LZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin was a German passenger-carrying hydrogen-filled rigid airship that flew from 1928 to 1937. It offered the first commercial transatlantic passenger flight service. The ship was named after the German airship pioneer Ferdinand von Zeppelin, a count in the German nobility. It was conceived and operated by Hugo Eckener, the chairman of Luftschiffbau Zeppelin.
Graf Zeppelin made 590 flights totalling almost 1.7 million kilometres. It was operated by a crew of 36 and could carry 24 passengers. It was the longest and largest airship in the world when it was built. It made the first circumnavigation of the world by airship, and the first nonstop crossing of the Pacific Ocean by air; its range was enhanced by its use of Blau gas as a fuel. It was built using funds raised by public subscription and from the German government, and its operating costs were offset by the sale of special postage stamps to collectors, the support of the newspaper magnate William Randolph Hearst, and cargo and passenger receipts.
After several long flights between 1928 and 1932, including one to the Arctic, Graf Zeppelin provided a commercial passenger and mail service between Germany and Brazil for five years. When the Nazi Party came to power, they used Graf Zeppelin as a propaganda tool. The airship was withdrawn from service after the Hindenburg disaster in 1937 and scrapped for military aircraft production in April 1940.
Background
The first successful flight of a rigid airship, Ferdinand von Zeppelin's LZ1, was in Germany in 1900. Between 1910 and 1914, Deutsche Luftschiffahrts-Aktiengesellschaft transported thousands of passengers by airship. During World War I, Germany used airships to bomb London and other strategic targets. In 1917, the German LZ 104 was the first airship to make an intercontinental flight, from Jambol in Bulgaria to Khartoum and back, a nonstop journey of.During and just after the war, Britain and the United States built airships, and France and Italy experimented with confiscated German ones. In July 1919 the British R34 flew from East Fortune in Scotland to New York and back. Luftschiffbau Zeppelin delivered LZ 126 to the US Navy as a war reparation in October 1924. The company chairman Hugo Eckener commanded the delivery flight, and the ship was commissioned as.
The Treaty of Versailles placed limits on German aviation which the Allies relaxed in 1925. Eckener saw an opportunity to start an intercontinental air passenger service, and began lobbying the government for funds and permission to build a new civil airship. Public subscription raised , and the government granted over .
Design and operation
The LZ 127 was designed by Ludwig Dürr as a "stretched" version of the zeppelin LZ 126 rechristened the USS Los Angeles). It was intended from the beginning as a technology demonstrator for the more capable airships that would follow. It was built between 1926 and September 1928 at the Luftschiffbau Zeppelin works in Friedrichshafen, on Lake Constance, Germany, which became its home port for nearly all of its flights. Its duralumin frame was made of eighteen 28-sided structural polygons joined lengthwise with of girders and braced with steel wire. The outer cover was of thick cotton, painted with aircraft dope containing aluminium to reduce solar heating, then sandpapered smooth. The gas cells were also cotton, lined with goldbeater's skins, and protected from damage by a layer containing of ramie fibre.Graf Zeppelin was long and had a total gas volume of, of which was hydrogen carried in 17 lifting gas cells, and was Blau gas in 12 fuel gas cells. The Graf Zeppelin was built to be the largest possible airship that could fit into the company's construction hangar, with only between the top of the finished vessel and the hangar roof. It was the longest and most voluminous airship when built, but it was too slender for optimum aerodynamic efficiency, and there were worries that the shape would compromise its strength.
Graf Zeppelin was powered by five Maybach VL II 12-cylinder engines, each of capacity, mounted in individual streamlined nacelles arranged so that each was in an undisturbed airflow. The engines were reversible, and were monitored by crew members who accessed them during flight via open ladders. The two-bladed wooden pusher propellers were in diameter, and were later upgraded to four-bladed units. On longer flights, the Graf Zeppelin often flew with one engine shut down to conserve fuel.
Graf Zeppelin was the only rigid airship to burn Blau gas; the engines were started on petrol and could then switch fuel. A liquid-fuelled airship loses weight as it burns fuel, requiring the release of lifting gas, or the capture of water from exhaust gas or rainfall, to avoid the vessel climbing. Blau gas was about the same density as air, so burning it had little effect on buoyancy. On a typical transatlantic journey, the Graf Zeppelin used Blau gas 90% of the time, only burning petrol if the ship was too heavy, and used ten times less hydrogen per day than the smaller zeppelin L 59 did on its Khartoum flight in 1917.
