The Hindenbug

The Hindenbug - WHY

February 25, 2017

By Bill Jones. There are many articles on the cause of the Hindenburg disaster. These articles discuss the possible causes. There are a number of theories. One important theory is that the fabric was ignited by a spark caused by the Hindenburg being electrically charged. It was certainly electrically charged, but the question in doubt is how did this electrical charge cause the fire.

Another theory is that the Hindenburg, on its final approach to landing made two sharp turns because of wind shifts. These turns were beyond the design specifications of the aircraft. It is suggested that a thin steel structure wire broke and whipped into a hydrogen gas bag. It is said that it broke because of the sharp turns. There were many such thin steel wires between the air bags.

The hydrogen then leaked from the bag and passed through air vents that were in the top of the aircraft. The hydrogen was then ignited by corona that was on the electrically charged aircraft. The Hindenburg had a fine record with seven trips to Rio de Janiero and ten trips to New York City. It was a large ship, being about as long as the Titanic – about 800 feet. The useful load is not clear. It was said that it had a lifting capacity of about 500,000 pounds.

It had a crew over of over forty, and a passenger load of fifty. The payload has been reported to be over 20,000 pounds, but the definition of payload is not defined. It did carry mail and freight. The actual load including freight, mail, passengers plus fuel and ballast is not clear.

It was a luxurious means of travel with many appointments. The ship had a dining room, a reading room, a right and left promenade. There were large slanted windows in the promenade room where the passengers could view the scenery below the ship. The ship had an aluminum piano. There was a dining room, a lounge, a writing room, a smoking room plus a small bar. The smoking room was pressurized for safety. The cabins were small, but the passengers were expected to spend their Addison Bain, a NASA Scientist thought the problem was with the fabric being set fire by a spark. He did not believe that hydrogen caused the fire. Bain believed that the spark was caused by the airship fabric being highly charged because it had been through charged rain clouds. This theory is certainly appropriate, and Bain did explore it very carefully. He had friends at the NASA labs that were willing to do the necessary fabric investigating on their own time.

Bain was convinced that the fire was caused by setting the fabric on fire because of a spark. The fabric was painted with a paint that is called aircraft dope. Aircraft dope is mostly lacquer, with other additives. One major additive is often aluminum. Aluminum is used as a preservative of the fabric covering. The aluminum reflects the Suns harmful rays. The fabric was cotton. The Aircraft dope is dangerous. Some of the pilots of WW1 carried pistols to use in case their airplane was ignited by machine gun fire from enemy aircraft. At the time of WW1 parachutes had not been invented. Burning to death was often not an option.

You seldom see aluminum colored aircraft, but the first coat of dope on a fabric aircraft is aluminized. Other lacquer paint is then applied over the aircraft to give it the desired color. The Hindenburg used only the aluminized lacquer to protect the aircraft fabric, and no other paint was added to reduce the weight – this is my assumption.

It was important to find the cause of the fire. Was it caused by a spark igniting the fabric or was it caused by a hydrogen leak that was ignited by a spark?

So why did the fabric catch fire? Addison Bain wanted to confirm the composition of the paint. While the use of aircraft dope would seem obvious it would have been possible that the manufacturer had a new formula for the paint.

Fortunately, Hepburn Walker Jr., a World War II airshipman, had some samples of LZ-129 (Hindenburg) fabric he had recovered from the Lakehurst, New Jersey mooring site where the Hindenburg fell. Cheryl Ganz, editor of The Zeppelin Collector, also lent one swatch from each of the two Graf Zeppelins.

The NASA Materials Science Laboratory at the Kennedy Space Center was Busy investigating the failure of an Italian tethered satellite when Bain approached with the fabric samples. Various types of detailed analysis would have to be performed to develop an exact list of the paint components, but the lab techs and scientists volunteered to help on what became known as "Project H.”

