The Hindenburg

Zeppelin dirigible Hindenburg LZ-129 arriving at its German base in early 1937, fromDeutsche Zeppelin Reederei
The 1936 home movie of the German dirigible Hindenburg was taken by a vacationing American family. The now unidentified group must have been among the only five hundred passengers who made the ten trips from Frankfurt to New Jersey during the Hindenburg's single year of operation. At 804 feet long, it was the largest rigid lighter-than-air craft ever constructed and could reach eighty-four miles per hour with the four diesel-driven propellers seen in the footage. Captured by the amateur filmmakers are the elegant dining room, observation salon, and control gondola. As was a practice in early home movies, the family edited in intertitles (commercially produced from text supplied by filmmakers). Less common in the thirties is the brief color footage also edited in.

The Hindenburg's spectacular demise at its first 1937 landing, in which thirty-six passengers and crew were killed, occurred at the Lakehurst Naval Air Station, seen here the previous year. Although it was speculated in Germany that the Hindenburg fell victim to an anti-Nazi plot, the likely cause was static electricity discharge in conjunction with flammable hydrogen gas leaking from the tanks that kept the Hindenburg aloft. After the disaster its sister ship the Graf Zeppelin was decommissioned, and so these home movies preserve the last days of commercial travel by dirigible.

Sources:

What happened to the Hindenburg?

by J. Gordon Vaeth who served with US. Navy airships in World War II and has known personally many of the people prominent in the Hindenburg story. He has written extensively on lighter-than-air flight.

The German zeppelin, Hindenburg, crashes to the ground after bursting into flames at the U.S. Naval Station in Lakehurst, N.J. on May 6, 1937. The Hindenburg was the largest airship ever built at 804 feet long and flew up to 85 miles per hour while held aloft by hydrogen, which was highly flammable. The disaster, which killed 36 people after a 60-hour flight from Germany, ended regular passenger service by the lighter-than-air airships. (AP Photo/Murray Becker) from Nando Times
The German airship Hindenburg was the largest man-made object that had ever flown. It offered transoceanic travel that was quiet, effortless, and vibration-free. Its sheer size (nearly three football fields long and 135 feet in diameter at its widest point), the smoothness and stability of its flight, and its ocean-linerlike comfort made most passengers forget they were buoyed aloft by more than 7 million cubic feet of highly flammable hydrogen stored just above their heads in 16 gas cells. The few who did worry were reassured by the fact that in commercial flying dating back to before World War I, German zeppelins had never had a single passenger fatality. Specifically designed for the North Atlantic route, the Hindenburg was built in Friedrichshafen by the Luft-schiff-bau-Zeppelin Company and bore the dockyard number LZ-129. It was powered by four 1,100-horsepower Daimler-Benz diesel engines, each driving a four-bladed wooden propeller almost 20 feet in diameter. They pushed the 240-ton dirigible through the air at 74 m.p.h. at cruising speed and 84 m.p.h. at maximum speed. Flight time between its German terminal, today's Frankfurt jetport, and its American terminal, the U.S. Naval Air Station at Lakehurst, New Jersey, averaged 52 hours eastbound (because of headwinds) and 64.5 hours westbound. No other aircraft provided commercial service across the North Atlantic at the time. In 1936, the year it began service, the Hindenburg crossed the Atlantic 34 times carrying 2,798 people, including 10 round trips between Germany and North America. Passengers liked its relatively fast speed and the plush accommodations built into its hull. These included a dining salon, a lounge, 25 double staterooms with running water, a bar, a smoking room (sealed and protected by an airlock), promenade decks with open windows, and a shower bath. In appointments, service, food, and drink, the Hindenburg was a flying luxury liner. The fare was $400 one way, $720 round trip (about $4,200 and $7,560 in today's currency).