Graf Zeppelin typically carried of ballast water and of spare parts, including an extra propeller. Calcium chloride was added to the ballast water to prevent freezing. The ship retained grey water from the sinks for use as additional ballast. Both fresh and wastewater could be moved forward and aft to control trim.
The airship usually took off vertically using static lift, then started the engines in the air, adding aerodynamic lift. Normal cruising altitude was ; it climbed if necessary to cross high ground or poor weather, and often descended in stormy weather. To measure the wind speed over the sea, and calculate drift, floating pyrotechnic flares were dropped.
When preparing to land, the crew advised the ground either by radio or signal flag. Ground crew lit a smoky fire to help the airshipmen judge wind speed and direction. The airship slowed, then adjusted buoyancy to neutral by valving off hydrogen or dropping ballast. Echo sounding with the report from an 11-mm blank round was used to measure altitude accurately. The ship flew in with its nose trimmed slightly down, made its final approach into the wind descending at per minute, then used reverse thrust to stop over the landing flag, where it dropped ropes to the ground. Landing in rough weather required a faster approach. Up to 300 people manhandled the airship into a hangar or secured it by the nose to a mooring mast.
Graf Zeppelin
Layout
The operational spaces, common areas, and passenger cabins were built into a gondola structure in the forward part of the airship's ventral surface, with the flight deck well forward in a "chin" position. The gondola was long and wide; its streamlined design reflected contemporary aesthetics, minimised overall height, and reduced drag. Behind the flight deck was the map room, with two large hatches to allow the command crew to communicate with the navigators, who could take readings with a sextant through the two large windows. There was also a radio room and a galley with a double electric oven and hot plates.The galley staff served three hot meals a day in the main dining and sitting room, which was square. It had four large arched windows, wooden inlays, and Art Deco-upholstered furniture. Between meals, the passengers could socialise and look at the scenery. On the round-the-world flight, there was dancing to a phonograph, fine wine, and Ernst Lehmann, one of the officers, played the accordion. A corridor led to ten passenger cabins capable of sleeping 24, a pair of washrooms, and dual chemical toilets. The passenger cabins were set by day with a sofa, which converted at night into two beds. The cabins were often cold, and on some sectors passengers wore furs and huddled under blankets to stay warm. There was a noticeable smell from the Blau gas, especially when the ship was stationary.
A ladder from the map room led up to the keel corridor inside the hull, and accommodation for the 36 crewmen. Officers' quarters were towards the nose; behind them were the baggage store, the crew mess room, and the quarters for the ordinary crew, who slept in wire-frame beds with fabric screens. Also along this corridor were petrol, oil and water tanks, and stowage for cargo and spare parts. Branches from the keel corridor led to the five engine nacelles, and there were ladders up to the axial corridor, just below the ship's main axis, which gave access to all the gas cells.
Electrical and communications systems
The main generating plant was in a separate compartment mostly inside the hull. Two Wanderer car engines adapted to burn Blau gas, only one of which operated at a time, drove two Siemens & Halske dynamos each. One dynamo on each engine powered the oven and hotplates, and one the lighting and gyrocompass. Cooling water from these engines heated radiators inside the passenger lounge. Two ram air turbines attached to the main gondola on swinging arms provided electrical power for the radio room, internal lighting, and the galley. Batteries could power essential services like radios for half an hour, and there were small petrol generators for emergency power.Three radio operators used a one-kilowatt vacuum tube transmitter to send telegrams over the low frequency bands. A 70 W antenna power emergency transmitter carried telegraph and radio telephone signals over 300–1,300 m wavelength bands. The main aerial consisted of two lead-weighted -long wires deployed by electric motor or hand crank; the emergency aerial was a wire stretched from a ring on the hull. Three six-tube receivers served the wavelengths from 120 to 1,200 m, 400 to 4,000 m and 3,000 to 25,000 m. The radio room also had a shortwave receiver for 10 to 280 m.
A radio direction finder used a loop antenna to determine the airship's bearing from any land radio station, or a ship with a known position. Two or more bearings would give the airship's position. During the first transatlantic flight in 1928, the radio room sent 484 private telegrams and 160 press telegrams.