Bain went into high gear, interviewing experts at the Fire Sciences Laboratory in Missoula Montana, airline pilots who had witnessed corona discharges- luminous discharges of electric energy—on the surfaces of their aircraft. He had to rule out sabotage. There were a number of theories. There had been threats that the ship should not be allowed to land in America –or else. This was under the investigation by the FBI. Bain visited the former airship mooring sites in Lakehurst and Akron, Ohio, and he talked to Harold Dick, a Goodyear/Zeppelin engineer who made many Hindenburg (LZ-129) voyages. At the picturesque village of Friedricshafen in Germany, where ironically, the Zeppelin Company was building new hydrogen tank domes for the space shuttle, Bain talked with LZ-129 survivors.

The Zeppelin Company and the Friedrichshafen Museum laid out the red carpet (see "Company Town,"Feb/Mar 1997). Bain returned with many treasures, including some handwritten letters concerning the crash. But this technical German document needed careful translation, and 50 pages of NASA lab reports were now waiting Bain’s interpretation. The lab reported that fabric from the LZ-130 - an airship that had been under construction at the time of the Hindenburg fire, displayed spectrograph spikes of sulfur and calcium that were used in earlier airships. The Germans had added calcium sulfamate, a textile fireproofing agent, to the new ship.

Actually, whatever the paint/fabric composition, it is clear that the fabric was combustible. But, the question as to what caused it was still unanswered. At the time of the Hindenburg all aircraft used cotton or linen fabric for covering with lacquer being used to shrink the fabric. The lifetime of the covering treated with aluminized lacquer paint was usually only five to ten years before it required recovering.

There are still many fabric covered aircraft flown today, but the covering is usually a manmade type of material that is long lasting. The covering requires some means of shrinking to tighten the material to the airframe. This present day material is tightened by using heat to shrink the fabric. The older cotton or linen covering was tightened by the aircraft dope.

There have been reports of the Hindenburg using a component in the paint that was a fire retardant, but even so a material using a fire retardant chemical is not fire-proof. It is just more difficult to ignite. Clearly the Hindenburg was not fireproof. The covering of the Hindenburg was an important part of the story.

It is interesting to ask “If the aircraft outer skin had been aluminum like todays aircraft, and there was a hydrogen leak that was ignited by a spark – what then, would have happened? I think that the answer to the question is that a hydrogen leak mixed with air would result in an internal explosion set by an outside fire from the exiting hydrogen/air mixture. This would likely have caused a similar crash.

In such case, an internal explosion might totally destroy the aircraft as it ruptured the other hydrogen bags. If the fire were on the outside of the airship it could then melt the aluminum causing further damage to the hydrogen bags. The conclusion is that the fabric covering was certainly a main factor in the crash, and a cover of real aluminum might not have saved the airship. I believe that the main factor was the hydrogen.

The crash could have been avoided by a proper corona safety treatment of the Hindenburg. It is likely that the aircraft would have had a much greater lifetime had proper safeguards been in place. Corona has been shown to be hot enough to ignite hydrogen. Today’s aircraft use corona discharge wicks.

It is reported that the Hindenburg was covered by sheets of painted cotton. These sheets were held to the frame of the airship by carbon impregnated rope. This rope would discharge the sheet even if the rope was of very high resistance. Even the exhaust of the engines can help to discharge the corona provided that the engine was electrically connected to the frame of the ship.

It was said that Captain Pruss and company had just chosen the wrong night to accept the American suggestion to make a "high" landing. The landing technique the more experienced Germans preferred was to drive the airships directly down to ground-level mooring masts. The American’s moored their ships high, thinking that it kept them safer in gusting winds. After mooring, the ships were gradually winched down to earth. The German method would have been desirable on this night because the airship would not have such a long distance to fall.

Thunderstorms had come through Lakehurst that day, and when the Hindenburg made its high landing approach, lightning was still flickering on the horizon. It has been said that If the Graf Zeppelin—or even our own USS Akron or Macon, which used nonflammable helium- had been in LZ-129’s place that night, they would have wound up the same way. In my mind it is quite doubtful that this is the case. The U.S. airships used helium.

