Дирижабль ВМС США «Акрон»: Первый летающий авианосец

U. S. Navy airship (1931–33) – purpose built flying aircraft carrier
the 1911 airship also constructed by Goodyear

USS Akron (ZRS 4) was a helium filled rigid airship of the U. S. Navy, the lead ship of her class, which operated between September 1931 and April 1933. It was the world's first purpose built flying aircraft carrier, carrying F9C Sparrowhawk fighter planes, which could be launched and recovered while it was in flight. With an overall length of 785 feet (239 m), Akron and her sister ship Macon were among the largest flying objects ever built. Although LZ 129 Hindenburg and LZ 130 Graf Zeppelin II were some 18 feet (5 m) longer and slightly more voluminous, the two German airships were filled with hydrogen, and so the two US Navy craft still hold the world record for the largest helium filled airships. Akron was destroyed in a thunderstorm off the coast of New Jersey on the morning of 4 April 1933, killing 73 of the 76 crewmen and passengers. The accident involved the greatest loss of life in any airship crash.

The airship's skeleton was built of the new lightweight alloy duralumin 17 SRT. The frame introduced several novel features compared with traditional Zeppelin designs. Rather than being single girder diamond trusses with radial wire bracing, the main rings of Akron were self supporting deep frames: triangular Warren trusses 'curled' round to form a ring. Though much heavier than conventional rings, the deep rings promised to be much stronger, a significant attraction to the navy after the in flight break up of the earlier conventional airships R38/ZR 2 and ZR 1 Shenandoah. The inherent strength of these frames allowed the chief designer, Karl Arnstein, to dispense with the internal cruciform structure used by Zeppelin to support the fins of their ships. Instead, the fins of Akron were cantilevered: mounted entirely externally to the main structure. Graf Zeppelin, Graf Zeppelin II, and Hindenburg used a supplementary axial keel along the hull centerline. However, the Akron used three keels, one running along the top of the hull and one each side, 45 degrees up from the lower centreline. Each keel provided a walkway running almost the entire length of the ship. The electric and telephone wiring, control cables, 110 fuel tanks, 44 water ballast bags, 8 engine rooms, engines, transmissions, and water recovery devices were placed along the lower keels. The inert gas helium was used instead of flammable hydrogen, which improved streamlining by allowing the engines to be safely placed inside the hull. A generator room, with 2 Westinghouse d. c. generators powered by a 30 h. p. internal combustion engine, was forward of the No. 7 engine room. Thus a position on the hull could be referred to, for example, as "6 port at station 102.5" (the number 1 engine room). While Germany, France and Britain used goldbeater's skin to gas proof their gasbags, Akron used Goodyear Tire and Rubber's rubberised cotton, heavier but much cheaper and more durable. Half the gas cells used an experimental cotton based fabric impregnated with a gelatin latex compound. This was more expensive than the rubberised cotton but lighter than goldbeater's skin. It was so successful that all the gasbags of Macon were made from it. There were 12 gas cells, numbered 0 to XI, using Roman numerals and starting from the tail. While the 'air volume' of the hull was , the total volume of the gas cells at 100 percent fill was At a normal 95 percent fill with helium of standard purity, the of gas would yield a gross lift of Given a structure deadweight of , this gives a useful lift of available for fuel, lubricants, ballast, crew, supplies and military load (including the skyhook airplanes)

