Hindenburg disaster
Overview
The Hindenburg disaster took place on Thursday, May 6, 1937, as the German passenger airship LZ 129 Hindenburg
LZ 129 Hindenburg
LZ 129 Hindenburg was a large German commercial passenger-carrying rigid airship, the lead ship of the Hindenburg class, the longest class of flying machine and the largest airship by envelope volume...

 caught fire and was destroyed during its attempt to dock with its mooring mast
Mooring mast
A mooring mast, or mooring tower, is a structure designed to allow for the docking of an airship outside of an airship hangar or similar structure...

 at the Lakehurst Naval Air Station
Naval Air Engineering Station Lakehurst
JB MDL Lakehurst is a United States Navy base located approximately south-southeast of Trenton, New Jersey. Lakehurst is under the jurisdiction of the Naval Air Systems Command...

, which is located adjacent to the borough of Lakehurst, New Jersey
Lakehurst, New Jersey
Lakehurst is a Borough in Ocean County, New Jersey, United States. As of the United States 2010 Census, the borough population was 2,654.Lakehurst was incorporated as a borough by an Act of the New Jersey Legislature on April 7, 1921, from portions of Manchester Township, based on the results of a...

. Of the 97 people on board (36 passengers, 61 crew), there were 35 fatalities as well as one death among the ground crew.

The disaster was the subject of spectacular newsreel
Newsreel
A newsreel was a form of short documentary film prevalent in the first half of the 20th century, regularly released in a public presentation place and containing filmed news stories and items of topical interest. It was a source of news, current affairs and entertainment for millions of moviegoers...

 coverage, photographs, and Herbert Morrison
Herbert Morrison (announcer)
Herbert Morrison was an American radio reporter best known for his dramatic report of the Hindenburg disaster, a catastrophic fire that destroyed the LZ 129 Hindenburg zeppelin on May 6, 1937, killing 36 people.-Hindenburg disaster:...

's recorded radio eyewitness report from the landing field, which was broadcast the next day.
Encyclopedia
The Hindenburg disaster took place on Thursday, May 6, 1937, as the German passenger airship LZ 129 Hindenburg
LZ 129 Hindenburg
LZ 129 Hindenburg was a large German commercial passenger-carrying rigid airship, the lead ship of the Hindenburg class, the longest class of flying machine and the largest airship by envelope volume...

 caught fire and was destroyed during its attempt to dock with its mooring mast
Mooring mast
A mooring mast, or mooring tower, is a structure designed to allow for the docking of an airship outside of an airship hangar or similar structure...

 at the Lakehurst Naval Air Station
Naval Air Engineering Station Lakehurst
JB MDL Lakehurst is a United States Navy base located approximately south-southeast of Trenton, New Jersey. Lakehurst is under the jurisdiction of the Naval Air Systems Command...

, which is located adjacent to the borough of Lakehurst, New Jersey
Lakehurst, New Jersey
Lakehurst is a Borough in Ocean County, New Jersey, United States. As of the United States 2010 Census, the borough population was 2,654.Lakehurst was incorporated as a borough by an Act of the New Jersey Legislature on April 7, 1921, from portions of Manchester Township, based on the results of a...

. Of the 97 people on board (36 passengers, 61 crew), there were 35 fatalities as well as one death among the ground crew.

The disaster was the subject of spectacular newsreel
Newsreel
A newsreel was a form of short documentary film prevalent in the first half of the 20th century, regularly released in a public presentation place and containing filmed news stories and items of topical interest. It was a source of news, current affairs and entertainment for millions of moviegoers...

 coverage, photographs, and Herbert Morrison
Herbert Morrison (announcer)
Herbert Morrison was an American radio reporter best known for his dramatic report of the Hindenburg disaster, a catastrophic fire that destroyed the LZ 129 Hindenburg zeppelin on May 6, 1937, killing 36 people.-Hindenburg disaster:...

's recorded radio eyewitness report from the landing field, which was broadcast the next day. The actual cause of the fire remains unknown, although a variety of hypotheses have been put forward for both the cause of ignition and the initial fuel for the ensuing fire. The incident shattered public confidence in the giant, passenger-carrying rigid airship
Airship
An airship or dirigible is a type of aerostat or "lighter-than-air aircraft" that can be steered and propelled through the air using rudders and propellers or other thrust mechanisms...

 and marked the end of the airship era.

Flight

After opening its 1937 season by completing a single round trip passage to Rio de Janeiro
Rio de Janeiro
Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...

 in late March, the Hindenburg departed from Frankfurt on the evening of May 3 on the first of its 10 round trips between Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 scheduled for its second year of commercial service. The United States' American Airlines
American Airlines
American Airlines, Inc. is the world's fourth-largest airline in passenger miles transported and operating revenues. American Airlines is a subsidiary of the AMR Corporation and is headquartered in Fort Worth, Texas adjacent to its largest hub at Dallas/Fort Worth International Airport...

, which had contracted with the operators of the Hindenburg, was prepared to shuttle fliers from Lakehurst to Newark for connections to airplane flights.

Except for strong headwinds which slowed its passage, the Hindenburg's crossing was otherwise unremarkable until the airship's attempted early evening landing at Lakehurst three days later on May 6. Although carrying only half its full capacity of passengers (36 of 70) and 61 crew members (including 21 training crew members), the Hindenburg's return flight was fully booked with many of those passengers planning to attend the festivities for the coronation
Coronation
A coronation is a ceremony marking the formal investiture of a monarch and/or their consort with regal power, usually involving the placement of a crown upon their head and the presentation of other items of regalia...

 of King George VI
George VI of the United Kingdom
George VI was King of the United Kingdom and the Dominions of the British Commonwealth from 11 December 1936 until his death...

 in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 the following week.

The airship was hours behind schedule when it passed over Boston
Boston
Boston is the capital of and largest city in Massachusetts, and is one of the oldest cities in the United States. The largest city in New England, Boston is regarded as the unofficial "Capital of New England" for its economic and cultural impact on the entire New England region. The city proper had...

 on the morning of 6 May, and its landing at Lakehurst was expected to be further delayed because of afternoon thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

s. Advised of the poor weather conditions at Lakehurst, Captain Max Pruss
Max Pruss
Max Pruss was the commander of the LZ 129 Hindenburg on its last voyage and a surviving crew member of the zeppelin disaster.-Biography:...

 charted a course over Manhattan, causing a public spectacle as people rushed out into the street to catch sight of the airship. After passing over the field at 4 p.m., Captain Pruss took passengers on a tour over the seasides of New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

 while waiting for the weather to clear. After finally being notified at 6:22 p.m. that the storms had passed, the airship headed back to Lakehurst to make its landing almost half a day late. However, as this would leave much less time than anticipated to service and prepare the airship for its scheduled departure back to Europe, the public was informed that they would not be permitted at the mooring location or be able to visit aboard the Hindenburg during its stay in port.

Landing timeline

Around 7:00 p.m. local daylight saving time, at an altitude of 650 feet (198.1 m), the
Hindenburg approached the Lakehurst Naval Air Station. This was to be a high landing, known as a flying moor, because the airship would drop its landing ropes and mooring cable at a high altitude, and then be winched down to the mooring mast. This type of landing maneuver would reduce the number of ground crew, but would require more time.

