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Aviation History
1938
1938 - 1214.PDF
424 FLIGHT. APRIL 28, 1938. stroke radial based on the Pegasus, received attention for a short time, and for Air Ministry experiments was in- stalled in a Westland Wapiti with satisfactory results. Ths Napier Culverin, a Jumo 205 built under licence in this country, received scanty support, even though Ger- many was employing the type successfully on several of her services. Three Culverins were installed in a Blackburn Iris military boat. The success of the Junkers firm is due to their develop- ment work in the field during the past twenty-five years— in particular the last ten. The Jumo 204 and 205 are of the two-stroke opposed-piston type, a design avoiding the complication of valves. The first Jumo 204 was in service with Lufthansa in 1932, and in 1933 several more were in regular use. The output at that time was 750 h.p. and the weight 1,650 lb. (2.2 lb.-h.p.). The latest Jumo 205 gives 600 h.p. as a maximum output and weighs 1,144 lb. At normal power the fuel consumption of the Jumo is 0.375 lb.h.p.-hour, which compares with 0.395 Ib.-h.p.- hour obtained with the Phoenix. A normal petrol engine consumption for comparison would be about 0.45 lb.-h.p.- hour and the weight-power ratio 1.3 lb.-h.p. These figures for petrol engines can be slightly bettered by sleeve-valve units, in which this country, as represented by Bristol, has recently specialised. It is known that for a fuel of given octane value the compression ratio can be approximately one whole number higher than in a com- parable poppet-valve engine, and that this higher compres- sion permits improved running economy. Bristol sleeve-valve Perseus engines have put in many hours of commercial use with Imperial Airways, and are in service with the R.A.F. Fuel oil, incidentally, has specific gravity of about 0.86 and petrol of 0.74, so that about 15 per cent, less space is needed to store the same weight of fuel oil as petrol. This and the cheapness are two most important points in favour of the C.-I. engine in commercial use. The inability to produce, even for a short time, a " bumped-up " power output places the diesel second to the petrol engine in take-off characteristics, and brings up again the subject of assisted take-off. In Germany the catapult is favoured, and for some time long-range com- mercial experiments have been in progress, using diesel- powered flying boats. Only moderate supercharging can be applied to a diesel engine. In this country two definite aircraft types serve two dif- ferent purposes. Roughly speaking, feeder lines operate over short routes at low altitudes, and the main and Empire lines over considerably longer distances at higher altitudes. Added to these, of course, are the specialise^ machines for Atlantic experiments. ; Even over its short routes this country has favoured multi-engined machines for passenger transport; thus light, four-engined types have been developed with low-powered unsupercharged engines. The Short Scion^and Scion Senior have two and four Pobjoy Niagara III engines respectively. These little air-cooled, seven-cylinder units give only 85-95 h.p., but serve their purpose admirably. Much the same comment is justified in the case of the De Havilland Rapide and 86, which are powered by Gipsy Six engines of 185-205 h.p. output. The Gipsy Major and Six, Series II, which both drive 1,000-size D.H. v.p. airscrews, are the smallest engines in the world equipped for v.p. operation. Gipsy-powered De Havilland and other machines are now operating in many parts of the world. Among the engines of the feeder-line machines the Arm- strong Siddeiey Cheetah IX, as fitted to the twin-engined Envoy, has done good work. This engine is moderately supercharged, and is rated at 6,000ft. to give 310-350 h.p. In the same class the Napier Rapier engine is an " H "- shaped, air-cooled, sixteen-cylinder unit, and although it appeared some years ago it is still of advanced and unique design. Four fully supercharged Rapier Vs power the Short Mayo Mercury Atlantic mailplane, each giving 305- 315 h.p. at 10,oooft. and 340 h.p. at 13,000ft. The low-drag installation of the four Gipsy Twelve engines in the De Havilland Albatross is of special interest. These are inverted, air-cooled" vee-twelve motors with ducted cooling. The engines are of 18.37 litres capacity and 500 h.p. output. Two high-powered British engines are fitted commercially at the present time, the Bristol Pegasus Xc and the Arm- strong Siddeiey Tiger IX. Various Pegasus models built under licence abroad are also used by operating com- panies. The Xc, which gives 785-815 rated h.p. at 3,500ft. and 920 h.p. for take-off, is the power unit of the fleet of Short Empire boats, and the 775-805 h.p. Tiger IX will power the Ensigns now in production for Imperial Airways. This engine gives its normal power at 6,250ft. A civil version of the Bristol Perseus, the XIIc, will be installed in the new D.H. 95. The take-off output will be about 850 h.p. A quite recent addition to the commercial market, the Alvis range, consists of Alcides, Pelides, Maeonides, and a new medium-supercharged nine-cylinder 400 h,p. engine. The two-row fourteen-cylinder Pelides has been type- tested, giving 1,025-1,065 h.p. at 5,000ft. as a normal out- put and 1,060 h.p. for take-off. THE LEGAL SIDE (Continued from page 422.) in respect of baggage. Where the carriage is international within the meaning of the Warsaw Convention the require- ments of that Convention as to the consignment note must be strictly complied with, and woe betide the air carrier who fails to use the correct form or to get the necessary details filled in. In respect of non-international carriage he is free to make his own terms, and if he wishes to con- tract out of liability he should say so specifically on the consignment note and make it clear (a) that goods are carried at owner's risk; (b) that he does not accept the liabilities of a common carrier and reserves the right to refuse any consignment without giving a reason; and (c) that he gives no warranty, expressed or implied, as to the fitness of the aircraft for the carriage of any particular type of consignment. He should also warn the consignor against the risk of sending prohibited goods by air and make him (the consignor) responsible for compliance with the Air Navigation Regulations in this respect. Insurance.—It is a matter for each operator to deter- mine for himself how far he is prepared to carry his own liabilities and how far he wishes to insure them. Gener- ally speaking, the insurers insist as a term of their carrier in many instances to contract out of all liability. I think that this argument is fallacious; experience has shown that however much care may be taken over the documents of carriage there is always a risk of loopholes for attack from several directions and, to put it at its low- est, the average carrier requires protection against the risk of having to contest at his own expense an action at law by an impecunious claimant, against whom he cannot re- cover damages even if he is successful. I think I may say without fear of contradiction that the insurance of such liabilities has on the whole proved well worth while to those who have effected it. One point that I should want to make as an insured would be that in addition to my normal cover I should also have a contingency cover up to reasonable limits protecting me against the failure of one of my employees to issue the necessary documents of carriage, provided that I had taken all reasonable steps to see that this was done. Obviously such a contingency cover requires an additional premium, since it goes out- side the basis on which the premium for the original cover was fixed. The amount of such additional premium will depend upon the insurer's estimate of the business organ- insurance of such risks that the carrier shall by his docu- isation of the air carrier, but unless it is a very low ments of carriage contract out of liability so far as the law estimate the additional premium should not be prohibi- permits. It is sometimes argued that on this basis it is tive, and if a very low estimate is justified then thf air really not worth insuring except in respect of international carrier concerned would be wise to retire from business transport m view of the fact that the law does permit the while h° is still solvent! '
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