Eight Maybach VL II gasoline engines were mounted inside the hull. Each engine turned a two bladed, 16 feet (5 m) diameter, fixed pitch, wooden propeller via a driveshaft and bevel gearing which allowed the propeller to swivel from the vertical plane to the horizontal. With the engines' ability to reverse, this allowed thrust to be applied forward, aft, up or down. It appears from photographs that the four propellers on each side were contra rotating, each one turning the opposite way to the one ahead of it. Thus it would appear that the designers were aware that running the propellers in the air disturbed by the one ahead was not ideal. While the external engine pods of other airships allowed the thrust lines to be staggered, placing all four engine rooms on each side of the ship along the lower keel resulted in Akrons propellers all being in line. This proved problematic in service, as it induced considerable vibration which was especially noticeable in the emergency control position in the lower fin. By 1933, Akron had two of her propellers replaced by more advanced, ground adjustable, three bladed, metal propellers. These promised a performance increase and were adopted as standard for Macon. The outer cover was of cotton cloth, treated with four coats of clear and two coats of aluminum pigmented cellulose dope. The total area of the skin was and it weighed, after doping,
The prominent dark vertical bands on the hull were condensers of the system designed to recover water from the engines' exhaust for buoyancy compensation. In flight fuel consumption continuously reduces an airship's weight and changes in the temperature of the lifting gas can do the same. Normally, expensive helium has to be released to compensate and any way of avoiding this is desirable. In theory, a water recovery system such as this can produce 1 lb of ballast water for every lb of fuel burned, though this is unlikely to be achieved in practice. Theoretical maximum ballast water capacity was in 44 bags, again distributed along her length, though normal ballast load at unmasting was
The F9C was not the ideal choice, being designed as a 'conventional' carrier borne fighter. It was heavily built to withstand carrier landings, downward visibility was not very good and it initially lacked an effective radio. But the primary role of Akrons airplanes was long range naval scouting. What was actually needed was a stable, fast, lightweight scouting airplane with a long range, but none existed capable of fitting between the structural members and into the airship's hangar, as the F9C could. The trapeze was lowered through the T shaped door in the bottom of the ship and into the slipstream, with an airplane attached to the crossbar by the 'skyhook' above its top wing, its pilot on board and its engine running. The pilot tripped the hook and the airplane fell away from the ship. On his return, he positioned himself beneath the trapeze and climbed up until he could fly his skyhook onto the crossbar, at which point it automatically latched shut. Now, with the engine idling, the trapeze and airplane were raised into the hangar, the pilot cutting his engine as he passed through the door. Once inside, the airplane was transferred from the trapeze to a trolley, running on an overhead 'monorail' system by which it could be shunted into one of the four corners of the hangar to be refueled and re armed. Having a single trapeze raised two problems: it limited the rate at which airplanes could be launched and recovered and any fault in the trapeze would leave any airborne scouts with nowhere to land. The solution was a second, fixed trapeze permanently rigged further aft along the bottom of the ship at station 102.5 and known as the 'perch'. By 1933 a perch was fitted and in use. Three more perches were planned (at stations 57.5, 80 and 147.5) but these were never fitted. The "angel basket" or "sub cloud observation car", allowed the airship to remain hidden in a cloud layer, while still observing the enemy below. The small car, rather like an airplane fuselage without wings, could be lowered on a 1000 foot long cable. The observer on board communicated with the ship by telephone. In practice, the device was unstable, almost looping over the airship during its only test flight. During the design stage, in 1929, the navy requested an alteration to the fins. It was considered desirable for the bottom of the lower fin to be visible from the control car. Charles E. Rosendahl had witnessed, from the control room, Graf Zeppelin almost snagging her fin on high tension power lines during her heavy take off into an unsuspected but very marked temperature inversion from Mines Field, Los Angeles at the start of the last leg of her round the world flight earlier that year. The design change would also allow direct vision between the main control car and the emergency control position in the lower fin. The control car was moved 8 feet (2 m) aft and all the fins were shortened and deepened. The leading edge root of the fins no longer coincided with a main (deep) ring and instead the foremost attachment was now to an intermediate ring at frame 28.75. This achieved the required visibility, improved low speed controllability, due to the increased span of the control surfaces, and simplified stress calculations, by reducing the number of fin attachment points. The designers and the navy's inspectors, led by the very experienced Charles P Burgess, were entirely satisfied with the revised stress calculations. However, this alteration has been the subject of much criticism as an "inherent defect" in the design and is often alleged to have been a major factor in the loss of Akrons sister ship Macon. Construction for both ships amounted to $8,800,000 (in 1931 dollars) with the Akron accounting $5,538,400 of the total.

Construction of ZRS 4 was begun on 31 October 1929 at the Goodyear Airdock in Akron, Ohio by the Goodyear Zeppelin Corporation. Because it was larger than any airship previously built in the US, a special hangar was constructed. Chief Designer Karl Arnstein and a team of experienced German airship engineers instructed and supported design and construction of both U. S. Navy airships USS Akron and USS Macon. On 7 November 1929, Rear Admiral William A. Moffett, the Chief of the U. S. Navy's Bureau of Aeronautics, drove the "golden rivet" into the main ring of "ZRS4". Erection of the hull sections began in March 1930. Secretary of the Navy Charles Francis Adams chose the name Akron (for the city near where it was being built), and Assistant Secretary of the Navy Ernest Lee Jahncke announced it in May 1930.