The Start of a New Season

The LZ-129 set out from Frankfurt on the evening of May 3, 1937 to begin a new season of 18 scheduled round-trip flights across the North Atlantic. Its cabin space had been expanded to accommodate 70 instead of 50 passengers. Only 36 were on board for the outbound flight, but the return passage was fully booked. Many of the Europe-bound ticket holders were planning to attend the Coronation of King George VI of England on May 12, 1937. There were also 61 crew members, many of them trainees. Captain Max Pruss was in command. The Atlantic crossing was uneventful. After flying over Nova Scotia and down the Northeast coast, the Hindenburg arrived over New York City at 3 p.m. EDT on May 6 and reached the vicinity of Lakehurst at 4 p.m., where a cold front was approaching from the west. Pruss continued south along the shoreline to wait out the weather. The cold front passed Lakehurst at 4:30 p.m. It was followed by heavy showers and thunderstorms as a well-defined squall line moved through Lakehurst. There was a thunderstorm directly over the station from 4:40 to 5:45 p.m., and several more heavy showers and thunderstorms were reported between 6 and 7 p.m. Following the cold front passage, the winds at Lakehurst shifted to the northwest with gusts to 20 knots, then went to west-southwest and gusty in the showers and thunderstorms. When these passed, the winds became light and variable. At 6:12 p.m., Lakehurst radioed the Hindenburg that the thunderstorm over the station was moving off to the north and conditions would soon be suitable for landing. The airship turned and headed for the station, flying through increasingly heavy rain. At 7:08 p.m., after the Germans were advised that conditions had definitely improved and they should land as soon as possible, the dirigible emerged from the rain clouds at 650 feet and roared over the station from the southwest at full cruising speed. It overflew the field, then made a sweeping turn to the left to reapproach from the west. A ground crew of 92 Navy men and 138 civilians was drawn up to receive it. There was a very light east wind at their backs. At 7:10, as the ship returned over the field heading east, the surface wind shifted to the southeast, while the wind at flight level went around to the south. Pruss maneuvered to respond to these changes, making another turn, a sharper one, this time to the right, so as to approach from a northerly direction and land facing into the wind. The ceiling was 2,000 to 3,000 feet, a light rain was falling from a stratus cloud deck, the sky showed signs of clearing to the west, the thermometer read 60 Fahrenheit, and distant lightning was flashing to the south and southwest. The surface wind at the precise moment of the beginning of the landing was southeast at one knot. Pruss valved hydrogen during the two turns, a normal landing procedure to adjust the zoppelin's buoyancy and trim. During the second turn, he also dropped a ton of water ballast and sent six crewmen forward to the bow to offset tail-heaviness. Jockeying his four engines "ahead," "astern," and "idle," he brought the great ship to a complete stop in midair, right over the ground crew. His skill in doing so was commented on by the U.S. Navy officers looking on. Pruss, a former enlisted helmsman on the zeppelins of the Imperial German Navy, had a reputation as an exceptional shiphandler.

