The Zeppelin Rebirth: Finding the Cause

129-guard-wreathLZ-130 was to have entered service early in 1938, replacing the retiring LZ-127. Instead, on the second transatlantic trip of 1937, LZ-129’s fabric caught fire during his “flying moor” at Lakehurst. Without hesitation, Captain Von Schiller insisted he should take off from Frankfurt with the full load of passengers for LZ-127’s next regularly scheduled flight to Rio on May 11th. (While there had been a few cancellations, there were also nine new requests for cabins.) In a fateful decision that had more far-reaching consequences than anyone dreamed at the time, Hugo Eckener over-ruled Von Schiller, canceling Zeppelin flights until further notice.

dsc00242-copyAs the days passed, speculation as to what caused the accident abounded. A supposed horrific fire or explosion in the tail got some press. Looking none the worse for wear, the four men who had been in the stern at the very moment of ignition posed for this photo on May 23rd. Left to right:  Tommy Doerflein, Heinrich Bower, Rudolf Sauter and Helmut Lau. Finally returning to Germany, insiders suggested that Captain Pruss had been read the riot act for agreeing to the American demand for the “flying moor” landing that night given the highly charged atmosphere the ship had been flying in for several hours. The results of the coming research would verify the wisdom of that set-aside caution. Regardless, no one could be satisfied to return to flight by simply enforcing the prohibition on high landings, irrespective of the weather.

The fire halted LZ-130 work for a time, but the accident was not a death knell. In fact, Propaganda minister Joseph Goebbels (whose 1935 memo had urged Hitler to nationalize the DELAG) let it be known the Third Reich could not lose face by ending with a failure. As serious resources would be called up to recover from the accident, the first step would be to figure out exactly how the fabric ignited. Samples of fabric were sent to experts in Germany. Within a few more weeks, testing had revealed the problem. One electrical expert, Otto Beyersdorf, had received samples from the Zeppelin factory and wrote, “The ‘Werf’ was kind enough to send me a sample of the covering material; with which I was able to perform tests in the laboratory matching the conditions of the accident and which proved the material to be extremely easy to inflame. An acquaintance of mine, an academic adviser, who took part in some of the tests, was amazed at the high degree of inflamability.” Of course everyone knew any nitrate-doped fabric was highly flammable; they key was to discover its ignition source of May 6th.  Beyersdorf wrote, “… [T]he reported details about the fire made the causes of the origination so s_h30_70501083definitely clear – namely, the ignition of the covering caused by electrostatic discharge…” In a letter dated 28 June 1937, Beyersdorf specified:  “1. The actual cause of the fire was the extreme easy inflammability of the covering material brought about by discharges of an electrostatic nature…” Beyersdorff cautions the covering material must be changed: “2. By using the same material, an ignition has to always happen again, when the proper circumstances are present, as for example Lakehurst.”

So, there was no longer any question how the fabric was ignited.

In other words, it the incredible expense of building a helium support infrastructure, the then non-existent method of shipping tens of millions of cubic feet of helium transatlantic had been built, and the LZ-129 had accepted half the passenger load, etc. – then his fabric would have caught fire in the exact same way given the conditions that fateful night.

The research would then focus on what was different about LZ-129 which made it more vulnerable to the static-rich environment than the much more traveled LZ-127. Edith Dieckmann (widow of Professor Dieckmann, Munich Technical Institute electrical expert close to the investigation) stated, “When my husband returned to Germany, after the accident, he conducted tests with fabric from the Graf Zeppelin and the Hindenburg. He never got a fire with the Graf testing but did every time with that from the Hindenburg. He could not release the results of his work for insurance reasons and not to embarrass the Third Reich.” Ordinary citizens certainly didn’t want to cause the Nazis any loss of face; even minor embarrassments had been known to be fatal.

None of this information was likely to have reached the English-speaking world had it not been for the research of retired NASA hydrogen fuels manager Dr. Addison Bain. Without what Dr. Bain had to discover by lab experimentation and sample analysis, any difference in the covering might have remained little more than the hints in a 1937 work translated and mentioned by Gordon Vaeth in 1990 and a German technical discussion in 1991. Locating the actual research that Frau Dieckmann had mentioned, Bauer and Duggan wrote, “In the course of his work, Professor Dieckmann from the DVG [Gräfelfing Research Institute] had discovered that the new covering “Cellon” had no electrical conductivity and could have been the cause of the Hindenburg disaster. Through a coating of graphite paint between the hull and the frame [sic] of the LZ-130 it was possible to improve conductivity, thus eliminating any risk of that “fatal difference” in voltage.”

