Hindenburg (LZ-129)

LZ 129 Hindenburg was a German zeppelin. Along with its sister-ship LZ 130 Graf Zeppelin II, it was the largest aircraft ever built. During its second year of service, it went up in flames and was destroyed while landing at Lakehurst Naval Air Station in Manchester Township, New Jersey, U.S., on 6 May 1937. Thirty-six people died in the accident, which was widely reported by film, photography and radio media.

The Hindenburg was named after Paul von Hindenburg (1847-1934), the President of Germany (1925–1934).

Design and construction

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The Hindenburg was built by Luftschiffbau Zeppelin in 1931 to a new, all-duralumin design. The man who headed the design team was Doctor Ludwig Dürr, who had headed the design of all Zeppelins except LZ-1 (on which he was a crew member), under the overall direction of Hugo Eckener, the head of the company. It was 245 m (804 ft) long and 41 m (135 ft) in diameter, longer than three Boeing 747s placed end-to-end, longer than four Goodyear Blimps end-to-end, and only 24 m (79 ft) shorter than the Titanic. It was originally equipped with cabins for 50 passengers and a crew complement of 40, though on the last flight there were an additional 21 crew members in training.

Though construction began in 1931, it was suddenly stopped when the Zeppelin Company became bankrupt. This led Dr. Eckener to make a deal with the Nazi Party. He needed money to build the airship, but in return he was forced to display the swastikas on the tailfins. Construction then resumed in 1935.

The Hindenburg was originally intended to be filled with helium, a gas which is lighter than air but which is not flammable. Most of the world's supply of helium comes from underground fields in the United States, but the United States had imposed a military embargo on helium against Germany. Eckener expected this ban to be lifted and modified the design to have double gas cells (an inner hydrogen cell protected by an outer helium cell). However, Dr. Eckener was told this ban was not lifted after all. This led the Germans to modify the design of the airship to use hydrogen as the lift gas, despite the fact that hydrogen, unlike helium, is extremely flammable. It contained 200,000 m³ (7,000,000 ft³) of gas in 16 bags or cells, with a useful lift of 1.099 MN (247,100 pounds).

Germany had extensive experience with hydrogen as lifting gas. Hydrogen-related fire accidents had never occurred on civil zeppelins, so the switch from helium to hydrogen did not cause much alarm. Hydrogen also gave the craft about 8% more lift capacity.

Four reversible 890 kW (1,200 horsepower) Daimler-Benz diesel engines gave the airship a maximum speed of 135 km/h (84 mph).

The duralumin frame was covered by cotton varnished with iron oxide and cellulose acetate butyrate impregnated with aluminium powder. The aluminium was added to reflect both ultraviolet, which damaged the fabric, and infrared light, which caused heating of the gas. This was an innovation with the LZ-126 which was operated by the US Navy from 1924 on. The LZ-130 fabric coating was changed to include bronze powder which is less flammable.

It officially made its first flight on 4 March 1936, though several test flights were made the previous year. The cost of a ticket from Germany to Lakehurst was US$400 (about US$5900 in 2008 dollars), which was quite a considerable sum for the Depression era. Hindenburg passengers were generally affluent, including many leaders of industry.

Passenger accommodation

To reduce drag, the passenger rooms were contained entirely within the hull, rather than in the gondola as on the Graf Zeppelin. The interior furnishings of the Hindenburg were designed by Professor Fritz August Breuhaus, whose design experience included Pullman coaches, ocean liners, and warships of the German Navy. The upper A Deck contained small passenger quarters in the middle flanked by large public rooms: a dining room to port and a lounge and writing room to starboard. Paintings on the walls of the dining room portrayed the Graf Zeppelin's trips to South America. A stylized world map covered the wall of the lounge. Long slanted windows ran the length of both decks. The passengers were expected to spend most of their time in the public areas rather than their cramped cabins. The lower B Deck contained washrooms, a mess hall for the crew, and a smoking lounge. Recalled Harold G. Dick, an American representative from the Goodyear Zeppelin Corporation, "The only entrance to the smoking room, which was pressurized to prevent the admission of any leaking hydrogen, was via the bar, which had a swivelling air-lock door, and all departing passengers were scrutinized by the bar steward to make sure they were not carrying out a lighted cigarette or pipe."

First year of service

During its first year of commercial operation in 1936, the Hindenburg flew 308,323 km (191,583 miles) carrying 2,798 passengers and 160 tons of freight and mail. It made 17 round trips across the Atlantic Ocean, with ten trips to the U.S. and seven to Brazil. In July 1936, the Hindenburg also completed a record Atlantic double-crossing in five days, 19 hours and 51 minutes. After defeating Joe Louis, the German boxer Max Schmeling returned home on the Hindenburg to a hero's welcome in Frankfurt.

