Experiments have been taking place in Germany which may have
an important bearing on the future development of air transport. These consist in towing an engine-less " glider 7 -behind a power-driven aeroplane. The possibilities of the scheme have been tested independently by two designers in different parts of the country, both apparently with equal success. In the one case, Herr Espenlaub, well known as the designer of successful gliders, allowed himself to be towed off the ground in a monoplane glider behind an aeroplane and, when a height of 5,000 feet had been reached, operated a -" quick-release" device on the towing cable and glided down to the ground. The other experiment was Made by Herr Raab and Herr Katzenstein, who took up a small biplane glider carrying a load of 400 lb. behind an aeroplane and towed it from Karlsruhe to Frankfurt with an intermediate landing at Darmstadt. A well-designed glider should offer little more re- sistance than the targets frequently towed behind aeroplanes for anti-aircraft practice, so that—provided the "tow" is long enough .—there is no reason to anticipate any ill-effects on the aero- plane, while control of the glider 'should be Comparatively easy. The - scheme should have possibilities', for freight. carrying purposes at any rate, as it is well known in other forms of transport that within certain limits of load it is more economical to put part of the load into a trailer than to provide two separate-powered vehicles. So long ago as 1912 a British airship which broke down on manoeuvres was towed back to its base at Farnborough by another airship, and the possibility of towing airship " freight-trailers " in this way has been suggested, but the system as applied to aeroplanes is new. One advantage would be that it would remove the difficulty already being met with--as in the case of the R.A.F. machine which made the recent gallant attempt to reach Karachi— of providing a strong enough undercarriage to Withstand the shocks of running across an aerodrome with a heavy load.
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