Looking back to LZ-129’s construction, the seemingly minor improvements made to the -129’s covering had inadvertently caused the airship to be vulnerable to the New Jersey environment that fateful night. Since all possible weather conditions and operational techniques could not be simulated, these were certainly honest mistakes, made with only the best of intentions to repel water weight,  and to prevent structural  corrosion.

Unwittingly creating blobs of thermite, and not electrically bonding the fabric to the girders, were fairly minor hiccups as Aerospace miscalculations go. dc-10Consider the McDonnell-Douglas DC-10 widebody airliner’s various design flaws and maintenance errors that killed over a thousand passengers before they were all reworked, and the airplane emerged as the MD-11 to sin no more.  (Likewise, the rush-to-production defects in the B-29 cost more US Army airmen’s lives than did the Japanese defending against it. When Boeing had time to address and fix the many design oversights and field-failed features, the Air Force had to renumber the all but completely different airplane the B-50.)  Compared to the list of horrible atrocities committed by the 3rd Reich, trying to save face (as well as avoiding actual lawsuits) might seem trivial indeed. To this day there has been no public admission of the separately harmless steps made on LZ-129′ covering and structure anti-corrosion steps that allowed a shorter accident chain to destroy the airship that fateful night.  However, what that fraud of silence ultimately did do was cost our civilization the sustainable – i.e., profitable—passenger rigid airship, giving us instead endless hand-wringing about the possible employment of nature’s most abundant element in any role whatsoever.

Naturally this was known only to a small number of experts inside Deutschland, but at least one report was published in the German language for internal consumption. The 1938 ‘Wireless Telegraph and Atmospheric Electrical Station’ report which is translated thusly: “The basic cause of the catastrophic fire is ultimately to be regarded as the poor conductivity of the aluminum paint coating on the outer skin and the good insulation of the blue anti-corrosion paint of the framework. Also, if the landing tow ropes had been attached to the ship’s hatches directly, then the total conductivity value of the tow lines probably could not have reached the required amount for discharge, or only then after the ship had been hauled down to a lower height, when the field strength would not have been sufficient.” So there was plenty of blame to go around, bow to (photo) stern. 129-wr-sternOf great importance, and surprisingly not exploited by the 3rd Reich, was the fact the Americans – also convinced they were doing the right thing – had put the final nail in the coffin with their seemingly innocent request for a “flying moor.”

Fed a constant stream of helium propaganda for more than a decade, it is perhaps understandable the radio reporter Herb Morrison, like many Americans, would have ignored the fabric they saw burning. It seemed more natural to assume the fire was, instead, somehow inside, originating with the lifting gas supposedly making the glow he’d witnessed. Since Herb recorded hearing an explosion, he further assumed that, like petroleum, explosion would be followed by fire. Moments after the bow settles, Herb records, “You see they’re using hydrogen, or they were using hydrogen, in this plane, and it’s EXTREMELY explosive…” Unlikely to have ever known of the easy ignition and high flammability of nitrate-doped fabrics on aircraft, Herb Morrison was the first American whose gut feeling became LZ-129 lore without benefit of investigative research.

Still, any scenario that even partially implicated the constructors would have cost the Nazi overlords considerable face – as well as hard currency, if lawsuits went against them.  Dr. Hugo Ecekner was faced with a dilemma somewhat unique in the history of technology, the problem occupying every waking moment as he backed his bags for America.

US Navy Commander Neil MacCoull, in 1936 at Lakehurst for training, years later recalled a lunch conversation with Hugo Eckener, staying over at Lakehurst on one of the LZ-129 trips. Bringing up helium, MacCoull remembered, “Dr. Eckener surprised me by replying that he was not sure that they wanted helium, because of the appreciable loss of pay load. [Appreciable indeed: according to CP Burgess, 59%,  before water recovery apparatus weight was added.] When I referred to the U. S. Navy’s policy of using helium for airships, because of safety from the danger of fire, he replied: “We Germans feel that we have developed the art of using hydrogen in airships to a point where there is practically no danger of fire.” He then elaborated that a fire could develop only from three simultaneous accidents occurring at the same place:
1 – A gas cell leak,
2 – A mixture with air in combustible proportions, – and
3 – A source of ignition.
He [Eckener] elaborated still further on the detailed precautions taken in design and the technique of airship handling which would make such a coincidence of these three factors almost impossible. This whole conversation, and Dr. Eckener’s attitude, seemed completely different from his attitude at the Board of Inquiry on the loss of the Hindenburg, a year later, when he testified that the fire was probably caused by static electricity.”