7:09: The airship made a sharp full speed left turn to the west around the landing field because the ground crew was not ready.

7:11: The airship turned back toward the landing field and valved gas. All engines idled ahead and the airship began to slow.

7:14: At altitude 394 feet (120.1 m), Captain Pruss ordered all engines full astern to try to brake the airship.

7:17: The wind shifted direction to southwest, and Captain Pruss was forced to make a second, sweeping sharp turn, this time towards starboard.

7:18: The airship made another sharp turn and dropped 300, 300 and 500 kg of water ballast in successive drops because the airship was stern heavy. Six men (three of whom were killed in the accident) were also sent to the bow to trim the airship. These methods worked and the airship was on even keel as it stopped.

7:21: At altitude 295 feet (89.9 m), the mooring lines were dropped from the bow, the starboard line being dropped first, followed by the port line. The port line was overtightened as it was connected to the post of the ground winch; the starboard line had still not been connected.

First hints of disaster

At 7:25pm, a few witnesses saw the fabric ahead of the upper fin flutter as if gas were leaking. Witnesses also reported seeing blue discharges—possibly static electricity
St. Elmo's fire
St. Elmo's fire is a weather phenomenon in which luminous plasma is created by a coronal discharge from a grounded object in an electric field in the atmosphere St. Elmo's fire is named after St. Erasmus of Formiae St. Elmo's fire (also St. Elmo's light) is a weather phenomenon in which luminous...

—moments before the fire on top and in the back of the ship near the point where the flames first appeared. Several other eyewitness testimonies suggest that the first flame appeared on the port side just ahead of the port fin, and was followed by flames which burned on top. Commander Rosendahl testified to the flames being "mushroom-shaped" and knew at once that the airship was doomed. One witness on the starboard side reported a fire beginning lower and behind the rudder on that side. On board, people heard a muffled explosion and those in the front of the ship felt a shock as the port trail rope overtightened; the officers in the control car initially thought the shock was due to a broken rope.

Disaster

At 7:25 p.m. proper time the Hindenburg caught fire and quickly became engulfed in flames. Where the fire started is unknown; several witnesses on the port side saw yellow-red flames first jump forward of the top fin, around the vent of cell 4. Other witnesses on the port side noted the fire actually began just ahead of the horizontal port fin, only then followed by flames in front of the upper fin. One, with views of the starboard side, saw flames beginning lower and farther aft, near cell 1. No. 2 Helmsman Helmut Lau also testified seeing the flames spreading from cell 4 into starboard. Although there were five newsreel cameramen and at least one spectator known to be filming the landing, no camera was rolling when the fire started and therefore there is no motion picture record of where it first broke out at the instant of ignition.

Wherever it started, the flames quickly spread forward. Instantly, a water tank and a fuel tank burst out of the hull due to the shock of the blast. This shock also caused a crack behind the passenger decks, and the rear of the structure imploded. The buoyancy was lost on the stern of the ship, and the bow lurched upwards as the falling stern stayed in trim.

As the Hindenburgs tail crashed into the ground, a burst of flame came out of the nose, killing nine of the 12 crew members in the the bow. There was still gas in the bow section of the ship, so the bow continued to point upward as the stern collapsed down. The crack behind the passenger decks collapsed inward, causing the gas cell to explode. The scarlet lettering "Hindenburg" became erased by flames while the airship's bow lowered. The airship's gondola wheel touched the ground, causing the bow to bounce up slightly as one final gas cell burned away. At this point, most of the fabric on the hull had also burned away and the bow finally crashed to the ground. Although the hydrogen had finished burning, the Hindenburg's diesel fuel burned for several more hours.

The time it took for the airship to be completely destroyed has been disputed. Some observers believe it took 34 seconds, others say it took 32 or 37 seconds. Since none of the newsreel cameras were filming the airship when the fire started, the time of the start of the fire can only be estimated from various eyewitness accounts, and will never be known accurately. One careful analysis of the flame spread, by Addison Bain
Addison Bain
Addison Bain is a retired NASA scientist and founding member of the National Hydrogen Association who is credited with postulating the Incendiary-Paint Theory , which posits that the Hindenburg disaster was caused by the electrical ignition of lacquer- and metal-based paints used on the outer hull...

 of NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

, gives the flame front spread rate across the fabric skin as about 49 ft/s (14.9 m/s), which would have resulted in a total destruction time of about 16 seconds (245 m / 15 m/s = 16.3 s). Some of the duralumin framework of the airship was salvaged and shipped back to Germany where it was recycled and used in the construction of military aircraft for the Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....

 as were the frames of the LZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin was a German built and operated passenger-carrying hydrogen-filled rigid airship which operated commercially from 1928 to 1937. It was named after the German pioneer of airships, Ferdinand von Zeppelin, who was a Graf or Count in the German nobility. During its operating life,...

and LZ 130 Graf Zeppelin II as well when both were scrapped in 1940.

Historic newsreel coverage

The disaster
Disaster
A disaster is a natural or man-made hazard that has come to fruition, resulting in an event of substantial extent causing significant physical damage or destruction, loss of life, or drastic change to the environment...

 is well recorded because of the significant extent of newsreel
Newsreel
A newsreel was a form of short documentary film prevalent in the first half of the 20th century, regularly released in a public presentation place and containing filmed news stories and items of topical interest. It was a source of news, current affairs and entertainment for millions of moviegoers...

 coverage and photographs, as well as Herbert Morrison
Herbert Morrison (announcer)
Herbert Morrison was an American radio reporter best known for his dramatic report of the Hindenburg disaster, a catastrophic fire that destroyed the LZ 129 Hindenburg zeppelin on May 6, 1937, killing 36 people.-Hindenburg disaster:...

's live coverage on-the-scene, eyewitness radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 report being made from the landing field for station WLS
WLS (AM)
WLS is a Chicago clear-channel AM station on 890 kHz. It uses C-QUAM AM stereo and transmits with 50,000 watts from transmitter and towers on the south edge of Tinley Park, Illinois....

 in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

 which was broadcast the next day. 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.) Parts of the Morrison report were later dubbed onto the newsreel footage and this gave the impression to many modern viewers, more accustomed to live television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...

 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 popular culture. Part of the poignancy of Morrison's commentary is due to its being recorded at a slightly slower speed to the disk, so when played back at normal speed it seems to be at a faster delivery and higher pitch. When corrected, his account is less frantic sounding, though still impassioned.
Spectacular motion picture 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 airships. Also contributing to the Zeppelins' downfall was the arrival of international passenger air travel and Pan American Airlines. Aircraft regularly crossed the Atlantic and Pacific oceans much faster than the 130 km/h (80 mi/h) 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.

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. Zeppelins had an impeccable safety record. The Graf Zeppelin
LZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin was a German built and operated passenger-carrying hydrogen-filled rigid airship which operated commercially from 1928 to 1937. It was named after the German pioneer of airships, Ferdinand von Zeppelin, who was a Graf or Count in the German nobility. During its operating life,...

had flown safely for more than 1.6 million km (1 million miles), including the first circumnavigation
Circumnavigation
Circumnavigation – literally, "navigation of a circumference" – refers to travelling all the way around an island, a continent, or the entire planet Earth.- Global circumnavigation :...

 of the globe by an airship. The Zeppelin company's promotions prominently featured the fact that no passenger had been injured on one of their airships.

