The Hindenburg disaster took place on 6 May 1937 as the German rigid airship Hindenburg caught fire and was destroyed within one minute while attempting to dock with its mooring mast at Lakehurst Naval Air Station in New Jersey. Of the 97 people on board, 35 people died in addition to one fatality on the ground. The disaster was the subject of spectacular newsreel coverage, photographs, and Herbert Morrison'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 theories have been put forward for both the cause of ignition and the initial fuel for the ensuing fire.

The accident served to shatter public confidence, and marked the end of the giant, passenger carrying rigid airships.

The flight

Post card carried on the D-LZ129 "Hindenburg" on its last flight and dropped enroute over Cologne (The Cooper Collections)

The airship was already eight hours behind schedule when it passed over Boston on the morning of 6 May, and its landing at Lakehurst was expected to be further delayed because of afternoon thunderstorms. After passing over the field at 4 p.m., Captain Max Pruss thus took passengers on a tour over the seasides of New Jersey 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 could 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 , the Hindenburg approached the Lakehurst Naval Air Station. This was to be a high landing, known as a flying moor, because the airship would be moored to a high mooring point, and then winched down to ground level. This type of landing maneuver would reduce the number of ground crew, but would require more time.

7:08: 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 , 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.

7:19: the airship made the second sharp turn and valved 300, 300 and 500 kg of water ballast in successive drops because the airship was stern heavy. Six men (four were killed in the accident^[1]) were also sent to the bow to trim the airship. None of these attempts to correct the problem worked and the airship seemed to sink even more, but Pruss was now permitted to land.

7:21: at altitude , the mooring lines were dropped from the bow, the starboard line being dropped first. At this point, the cameramen who were filming the lines being caught by the ground crew stopped rolling film altogether, and missed what was about to happen.

First hints of disaster

At 7:25, a few witnesses saw the fabric ahead of the upper fin flutter as if gas were leaking. At the same time another witness saw what looked like static electricity moving up the hull from the bottom.

Immediately after this, witnesses started to report a small flame ahead of the upper fin. Commander Rosendahl testified it 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 (however, this may have happened after the initial fire on the port side).

The disaster

Ground Photograph of Disaster

Wherever it started, the flames quickly spread forward. Almost instantly, a water tank and a fuel tank burst out of the hull. At the same time, a crack appeared behind the passenger decks. The airship's back broke, and the section from the nose to the aft engine cars lurched upwards, while the stern stayed in trim.

A rare surviving fire-damaged 9" duralumin cross brace from the frame of the "Hindenburg" salvaged in May 1937 from the crash site at NAS Lakehurst, NJ. (The Cooper Collections)

Historic newsreel coverage

The disaster is well recorded because of the significant extent of newsreel coverage and photographs, as well as Herbert Morrison's recorded, on-the-scene, eyewitness radio report being made from the landing field for station WLS in Chicago 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 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. 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.

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.^[2] 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.

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 rudimentary 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 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, 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, 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.^[3] 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. ^[4] Nonetheless, some did manage to escape from the starboard passenger decks. A number of others unfortunately 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. Almost twice as many perished when the helium filled USS Akron crashed.

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 would later tell 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 would survive.

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. ^[5]

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, of course, 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. ^[6] 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 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.^[7]

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 ? see below.)

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.^[8]

In 1962, A. Hoehling published Who Destroyed the Hindenburg?, a book that rejects all theories but sabotage. It even names the likely saboteur ? Eric Spehl, a rigger on the Hindenburg who died in the fire. Ten years later, Michael MacDonald Mooney's book, The Hindenburg, also identified Spehl as the saboteur. Mooney's book was made into the movie The Hindenburg, whose producers were sued by Hoehling for plagiarism, but Hoehling lost.^[9]

The historians and researchers putting Spehl forward as a saboteur cite:

• His girlfriend's anti-Nazi connections; she reportedly was a communist.
• The fire's origin near Gas Cell 4, Spehl's duty station.
• Rumours that in 1938 the Gestapo was investigating Spehl's involvement.
• Spehl's interest in amateur photography, making him familiar with flashbulbs that could have served as an igniter. A dry cell battery that might have powered a flashbulb was found in the wreckage.
• A flash or a bright reflection that crew members near the lower fin had seen just before the fire.