A Flying Moor

The Hindenburg came to a halt at an altitude of about 180 feet, hovering overhead like an enormous cloud. At 7:21, the starboard handling line was dropped from the bow, followed by the port line. Dust flew from the ropes when they hit the ground. They were dry then, but would soon become wet in the rain. At the Navy's request, the Hindenburg was executing a "flying moor," a favorite technique of U.S. Navy airmen in landing to a mast (you needed fewer ground handlers), but not of zeppelin airmen. The Germans preferred to approach the landing party close to the ground so the lines could be taken in hand and the ship "walked" up to the mast and secured. In a flying moor, ropes were dropped from the bow and coupled to corresponding lines on the ground, then led out to the side as guys to steady the airship and keep it headed into the wind. The zeppelin's steel mooring cable, connected to another cable coming out of the top of the mast, would then be used to pull the ship down and to the masthead. The port bow rope was connected with its ground rope and a strain taken. The Hindenburg began to move upward and astern, and also to swing slowly to starboard as a light wind gust hit the port side. The ship then settled back down to an altitude between 135 and 150 feet. Its trailing radio antenna had been reeled in, so it was out of radio communication with the station. As the ground crew worked to couple the starboard line, the dirigible's outer cover began to flutter. Waves could be seen rippling the skin on the top port side near or over gas cell 5, about two-thirds of the way toward the stern.
The German zeppelin, Hindenburg, bursts into flames at the U.S. Naval Station in Lakehurst, N.J. on May 6, 1937.
About 15 seconds later--at 7:25 p.m.--a small bright flame burst forth from the top of the hull near where the fluttering had been observed, just forward of the leading edge of the vertical fin over cells 4 and 5, and a reddish glow became visible inside the ship. Almost immediately, this was followed by a burst of flaming hydrogen between the equator and the top of the ship on the port side. For perhaps 15 seconds the fire burned its way forward 60 to 100 feet along the dirigible's back. Then there was a muffled explosion and the rear half of the Hindenburg was instantly enveloped in a hydrogen fire. The great ship fell tail-first onto the sandy New Jersey soil, telescoping and breaking up, while its nose, still briefly airborne, pointed skyward and shot out flames "as from a blowtorch." Within seconds the whole ship lay on the ground, its cotton cover burning away, its framework collapsing. The interval between the first flame and the impact of the main body with the ground was 32 seconds. The ensuing inferno killed 13 passengers, 22 crewmen, and 1 civilian ground handler. Many other crewmen and passengers suffered serious injuries. Of the 97 people on board, 62 survived. Pruss, his face horribly burned, was one of them. Many survivors owed their lives to the Navy ground handlers. As the flaming ship fell onto the field, the steadying bullhorn voice of Aviation Chief Rigger Frederick J. Tobin began booming: "Navy men, stand fast! There are people in there and we've got to get them out!" His words rang out above the noise and tumult: "Stand fast! Stand fast!" Led by Tobin, R. H. ("Ducky") Ward, and other veteran Lighter-than-Air chiefs, the ground crew braved the burning wreckage to pull out survivors. Navy men performed many acts of heroism that evening.

The Investigation

Investigating teams appointed by the U.S. and German governments focused on two points: the Hindenburg's tail-heaviness while landing --perhaps caused by a hydrogen leak --and the fluttering of the outer cover, which could have been caused by loose hydrogen trying to escape. The area where the fabric fluttered and where the flame erupted roughly coincided. What could have caused hydrogen to collect under the cover? Was it gas that had been valved but had failed to be exhausted through the ventilating shafts due to the ship's low airspeed during landing? Had there been a damaged gas cell? Both reports suggested a bracing wire might have broken during the second, sharper turn and slashed open a gas cell. Though they exhaustively investigated every conceivable possibility, neither the American nor German investigators could find any evidence of sabotage. Instead, both teams of experts thought the ignition of the ship's hydrogen was probably due to some type of atmospheric electrical discharge. The Americans thought St. Elmo's fire, a discharge of static electricity from objects in or near thunderstorm activity, was the most likely agent, but none of the many witnesses who testified at the subsequent inquiry had seen the eerie bluish electrical glow that accompanies this phenomenon. The Germans thought that because of rapid changes in the atmospheric electrical field associated with the thunderstorm activity, potential differences might have built up between spots on the ship's exterior and its framework, differences that could have caused a spark if the spots were wet.

Professor Max Dieckmann of the German investigating team, an expert in atmospheric electricity, would later offer the most comprehensive explanation of the chain of events that led to the Hindenburg disaster. According to Dieckmann, the great airship's gas could have been ignited by a spark that jumped between its outer cover and its duralumin framework in the presence of loose hydrogen when wet landing ropes grounded the ship in a highly charged atmosphere. According to Dieckmann, five conditions had to be met for this to happen. There had to be: (1) a combustible hydrogen-air mixture inside the airship, (2) a wet outer cover, (3) a "high" landing, (4) a highly charged atmosphere, and (5) wet, conductive landing ropes. In October 1937, after he returned to Germany, Dieckmann read a paper before the Lilienthal Society for Aeronautical Research that set forth his theory and explained how his five conditions had been met. First, a flammable mixture of hydrogen and air had to be loose in the stern. Normally there would have been none, since the gas was confined within gaslight, rubberized-cotton cells. The fluttering cover, however, was taken to mean that free hydrogen had somehow escaped and was trying to leave the ship. Dieckmann's first condition had been met. So had his second, a wet outer cover. The Hindenburg had been flying through rain. The third condition required a "high" landing. Dieckmann considered the Hindenburg an electrical conductor that would acquire the charge of the atmosphere at flight level. By landing "high" at the Navy's request, Pruss unwittingly created a greater electrical potential between ground and airship than if he had landed "low." Condition four required a highly charged atmosphere, such as would be expected with thunderstorm activity. Moreover, after examining the traces of the recording meteorological instruments, Dieckmann concluded that a light, secondary thunderstorm was probably occurring during the landing and the electrical gradient over the field must have fluctuated violently.