Akron was to have taken part in Fleet Problem XIII, but an accident at Lakehurst on 22 February 1932 prevented her participation. While the airship was being taken from her hangar, the tail came loose from her moorings, was caught by the wind, and struck the ground. The heaviest damage was confined to the lower fin area, which required repair. Also, ground handling fittings had been torn from the main frame, necessitating further repairs. Akron was not certified as airworthy again until later in the spring. Her next operation took place on 28 April, when it made a nine hour flight with Rear Admiral Moffett and Secretary of the Navy Adams aboard.

Soon after returning to Lakehurst to disembark her distinguished passengers, Akron took off again to conduct a test of the "spy basket"—something like a small airplane fuselage suspended beneath the airship that would enable an observer to serve as the ship's "eyes" below the clouds while the ship herself remained out of sight above them. The first time the basket was tried (with sandbags aboard instead of a man), it oscillated so violently that it put the whole ship in danger. The basket proved "frighteningly unstable", swooping from one side of the airship to the other before the startled gaze of Akrons officers and men and reaching as high as the ship's equator.

Akron and Macon (which was still under construction) were regarded as potential "flying aircraft carriers", carrying parasite fighters for reconnaissance. On 3 May 1932, Akron cruised over the coast of New Jersey with Rear Admiral George C. Day, and the Board of Inspection and Survey, on board, and for the first time tested the "trapeze" installation for in flight handling of aircraft. The aviators who carried out those historic "landings"—first with a Consolidated N2Y trainer and then with the prototype Curtiss XF9C 1 Sparrowhawk—were Lieutenant D. Ward Harrigan and Lieutenant Howard L. Young. The following day, Akron carried out another demonstration flight, this time with members of the House Committee on Naval Affairs on board; this time, Lieutenants Harrigan and Young gave the lawmakers a demonstration of Akrons aircraft hook on ability. before being hoisted on board the airship an hour later. Akron moored at Camp Kearny later that day before proceeding to Sunnyvale, California. Footage from the accident appears in the film Encounters with Disaster, released in 1979 and produced by Sun Classic Pictures.

Over the weeks that followed, Akron "showed the flag" on the West Coast of the United States, ranging as far north as the Canada–US border before returning south in time to exercise once more with the Scouting Fleet. Serving as part of the "Green Force", the Akron attempted to locate the "White Force". Although opposed by Vought O2U Corsair floatplanes from "enemy" warships, the airship located the opposing forces in just 22 hours, a fact not lost upon some of the participants in the exercise in subsequent critiques. It then resumed operations capturing aircraft on the "trapeze" equipment. Admiral Moffett again boarded Akron on 20 July, but the next day left the airship in one of her N2Y 1s which took him back to Lakehurst after a severe storm had delayed the airship's own return to base. at 22:00. According to Richard K. Smith, "[u]nknown to the men on board the Akron, they were flying ahead of one of the most violent stormfronts to sweep the North Atlantic States in ten years. It would soon envelop them." Enveloped in fog, increased lightning and heavy rain, it became extremely turbulent at 00:15. The Akron began a rapid nose down descent, reaching 1100 feet (335 m) while still falling. Ballast was dumped, which stabilized the ship at 700 feet (213 m), and climbed back to 1600 feet (488 m) cruising altitude. Then a second violent descent sent the Akron downwards at "Landing stations" alerted the crew, as the ship descended tail down. The lower fin struck the sea, water entered the fin, and the stern was dragged under. The engines pulled the ship into a nose high attitude, then the Akron stalled, and crashed into the sea. The U. S. Coast Guard cutter Tucker—the first American vessel on the scene—arrived at 06:00, taking the airship's survivors and the body of Copeland on board. Among the other ships combing the area for survivors were the heavy cruiser Portland, the destroyer Cole, the Coast Guard cutter , and the Coast Guard destroyers USCGD McDougal and USCGD Hunt, as well as two Coast Guard aircraft. The fishing vessel Grace F from Gloucester, Massachusetts, also assisted in the search, using her seining gear in an effort to recover bodies. Most casualties had been caused by drowning and hypothermia, since the crew had not been issued life jackets, and there had not been time to deploy the single life raft. The accident left 73 dead, and only three survivors. Wiley, standing next to the two other survivors, gave a brief account on 6 April.