On 1 August, the Hindenburg was present at the opening ceremonies of the 1936 Summer Olympics in Berlin. Moments before the arrival of Adolf Hitler, the airship crossed over the Olympic stadium, trailing the Olympic flag from its gondola.

During its first year of service, the airship had a special aluminium Blüthner grand piano placed on board in the music salon. It was the first piano ever placed in flight and helped host the first radio broadcast "air concert." The piano was removed after the first year to save weight.

The Hindenburg's success encouraged the Luftschiffbau Zeppelin Company to plan the expansion of its airship fleet and transatlantic services.

During the winter of 1936–37, several changes were made. The greater lift capacity allowed ten passenger cabins to be added, nine with two beds and one with four beds, increasing the total passenger capacity to 72.

Last flight

The Zeppelin Hindenburg (LZ 129) igniting on May 6, 1937 at Lakehurst Naval Air Station in New Jersey.

On the night of 3 May 1937, the Hindenburg left Frankfurt for Lakehurst. This was the first transatlantic trip of the 1937 season.

The crossing was uneventful, except for strong headwinds. The airship was half full, with 36 passengers and 61 crew members (21 more than usual who were crew members in training), but the return flight was fully booked by people attending the coronation of King George VI of the United Kingdom, which would take place on 12 May, at Westminster Abbey, London.

The low number of passengers was probably because of concerns of a bomb on board. A letter was sent to the German Ambassador predicting that the airship would be destroyed by a bomb after flying over New York City.

On 6 May, the airship arrived in the United States. The airship was already late, and the landing was further delayed because of bad weather. Captain Max Pruss took passengers on a tour through New York City, and the seasides of Boston and New Jersey.

Historic newsreel coverage

The disaster is well recorded because of the extraordinary extent of newsreel coverage and photographs, as well as Herbert Morrison's recorded, on-the-scene, eyewitness radio report from the landing field. Heavy publicity about the first transatlantic passenger flight of the year by Zeppelin to the U.S. attracted a large number of journalists to the landing. (The airship had already made one round trip from Germany to Brazil that year.) Morrison's recording was not broadcast until the next day. Parts of his report were later dubbed onto the newsreel footage, giving the impression to many modern viewers, more accustomed to live television reporting, that the words and film were recorded together intentionally. Morrison's broadcast remains one of the most famous in history. His plaintive words, "Oh, the humanity!" resonate with the impact of the disaster, and have been widely used in culture (See below). Part of its poignancy is due to its being recorded at a slightly slower speed to the disk, so when played back at normal speed seeming to be at a faster delivery and higher pitch; when corrected, his account is less frantic sounding, though still impassioned.

Morrison's famous words should be understood in the context of the broadcast, in which he had repeatedly referred to the large ground crew engaged in landing the airship as a "mass of humanity." He used the phrase when it became clear that the burning wreckage was going to settle onto the ground and that the people underneath would probably not have time to escape it.

Spectacular movie footage and Morrison's passionate recording of the Hindenburg fire shattered public and industry faith in airships and marked the end of the giant, passenger-carrying dirigibles. Also contributing to the Zeppelins' downfall was the arrival of international passenger aeroplane travel and Pan American Airlines. Aircraft regularly crossed the Atlantic and Pacific oceans much faster than the 130 km/h (80 mph) of the Hindenburg. The one advantage that the Hindenburg had over aircraft was the comfort it afforded its passengers, much like that of an ocean liner.

Incredibly, despite there being four newsreel cameramen and one spectator filming at the time of the fire, none of the five film cameras were rolling at the moment the airship caught fire. The four newsreel cameras were aiming at the ground crew, possibly expecting ground crewmen to be pulled off the ground as had happened to the USS Akron on 10 May 1932, with two men falling to their deaths.

There had been a series of other airship accidents, none of them Zeppelins, prior to the Hindenburg fire. Many were caused by bad weather, and most of these accidents were dirigibles of British or U.S. manufacture. Both nations' techniques for dirigible manufacture were primitive compared to the expertise of the Germans. Zeppelins had had an impeccable safety record. The Graf Zeppelin had flown safely for more than 1.6 million km (1 million miles), including the first circumnavigation of the globe. The Zeppelin company prominently featured the fact that no passenger had been injured on one of their airships.

Death toll

Despite the violent fire, most of the crew and passengers survived. Of the 36 passengers and 61 crew, 13 passengers and 22 crew died. Also killed was one member of the ground crew, Navy Linesman Allen Hagaman. The two dogs on board the airship also died. Most deaths were not caused directly by the fire but were from jumping from the burning airship. Those passengers who rode the airship on its descent to the ground survived. Some deaths of crew members occurred because they wanted to save people on board the airship. In comparison, almost twice as many perished when the helium-filled USS Akron crashed.