Death toll

Despite the violent fire, many 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, civilian linesman Allen Hagaman. The majority of the crew who died were up inside the ship's hull, where they either did not have a clear escape route or else were close to the bow of the ship, which hung burning in the air too long for most of them to escape the fire. Most of the passengers who died were trapped in the starboard side of the passenger deck. Not only was the wind blowing the fire toward the starboard side, but the ship also rolled slightly to starboard as it settled to the ground, with much of the upper hull on that part of the ship collapsing outboard of the starboard observation windows, thus cutting off the escape of many of the passengers on that side. To make matters worse, the sliding door leading from the starboard passenger area to the central foyer and the gangway stairs (through which rescuers led a number of passengers to safety) jammed shut during the crash, further trapping those passengers on the starboard side. Nonetheless, some did manage to escape from the starboard passenger decks. A number of others did not. By contrast, all but a few of the passengers on the port side of the ship survived the fire, with some of them escaping virtually unscathed. Although the most famous of airship disasters, it was not the worst. Just over twice as many perished (73 of 76 on board) when the helium-filled U.S. Navy scout airship USS Akron crashed at sea off the New Jersey coast four years earlier on April 4, 1933.

Some of the survivors were saved by luck. Werner Franz, the 14 year-old cabin boy, was initially dazed by the realization that the ship was on fire. As he stood near the officer's mess where he had been putting away dishes moments before, a water tank above him burst open, and he was suddenly soaked to the skin. Not only did this snap him back to his senses, as he later told interviewers, but it also put out the fire around him. He then made his way to a nearby hatch through which the kitchen had been provisioned before the flight, and dropped through it just as the forward part of the ship was briefly rebounding into the air. He began to run toward the starboard side, but stopped and turned around and ran the other way, because the flames were being pushed by the wind in that same direction. He made it clear of the wreck with little more than singed eyebrows and soaking wet clothes. Werner Franz is one of the two people aboard who are still alive as of 2008.

When the control car crashed on the ground, most of the officers had leapt through the windows, but became separated. First Officer Captain Albert Sammt found Captain Max Pruss trying to re-enter the wreckage to look for survivors. Pruss's face was badly burned, and he required months of hospitalization and reconstructive surgery, but he survived.

Captain Ernst Lehmann escaped the crash with burns to his head and arms and severe burns across most of his back. Though his burns did not seem quite as severe as those of Pruss, he died at a nearby hospital the next day.

When passenger Joseph Späh, a vaudeville comic acrobat, saw the first sign of trouble he smashed the window with his movie camera, with which he had been filming the landing (the film survived the disaster). As the ship neared the ground he lowered himself out the window and hung onto the window ledge, letting go when the ship was perhaps 20 feet above the ground. His acrobat's instincts kicked in, and Späh kept his feet under him and attempted to do a safety roll when he landed. He injured his ankle nonetheless, and was dazedly crawling away when a member of the ground crew came up, slung the diminutive Späh under one arm, and ran him clear of the fire.

Of the 12 crewmen in the bow of the airship, only three survived. Four of these 12 men were standing on the mooring shelf, a platform up at the very tip of the bow from which the forward-most landing ropes and the steel mooring cable were released to the ground crew, and which was directly at the forward end of the axial walkway and just ahead of gas cell #16. The rest were standing either along the lower keel walkway ahead of the control car, or else on platforms beside the stairway leading up the curve of the bow to the mooring shelf. During the fire the bow hung in the air at roughly a 45-degree angle and flames shot forward through the axial walkway, bursting through the bow (and the bow gas cells) like a blowtorch. The three men from the forward section who survived (elevatorman Kurt Bauer, cook Alfred Grözinger, and electrician Josef Leibrecht) were those furthest aft of the bow, and two of them (Bauer and Grözinger) happened to be standing near two large triangular air vents, through which cool air was being drawn by the fire. Neither of these men sustained more than superficial burns. Most of the men standing along the bow stairway either fell aft into the fire, or tried to leap from the ship when it was still too high in the air. Three of the four men standing on the mooring shelf inside the very tip of the bow were actually taken from the wreck alive, though one (Erich Spehl, a rigger) died shortly afterward in the Air Station's infirmary, and the other two (helmsman Alfred Bernhard and apprentice elevatorman Ludwig Felber) were reported by newspapers to have initially survived the fire, and then to subsequently have died at area hospitals during the night or early the following morning.

The four crew members in the tail fin all survived; they were closest to the origin of the fire but sheltered by the structure of the lower fin. They escaped by climbing out the fin's access hatch when the tail hit the ground.

Hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 fires are notable for being less destructive to immediate surroundings than gasoline explosions because of the buoyancy of H2, which causes heat of combustion to be released upwards more than circumferentially as the leaked mass ascends in the atmosphere; hydrogen fires are more survivable than fires of gasoline and of wood. The hydrogen in the Hindenburg burned out within about 90 seconds.

Sabotage hypothesis

At the time of the disaster, sabotage was commonly put forward as the cause of the fire, initially by Hugo Eckener
Hugo Eckener
Dr. Hugo Eckener was the manager of the Luftschiffbau Zeppelin during the inter-war years, and was commander of the famous Graf Zeppelin for most of its record-setting flights, including the first airship flight around the world, making him the most successful airship commander in history...

, former head of the Zeppelin Company and the "old man" of German airships. Eckener later publicly endorsed the static spark hypothesis. Eckener, who was at the time on a lecture tour in Austria, was awakened at about 2:30 in the morning (8:30 PM Lakehurst time, or approximately an hour after the crash) by the ringing of his bedside telephone. It was a Berlin representative of the New York Times with news that the Hindenburg "exploded yesterday evening at 7 p.m [sic] above the airfield at Lakehurst." By the time he left the hotel the next morning to travel to Berlin for a briefing on the disaster, the only answer that he had for the reporters waiting outside to question him was that based on what he knew, that the Hindenburg had "exploded over the airfield", sabotage might be a possibility. However, as he learned more about the disaster, particularly that the airship had burned rather than actually "exploding", he grew more and more convinced that static discharge, rather than sabotage, was the actual culprit.

Commander Charles Rosendahl, commander of the Naval Air Station at Lakehurst and the man in overall charge of the ground-based portion of the Hindenburg's landing maneuver, also came to believe that the Hindenburg had been sabotaged. He laid out a general case for sabotage in his 1938 book What About the Airship?, which was as much an extended argument for the further development of the rigid airship as it was an historical overview of the airship.

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.

The airship's crew refused to believe that one of them would commit an act of sabotage, insisting only a passenger could have destroyed the airship. A suspect favored by Commander Rosendahl, Captain Pruss, and others among the Hindenburg's crew, was passenger Joseph Späh, a German acrobat who survived the fire. He brought with him a dog, a German shepherd named Ulla, as a surprise for his children. (Ulla did not survive.) He reportedly made a number of unaccompanied visits to feed his dog, who was being kept in a freight room near the stern of the ship. Those who suspected Späh based their suspicions primarily on those trips into the ship's interior to feed his dog, that according to some of the stewards Späh had told anti-Nazi jokes during the flight, recollections by stewards that Späh had seemed agitated by the repeated delays in landing, and that he was an acrobat who could conceivably climb into the airship's rigging to plant a bomb.

