HELICOPTERS.

Auckland Star, Volume LXIX, Issue 167, 18 July 1938, Page 6

HELICOPTERS.

AIR MINISTRY'S INTEREST.

A programme of helicopter development has been embarked upon by the British Air Ministry, and the first move* have been made to enable the latest idea* in thie form of flight to be studied. Although helicopter flight, which differe from auto-giroplane flight, is probably the oldest form of mechanical flight —it is thought to derive from the Japanese toy in which an airscrew ie made to ascend by being forced up a helical stick—it is only just beginning to become practical for man-carry-ing purposes (eays the London "Observer").

Technically, therefore, thie is one of the most interesting steps taken by the Air Ministry for several years. Since work was abandoned on the Brennan helicopter (patented in 1923), since the 1024 and 1925 Air Ministry helicopter competitions failed to draw entries, and since the -1927 proposal to build a helicopter in England failed to materialise, no official interest in helicopter flight has been displayed in thie country.

Now, not only are negotiations fn progress for, the trial and purchase of a certain type of helicopter which hae been built and flown successfully in Germany, but in addition new designs produced in thie country have been submitted to the technical departments.

It is believed that if an efficient helicopter could be produced it would be exceptionally well suited to private flying, commercial air line "feeder" operation, and Army and Navy co-operation. Vertical Climb. A true helicopter can take off without a run, and climb vertically; it can hover in still air, and even fly backwards at a slow rate, and it can descend vertically and land without a run. It differs from an auto-giroplane such as the Autogiro, the Hafner and the Kay, in that the lifting rotor is power driven when the machine is in the air. This is an important difference. In the auto-giroplanes the rotor may be ■power driven when the machine is on the ground preparing to take off either by jumping—ae in the Autogiro—or by "towering"— as in the Hafner—but when it is in flight all connection between rotor and engine is severed and the rotor becomes a windmill, turned by the relative air stream as the machine ie drawn through the air by the ordinary airscrew. ' , Work on auto-giroplanes has reached a more advanced stage of development in England than in any other country, and this work has influenced helicopter progress. For instance, if the engine of a helicopter fails, it is essential that the design should provide, that it becomes in effect an auto-giroplane, otherwise it would fall to the ground. In the Focke helicopter, which now holds the world helicopter records, it is claimed that this change from helicopter to auto-giroplane, if the engine fails, is achieved ami that the machine can descend at a safe rate without engine. Calculations on helicopter flight made by H. B. Squire, and given in Aeronautical ■Research Committee Report No. 1730, show that a performance comparing well with that of an auto-giroplane' or aeroplane should theoretically be attainable. Professor Focke claims that his machine ehows a greatly improved performance. His helicopter has recorded a top speed of 90 m.p.h., a backward speed of 20 m.p.h., a duration of 1 hour 22 minutes, and a distance of 68 miles. He -employe two rotors, whereae the Cierva, Hafner and Kay auto-giroplanes all employ a single rotor. From what hae been eaid it will be clear that the true helicopter has no airscrew in the ordinary sen*<s but the Focke has a fan in front for cooling the engine. The auto-giro-i planes have ordinary airscrews. M. Breguet, the pioneer aircraft constructor, is a firm believer in the helicopter. Indeed, his calculations suggest that this type of machine ought to «riv e a performance comparing favourably with that of the ordinary aeroplane in such things as load carrying.