Since it is very unlikely that Spehl wanted to kill people, proponents of this sabotage theory say that he wanted the airship to explode after the landing (already over 12 hours late) but was too busy to reset the 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. When both men looked up toward the front of the airship, they were surprised by what they saw.

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.^[10]

Another suspect was a passenger, a German acrobat named Joseph Spaeh, 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 often made unaccompanied visits to the stern to feed, talk and play with the dog. Some, noting that Spaeh told many anti-Nazi jokes, and that he was an acrobat who could climb into the airship's rigging, accuse him of planting a bomb when he was with his dog.

It has even been suggested that Adolf Hitler himself ordered the Hindenburg to be destroyed in retaliation for Eckener's anti-Nazi opinions.^[11].

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 unable to refute the accusations. The FBI investigated Joseph Spaeh and reported finding no significant evidence of sabotage. According to Spaeh's wife, Evelyn, Spaeh was upset over the accusations and almost fell off a ladder when he was told about it while cleaning windows. ^[12].

Neither the German nor the American investigation endorsed any of the sabotage theories. Proponents of the sabotage theory 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 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.^[13].

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 which had been lightly covered in metal to improve conductivity, however not very effectively, allowing a large 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.

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 theory, 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 most other witnesses to the fire, whose view had been of the port side of the ship with the light of the setting sun behind it, Professor Heald's view was of the starboard side of the ship, against a backdrop of the darkening eastern sky, which would naturally make the dim blue light of static discharge 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 Luftshiffbau Zeppelin took the static discharge theory seriously and considered the insulation of the fabric from the frame to be a design flaw in the Hindenburg.

A variant of the static spark theory, presented by Addison Bain, 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". It is a common term for a plasticised lacquer 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 butyrate dope being far less flammable than cellulose nitrate, for example. When the mooring line touched the ground, a resulting spark could have ignited the dope in the skin.

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.^[13].

Engine exhaust sparks theory

On the 70th anniversary of the accident, The Philadelphia Inquirer carried an article^[14] 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.^[15] 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.^[13] 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 aluminum-impregnated cellulose acetate butyrate (CAB). These components are potentially reactive, even after fully setting. In fact, iron oxide and aluminum are sometimes used as components of solid rocket fuel or thermite. The propellant for the Space Shuttle solid rocket booster includes "aluminum (fuel, 16%), (and) iron oxide (a catalyst, 0.4%)."

Addison Bain received permission from the German government to search its archives and discovered that during the Nazi regime, German scientists concluded that 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 confirmed 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.^[16]

The paint theory is limited to the source of ignition and to the flame front propagation, not to the source of most of the burning material as that was clearly the 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 it was a hydrogen fire feeding on the whole cell). Newsreel footage supports this.^[12] Proponents of the paint theory 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 structure, 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 theory.

MythBusters further debunked the theory, finding that the aluminum/iron oxide ratios in the Hindenburg's skin, while sufficient to create some thermite, were ultimately insufficient to destroy the zeppelin on their own. Had the skin in fact contained pure thermite, the Hindenburg would have been too heavy to fly. The MythBusters team also discovered that the Hindenburg's coated skin was more resistant to fire than untreated material, however, when ignited, reacted more violently. This led to the hypothesis that the paint may have contributed to the disaster but was not entirely at fault; rather, it was a combination of the paint and the hydrogen that fueled the fire.

The hydrogen theory

Those who believe hydrogen was the initial fuel discount arguments for the incendiary paint theory as not credible. They point out that cellulose acetate butyrate (CAB) varnish is rated within the plastics industry as combustible but nonflammable. That is, it will burn when placed in a fire but is not readily ignited by itself. In fact, it is considered to be self extinguishing.^[17] That many pieces of the Hindenburg's skin survived despite such a fierce fire is cited as proof. In his experiment, Addison Bain used a high energy ignition source (a spark) to make it burn.