In 1962, A. A. Hoehling published Who Destroyed the Hindenburg?, where he rejected all theories but sabotage, and named a crew member as the suspect. Eric Spehl, a rigger on the Hindenburg who died in the fire, was named as the saboteur. Ten years later, Michael MacDonald Mooney's book, The Hindenburg, which was based heavily on Hoehling's sabotage hypothesis, also identified Spehl as the saboteur; Mooney's book was made into the movie The Hindenburg
The Hindenburg (film)
The Hindenburg is a 1975 American film based on the disaster of the German airship Hindenburg. The film stars George C. Scott. It was produced and directed by Robert Wise, and was written by Nelson Gidding, Richard Levinson and William Link based on the book of the same name by Michael M. Mooney .A.A...

,
whose producers were sued by Hoehling for plagiarism, but Hoehling lost because he had presented his sabotage hypothesis as historical fact, and one cannot claim ownership of historical facts.

Hoehling claimed the following in naming Spehl as the culprit:
  • Spehl's girlfriend had communist beliefs and anti-Nazi connections.
  • The fire's origin was near the catwalk running through Gas Cell 4, which was an area of the ship generally off-limits to anyone other than Spehl and his fellow riggers.
  • Rumors that the Gestapo had investigated Spehl's possible involvement in 1938.
  • Spehl's interest in amateur photography, making him familiar with flashbulbs that could have served as an igniter.
  • The discovery by representatives of the NYPD Bomb Squad of a substance that was later determined to likely be "the insoluble residue from the depolarizing element of a small, dry battery." (Hoehling postulated that a dry cell battery could have powered a flashbulb in an incendiary device.)
  • The discovery by FBI Agents of a yellow substance on the valve cap of the airship between cells 4 and 5 where the fire was first reported. Some have suggested this to be sulfur, which can ignite hydrogen. (However, a further investigation into this suggested that the residue was actually from a fire extinguisher in the stern of the ship.)
  • A flash or a bright reflection that crew members near the lower fin had seen just before the fire.


Hoehling's (and later Mooney's) hypothesis goes on to say that it is unlikely that Spehl wanted to kill people, and that he intended for the airship to burn after the landing instead. However, with the ship already over 12 hours late, Spehl was in the end unable to find an excuse to reset the timer on his bomb.

During the landing maneuver, rigger Hans Freund dropped a landing line in front of the lower fin. The line became caught in the bracing wires of the airship, so No. 2 helmsman Helmut Lau climbed up from the lower fin to release it. According to Hoehling, Freund described a flash like a flashbulb's, and Lau said he saw a brilliant reflection between cells 4 and 5. They then heard a muffled detonation and a thud as the Hindenburg's back broke. Some believe that this is evidence for sabotage. Others believe Freund was actually looking rearward, away from cells 4 and 5, but that Rudolf Sauter, another crew member in the lower fin had seen the flash.

Since the publication of Hoehling's book, most airship historians, including Dr. Douglas Robinson, have dismissed Hoehling's sabotage hypothesis because no solid evidence was ever presented to support it. No pieces of a bomb were ever discovered (and in fact there is no evidence in existing documentation that the sample collected from the wreckage, and determined to be residue from a dry cell battery, was found anywhere near the stern of the airship), and on closer examination the evidence against Spehl and his girlfriend turned out to be largely circumstantial.

It has even been suggested that Adolf Hitler
Adolf Hitler
Adolf Hitler was an Austrian-born German politician and the leader of the National Socialist German Workers Party , commonly referred to as the Nazi Party). He was Chancellor of Germany from 1933 to 1945, and head of state from 1934 to 1945...

 himself ordered the Hindenburg to be destroyed in retaliation for Eckener's anti-Nazi opinions.

However, opponents of the sabotage hypothesis argued that only speculation supported sabotage as a cause of the fire, and no credible evidence of sabotage was produced at any of the formal hearings. Eric Spehl died in the fire and was therefore unable to refute the accusations that surfaced a quarter of a century later. The FBI investigated Joseph Späh and reported finding no evidence of Späh having any connection to a sabotage plot. According to his wife, Evelyn, Späh was quite upset over the accusations - she later recalled that her husband was outside their home cleaning windows when he first learned that he was suspected of sabotaging the Hindenburg, and was so shocked by the news that he almost fell off the ladder on which he was standing.

Neither the German nor the American investigation endorsed any of the sabotage theories. Proponents of the sabotage hypothesis argue that any finding of sabotage would have been an embarrassment for the Nazi regime, and they speculate that such a finding by the German investigation was suppressed for political reasons.

Eckener believed that the reason why Pruss, Lehmann, and Rosendahl 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 hypothesis

Hugo Eckener argued that the fire was started by an electric spark
Electric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...

 caused by a buildup of static electricity
Static electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...

 on the airship. The spark ignited hydrogen or the outer skin (see Incendiary paint hypothesis below).

Proponents of the static spark hypothesis point out that the airship's skin was not constructed in a way that allowed its charge to be distributed evenly throughout the craft. The skin was separated from the duralumin
Duralumin
Duralumin is the trade name of one of the earliest types of age-hardenable aluminium alloys. The main alloying constituents are copper, manganese, and magnesium. A commonly used modern equivalent of this alloy type is AA2024, which contains 4.4% copper, 1.5% magnesium, 0.6% manganese and 93.5%...

 frame by non conductive ramie
Ramie
Ramie is a flowering plant in the nettle family Urticaceae, native to eastern Asia. It is a herbaceous perennial growing to 1–2.5 m tall; the leaves are heart-shaped, 7–15 cm long and 6–12 cm broad, and white on the underside with dense small hairs—this gives it a silvery appearance;...

 cords which had been lightly covered in metal to improve conductivity, however not very effectively, allowing a large difference in potential
Potential
*In linguistics, the potential mood*The mathematical study of potentials is known as potential theory; it is the study of harmonic functions on manifolds...

 to form between them.

In order to make up for the delay of more than 12 hours in its transatlantic flight, the Hindenburg passed through a weather front of high humidity and high electrical charge. The storm could have made the airship's mooring lines wet and thus conductive, and may also have built up an electrical charge in its skin. The mooring lines also could have gotten wet as a light rain continued to fall at Lakehurst.

When the mooring lines, which were connected to the frame, touched the earth they would have grounded the frame but not the skin. This would have caused a sudden potential difference between skin and frame (and the airship itself with the overlying air masses) and would have set off an electrical discharge — a spark. Seeking the quickest way to the ground the spark would have jumped from the skin onto the metal framework, igniting the leaking hydrogen.

In his 1964 book, LZ-129 Hindenburg, Zeppelin historian Dr. Douglas Robinson points out that although ignition of free hydrogen by static discharge had become a favored hypothesis, no such discharge was seen by any of the witnesses who testified at the official investigation into the accident back in 1937. He goes on to write:
Unlike other witnesses to the fire whose view of the port side of the ship had the light of the setting sun behind the ship, Professor Heald's view of the starboard side of the ship against a backdrop of the darkening eastern sky would have made the dim blue light of a static discharge (or burning hydrogen) atop the ship more easily visible.

