ZMC-2

The under the name ZMC -2 from 1929 to 1941 operated in the years in the U.S. Navy airship was an attempt pattern of all-metal airship to test this type. Its envelope was not in a tissue, but from 0.24 mm ( 0.0095 inches) and 0.2 mm ( 0.0080 inch) thick Duraluminiumblech unlike conventional airships. The envelope was simultaneously gas cell. This design and its compact shape, it also received his nickname Tin Bubble or Tinship ( German: sheet bubble sheet or ship).

Concept of all-metal airship

The concept of an all-metal airship was already conceived by Konstantin Ziolkowski Eduardo, who published some theoretical studies on all-metal dirigible airships in the 1880s. Before ZMC -2, only one airship rose with an outer skin of metal in the sky. It was the airship by David Black. It led on November 3, 1897 in Berlin, just a drive through, the landings it was irreparably damaged. This ship was the first application of the then-new, until 1889 presented at the Paris World Exhibition material aluminum in aviation.

1926, was about the same time, in the ZMC -2, Thomas Benton Slate started in a hall of the airport from Glendale, California, USA, to build from private drive an all-metal airship. Slate used aluminum checker plate, which he riveted to a rigid shell. During the construction Slate fathers invited to bring their children and watch him build the ship. Tens of thousands came. On 19 December 1929, the "City of Glendale " named airship pulled under the impressed eyes several hundred people from the hall. A journey should never experience it, however. The sun shone on the float and the shell began to buckle. The rivets tore with a loud bang that was reminiscent of shots and the carrying gas escaped. When the ship got flip side, ran the onlookers for fear of the hydrogen- filled airship could turn into a fireball of it. However easy it was only loud clatter to the floor. The reason for this debacle is not clearly preserved. It is mentioned a faulty pressure control valve. The ship was too badly damaged to repair it. Almost the entire shell would have to be dismantled and reassembled. The project was abandoned and the era of airships in Glendale was completed.

ZMC -2

The U.S. Navy designation ZMC -2 is divided into the letters Z, MC and the number 2, the Z as the first letters used the U.S. Navy to classify all their airships and lighter- than-air devices. The MC stood for Metal Clad to German about metallbeplankt. The 2 resulted from the lifting gas volume of approximately 200,000 cubic feet, exactly, it was 202,200.

The specified at various sources of aluminum thickness of 2 mm (0.08 inches) and the resulting weight per unit area is related to the means available to available lift to have been used for large parts of the ship too high.

Development and construction

The plans for ZMC -2 were developed by the American engineer Mr. Upson, who also drove the first B - class blimp in the service of Goodyear, from about 1922. He founded his own development company, the Aircraft Development Co. in 1926 ordered the U.S. Navy test pattern. Became possible was this design by developing a automatic riveters by Edwin J. Hill, who was able to connect the thin aluminum plate using a new gasket materials gastight. The built for this purpose riveter could put 5000 rivets with 0,9 mm diameter per hour. They drilled three rows of rivets at the same time and was operated by two persons. The rivets were set in the machine of endless supplied wire into the holes and provided with circumferential cam with heads. As bitumen sealant was used.

In 1924, the U.S. military was a "MC- 0.8" ( all-metal airship with 80,000 cubic feet of volume, about 2266 m³) offered. It should be built on the Scott airfield. It is reported that "MC- 1" has been partially made, but showed corrosion and embrittlement of the material attempts Duraluminiums. A sheath section of 8.8 x 10.4 m ( 29 x 34 ft ) with a weight of 181 kg ( 400 lbs ) was tested to destruction to verify the design assumptions. The gas-tightness was also investigated and found to be lower than expected. Further experiments were related to the behavior of the gas shell when the pressure drops inside. The material was provided with wrinkles and it looked as if it would remain forever distorted, but the material took after increasing the internal pressure his old form, and it was no longer recognizable, where previously had found the wrinkles. After these experiments, it was decided to " Alclad " aluminum that has been manufactured by the Aluminum Company of America. These were a sandwich material. The core consisted of duralumin ( Dural 17S, 24S Alcad later ), which was coated with pure aluminum.

In May 1927, the Aircraft Development Corporation began on the Detroit Grosse Ile Airport to build a 37x55x37 m ( LxWxH - 120x180x120 ft) large airship hangar, which was completed in September. There should ZMC -2 are built. For operations in which they set up north of the hall a 914 -meter circle (3000 ft) ago. This concrete box is still preserved between the runways of the airfield.

The construction of ZMC -2 began on 7 March 1928, the first rivet in the nose section. The airship was similarly built in two vertical halves of two egg shells, which were connected to each other in February 1929. In June, the motors have been installed in the nacelle, it was placed in the on July airship body. The following August ZMC -2 was filled with helium.

Construction

The held together by 3.5 million rivets metal sheath, which was internally supported by 24 longitudinal belts and 12 ring profiles in the form had with a measured gas loss of about two liters per day per square meter of a similar quality to that time, for example at Zeppelin used for the lifting gas cells Goldschläger skin, but was not resistant to aging. To obtain the form of ZMC -2, had the buoyancy body is constantly an excess pressure be maintained. Therefore, it was classified by the Navy in spite of the rigid metal construction as a blimp. The internal pressure was two ballonets with a maximum volume of 640 cubic meters ( 22,600 cubic feet ) in the front and 793 cubic meters ( 28,000 ft ³) maintained at the back ballonet.