Although Dieckmann did not say what weather data led him to this conclusion, the earlier report of the German investigating team had also mentioned the probability of a secondary thunderstorm or "thunder front." Their report associated it with the change to southeast winds, a slight pressure fall, and a change from a falling to a steady temperature that began at about 7:10 p.m. and lasted until about 7:55, when the wind shifted back to the northwest, the pressure began rising, and the temperature again began to fall rapidly. However, no distinctive clouds or precipitation accompanied these changes, and there was no thunder or lightning observed. As we shall see, whether there was a secondary thunderstorm or not (and the evidence is hardly conclusive), it would not have been the essential element in establishing a deadly difference in electrical potential between the Hindenburg's exterior and its metal framework. Dieckmann's fifth condition was that the handling lines had to be wet and therefore conductive--which they were. Dieckmann's paper concluded: ". . . after the completion of exhaustive preparations, model experiments were conducted, in which airship [Hindenburg] material was used and in which the atmospheric electrical field was represented by an artificial one of proportionate size. With obvious fulfillment of all five conditions, ignition of the hydrogen-air mixture always [author's italics] occurred." However, this was not the whole story.

A Fatal Flaw?

During the investigation, Dieckmann had been particularly suspicious of the Hindenburg's cover. While being driven from New York to Lakehurst for the inquiry, he had remarked that the airship had been painted with a different type of aircraft dope than previous zeppelins, and that they had better examine its dielectric properties. Back in Germany, he did just that, but, surprisingly, his paper to the Lilienthal Society made no mention of the outer cover and its dope. In August 1938, Ray E. Brown, civilian head of the helium program of the U.S. Navy's Bureau of Aeronautics, translated Dieckmann's paper, appending to it information he had obtained from people who had visited Dieckmann in his laboratory and witnessed his tests. Brown did not identify his sources, perhaps because they were German and he wanted to protect them. It was, after all, unwise for Germans under Nazi rule to volunteer such information to foreigners, particularly concerning a major national embarrassment like the Hindenburg disaster. Brown's appendix contains an extraordinary statement concerning Dieckmann's experiments: "When the [Hindenburg's] outer cover material was painted with the original dope used on the Graf Zeppelin, no explosions were obtained under any conditions, but explosions resulted whenever the Hindenberg type of dope was used." (Italics added.) Apparently, the dielectric character of the new Hindenburg dope was the critical catalyst for the laboratory explosions. Had Dieckmann found a fatal flaw in the Hindenburg?

Reconstructing the Disaster

According to Brown's appendix, Dieckmann used a 10-foot-square section of the Hindenburg's outer cover in his experiments, mounted horizontally 10 feet above the ground. Below it he placed a rubberized bag containing hydrogen, and inside the bag, a piece of metal representing the airship's frame. According to Brown, the tests "consisted of filling the bag with hydrogen to represent hydrogen escaped from a cell and pocketed beneath the outer cover, and setting up a difference of potential on the order of that which it is thought could have existed in the Hindenburg at the time of the accident. When the outer cover was dry, nothing resulted from the presence of this difference in potential, but when the cover was dampened, explosion of the hydrogen occurred." If we use Dieckmann's theory- and all his experimental results- we can reconstruct the Hindenburg fire as follows: The airship arrived over Lakehurst with hydrogen and air trapped under its outer cover near cell 5 (the source of the free gas perhaps a cell slashed open by a breaking wire). The crew dropped the bow lines, 400 feet of Manila hemp, attached to the structure of electrically bonded, duralumin girders and steel wires. The lines became wet in the rain, thus electrical conductors. They grounded the framework almost immediately but, because of the new dope, not the wet spots on the comparatively nonconducting outer cover. Thus, an electric potential developed between the two surfaces, a potential that was high because of thunderstorm activity. A spark shot between a wet spot on the cover and the metal frame. By sheer bad luck, the spark jumped just where there happened to be free hydrogen.