Harold G. Dick was Goodyear Zeppelin's representative with Luftschiffbau Zeppelin during the mid-1930s. He flew on test flights of the Hindenburg and its sister ship, the Graf Zeppelin II. He also flew on numerous flights in the original Graf Zeppelin and 10 round trip crossings of the north and south Atlantic in the Hindenburg. In his book The Golden Age of the Great Passenger Airships Graf Zeppelin & Hindenburg, he observes:
In addition to Dick's observations is the fact that during the Graf Zeppelin II's early test flights, measurements were taken of the airship's static charge. It is clear that Dr. Ludwig Durr and the other engineers at Luftschiffbau Zeppelin took the static discharge hypothesis seriously and considered the insulation of the fabric from the frame to be a design flaw in the Hindenburg. Thus, the German Inquiry concluded that the insulation of the outer covering caused a spark to jump onto a nearby piece of metal, therefore igniting the hydrogen. In lab experiments, using the Hindenburg's outer covering and a static ignition, hydrogen was able to be ignited, but with the covering of the LZ 127 Graf Zeppelin, nothing happened. These findings were not well-publicized and covered up, perhaps to avoid embarrassment of such an engineering flaw in the face of the Third Reich.

A variant of the static spark hypothesis, presented by Addison Bain
Addison Bain
Addison Bain is a retired NASA scientist and founding member of the National Hydrogen Association who is credited with postulating the Incendiary-Paint Theory , which posits that the Hindenburg disaster was caused by the electrical ignition of lacquer- and metal-based paints used on the outer hull...

, is that a spark between inadequately grounded fabric cover segments of the Hindenburg itself started the fire, and that the spark had ignited the "highly flammable" outer skin. The Hindenburg had a cotton skin covered with a finish known as "dope"
Aircraft dope
thumb|right|[[United Kingdom military aircraft serials|2699]] a [[World War I]] [[Royal Aircraft Factory B.E.2]] finished in a clear dopeAircraft dope is a plasticised lacquer that is applied to fabric-covered aircraft...

. It is a common term for a plasticised
Plasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...

 lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...

 that provides stiffness, protection, and a lightweight, airtight seal to woven fabrics. In its liquid forms, dope is highly flammable, but the flammability of dry dope depends upon its base constituents, with, for example, butyrate dope being far less flammable than cellulose nitrate. Proponents of this hypothesis claim that when the mooring line touched the ground, a resulting spark could have ignited the dope in the skin.

Lightning hypothesis

A. J. Dessler, former director of the Space Science Laboratory at NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's Marshall Space Flight Center
Marshall Space Flight Center
The George C. Marshall Space Flight Center is the U.S. government's civilian rocketry and spacecraft propulsion research center. The largest center of NASA, MSFC's first mission was developing the Saturn launch vehicles for the Apollo moon program...

 and a critic of the incendiary paint hypothesis (see below), favors a much simpler explanation for the conflagration: lightning
Lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...

. 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 as ballast in preparation for landing, which the Hindenburg was doing at the time of the disaster. The vented hydrogen mixes with the 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. He also asserted that witnesses did not see any lightning storms during the airship's final approach.

Engine failure hypothesis

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

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. After being interviewed by Addison Bain, Buchanan believed that the airship's outer skin was ignited by engine sparks. Another ground crewman, Robert Shaw, saw blue ring behind the tail fin and had also seen sparks coming out of the engine. Shaw believed that the blue ring he saw was leaking hydrogen which was ignited by the engine sparks.

Dr. Eckener rejected the idea that hydrogen could have been ignited by an engine backfire when that hypothesis was mentioned at an unofficial inquiry, which was a chat with crew members. Dr. Eckener 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 (1,292 °F), but the sparks from the exhaust only reach 250 °C (482 °F). The Zeppelin Company also carried out extensive tests and hydrogen had never ignited. Additionally, the fire was first seen at the top of the airship, not near the bottom of the hull.

Fire's initial fuel

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

Incendiary paint hypothesis

The incendiary paint hypothesis was proposed in 1996 by retired NASA scientist Addison Bain
Addison Bain
Addison Bain is a retired NASA scientist and founding member of the National Hydrogen Association who is credited with postulating the Incendiary-Paint Theory , which posits that the Hindenburg disaster was caused by the electrical ignition of lacquer- and metal-based paints used on the outer hull...

, stating that the doping compound of the airship was the cause of the fire. The hypothesis is limited to the source of ignition and to the flame front propagation, not to the source of most of the burning material, as once the fire started and spread the hydrogen clearly must have burned (although proponents of the IPT claim that hydrogen burned much later in the fire). Instead, for this topic the incendiary paint hypothesis asserts that the major component in starting the fire and feeding its spread was the canvas skin because of the compound used on it.

Proponents of this hypothesis point out that the coatings on the fabric contained both iron oxide and aluminum-impregnated cellulose acetate butyrate (CAB). These components remain potentially reactive even after fully setting. In fact, iron oxide and aluminum can be used as components of solid rocket
Solid rocket
A solid rocket or a solid-fuel rocket is a rocket engine that uses solid propellants . The earliest rockets were solid-fuel rockets powered by gunpowder; they were used by the Chinese in warfare as early as the 13th century and later by the Mongols, Arabs, and Indians.All rockets used some form of...

 fuel or thermite
Thermite
Thermite is a pyrotechnic composition of a metal powder and a metal oxide that produces an exothermic oxidation-reduction reaction known as a thermite reaction. If aluminium is the reducing agent it is called an aluminothermic reaction...

. For example, the propellant for the Space Shuttle solid rocket booster includes both "aluminum (fuel, 16%), (and) iron oxide (a catalyst, 0.4%)". However, the coating applied to Hindenburg's covering did not have a sufficient quantity of any material capable of acting as an oxidizer, which is a necessary component of rocket fuel.

Bain received permission from the German government to search their archives and discovered evidence that, during the Nazi regime, German scientists concluded the dope on the Hindenburg's fabric skin was the cause of the conflagration. Bain interviewed the wife of the investigation's lead scientist, and she stated that her husband had told her about the conclusion and instructed her to tell no one, presumably because it would have embarrassed the Nazi government.

In television shows, Bain tried to prove the flammability of the fabric by igniting it with an electrical machine. Although Bain's fabric ignited, critics point out that Bain had to correctly position the fabric so it would be ignited, and he used a Jacob's Ladder
Spark gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the voltage difference between the conductors exceeds the gap's breakdown voltage, a spark forms,...

 with a continuous electric current inconsistent with atmospheric conditions. However, critics point out it was not possible for the fabric to have been ignited by a brief and low temperature static spark. Additionally, the German scientists at the time concluded that it was the poor conductivity, not the flammability of the doping compound, that lead to the ignition of hydrogen.

Critics point out that port side witnesses on the field, as well as crew members stationed in the stern, saw a glow inside Cell 4 before any fire broke out of the skin, indicating that the fire began inside the airship or that after the hydrogen ignited, the invisible fire fed on the gas cell material. Newsreel footage clearly show that the fire was burning inside the structure.

