THE AIRSHIP'S PART IN COMMERCIAL AVIATION.
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Important Memorandum from the Air Ministry Comparing Airships and Aeroplanes for Commercial Purposes.
1.‘_N EXCEPTIONALLY interestilioand informative memorandum on. the question .a the relative advantages of airships and aeroplanes for commercial purposes has been issued by the Air Ministry. It is pointed out that it would appear that the future uses of the two types for commercial. purposes will not conflict. The airship is essentially a long-distance, weightcarrying craft as compared with, the short-distance, high-speed aeroplane, although, even in the 'matter. of speed, the airship of to-day, with a speed in excess of 77 miles per hour, can be considered slow only relatively to the aeroplane, as she is -unquestionably fast in comparison with land and sea methods of transport.
In addition to this the airship has the advantage of not being dependent upon her speed through the air for her ability to remain aloft, and is not, therefore, liable to forced descent in the case of engine failure as is the aeroplane. Quite large repairs toengines, such as the changing of a cylinder, are possible in an airship while travelling The airship, therefore, is worthy of consideration for commercial flights over sea or land of a wooded or broken nature, such as to be unsuitable for the landing of aeroplanes, and on journeys hnvolving non-stop flights of a 1000 miles and upwards.
The airship is the most suitable aircraft for the carrying of passengers where speed, safety, comfort and reliability are essential. She always remains on an even keel, so that there is no danger in flying at night, in fog, or clouds, and there is more DOOM to move about. There need be no fear due to the presence of inflammable gas; only one airship has been lost in this country owing to catching fire in the air, although 2i million miles have been covered during the war. In the case referred to, the flight was an experimental one with a new type of ship, and the cause has since been ascertained and eliminated.
The opinion is expressed that, for commercial purposes, large airship stations should be established at distances of from 2000 to 3000 miles apart, mainly for trans-oceanio traffic, whilst the areoplane would be used for conveying passengers and merchandise to these stations from neighbouring countries. There is briefly outlined an airship service which would run from Lisbon to New York, passengers being taken to Lisbon by aeroplane. The advantage in time saved by this means is enormous, as the passengers could be conveyed to Lisbon at a speed of 100 miles per hour as compared with the fastest train journey of, say, 45 miles per hour, whilst the journey by airship would be materially faster than the journey by steamship. Railways in Central Africa could be linked up by the airship where the country is difficult both for aeroplanes and land transport. With regard to the question of the weather and its effect upon reliability of service, it is worthy of note that although airships are generally considered to be fair-weather'craft, in 1918, -to the end of November, there were only nine days on which no airship flight took place in the British Isles—notorious for possessing the worst weather conditions of any country in the world. On days when fog and low-lying clouds are prevalent, which might be considered unsuitable for aeroplanes, airships are able to fly. The latest German rigid airship has a disposable 'lift available for crew, fuel, merchandise, etc., of over 38 tons. If all this lift be employed in carrying passengers, she would have a theoretical endurance of about seven days at a cruising speed of 45 miles per hour, the maximum speed being 77.6 miles per hour.
Four types of non-rigid airships have been built in this country, their capacities being as follow :—The S.S.Z. (single engine), 70,000 cubic ft. ; the S.S.T. (twin engine), 100,000 cubic ft. ; the "Coastal Star," 200,000 cubic ft. ; and the N.S., 360,000 cubic ft., the lengths of the vessels being from 143 ft. in the case of the S.S.Z. to 262 ft. in the case of the N.S. The available lifts for fuel and freight for each of these types are respectively : S.S.Z., 1370 lb. ; S.S.T., 1560 lb. ; "Coastal Star," 4050 lb. ; N.S., 6900 lb. In one of the appendices of the memorandum, full details are given of fuel and oil consumption, the cost of hydrogen, and the cost of upkeep.
The capital outlay on these four types, which are the non-rigid types, is :—S.S.Z.. £5000; S.S.T., £8200; "Coastal Star," £12,750; N.S., 224,000, less 40 per cent. reduction on the capital outlay for peacetime figures ; whilst 20 per cent. of the capital outlay on non-rigid airships is considered sufficient allowance for all spare parts, envelopes, etc., required in the course of a,year.
Of the rigid airship there. are two types, viz., the one having a length of 693 ft., with a capacity of 2,000,000 cubic ft., costing 2150,000, and a vessel of 1100 ft. in length with a capacity of 10,000,000 cubic ft., and costing from 2200,000 to 2300,000. The smaller vessel has a disposable lift of 38.8 tons, and after allowing 11 tons for crew, water ballast, etc,. there is an available lift for fuel and freight of 27.8 tons. These figures are based on the knowedge of what has been done by the Zeppelin L70. It is a rernarkablafact that in 1914 the endurance of a German rigid at cruising speed was less than one day, and the maximum speed was about 50 m.p.h., whilst in 1918 the German L70 had an endurance, at 45 m.p.h. of seven days, and it could rise to a height of 23,004 ft. as compared with 6000 ft, which was the maximum in 1914. The British R38 class, which has a capacity of 2,720,000 cubic ft., has an estimated cruising endurance of 8.8 days. The 10,000,000 cubic ft. ship is estimated to have an available lift for fuel and freight of 170 tons, its petrol consumption being 278 gallons per hour and its oil consumption 22 gallons, whilst the cost -of the hydrogen would run to 26 per hour.
The outlay for airship stations is necessarily large, but it is only necessary to establish large stations at big intervals, with sub-stations made up of cheap portable sheds and a few tents or huts at other places. The main station, of course, has permanent sheds, quaaters, etc.
Experiments have been made with mooring out an airship, with considerable success. The airship was moored out for six weeks, in a Perfectly open expanse, to a specially-designed mast, only two or three men being required to look after the ship, whilst winds of 52 m.p.h. have been ridden out without any -damage resulting. We well remember in the early days of aviation that Mr. A. V. Roe suggested the mast as a suitable means of anchoring an airship: This method has only been tried with non-rigid airships, but it is on the point of being tried with rigids, and it is claimed that there is no reason to expect other than real success. The use of the mooring mast will greatly increase the regularity of any airship service, as the chierdifficulty at present, consists in taking airships in and out of sheds. The possibilities of using floating sheds on water are being inquired iito.• Reference is made in the memorandum -to the fact that nine airship stations of various sizes; will, in all probabiiity, shortly cease to be in use by the Admiralty, and these will therefore become available for disposal, whilst a certain number of the S.S.Z. and the "Coastal Star" non-rigid airships will become available for disposal.
A shed 750 ft. long to house two rigid airships with their gas plant, quarters, roads, drainage, railway and water supply would cost 2279,840, plus, say, 40 per cent increased expenditure on account of war prices, whilst a shed 350 ft. long to house four S.S.T. or two "Coastal Star" non-rigid ships would cost 2122,460, plus the same war-time increase. A tem-. porary base for a non-rigid airship need not cost more than 25400, subject to war-time increase.
The other appendices of the memorandum give the crew and station personnel required, the estimated wages and salaries for different types of stations, and wages for pilots, crews, skilled and unskilled labour, so that the memorandum constitutes quite a valuable document for those who wish to study the possibilities of commercial aviation.