They point to pictures that show the fire burning along straight lines coinciding with the boundaries of gas cells. This suggests that the fire was not burning along the skin, which was continuous. Crew members stationed in the stern reported actually seeing the cells burning.^[18]

Although the hydrogen was odorized with garlic, nobody reported smelling the odor. Odorised hydrogen would have been detected only in the area of a leak. The fire started near the top of the airship far from any crew or passengers. Once the fire was underway, more powerful smells would have masked any garlic odor. There is however, no official document that the hydrogen was even odorized.

Support that any leak happened was that the airship remained stern heavy for the last few minutes. Though Pruss believed that this stern heaviness was normal, attempts to correct it had failed and the airship seemed to get even heavier after the second and last sharp turn. This suggests a massive leak of gas occurred and it started to fill up the space in between the outer skin and the cells.^[13]

How gas could have leaked remains debatable. Many believe it was that a bracing wire cracked (see below), while others believe that a vent was stuck open and gas leaked through the vent. During a trip to Rio a gas cell was nearly emptied when a vent stuck open; gas had to be transferred from other cells.^[12].

One hole in this theory that should be noted however is that the fire was reported as burning bright red, while hydrogen always burns blue if visible at all.^[19]

Puncture theory

A variant of the theory above cites the newsreels of the landing approach. Newsreels show the Hindenburg making sharp turns towards port, and then starboard just before bursting into flames. Some speculate that one of the many bracing wires within the airship snapped and punctured at least one of the internal gas cells. Gauges found in the wreckage showed the tension of the wires was much too high. Some of the wires may have been substandard. One bracing wire tested after the crash broke at only 70% of its rated load.^[12] A punctured cell would have freed hydrogen into the air and could have been ignited by a static discharge (see above).

It is also possible that the broken bracing wire then whipped a girder, causing sparks to ignite the leaking hydrogen.^[12].

A ground crew member, R.H. Ward, reported seeing a piece of the airship fluttering, perhaps providing an opening for a spark to reach escaping hydrogen inside the airship, or vice versa. He said that the fire began there, but that no other disturbance occurred at the time when the fabric fluttered.^[13] Another man on the top of the mooring mast had also reported seeing a flutter too.^[20] People on board the airship also 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.^[12]

Advocates of this theory believe that the hydrogen began to leak approximately five minutes before the fire.^[13]

Dr. Eckener was the one to conclude that the puncture theory was the most likely cause of the disaster. After this, he believed that Captains Pruss and Lehmann, and Charles Rosendahl were to blame for the whole disaster.^[13] 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.^[13] But in his heart, he found himself to blame, for a decision eight years earlier, which was a close secret.^[21][13]

Eckener concluded that the fire was caused by the ignition of hydrogen by a static spark:

^[13]

The airship's landing approach actually proceeded in two sharp turns. The first turn was towards port at full speed as the airship circled the landing field. After circling the landing field, the wind shifted direction towards southwest, and a sharper turn towards starboard was ordered near the end of the landing maneuver. After the last turn the airship seemed to drop even more at the stern, though a slight stern heaviness was already noticed before this turn. One or both of these turns towards opposite directions could also have weakened the structure.

Other controversial hypotheses

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. Even a 10-meter, full scale replica of the Hindenburg's passenger quarters, displayed in the Zeppelin Museum in Friedrichshafen, has developed some metal fatigue.

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

In March 1936, the Graf Zeppelin and the Hindenburg made three-day flights to drop leaflets and broadcast speeches via loudspeaker. Before the airship's takeoff on 26 March 1936, Captain 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.^[22] Many spectators' cameras were confiscated to prevent negative publicity, but Harold G. Dick concealed his camera and took pictures of the damaged fin. Dr. Eckener was very upset and rebuked Captain Lehmann:

^[10]

Though the damage was repaired, the force of the crash may have already forced up the fin and caused internal damage.

Only six days before the disaster, there was a plan assisted by the U.S. Navy 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. However, the trials were unsuccessful; the biplane had bashed the hook several times. This could have also caused an amount of damage weakening the structure.