Proponents of the paint hypothesis claim that the glow can be explained. They claim that what witnesses saw was the fire on the starboard side (another proponent claims that a witness saw the fire start from the starboard side) through the outer skin, looking like a glow. However, photographs of the early stages of the fire show the gas cells of the Hindenburg's entire aft section fully aflame. Burning gas spewing upward from the top of the airship was causing low pressure inside, allowing atmospheric pressure to press the skin inwards. It should also be noted that not all fabric on the Hindenburg burned. The fabric on several of the tail structures was not completely consumed. That the fabric not near the hydrogen fire extinguished itself is not consistent with the "explosive" dope hypothesis.

Occasionally the Hindenburg's varnish is incorrectly identified as, or stated being similar to, cellulose nitrate, which, like most nitrates burns very readily. Instead, the cellulose acetate butyrate (CAB) used to seal the zeppelin's skin is rated by the plastics industry as combustible but nonflammable. That is, it will burn if placed within a fire but is not readily ignited. In fact, it is considered self extinguishing without some kind of additional fuel. That many pieces of the Hindenburg's skin survived despite such a fierce fire is cited as proof.

While not issuing an opinion about whether it was the hydrogen or the treated skin of the airship that ignited first, the TV show MythBusters
MythBusters
MythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...

explored the incendiary paint hypothesis. Their findings indicated that the aluminum/iron oxide ratios in the Hindenburg's skin, while certainly flammable, were not enough on their own to destroy the zeppelin. Had the skin in fact contained enough metal to produce pure thermite, the Hindenburg would have been too heavy to fly. And even if it somehow did, a pure thermite reaction (at ~ 2500 °C (4,532 °F)) would have completely melted the airframe (assuming Aluminium 2024
2024 aluminum
Aluminium alloy 2024 is an aluminium alloy, with copper as the primary alloying element. It is used in applications requiring high strength to weight ratio, as well as good fatigue resistance. It is not weldable, and has average machinability...

's melting point of ~630 °C (1,166 °F) for the duralumin
Duralumin
Duralumin is the trade name of one of the earliest types of age-hardenable aluminium alloys. The main alloying constituents are copper, manganese, and magnesium. A commonly used modern equivalent of this alloy type is AA2024, which contains 4.4% copper, 1.5% magnesium, 0.6% manganese and 93.5%...

 of the day), whereas the real disaster left the spars and ribs recognizable. The MythBusters team also discovered that the Hindenburg's coated skin required a higher temperature to ignite than untreated material and would initially burn slowly, but after some time the fire would begin to accelerate considerably. From this they concluded that the proponents against the IPT may have been wrong about the airship's skin being inflammable due to being separated in different layers. The Mythbusters concluded that the paint may have contributed to the disaster, but that it was not the sole reason for such rapid combustion.

Hydrogen hypothesis

Offering support for the hypothesis that there was some sort of hydrogen leak prior to the fire is that the airship remained stern-heavy before landing. This could have been caused by a massive leak of the gas, which started mixing with air and filling up the space between the skin and the cells. Pictures that show the fire burning along straight lines that coincide with the boundaries of gas cells suggest that the fire was not burning along the skin, which was continuous. Crew members stationed in the stern reported actually seeing the cells burning.

There are many theories about how that gas might have leaked, but the actual cause remains unknown. Many believe it was that a bracing wire cracked (see below), while others believe that a vent was stuck open and gas leaked through. During one trip to Rio, a gas cell was nearly emptied when a vent was stuck open, and gas had to be transferred from other cells to maintain an even keel.

Although proponents of the IPT claim that the hydrogen was odorized with garlic, it would have been detectable only in the area of a leak. Once the fire was underway, more powerful smells would have masked any garlic odor. There were no reports of anyone smelling garlic during the flight, but no official documents have been found to prove that the hydrogen even was odorized.

Opponents of this hypothesis note that the fire was reported as burning bright red, while pure hydrogen burns blue if it's visible at all, although there were many other materials that were consumed by the fire which could have changed its hue.

Most of the airshipmen at the time, including Captain Pruss, believed that the stern heaviness was normal, since aerodynamic pressure would push rainwater towards the stern of the airship. However, reports of the amount of rain the ship had collected have been inconsistent. Several witnesses testified that there was no rain as the ship approached until a light rain fell minutes before the fire, while several crew members stated that before the approach the ship did encounter heavy rain. The stern heaviness was also noticed minutes before the airship made its sharp turns for its approach, and crew members stated that it was corrected as the ship stopped (after sending six men into the bow section of the ship). Additionally, the gas cells of the ship were not pressurized, and a leak would not cause the fluttering of the outer cover, which wasn't seen until seconds before the fire.

Puncture hypothesis

One hypothesis on how gas could have leaked is that one of the many bracing wires within the airship snapped and punctured at least one of the internal gas cells during one of the sharp turns in the landing maneuver. Advocates of this hypothesis believe that the hydrogen began to leak approximately five minutes before the fire. Newsreels as well as the account of the landing approach show the Hindenburg made several sharp turns, first towards port and then starboard, just before the accident. Gauges found in the wreckage showed the tension of the wires was much too high, and some of the bracing wires may have even been substandard. One bracing wire tested after the crash broke at a mere 70% of its rated load. A punctured cell would have freed hydrogen into the air and could have been ignited by a static discharge (see above), or it is also possible that the broken bracing wire struck a girder causing sparks to ignite hydrogen.

A ground crew member, R.H. Ward, reported seeing a piece of the airship fluttering, "as if gas was rising and escaping" from the cell. He said that the fire began there, but that no other disturbance occurred at the time when the fabric fluttered. Another man on the top of the mooring mast had also reported seeing a flutter in the fabric as well. When the fire started, people on board the airship reported hearing a muffled sound, and another ground crew member on the starboard side reported hearing a crack. Some speculate the sound was from a bracing wire snapping.

Dr. Eckener concluded that the puncture hypothesis was the most likely explanation for the disaster. Because of this, he felt that Captains Pruss and Lehmann, and Charles Rosendahl were to blame for the rushing the landing procedure. He believed that Lehmann told Pruss to make the sharp turn, and that Pruss and Rosendahl were concerned more about the time delay than the weather, because an unobserved storm front occurred just when the Hindenburg approached. But Eckener knew that he was to blame as much as anyone else, for in 1928 he decided against using helium offered by the US government for economic reasons.

Concluding the United States Inquiry on the disaster, Eckener testified that he believed that the fire was caused by the ignition of hydrogen by a static spark:

Structural failure

Captain Pruss believed that the Hindenburg could withstand tight turns without significant damage. Other engineers and scientists believe that the airship would have been weakened by being repeatedly stressed.

The airship's landing approach proceeded in two sharp turns. The first turn was towards port at full speed as the airship circled the landing field. After it had circled the landing field, the wind shifted direction towards the southwest, and a sharper turn to starboard was ordered near the end of the landing maneuver. One or both of these turns in opposite directions could have weakened the structure.