Some of the survivors were saved by luck. Werner Franz, the fourteen year-old cabin boy, had been saved from the fire by a shower of water. A water ballast tank burst open, and he was soaked. He then made his way to the hatch and turned around and ran the other way, because the flames were being pushed by the wind towards the starboard side. Franz is one of the two people aboard who are still alive as of 2007. When the control car crashed on the ground, the officers had run, but became separated. First Officer Captain Albert Sammt found Captain Max Pruss rescuing passengers, Pruss's face was badly burned, but he would survive.

Captain Ernst Lehmann survived the crash, but though his burns were not as severe as those of Pruss, he seemed to have lost his will to live. He died the next day.

When the passenger Joseph Spahl saw the first sign of trouble he smashed the window with his movie camera (the film survived the disaster) and hung onto a nearby landing line (a parody to his stage acts; he was an acrobat) and jumped down when the airship was closer to the ground. He broke his ankle, but survived. His dog Ulla, one of the two dogs on board during the flight, died in the fire.

Of the six people in the bow of the airship, three survived; the flames shot through the nose like a blowtorch and the airship tilted upwards. Most of the people had fallen into the fire but the three hung on tight.

The four crew members in the tail fin all survived; they were closest to the origin of the fire but escaped when the tail hit the ground.

Cause of ignition

Sabotage theory

At the time of the disaster, sabotage was commonly put forward as the cause of the fire, in particular by Hugo Eckener, former head of the Zeppelin company and the "old man" of German airships. (Eckener later publicly endorsed the static spark theory.)

Another proponent of the sabotage hypothesis was Max Pruss, commander of the Hindenburg throughout the airship's career. Pruss flew on nearly every flight of the Graf Zeppelin until the Hindenburg was ready. In a 1960 interview conducted by Kenneth Leish for Columbia University's Oral History Research Office, Pruss said early dirigible travel was safe, and therefore he strongly believed that sabotage was to blame. He stated that on trips to South America, which was a popular destination for German tourists, both airships passed through thunderstorms and were struck by lightning but remained unharmed.

Eckener believed that the reason why Pruss, Lehmann, and Rosendahl all supported sabotage was because they may have felt guilty for their acts. Pruss made the sharp turn, Lehmann pressured Pruss to make it, and Rosendahl called the airship in..

Static spark theory

Another theory posits that the fire was started by a spark caused by a build-up of static electricity on the airship. Whether the spark ignited hydrogen or the outer skin has been disputed.

Proponents of the static spark theory point out that the airship's skin was not constructed in a way that allowed its charge to be evenly distributed throughout the craft. The skin was separated from the duralumin frame by non-conductive ramie cords, in effect electrically insulating the skin from the frame and allowing a difference in potential to form between them.

In order to make up for a delay of more than 12 hours in its transatlantic flight, the Hindenburg passed through a weather front of high humidity and high electrical charge. This made the airship's mooring lines wet and thus conductive and may have given its skin an electrical charge. When the mooring lines, which were connected to the frame, touched the ground, they would have grounded the frame but not the skin. Though they were dry, they could have gotten wet as the light rain fell. This could have caused a sudden potential difference between skin and frame (and the airship itself with the overlying air masses) and set off an electrical discharge — a spark. The spark would have jumped from the skin onto the metal framework. At the same time, hydrogen was leaking, and was ignited by the spark.

Some witnesses reported seeing a glow consistent with St. Elmo's fire along the tail portion of the airship just before the flames broke out, but these reports were made after the official inquiries were completed.

Lightning theory

A. J. Dessler, former director of the Space Science Laboratory at NASA's Marshall Space Flight Center and a critic of the incendiary paint theory (see below), favors a much simpler explanation for the conflagration: natural lightning. Like many other aircraft, the Hindenburg had been struck by lightning several times. This does not normally ignite a fire in hydrogen-filled airships, because the hydrogen is not mixed with oxygen. However, many fires started when lightning struck airships as they were venting hydrogen in preparation for landing, as the Hindenburg was doing at the time of the disaster. The vented hydrogen is mixed with air, making it readily combustible.

However, Dr. Eckener believed that the way the fire appeared was not consistent with that of a fire caused by lightning. Witnesses described the fire appearing in a wave motion. Eckener believed that the shape of the fire was consistent with that of a static spark.

Engine exhaust sparks theory

On the 70th anniversary of the accident, The Philadelphia Inquirer carried an article with yet another theory, based on an interview of ground crew member Robert Buchanan. He had been a young man on the crew manning the mooring lines.