A Prophet without Honor

As might be expected, Dieckmann's explanation was not popular in Luft-schiffbau-Zeppelin, which had built the airship, nor in the Deutsche Zeppelin Reederei which had operated it. The Zeppelin family believed completely in the soundness of the Hindenburg and in their ability to operate safely with hydrogen. If something went wrong, it must have been the work of outside agents. This mindset led many, Pruss, included, to insist that the ship had to have been sabotaged. They held to this view despite the lack of any hard evidence to support it. Dr. Hugo Eckener, however, a member of the German investigating team, the world's most experienced airship commander, and the director of the Luftschiffbau-Zeppelin (as well as an anti-Nazi always in hot water with the Hitler regime), refused to accept the sabotage theory. He also thought an electrical discharge was the cause of the catastrophe, though he did not agree with Dieckmann on all particulars. The assertion that Eckener and his colleagues knew the airship had been sabotaged but were muzzled and kept from saying so by orders from Berlin is hard to swallow. With the war over and the Nazis gone, he would have been bursting to say so. But he wasn't and he didn't; his memoirs confirm that he did not consider sabotage the cause. Despite Eckener's concurrence, German airshipmen were reluctant to even consider that their creation could have been destroyed by natural causes. The Germans also had a very human and understandable unwillingness to believe they themselves could have fatally flawed it with the new dope. As a result Dieckmann's views never gained much acceptance. He himself didn't push them publicly, claiming only that the presence of the conditions in his experiment could have caused it. Perhaps this modesty reflected prudent recognition that citizens of the Third Reich did not point out flaws in symbols of the Fatherland's pride. In any event, Dieckmann was never credited in his lifetime with having explained the Hindenburg fire. Implicit recognition did come, however, when Luftschiffbau-Zeppelin built the LZ-130, a Hindenburg twin and the last of the great zeppelins. It modified the lacings that attached the outer cover to the metal frame, graphiting them to make them more electrically conductive! Also, when that hydrogen-filled airship, called the Graf Zeppelin 11, began flying in the fall of 1938, its crew carefully monitored the electrical gradient between the ship and the ground during landings. As for what dope was used on the new airship, there may no longer be anyone who knows.

End of an Era

Though the Hindenburg disaster ended the dirigible era, it was only the latest of many airship tragedies between 1919 and 1937. Of the U.S. Navy's airships, the Shenandoah was wrecked in a storm over Ohio in 1925, killing 14 people; the Akron was lost over the Atlantic in 1933, killing 73; and the Macon plunged into the Pacific in 1935, killing 2 more. Ironically, the fate of the dirigibles may have been sealed more by Air Minister Hermann Goering's distaste for them than by the accidents. Early in the '30s, the Zeppelin company had received crucial support from Propaganda Minister Joseph Goebbels, who recognized the value of the airships as a symbol of Nazi technological achievement. Goering reluctantly followed suit with money for the company, despite the proven ineffectiveness of dirigibles in military operations. At the outbreak of World War II, Goering grounded the last operational dirigible, Graf Zeppelin II. It joined the old Graf Zeppelin at their Frankfurt hangars. There, in May 1940, Goering had the great ships scrapped and their metal frames melted down to make Luftwaffe dive bombers.

Source: Vaeth, J.G. "What happened to the Hindenburg?" Weatherwise, Dec. 1990, Vol. 43 Issue 6, pp. 315-323.