However, evidence against this hypothesis is the fact that the first sharp turn was too wide and circular to cause any damage, and that the final turn, while considered sharp, was far too slow for any structural failure to occur.

The airship did not receive much in the way of routine inspections even though there was evidence of at least some damage on previous flights. It is not known whether that damage was properly repaired or even whether all the failures had been found. The Hindenburg had once lost an engine and almost drifted over Africa, where it could have crashed. Afterwards, Dr. Eckener ordered section chiefs to inspect the airship during flight.

In March 1936, the Hindenburg and the Graf Zeppelin made three-day flights to drop leaflets and broadcast speeches via loudspeaker. Before the airship's takeoff on March 26, 1936, Ernest Lehmann chose to launch the Hindenburg with the wind blowing from behind the airship, instead of into the wind as per standard procedure. During the takeoff, the airship's tail struck the ground, and part of the lower fin was broken. Many spectators' cameras were confiscated to prevent negative publicity, but Harold G. Dick
Harold G. Dick
Harold Gustav "Hal" Dick was an American mechanical engineer employed by Goodyear, who flew on almost all of the Hindenburg flights. He was called to the UK for a meeting before the last flight of the Hindenburg and was not aboard during the disaster...

 concealed his camera and took pictures of the damaged fin. Dr. Eckener was very upset and rebuked Captain Lehmann:
Though that damage was repaired, the force of the impact may have caused internal damage.

Only six days before the disaster, there was a plan assisted to make the Hindenburg have a hook on her hull to carry aircraft in a similar way to what the Navy did with the USS Akron and the USS Macon
USS Macon (ZRS-5)
USS Macon was a rigid airship built and operated by the United States Navy for scouting. She served as a "flying aircraft carrier", launching Curtiss F9C Sparrowhawk biplane fighters. In service for less than two years, in 1935 Macon was damaged in a storm and lost off California's Big Sur coast,...

. However, the trials were unsuccessful; the biplane hit the Hindenburg's trapeze several times.

Photographs and newsreels of the initial stages of the fire show that the stern section of the airship collapsed inward in a similar way to an eggshell, as well as a "crack" directly behind the passenger decks. When the stern of the ship hit the ground and collapsed, this part collapsed inward, causing another plume of fire to start.

This hypothesis has not been very popular because it is not so much about what caused the fire as an element of support for the puncture hypothesis. However, the hypothesis that a bracing wire snapped during the two sharp turns prior to landing would explain the hypothesis about leaking hydrogen, which would provide a possible explanation as to how the fire began.

Fuel leak

The 2001 documentary Hindenburg Disaster: Probable Cause suggested that 16-year-old Bobby Rutan, who claimed that he had smelled "gasoline" when he was standing below the Hindenburg's aft port engine, had detected a diesel fuel leak. During the investigation, Commander Charles Rosendahl dismissed the boy's report. The day before the disaster, a fuel pump had broken during the flight. A crew member said this was fixed but it may not have been done properly. The resulting vapor would have been highly flammable and could have self combusted. The film also suggested that overheating engines may have played a role.

Critics say the documentary is misleading because it misconstrued the statements by the crewmen in the Hindenburg's lower fin. The crewmen said they saw a flash in the axial catwalk, but the film placed the flash in the keel catwalk closer to the passenger areas.

Luger pistol among wreckage

Some more sensational newspapers at the time said that a person on board committed suicide because a Luger pistol
Luger pistol
The Pistole Parabellum 1908 or Parabellum-Pistole , popularly known as the Luger, is a toggle-locked recoil-operated semi-automatic pistol. The design was patented by Georg J...

 with one shell fired was found among the wreckage. Yet, there is no such evidence suggesting an attempted suicide.

Rate of flame propagation

Regardless of the source of ignition or the initial fuel for the fire, there remains the question of what caused the rapid spread of flames along the length of the airship. Here again the debate has centered on the fabric covering of the airship and the hydrogen used for buoyancy.

Proponents of both the incendiary paint hypothesis and the hydrogen hypothesis agree that the fabric coatings were probably responsible for the rapid spread of the fire. The combustion of hydrogen is not usually visible to the human eye in daylight, because most of its radiation is not in the visible portion of the spectrum but rather ultraviolet. Thus what can be seen burning in the photographs cannot be hydrogen. However, black-and-white photographic film of the era had a different light sensitivity spectrum than the human eye, and was sensitive farther out into the infrared and ultraviolet region than the human eye. And while hydrogen tends to burn invisibly, the materials around it, if combustible, would change the color of the fire.

The motion picture films show the fire spreading downward along the skin of the airship. While fires generally tend to burn upward, especially including hydrogen fires, the enormous radiant heat from the blaze would have quickly spread fire over the entire surface of the airship, thus apparently explaining the downward propagation of the flames. Falling, burning debris would also appear as downward streaks of fire.

One note is that in 1935 a helium filled blimp with an acetate aluminium skin burned near Point Sur in California with equal ferocity. Even the USS Macon
USS Macon (ZRS-5)
USS Macon was a rigid airship built and operated by the United States Navy for scouting. She served as a "flying aircraft carrier", launching Curtiss F9C Sparrowhawk biplane fighters. In service for less than two years, in 1935 Macon was damaged in a storm and lost off California's Big Sur coast,...

, a U.S. Navy airship, burned after crashing into the Pacific off Monterey Bay. Those critical of these claims insist these two incidents had nothing to do with the dope; the small blimp burned because gasoline was ignited during a lightning strike, and the Macon burned because its signal flares fired ignited gasoline.

Those skeptical of the incendiary paint hypothesis 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.

Modern experiments that recreated the fabric and coating materials of the Hindenburg seem to discredit the incendiary fabric hypothesis. They conclude that it would have taken about 40 hours for the Hindenburg to burn if the fire had been driven by combustible fabric. Two additional scientific papers also strongly reject the fabric hypothesis.

However these claims do not agree with the results the Mythbusters
MythBusters
MythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...

 achieved on their Hindenburg special of their TV show and others feel the criticisms does not take into account the conditions that lead to firestorm
Firestorm
A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires...

s, such as convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....

 and ignition from radiant energy.

The most conclusive proof against the fabric hypothesis is in the photographs of the actual accident as well as the many airships which were not doped with aluminum 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 Ahlhorn disaster on January 5, 1918, explosions of airships in one hangar caused the explosions of others in three adjoining hangars, wiping out all five Zeppelins at the base.

The photos of the Hindenburg disaster clearly show that after the cells in the aft section of the airship exploded and the combustion products were vented out the top of the airship, the fabric on the rear section was still largely intact, and air pressure from the outside was acting upon it, caving the sides of the airship inward due to the reduction of pressure caused by the venting of combustion gases out the top.

The loss of lift at the rear caused the airship to nose up suddenly and the back to break in half (the airship was still in one piece), at that time the primary mode for the fire to spread was along the axial gangway which acted as a chimney, conducting fire which burst out the nose as the airship's tail touched the ground, and as seen in one of the most famous pictures of the disaster.

