AIR TRANSPORT

Lake Wakatip Mail, Issue 4324, 27 July 1937, Page 2

AIR TRANSPORT

FUTURE OF THE DIRIGIBLE i —> — FLYING BOATS TWICE AS FAST The deplorable disaster that has so suddenly overtaken Germany’s giant airship Hiudenburg must raise again the question whether the airship can ever be made safe if it is operated with hydrogen as its lifting gas (writes Commander Sir Charles Den--1 nistoun Burney, in the Loudon i 1 Daily Telegraph ’). Hydrogen, as everyone knows, forms an explosive mixture if diluted with air, and consequently there is the ever-present danger of this dilution taking place in a structure such as an airship, i The only other lifting gas so far known which gives a lift comparable with that of hydrogen is helium. Helium is an inert gas and cannot form an explosive mixture when diluted with the air, and it would, of course, be used to the exclusion of hydrogen if it were not for the difficulty of obtaining and transporting it, and also, of course, the economic disadvantage of its high cost. Germany has shown that a safe and regular service across both the north and south Atlantic can be maintained in so far as navigation and ordinary flying practice are concerned, but this disaster must qualify any optimistic view of the future of airship transport.

Great Britain closed down British airship construction after the 11101 disaster. Although the circumstances of the two accidents are' different, hydrogen was ultimately ignited both in the case of RlOl and the Hindenburg, and it was the fire and explosion of tlie ignited hydrogen that cost so many lives in both cases. Jt would seem that there are two questions to examine if an estimate is to be made of the place that airships may take in the future of aviation. Can an economic service be operated on helium, and, if it can, is the airship likely to compete with the lieavier-than-air machine ?

The United States has operated its naA r al airships on helium for several years, and the United States naval authorities have fairly accurate figures as to the cost of that gas. In a naval service, Avhere cost is not of prime importance, the decision has been made to operate on helium.

The United States Avas in a favourable position. Supplies of helium in any quantity can only be obtained in that country. It is derived from the gases contained in certain oilfields and, having been separated and extracted, has to be compressed into steel cylinders for transportation. Even in the United States the cost of inflating a ship the size of the Hindenburg Avould be no less than £20,000 and if the helium had to be transported to Europe in order to make up losses on the voyage, the cost of its handling and transport Avould ha\-e to be added. This is no small charge. The Aveight of metal containers numerous enough to hold sufficient helium to inflate the Hindenburg Avould be some hundreds of tons.

Another disadvantage of helium is that its actual lift is some 7 per cent, less than that of hydrogen, and the whole of this has to come off the payload. Therefore, assuming a pay-load of some 14 per cent, of the displacement, a change from hydrogen to helium would reduce the pay-load by bO per cent, of what is possible with hydrogen. It is easy to see why the Zeppelin Company has used the utmost ingenuity of its designers in trying to make a hydrogen ship safe lather than use helium!

Assuming, however, that an inert gas such as helium could be used upon an economic basis, what are the prospects of the airship competing with the large flying-boat on ocean crossings ?

All that aviation ha,s to sell to the travelling public is higher speed, and the difference in speed both actual and potential between the airship and the living boat is considerable. It is unlikely that an airship can be constructed with a higher speed than 90 m.p.h. Iho Hindenbnrg has a top speed of 84 m.p.h, and a cruising speed nf about 75-77 m.p.h., whilst the new Imperial Airways flying boats have a top speed of 200 m.p.h and a cruising speed of ICO m.p.h.

TWICE AS FAST. In other words, the flying boat is twice as fast as the airship to-day, and if development proceeds at the present pace it would not he unduly optimistic to predict that within a few years flying boats of 250 m.p.h. cruising speed will he practicable. Again the difference in accomodation for passengers between the flying boat and the airship will tend to narrow. The larger the flying boat the better the accomodation, and to-day more than one American firm have flying boats on the stocks double the size of the Imperial Airways’ latest type. In these latest designs the accomodation will be but little inferior to that of the Hindenbnrg, and when the great difference in speed is considered it would seem that travellers in a hurry would be more inclined to book their passages by flying boat than by airship. If speed is not a vital factor the competition of a crack liner such as the Queen Mary becomes a pertinent consideration.

iho Hindoo burg lias crossed the Atlantic; in less than 48 hours, but its average time is about three days, against the Queen Mary’s five days, ami the possible 24 hours or less of the aeroplane when the Hying boat service is m existence. In speed, therefore, the airship ranks midway between the flying boat and the ocean liner. Its one advantage over both is its smooth and silent passage through the air and lack of motion. No airship passenger need fear seasickness or airsickness, and to bad sailors this would have a great appeal. , Again, however, as the flying boat increases in size this advantage may become correspondingly loss, as there is no doubt that the larger the flying boat the more it is affected by the air condiiions.

ft might be said that the greater radius of action of the airship should enable it to till a role that the flying boat cannot fill. This, again, is a moot point._ Air stransport on regular schedule is to-day economically possible only between considerable centres of population, and the richest ocean

i routes are undoubtedly the European- ! South American and European-North American routes. Airships have flown on both; the flying boat or heavier-than-air craft on the former, while plans are in progress to test it upon the latter. In neither case should the more restricted radius factor prevent the flying boat service being operated. One is forced, therefore, to the conclusion that the airship has been developed, and could perhaps have been further developed, as an ocean transport to serve for a short era. That era would seem to be the period required for the flying boat to develop sufficiently to become capable of fast, regular, and reliable oceanic services. Once the flying boat is sufficiently developed the airship’s chances of economic survival would seem to be precarious.

FOR ECONOMIC GAIN. It should have perhaps another decade or even two, of usefulness, but if, and only if, a safe lifting gas can bo used. Is this possible ? It may be As the airship increases in size it becomes more efficient, and consequently the handicap of the reduced lift of helium would be minimised. Moreover, the cost of operating the vessel would not increase in direct proportion to the increase in size. It may be, therefore, that if a ship double the size of the Hindenbnrg were built and operated on helium its operating cost per passenger-mile might be no more than the Hindenburg’s cost operated upon hydrogen. One could no doubt have full confidence in the ability of the Zeppelin Company to build and operate a vessel of so large a capacity, but it would take perhaps three years to build the first and six to build a fleet.

fn six years a regular daily flying boat service will probably be operating between New York and Southampton, and the question of competition would have to be faced. Technically a safe airship service can in all probability be achieved. Financially it must depend upon whether the German Government desires to maintain the service it has inaugurated and develop it to a higher degree of safety. One doubts whether private capital would be attracted, as the airship seems to have only a limited span of life. If a consistent policy of development had been pursued in Britain and Germany since the war, regular services by airship would by now have been in operation and might have lasted until the 1960’s and fulfilled a useful role. To-day, however, one could not advise this country again to entertain them, as it would have to be done with public money and the money would be better expended in fostering the development of the ocean flying boat. Whatever the future of the airship the sympathy of this country and the world will go out to Dr Eckener, head of the Zeppelin Company, as his enthusiasm, doggedness and perserverence in the face of great difficulties have been the admiration of the world. He has developed a wonderful technical instrument that has played its part in the development of world aviation. His name and that of his brilliant lieutenant, Captain Lehmann, will secure a place in history.