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. Some experts have suggested that the collapsing of the structure in this manner suggests problems in strength within the cell bulkheads and the bracing wires.

This theory has not been very popular, because it is not a theory about what caused the fire, but is an element that supports the puncture theory.

Fuel leak

The 2001 documentary Hindenburg Disaster: Probable Cause suggested that 16-year-old Bobby Rutan, who said he had smelled "gasoline" when he was standing below the Hindenburg's aft port engine, had detected a diesel fuel leak. 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. 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.

During the investigation, Commander Charles Rosendahl dismissed the boy's report.

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 with one shell fired was found among the wreckage.^[10] Yet, there is no such evidence suggesting an attempted suicide.

Rate of flame propagation

Fabric of the Hindenburg, held in the Steven F. Udvar-Hazy Center

Proponents of the incendiary paint theory also contend that the fabric coatings were responsible for the rapid spread of the fire. They point out that 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. 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. The motion picture films show the fire spreading downward along the skin of the airship.

Proponents claim that in 1935, a helium filled blimp with an acetate aluminium skin burned near Point Sur in California with equal ferocity.^[23] Proponents also claim that even the USS Macon burned. Opponents point out that these two incidents had nothing to do with the dope. The small blimp burned because of a fuel leak, and the Macon burned because it was firing flares.

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.^[24] Proponents claim that this criticism does not take into account the conditions that lead to firestorms, such as convection and ignition from radiant energy.

Also, while hydrogen tends to burn invisibly, the materials around it would be combustible and change the color of the fire. While fires generally tend to burn upward, including hydrogen fires, the enormous radiant heat from the blaze would have quickly spread fire over the entire surface of the airship, thus explaining the downward propagation of the flames. Falling, burning debris would appear as downward streaks of fire.

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 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 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.

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 right when the airship's tail touched the ground, as seen in one of the most famous pictures of the disaster. As the flames burst from the nose, the fabric on most of the forward part of the airship was still intact, showing that the propagation of the fire was via hydrogen, not the fabric.

Also supporting the fact that hydrogen was burning was that a few seconds after the fire burst out the nose a fire started in the cell behind the passenger decks when the airship bent on the side due to a crack in the side just behind the passenger decks.

Modern experiments that recreated the fabric and coating materials of the Hindenburg seem to discredit the incendiary fabric theory.^[25] 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 theory.^[24]

Even if the fire was started by the fabric, it would have set off the leaking hydrogen. Hydrogen would still be required to increase the burn speed of the fire, regardless of what was ignited first. If the Hindenburg was filled with helium and still burned, the fire would be slower and most people, if not all, would have survived.

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.^[26] 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 veteran 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, 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 fatal accelerant. Feith's investigations concluded that a gas bag was punctured, probably by a bracing wire broken from the two sharp turns, and that electrostatic discharge from the skin to the ship skeleton ignited the leaked hydrogen.

In Search of..., hosted by Leonard Nimoy, made an episode based on this tragic accident, and it immediately raised the question of whether it was an accident or sabotage by then-Nazi Germany.

Memorial

Current marker at the disaster site, shown with Hangar #1 in background

Popular culture

Audio

• English rock group Led Zeppelin's eponymous first album has a picture of the Hindenburg disaster on the front cover. The band's name itself is a reference to Keith Moon's quotation that the band would "go over like a lead balloon." The album cover is in fact a pen and ink illustration of the famous UPI photograph drawn with a Rapidograph pen by graphic artist George Hardie. Their 2007 compilation album Mothership also has a picture of the Hindenburg on the album cover.

Film and television

• The Hindenburg (1975 movie) is a speculative thriller based on the events leading up to and including the disaster.
• In the The Waltons season 5 episode "The Inferno", first aired on 10 February 1977, John-Boy goes to Lakehurst, New Jersey, to report on the landing of the Hindenburg.