Television investigations

As mentioned previously, the Discovery Channel
Discovery Channel
Discovery Channel is an American satellite and cable specialty channel , founded by John Hendricks and distributed by Discovery Communications. It is a publicly traded company run by CEO David Zaslav...

 series MythBusters
MythBusters
MythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...

explored the incendiary paint hypothesis and the hydrogen hypothesis in an episode that aired January 10, 2007. While their experiments didn't concern what actually started the fire, the show's hosts, Adam Savage
Adam Savage
Adam Whitney Savage is an American industrial design and special effects designer/fabricator, actor, educator, and co-host of the Discovery Channel television series MythBusters. His model work has appeared in major films, including Star Wars: Episode II - Attack of the Clones and The Matrix...

 and Jamie Hyneman
Jamie Hyneman
James Franklin "Jamie" Hyneman is an American special effects expert, best known for being the co-host of the television series MythBusters. He is also the owner of M5 Industries, the special effects workshop where MythBusters is filmed...

, 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. Combustion was observed in the burning skin, which would have accelerated the fire, but their experiments showed 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. That program concluded that the IPT myth was "Busted".

The MythBusters constructed three 1/50 scale models made out of welded steel wire and covered in cotton fabric. They were suspended from a hangar ceiling and stayed horizontal the entire time. The first model was painted with iron-oxide and then aluminum powder dopes, closely replicating the actual skin of the Hindenburg. Ignited with a blowtorch, it took about 2 minutes to burn, with thermite-like events (sparkling blazes) noted in a few places. The second model had the same skin, but a water trough inside diffused hydrogen gas at sub-explosive concentrations. This one burned about twice as fast, with more thermite burning. The third model, done more for spectacle than anything else, had the skin painted with a thermite-like iron-oxide and aluminum powder enriched dope. It was noted that it would probably be far too heavy to fly. With model 2's hydrogen enrichment, it took 30 seconds to completely consume the skin. The conclusion was that neither the hydrogen gas nor the flammable skin bore sole responsibility for the speed of the fire, but both contributed.

The National Geographic program Seconds From Disaster
Seconds From Disaster
-By original broadcast date:National Geographic Channel has broadcast many episodes under multiple titles. The title currently or most recently listed on the NGC Calendar is shown first...

had veteran air crash investigator Greg Feith
Greg Feith
Gregory "Greg" Feith is a former American Senior Air Safety Investigator with the National Transportation Safety Board. During his time at the NTSB, Feith worked as an Air Safety Investigator Unit Supervisor, Regional Director, and Senior Air Safety Investigator. Feith was also the U.S...

 study all of the available evidence, including eyewitness accounts, interviews with the last two living survivors, newsreel footage, weather reports, and the Hindenburg blueprints. Feith burned a sample of doped cloth and it took one minute to consume the whole piece, ruling out the skin as the primary accelerant. Feith's investigation came to a conclusion that the hydrogen puncture hypothesis was most probable. He also proved that by adding white cloth to a hydrogen flame that it would change the fire's color from invisible to orange.

In Search of..., a show mainly focused on paranormal investigations and conspiracy theories, made an episode based on this tragic accident, and immediately raised the question of whether it was really an accident or instead sabotage by then-Nazi Germany.

Memorial

The actual site of the Hindenburg crash at Lakehurst Naval Air Station (reestablished 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 May 6, 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.

Television

In season 2, episode 17 of Beyond Belief: Fact or Fiction
Beyond Belief: Fact or Fiction
Beyond Belief: Fact or Fiction is an American television anthology series created by Lynn Lehmann, presented by Dick Clark Productions, and produced and aired by the Fox network from 1997 to 2002. Each episode featured five stories, all of which appeared to defy logic, and some of which were...

, the twist at the end of 'Bon Voyage' reveals that the story has been taking place on the Hindenburg moments before the crash.

The Hindenburg disaster is chronicled in the popular 1970s television drama, The Waltons
The Waltons
The Waltons is an American television series created by Earl Hamner, Jr., based on his book Spencer's Mountain, and a 1963 film of the same name. The show centered on a family growing up in a rural Virginia community during the Great Depression and World War II. The series pilot was a television...

where John Boy Walton wins a writing contest to cover the landing of the Hindenburg, witnessing the unforeseen tragedy up close and in person. Original newsreel footage of the event was integrated into the episode's scenes.

Music

The cover of Led Zeppelin
Led Zeppelin
Led Zeppelin were an English rock band, active in the late 1960s and throughout the 1970s. Formed in 1968, they consisted of guitarist Jimmy Page, singer Robert Plant, bassist/keyboardist John Paul Jones, and drummer John Bonham...

's self-titled debut album
Led Zeppelin (album)
Led Zeppelin is the debut album of the English rock band Led Zeppelin. It was recorded in October 1968 at Olympic Studios in London and released on Atlantic Records on 12 January 1969 in the United States and 31 March 1969 in the United Kingdom. The album featured integral contributions from each...

 shows a stylized photo of the Hindenburg disaster with the band's name in the upper left corner. The name of the band itself is in reference to a crashing zeppelin.

See also

  • LZ 129 Hindenburg
    LZ 129 Hindenburg
    LZ 129 Hindenburg was a large German commercial passenger-carrying rigid airship, the lead ship of the Hindenburg class, the longest class of flying machine and the largest airship by envelope volume...

  • Crash cover
    Crash cover
    A crash cover is a philatelic term for a type of cover, meaning an envelope or package that has been recovered from a fixed-wing aircraft, airship or aeroplane crash, train wreck, shipwreck or other accident...

  • Hindenburg Disaster Newsreel Footage
    Hindenburg Disaster Newsreel Footage
    Hindenburg Disaster Newsreel Footage refers to the footage filmed by several newsreel companies of the Hindenburg disaster where the zeppelin Hindenburg crashed and burned on May 6, 1937....

  • Hindenburg Omen
    Hindenburg omen
    The Hindenburg Omen is a technical analysis pattern that is said to portend a stock market crash. It is named after the Hindenburg disaster of May 6, 1937, during which the German Zeppelin Hindenburg was destroyed.- History :...

  • Herbert Morrison (announcer)
    Herbert Morrison (announcer)
    Herbert Morrison was an American radio reporter best known for his dramatic report of the Hindenburg disaster, a catastrophic fire that destroyed the LZ 129 Hindenburg zeppelin on May 6, 1937, killing 36 people.-Hindenburg disaster:...

  • List of airship accidents
  • Hindenburg: The Untold Story
    Hindenburg: The Untold Story
    Hindenburg: The Untold Story known in Germany as Das Geheimnis der Hindenburg and Die Hindenburg: die ungeklärte Katastrophe, is a two-hour docudrama about the disaster of the Hindenburg, and the investigation that followed. It aired on May 6, 2007 to celebrate the 70th anniversary of the disaster...

    was a docudrama
    Docudrama
    In film, television programming and staged theatre, docudrama is a documentary-style genre that features dramatized re-enactments of actual historical events. As a neologism, the term is often confused with docufiction....

     aired on the 70th anniversary of the disaster, May 6, 2007.
  • Timeline of hydrogen technologies
    Timeline of hydrogen technologies
    Timeline of hydrogen technologies — A timeline of the history of hydrogen technology.-1600s:* 1625 - First description of hydrogen by Johann Baptista van Helmont...


External links

Video

Articles and reports

Websites

Flammable fabric disaster hypothesis
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