The Aviation World

New Zealand Herald, Volume LXVIII, Issue 20922, 11 July 1931, Page 16

The Aviation World

GIANT DIRIGIBLE. UNITED STATES VENTURE. ' Christening ceremonies for the U.S.S. Akroti, the world's largest dirigible, which is being Iniilt for the United States Navy at the giant hangar of the GoodyearZeppelin Corporation, near Akron, Ohio, will be, held iri the luftcr part of July. The exact date for the dedication has not been determined, as ifc is contingent upon the completion of certain technical requirements now entering the final stages, The framework of the airship, which is larger than the famous Graf Zeppelin and three times the size of the American dirigible Los Angeles, has been completed, and approximately one-hajf of the outer cover is now in place. Many interior refinements and adjustments, however, will have to be effected after the christening of the ship, as is the custom on a marine vessel after it has been dedicated and launched. Therefore, the first trial flight of tho Akron will not be held the day of the dedication, but some time within the following three or four weeksT Under the command of Lieutenant-Commander Charles E. Rosenthal, former commander of the U.S.S. Los Angeles and one of the. foremost authorities on Ikrhter-than-air craft in the country, it will be taken aloft for conclusive tests on speed, rate of climb, fuel consumption, control ability and various other factors.

This flight and other test trips will be held from the Akron base and will vary from three or four hours to 24 hours. Ultimately it is expected that the Akron will form a unit of the Pacific I'leet and will operate out of Sunnyvale, near San Francisco, where a hangar is now being built. Preparations for the first flight have already been made in the construction of a huge mobile mooring mast, which will pull the ship in and out of the dock. The mast, which is 76ft. high and weighs 130 tons, is of the open pyramid or trypod type, and has a caterpillar tractor tit each corner of its triangular base. Power to drive the two rear tractors is furnished by n 240 horse-power gasoline motor, while the forward tractor is used for steering. The dedication of the Akron is expected to attract, more than 100.000 people. Special trains will be run from various parts of the country and elaborate provisions are being made at the airport to efficiently handle the heavy traffic over the various airlines on that day. Arrangements are. also being made to accommodate more thnn 25.000 automobiles in one large -parking area.

Details of Construction. For the last two months the huge hangar on the outskirts of the city has been the mocea for more than 50,000 people each week, The hangar in itself has attracted as much attention as tho giant dirigible within. The dock is built in the form of a hollow half-eggshell and is 1175 ft. long, 325 ft. wide and 211 ft. high. It is the largest building in the world without interior supports. The hangar was built on rollers to allow the entire mammoth structure to "stretch" and contract. Being entirely of steel, both frame and roofing, the building gradually change* its dimensions as temperatures vary. It expands as the eir becomes warmer and contracts as it gets cooler. The rollers allow it to breathe. The huge steel girders, which support the building, are hinged on these rollers, and these in turn rest, on concrete footings built, upon concrete piles driven to the sock 30ft. below ground. The same hangar will he used for the construction of a second airship for the United States Navv. a sister ship of the Akron, which will be the same size and capacity. Active const ruction on this dirigible, however, will probably not start for some time. The Akron, which is inflated with helium, a non-inflammable, non-explosive gas, lias a capacity of 6,500,000 cubic feet, is 785 ft. long and has a diameter of 133 ft. Eight 560 horse-power engines will propel the ship through the air at a speed of more than 80 "miles an hour, and it is estimated that it will be able to tly for 10,500 miles without refuelling. One of the novel features in the Akron's construction will be the inclusion in a special compartment, for five aeroplanes, These planes, through a trapeze arrangement, can bo lowered through the hull and released while ,in mid-air. The trapeze attachment will then pick up tho planes upon their return and haul them back into the ship. The only structure protruding from the streamlined hull of the Akron is the control cabin. All quarters for officers and crew, and the motorrooms, are within the ship itself. In previous Zeppelins motors were contained in gondolas suspended away from the hull. In the Akron, because of the use of non-explosive helium gas, the motors are inside the hull and power is transmitted to the propellers through an outrigger containing a rigid shaft and a bevel-gear device.

FRENCH RACING PLANES.

It is reported that the French machines which are being designed to compete in the 1931 Schneider Trophy contest will be, unlike the possible Italian competitors, conventional low-wing, wire-braced monoplanes, with tractor airscrews and twin floats. The Bernard, Nieuport and Drwoitine companies are designing machines for a theoretical maximum speed of 390 and 400 tn.p.h. An increase in power, accompanied by a reduction in proportionate weight, will result in the dimensions of the machines being almost the same as those designed for the 1929 contest The new Lorraine engine which has been designed for the contest is claimed to offer a cross-sectional area no larger than that of a normal pilot to be accommodated^behind it. It is an inverted 12-cylinder Yoe water-cooled engine and has a designed horse-power of 2200. developed at something over 4000 r.p.m., with a supercharger driven at 28,000 r.p.m. The engine, is said to weigh only 0.521b. per h.p., as compared with the designed 0.681b, per h.p. of the RollsRoyce "I!" engine of 1929. The new Renault engine is a normal upright 12cylinder Vee type, with a maximum output of 2300 h.p. and weighing about 0.671b. per h.p.

HEAVY-OIL ENGINES. Leading British aero engine builders are spending much time and money at present on a study of the problems involved in building compression-ignition engines' burning heavy oil instead of petrol. The engines fitted to the airship RlOl belonged to this type, of unit, but, their excessive weight prevented their use in aeroplanes. The advantages of using compression ignition motors are increased (iinge on account of Jowor weight of fuel, economy, simplification because an electrical ignition system is not required and freedom from fire risks. These are suflb eiently attractive to make experiments worth while. The greatest, difficulty is to reduce the weight of tho engine, but recent development luis succeeded in reducing it to a reasonable figure and a British aeroplane fitted with a heavy-oil motor is expected to take the air during the summer.

In accordance with normal Air Ministry procedure, research work on this subject is secret, but it is possible to state that the British experiments have produced a rriotov at least the equal in efficiency of any constructed abroad, Air experts will watch its future with keen interest.