Once the bow landing lines were dropped, Mother Nature saw six and three quarter acres of electrically retentive surface area kiting in a highly charged atmosphere.

One witness, a college professor named Mark Heald, had reported seeing a blue glow of electrical activity dancing along the ship’s starboard topside for about a minute just before the ship caught fire. Although such plasma events are typically short-lived, airplane pilots have reported seeing some lasting for up to 80 seconds on their aircraft. The blue light is indicative of the high local temperatures a corona discharge can yield. The corona is hot enough to set fire to hydrogen.

So there was a hot plasma hugging the retentive hull for some time before the fire. The ship was bathed in a charged atmosphere.

Bain’s theory could be proven only by duplicating the actual cause of the real LZ-129 material fire. Luckily Bain had obtained two 60-year-ol samples of fabric. But the fabric on the Hindenburg had been less than two years old when the fire broke out. Would his samples still be volatile after six decades? Investigators at the NASA lab placed one sample in a chamber for a flame propagation test. To their surprise, the fabric went up in seconds. Then lab workers blasted the remaining fabric sample in a device that produces high-voltage electrical fields, a test more closely replicating conditions of that May 1937 evening. A thread-like electric arc burned a hole in the fabric, duplicating reports of zeppelins having been struck by lightning and suffering only localized damage. But when the fabric was mounted so it remained parallel to an arc, the electrical energy ignited the fabric and it disappeared in seconds.

An arc would not be caused by a small electrical source because an arc requires a steady source. An arc would be much like holding a match to the fabric. In such case the fabric would certainly catch fire. Since lighting had struck such aircraft without a fabric fire it would indicate that a spark would not cause the fabric to burst into flame. This would then rule out a spark causing the fabric fire. Hugo Eckner himself blamed hydrogen for the fire.

As I read these background materials to prepare this post, it was noted that an actual witness saw corona on the top of the airship. Mark Heald, a Princeton professor who was an eye-witness, along with his wife and son, was quoted to the effect he had seen. The corona on the craft was what was commonly known as St Elmo’s fire. This was seen moments before the airship caught fire, as seen by the professor. The professor had a distinguished career.

A short biography for Professor Mark M. Heald is provided. He was a Princeton and Rutgers Professor. He was born on February 20, 1892, in Canton, Illinois. He was the son of Edward Aiken (OC '84) and Mary Chaffee Heald. He received his A.B. from Oberlin College in 1914, and an A.M. in 1925 from Columbia. He completed additional studies at the University of Minnesota, where he was a teaching fellow from 1916-17.

While others had observed the corona I believe the Heald report was proof that the corona was present at the time of the disaster.

It has been reported that the Hindenburg was venting hydrogen during landing. The venting of the hydrogen would always be a danger because it could be set fire by a spark. In the case of a damaged hydrogen bag there would have likely been a great amount of hydrogen available for the corona to ignite. I believe the theory of a damaged hydrogen bag is correct and a damaged bag supplied the hydrogen for the corona to ignite.

An important theory for the loss of the Hindenburg is that while on the approach to landing the craft made two sharp turns because of wind shifts. These tight turns would be called pilot error. The turns stressed the ship beyond its design limits. The ship was late in arrival. It was scheduled to leave the next day. The Captain was under pressure to land the airship as quick as possible. Such sharp turns exceeded the design specifications of the ship, and were prohibited.

The ship used many thin steel wires to strengthen the structure. It was then hypothesized that one or more of these steel wires broke and whipped into one of the aft air bags causing a rupture of the bag. The bag then released hydrogen through the air vents. Corona ignited the leaking hydrogen. The fabric was quite flammable, and caught fire, it ignited other hydrogen bags, causing the crash.

This crash actually caused the demise of the Airship industry.

The building of such a beautiful machine was certainly incredibly expensive. It had great political monetary support for the building such airships.