Before leaving Germany, Hugo Eckener had publicly made amends for his initial published statement he did not think it was an accident. Later, at the American inquest, Dr. Eckener offered speculation that a bracing wire had broken, an amazingly convenient idea devoid of evidence, or experience, that at least seemed to offer a way to get the airless hydrogen out of the cell, where it could mix with the oxygen in the airspace in between cell and outer cover.

Somewhat interesting, the layman Morrison was actually the first to seem to record a sort of understanding the airless gas in the cells could not get oxygen for combustion, let alone explode. As the ship is burning in front of him, he records, “Now something may have slipped causing a spark to set off some hydrogen that leaked out into the structure…”  Minutes later, realizing that the hydrogen must be long gone and unable to fathom the tonnage of diesel fuel that would keep belching black smoke for hours to come, Herb admits, “It’s still burning, I don’t know what’s burning, perhaps some of the cargo.” Morrison, like many today, would be surprised to learn of the British practice of suspending their North Sea airship’s gasoline tanks within the airless hydrogen envelope, thereby preventing explosive ullage from forming an accident awaiting an ignition source.

In response to Eckener’s broken wire invention, both Rosendahl (and later, Harold Dick) pointed to experience with broken wires as causing no damage. Actually more similar to a bicycle spoke than a sprung wire, Rosendahl explained such breaks had been noted in rigids but had never effected a gas cell.

Eckener’s testimony gave the broken bracing wire significance because, he went on, it had then actually slashed a cell, which allowed gas to escape its containment.  Nothing new there; his previous ship, the LZ-127 Graf Zeppelin, had such porous cattle-gut shingled cells there was a constant leakage of hydrogen under the cover, where it could mix with air. So this was also of no consequence.

Eckener nonetheless offered the next step, that the resulting hydrogen-air mix would somehow “pool” under the covering.

In his testimony, another expert, Earle, testified he doubted a combustible mix could accumulate under the cover. Earle had good reason to say so; the outer cover was no substitute gas cell. Specifically designed to “breathe” to allow the airship to change altitude harmlessly, escaping gas would be quickly diluted as it climbed toward the stratosphere at three meters a second. Again, more than 500 flight experiences with the leaky Graf Zeppelin in all weather conditions around the world provided the obvious example.

The weave of the outer cover was so porous in relation to nature’s smallest two-atom element – think of pin heads in relation to road mesh or larger – it would have easily slipped through. Hence why some rigid airship builders did not bother with the German’s complex and weighty vent tower system.

As the photo shows, a British ship’s very large safety valve is seen ready to vent hydrogen directly under the outer cover. Never a problem, since vented gas would quickly dissolve in the ventilated space, while simultaneously rising quickly away from possible ignition sources.

This little known fact was overlooked many years later when, faced with the impossibility of Eckener’s five-miracles-in-a-row to place hydrogen in the fabric’s ignition sequence, the “stuck valve” was introduced into the LZ-129 lore. Forgetting the isolation of its vent towers, again, the fabric was no substitute gas cell.

Which brings us to the even larger problem:  how to ignite this magically loitering and defiantly combustible gas-air mixture.  Already stacking four extremely unlikely – i.e. miraculous – events in the right order in time, it seemed a simple matter to imagine some source of ignition, even with the dirigible’s construction and operation carefully geared to eliminating possible ignitors inside the ship.

Even given the four miracles, the major trouble with all the hydrogen-first-then-fabric hopefuls was the missing explanation as to how an ignition source reached this unlikely loitering combustible mixture without first lighting off the covering, whose ignition temperature was half that of oxy-hydrogen. No expert speculated how ignition conveniently materialized under the cover precisely at the point of the supernaturally lingering accumulation. (Later, others have added a six miracle, that a hole appeared in the covering to allow an un-named ignition source to slip through. Likewise, the wire breaking had heated its tip, or the supposedly corroded structure breaking just in the right place and time, etc. etc. ad naseum.)

Without establishing the source of ignition, Eckener quickly admitted the several unlikely occurrences happening first in close proximity and in the correct order was rather far-fetched, just as he had told MacCoull in 1936 and others long before.

Few other Americans besides Rosendahl and Earle felt compelled to cry foul. Likewise, the NAS Lakehurst station record matter-of-factly logged the ship was destroyed by hydrogen fire. Done deal, as far as the Americans were concerned.