The excessively stormy day had not only delayed the dirigible's arrival but also soaked him and many of the other mooring crew. As the airship was approaching the mooring mast, he noted that one of the engines, thrown into reverse for a hard turn, backfired, and a shower of sparks was emitted. He and others think that this was the trigger that ignited the craft, not static electricity, as the official version goes.

When the Hindenburg ignited, instead of an explosion there were just three sequential plumes of flame on the outer shell. Another ground crewman named Robert Shaw saw what looked like a blue ring behind the tail fin. He too had seen sparks coming out of the engine . The cotton cover with its coating, was quite flammable (this is disputed), and the heat and sparks from the backfiring engine may have been the ignition source.

However, it is unknown if sparks could ignite the doping compound, and Dr. Eckener rejected that hydrogen could be ignited when the theory was mentioned at an unofficial inquiry at night. This was a chat with crew members. He believed that the hydrogen could not have been ignited by any exhaust because the temperature is too low to ignite the hydrogen. The ignition temperature for hydrogen is 700 °C, but the sparks from the exhaust only reach 250 °C. The Zeppelin Company also carried out extensive tests, and hydrogen could never be ignited. Additionally, the fire was first seen at the top of the airship, not near the bottom.

Fire's initial fuel

Most current analysis of the fire assumes that ignition due to some form of electricity was the cause. However, there is still controversy over whether the fabric covering of the airship or the hydrogen used for buoyancy was the initial fuel for the fire.

The incendiary paint theory

The incendiary paint theory asserts that the major component in the fire was the skin because of the doping compound used on it.

Proponents point out that the coatings on the fabric contained both iron oxide and aluminium-impregnated cellulose acetate butyrate (CAB). These components are potentially reactive, even after fully setting.

Those skeptical of the incendiary paint theory cite recent technical papers which claim that even if the airship had been coated with actual rocket fuel, it would have taken many hours to burn — not the 32 to 37 seconds that it actually took. Proponents claim that this criticism does not take into account the conditions that lead to firestorms, such as convection and ignition from radiant energy.

The most conclusive proof against the fabric theory is in the photographs of the actual accident as well as the many airships which were not doped with aluminium powder and still exploded violently. When a single gas cell explodes, it creates a shock wave and heat. The shock wave tends to rip nearby bags which then explode themselves. In the case of the Alhorn disaster during World War I, explosions of airships in one shed caused the explosions of others in sheds nearby, wiping out the airships at the base.

Television investigations

The Discovery Channel series MythBusters explored the incendiary paint theory (IPT) and the hydrogen theory in an episode that aired 10 January 2007. The show's hosts, Adam Savage and Jamie Hyneman, demonstrated that when set alight with a blowtorch a 1:50 scale model of the Hindenburg burnt twice as fast in the presence of diffused hydrogen as without it. A thermite reaction was observed in the burning skin which would have accelerated the fire but they concluded that hydrogen was the main fuel. The hydrogen filled model produced a fire with flames that came out of the nose and resembled the newsreel footage of the Hindenburg disaster.

The program concluded that the IPT myth was "Busted".

The National Geographic program Seconds From Disaster had air crash investigator Greg Feith study all of the available evidence, including eyewitness accounts, interviews with the last two living survivors, newsreel footage, weather reports, & the Hindenburg blueprints. In the program Feith burns a sample of doped cloth and it took one minute to burn the whole piece. He concludes that the skin could not be the fatal accelerant. The program concludes that the puncture theory remains the most probable cause, as the airship made two sharp turns.

Memorial

The actual site of the Hindenburg crash at Lakehurst Naval Air Station (re-established as Naval Air Systems Command (NAVAIR) at Naval Air Engineering Station (NAES) Lakehurst, or "Navy Lakehurst" for short ) is marked with a chain-outlined pad and bronze plaque where the airship's gondola landed. It was dedicated on 6 May 1987; the 50th anniversary of the disaster. Hangar #1, which still stands, is where the airship was to be housed after landing. It was designated a Registered National Historic Landmark in 1968. Pre-registered tours are held through the Navy Lakehurst Historical Society. Due to security concerns, no foreign nationals are permitted on the tours.

See also

• Crash cover
• Hindenburg Disaster Newsreel Footage
• Herbert Morrison (announcer)
• List of airship accidents

• Zeppelin
• Harold G. Dick was an American engineer who flew on most of the Hindenburg flights.
• The Zeppelin Museum Friedrichshafen displays a reconstruction of a 33 m section of the Hindenburg.
• Hindenburg: The Untold Story was a docudrama aired on the 70th anniversary of the disaster, 6 May 2007.