It would have been a great way to travel. It was certainly not an industry that could make a profit. It was an industry that did show what a country could do. The Nazi’s knew that these machines were admired. They were certainly proud of their accomplishments. Germany built many of the craft and showed the world what they could do. And then a great publicized disaster, and destruction of an industry.

As it turns out I believe that the Hindenburg (or any hydrogen craft) would have eventually been destroyed by fire because of the hydrogen release on landing. The aircraft had no corona protection. Corona is developed on aircraft as they encounter electrons. Rain droplets may increase the electric charge. The Hindenburg had been through rain, and there was still lightening in the distance when the aircraft was landing. Without corona protection, any aircraft builds an electric charge. Corona protection was discovered in the 1940’s as far as I can tell.

The protection consists of static wicks attached to the aircraft. These wicks carry corona current to the end of the wick that has hundreds of fine wires that dissipate the corona or static current. The wicks are likely called static wicks because they dissipate the corona current without a spark. During WW2 it was noted that radio reception was disturbed by static. It was found that the static was actually sparks from the aircraft itself. These wicks solved this problem.

I suspect that this problem was known before WW2 but have not found the actual date of the first use of static wicks. The rudders, elevators and ailerons must be electrically connected to the main frame or they will cause electrical discharges. The motors must also be electrically connected to the aircraft because the exhaust from the engines will help to discharge the corona. This exhaust forms a high resistance connection to the air surrounding the aircraft. The exhaust has water vapor in the exhaust discharge, the water providing the resistance to the air.

Then the Hindenburg had no corona protection, and further it was likely that the control surfaces were not properly connected to the airframe. Since it had no corona protection it would, of course, have had sparks occur around the fabric on every flight. It likely had sparks occur on its very first flight. These sparks did not cause a problem. The corona, and spark safety means were unknown at the time the Hindenburg was built.

There was a good probability that the hydrogen would, sooner or later, catch fire because the craft would always be emitting sparks on every flight - very likely on the rear surfaces. It would catch fire when the hydrogen was released for the purpose of landing.

I accept the theory that there was a hydrogen loss. And, that it was caused by the maneuvering of the craft while landing. An airbag was ruptured because the craft was sharply turned twice - thus breaking the steel structure wire or wires. It is known that the craft was tail heavy on its final approach. The captain ordered rear ballast water to be deployed three times during the final approach. This is very unusual. You normally release ballast when you want to go up. I believe the loss of lift in the aft of the Hindenburg was proof that there was a massive hydrogen loss.

I then believe that hydrogen was leaking in such a large amount that it did cause the captain to have to release water ballast three times on the final approach. He then also called crew members to the front to level the craft. Since there were no means for removal of corona the hydrogen was then set fire. This then destroyed the craft.

The design of the craft was such that the airships would eventually catch fire because of the hydrogen venting was required for landing. If corona had been understood, the hydrogen aircraft would have been much safer. The use of hydrogen in the aircraft always presented a problem.

The airships were often caught in bad weather, and the weather was a very large factor in the airship crashes. Weather may have been as much of a problem as the use of hydrogen. Weather forecasting was poor at the time of the airships. Lightning had caused the crash of some airships.

The use of helium was in the plan for the initial design phase of the Hindenburg by the Zeppelin Company. The Company had been told that America would allow helium to be sold to the Zeppelin Company. I believe that politics got in the way and Germany was finally denied the helium.

In any case the release of hydrogen during landing was required. Since the use of spark or corona removal was unknown, I believe the corona or sparks would have eventually set the venting hydrogen on fire. The use of corona discharge and proper release of the hydrogen were not considered in the design of the craft since the danger of corona was unknown at the time of the design. The use of hydrogen in the aircraft without corona or spark protection was an accident waiting to happen.

While the fabric was an important factor, the fabric was not set fire by a spark. A hydrogen leak was set fire by the corona, and this caused the fabric blaze which then set the other hydrogen bags on fire. I believe that this was the cause of the disaster.