The carrier gas volume of ZMC - 2 was without ballonets around 5727 cubic meters ( 202,200 cubic feet ) of helium. The ship had a length of 45.52 meters ( 149 ft 4 in), with a maximum diameter of 16.03 meters ( 52 ft 7 in ). Thus, it corresponded approximately to the size of small blimps, but the relatively low aspect was prominent. Exceptional were the eight relatively short tail fins at the rear, which were provided with movable control surfaces and an area of ​​40.9 m² (440 ft ²) possessed.

The payload was about 340 kg ( 750 lbs). Compared with inflatable airships similar size which is only a relatively small value, but it was a test vehicle, which was designed to test the design for larger models. From the volume and payload is an empty weight of the vessel can t be estimated in the order of 4.5 through 5.

The drive consisted of two seven-cylinder radial engines of the type Wright J -5 Whirlwind, which were attached to the gondola left and right and one two -bladed metal propeller with 2.8 m diameter (9 ft 2 in ) drives. The engines had an output of 164 kW ( 220 hp ). The top speed was up to 113 km / h ( 62-70 mph; 440 hp engine power), cruising speed at about 84 km / h ( 50-52 mph at 220 hp engine power). The range at cruising speed (about 675 mi) specified with just over 1000 km with a flight duration of up to 11 hours, the maximum range with no wind was approximately 1610 km (1000 mi). The airship was piloted by two crew members.

Operation

The maiden voyage of 49 minutes and 55 seconds was held at the Detroit Grosse Ile Airport on 19 August 1929. Pilots were U.S. Army Air Corps Captain William J. Kepner and flight engineer MSgt Joseph Bishop. In the following days more runs were carried out, including a 30 -hour loss journey. On August 25, the airship over the Cleveland National Air Races visited.

On September 12, it then left Detroit to begin his future home air base at Lakehurst, where it arrived the next day after a nearly 1000 km long uninterrupted ride (600 mi) and the U.S. Navy was passed. It was awarded the Navy serial number A- 8282nd In the following days, several holes were found in the shell. ZMC -2 had to insert some hits from the guns high-spirited Americans on his journey.

On September 16 trips across New York City have been made and the Atlantic Ocean after the speed tests were completed. All flight tests were successfully completed by 25 September. ZMC -2 met all contractual requirements and had passed all the tests in the first test with small safety margins.

In the near future many voyages were made around Lakehurst. This 9 -hour trips were common. For a time, the ship of the airship base of the U.S. Army, the Langley airfield was operated. On 31 May 1931, took with K-1, a Navy blimp on the New York fleet parade.

End of 1933, the carrying gas was drained to inspect the ship from the inside first. The metal surface was in good condition and the airship was put back into operation. There were only occasional trips. It is reported that it was his " birthday " in the air every year on August 19. After the last overhaul in December 1938 the ship completed only 5 hours flight time.

In Lakehurst met ZMC -2 on the big rigid airships that time and even led joint trips with them, (ie with the USS Los Angeles ), or was during the visit of LZ 129 "Hindenburg" housed in the same hall.

After six years, the airship had traveled approximately 92,000 kilometers for 752 runs in over 1400 flight hours. In the meantime, it has also a new set of engines. Some sources indicate a drive power of 300 hp (224 kW ) as opposed to the original 220 hp. Presumably, the new engines were ( also Wright J5) with enhanced performance. The airship was up to his withdrawal after the planned time of use in 1941 in the service of the U.S. Navy and was until then 2256.6 hours in the air, what this test pattern is regarded as evidence of the capabilities and robustness. The last ride was ( not entirely coincidentally ) on 19 August 1939, the 10th anniversary instead, then further tests were not carried out on the ground.

Admiral Moffett had 1926 described in its annual report, the main function of the airship: ... to test a purely experimental ship, thought about the applicability of the new construction technique, in which it was created. The ship was accordingly used mainly for testing, but was also involved in various training programs, supplies, rescue and disaster relief operations. The airship could be steered only unsatisfactory in bad weather and at slow speed, but this was attributed mainly to the small size and not the design principle. Another problem was the temperature of the shell, she could fluctuate greatly between the sidewalk and the flight altitude.

The gondola was preserved at the request of the commanding officer of the Marine airbase Lakehurst from the scrapyard and passed as a training object fully equipped together with the motors to the aeronaut school in Lakehurst.

Other projects

The Metalclad Airship Co., which had won a tender for the construction and design of all-metal airships against the ZMC -2 Manufacturer Aircraft Development Co., was in 1932 awarded by the U.S. Air Ministry a contract for the development of all-metal airships.

In online archive directories entries on tender documents and drawings of the Metalclad Airship Corp. exist. for a sixth U.S. Navy rigid airship under the name ZMC - 12th There is also a note about a lifting gas volume of 1,200,000 cubic feet, almost 34,000 m³. That is about six times the size of ZMC -2. Two other entries relate to this company's for all-metal airships, named MC -20 and MC -74 from the years 1934 and 1935.

Early 1970s was developed by the Dornier AG a concept study for a passenger and a cargo airship which an aluminum shell would also have to have. The study, however, was never realized.

In total, more airships of this type were never made ​​. ZMC - 2, built by David Black airship and the "City of Glendale " are therefore remained the only airships with a metal shell, despite the promising concept to the present day.