Small wonder Max Pruss (photo), who was keenly aware of all this as well, said, “Certainly, the cause of the accident is not clear.” His shipmate Lehmann, equally knowledgeable, with his last breath said, “I don’t understand it.” Indeed, writing to Dr. Karl Arnstein about the accident, his project engineer H. R. Liebert complained, “The missing link, this is the presence of free hydrogen, is yet to be explained.”

The basic impossibility of the required five miracles in perfect sequence lead to seemingly more acceptable, alternative speculations, such as the return-from-Rio pressure-height-chattering stuck valve incident somehow happening again at landing. Given the cells being “quite a bit up” from venting during the crossing,  the individual is left to fill in the rest of the requirements himself. Historian Doug Robinson used his Professor Held interview to formulate a stuck-valve theory that has developed its own loyal following, likewise leaving undefined its hovering hydrogen, ignition sequence, fire u-turn, or subsequent fabric spread. The isolated vent towers demonstrated they could safely discharge even stuck-wide-open valves, into much higher altitude with its higher voltage potentials, as they had on that first South American return in 1936.

Like Eckener’s first outburst when told of the fire, there was also the romantic lure of some mysterious saboteur, with the evidence to support same conveniently burned up in the fire.  Happily for him, no mad bomber search had to be conducted. Eckener had an American audience ready, willing and able to accept anything that showed God’s gift of helium to America as being the just and righteous path for buoyant craft. No harm to the Germans, either, since partial blame was shared with the Aemricans – not because of the ordered “high” landing, but because of their supposedly refusing to sell helium.

Nonetheless the basic improbability of Eckener’s five-miracles-in-a-row and/or the chattering-stuck open valve explanations, an entire culture later grew up around the mad bomber “savior.” Author A. A. Hoehling did not ask “what,” but rather “Who Destroyed the Hindenburg?” in his 1962 book. He fingered a 27-year old loner crewman named Eric Spehl as the culprit (photo). Hoehling suggested a photo flash bulb would have been sufficient to ignite the airless gas cell, because it contained a little air (!)

Many Zep crewmen were still alive in 1962, and they laughed at the suggestion. Some of his shipmates speculated Spehl “didn’t have the smarts” to make a bomb. Indeed, he must have been somewhat insufficient (unless suicidal as well) seeing as his landing station put him  at the very tip of the bow, right behind the mooring spindle, and he did not survive.

The mad bomber was not going away quietly, as a decade later author Mike Mooney got paid to revisit this story. His mad bomber flashed across big screens in the movie version.

So it came to pass, Eckener’s broke wire-cell slash-cell H2/O2 mix – U-turn at the cover- spark through the cover without igniting the fabric – inquest musings were eagerly accepted by most Americans for decades. These carefully constructed comments became basis for what can only be described as a maniacal fervor bordering on a state-sponsored religion.  As such, we forever divorce nature’s simplest element from not just cloth-covered rigid airships, but any air-displacing applications, even in nonflammable containers, to this day!

Part and parcel to covering up the oversights in LZ-129’s covering came the implication that the accident was an “Act of God.” After all, the Almighty could not be sued. Then, by hinting that the lifting gas played at least an intermediate role, i.e. energy carrier in between ignition and fabric, the Nazi regime had a way out of their failure loss of face. They’d say nothing about the fabric and just use helium the next time they carried passengers. After all, they’d had some serious thoughts about it before.  The Americans had learned to live with helium in their airships; why not? It was just a question of money, it seemed. The Americans agreed, passing legislation that would allow helium to be sold for the seemingly humanitarian purpose of carrying passengers more safely.

It must be noted that, out of an abundance of caution, on the LZ-130, additional vents were added atop the vertical stabilizer. The reason for this change is hinted in the literature, speculating that oxy-hydrogen flame may have somehow originated in the upper reaches of the LZ-129 vertical stabilizer. (Remember Herb Morrison repeatedly recorded that the fire had originated in the uppermost part of the tail. ) More calmly than Morrison, speculation was the unnoticed invisible flames, though they could not have illuminated the girders from behind like witnesses described, may have spread before igniting something that made visible combustion.  Also related to the static found on the top of the hull at most all times, seamless vent hoods (photo) were specified in the drawing.

These and other  behind-the-scenes changes went unnoticed then – and escape notice of most people even today. The Zeppelin Rebirth would involve extensive investment in a highly visible face-saving effort that, based on a lie still widely believed today, would all be for naught.

Read on to The Zeppelin Reborn: LZ-130


Read on to ZRN: The Rigid’s Last Best Hope


Read on to ZRCV: The Giant That Almost Was

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