that the Germans may have found a practical way of using it in large bombs undei* such conditions that the time the explosive mixture is being carried is short. But the whole story is very dubious.