Other

• Hindenburg is the primary motif of the first section of Three Tales by Steve Reich and Beryl Korot.
• Hindenburg is the main setting of the 2000 mystery novel "The Hindenburg Murders" by Max Allan Collins.
• The last flight of the Hindenburg is a major plot element in Allen Steele's science fiction fix up novel Chronospace.
• In the novel The Never War by D.J. MacHale, the main character can choose to keep the Hindenburg accident from happening, which he thought would keep World War II from starting. However, he decides not to, since he discovers that the airship is carrying payment to German spies that would allow the Nazis to develop atomic weapons before the Allies.

See also

• LZ 129 Hindenburg
• Crash cover
• Hindenburg Disaster Newsreel Footage
• Herbert Morrison (announcer)
• List of airship accidents
• Hindenburg: The Untold Story was a docudrama aired on the 70th anniversary of the disaster, 6 May 2007.
• Timeline of hydrogen technologies
• High Resolution Version of Image of Explosion * http://www.flickr.com/photos/69805768@N00/2087961122/

References

Notes

Bibliography

• Archbold, Rick. Hindenburg: An Illustrated History. Toronto: Viking Studio/Madison Press, 1994. ISBN 0-670-85225-2.
• Birchall, Frederick. "100,000 Hail Hitler; U.S. Athletes Avoid Nazi Salute to Him". The New York Times, 1 August 1936, p. 1.
• Botting, Douglas. Dr. Eckener's Dream Machine: The Great Zeppelin and the Dawn of Air Travel. New York: Henry Holt & Co., 2001. ISBN 0-80506-458-3.
• Deutsche Zeppelin-Reederi. Airship Voyages Made Easy (16 page booklet for "Hindenburg" passengers). Luftschiffbau Zeppelin G.m.b.H., Friedrichshafen, Germany, 1937.
• Dick, Harold G. and Douglas H. Robinson. The Golden Age of the Great Passenger Airships Graf Zeppelin & Hindenburg. Washington, D.C. and London: Smithsonian Institution Press, 1985. ISBN 1-56098-219-5.
• Duggan, John. LZ 129 "Hindenburg": The Complete Story. Ickenham, UK: Zeppelin Study Group, 2002. ISBN 0-9514114-8-9.
• Hoehling, A.A. Who Destroyed The Hindenburg? Boston: Little, Brown and Company, 1962. ISBN 0-44508-347-6.
• Lehmann, Ernst. Zeppelin: The Story of Lighter-than-air Craft. London: Longmans, Green and Co., 1937.
• Majoor, Mireille. Inside the Hindenburg. Boston: Little, Brown and Company, 2000. ISBN 0-316-123866-2.
• Mooney, Michael Macdonald. The Hindenburg. New York: Dodd, Mead & Company, 1972. ISBN 0-396-06502-3.
• National Geographic. Hindenburg's Fiery Secret (DVD). Washington, DC: National Geographic Video, 2000.

External links

Video

• Footage from Castle and Pathé coverage of the Hindenburg disaster at [[Internet Archive]]
• YouTube video: Universal Newsreel - [[10 May] 1937 Special report on the Hindenburg disaster.]
• YouTube video of Herb Morrison's famous report synchronized with newsreel footage
• YouTube video with audio at corrected speed

Articles

• Hindenburg & Hydrogen
• FBI investigation into the Hindenburg disaster
• "The Hindenburg" - Failure Magazine (January 2002)
• ''Thirty-Two Seconds'' - An article about the disaster that features rare photos of the disaster, a photograph of the surviving crew and a report on Cabin Boy Werner Franz.
• "What Happened to the Hindenburg?" Transcript: ''Secrets of the Dead'' ([[15 June] 2001, PBS)]
• Passenger and Crew List of the ''Hindenburg'' on its final voyage

Flammable fabric disaster theory

• An Article Supporting the Flammable Fabric Theory. Retrieved with the [[Internet Archive#Wayback Machine|Wayback Machine]]
• Two Articles Rejecting the Flammable Fabric Theory
• Experiments Reject the Flammable Fabric Theory
• An article supporting the engine exhaust spark theory: "The real cause of the Hindenburg disaster?" ''Philadelphia Inquirer'', [[6 May] 2007 (the 70th anniversary of the Hindenburg disaster)]

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