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; it was 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 research Frau Dieckmann 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 prevent corrosion. Unwittingly creating blobs of thermite and not electrically bonding the fabric to the girders dc-10were fairly minor hiccups as Aerospace miscalculations go. Consider the DC-10’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 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 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.

Little of this was known outside of Deutschland of course, 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 129-wr-sterninsulation 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. Of 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.”

Of course there are those persons who, then as now, looked to invent a scenario to blame the hydrogen lifting gas in some capacity for the original ignition of the fabric. Hugo Eckener, after making amends for his initial published statement he did not think it was an accident, had later offered speculation at the inquest that a bracing wire had broken, which then slashed a cell, which then supposedly allowed a hydrogen-air mix to “pool” under the covering, which then found some ignition source in there. Eckener immediately admitted these several unlikely occurrences happening in close proximity and in the correct order was rather far-fetched. Nor was any explanation offered as to how an ignition source reached this unlikely combustible mixture without first lighting off the covering, whose ignition temperature was half that of oxy-hydrogen. In response, both Rosendahl and Dick pointed to experience with broken wires as causing no damage. Another expert, Earle, testified he doubted a combustible mix could accumulate under the cover.  No expert speculated how ignition conveniently materialized under the cover at the point of the supernatural accumulation.

The basic impossibility of the required five miracles in perfect sequence lead to alternative speculations, such as the return-from-Rio stuck valve incident somehow happening again at landing, then the individual is left to fill in the rest of the requirements himself. Like Eckener’s first outburst, there was also the romantic lure of some mysterious saboteur.  Nonetheless, Eckener’s broke wire-cell slash-H2/O2 mix – stopping at the cover – inquest musings became basis for what can only be described as a maniacal fervor bordering on a state-sponsored religion to 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, 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’s had some serious discussion 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.

zz-lz-130-farbbild-09Whatever else the Nazi-government dominated operation might be accused of, they were not stupid. Beyersdorff pointed out it did not matter what gas was inside. The LZ-129 fabric would burn from the outside, regardless if the cells were filled with nitrogen. He wrote: “…that an incombustible gas cannot prevent a burning of the covering as long as this one has the characteristics of the test results.” Quietly, behind the headlines, all LZ-130 fabric would be recreated to be treated with fire-retardant calcium sulfamate. Never admitted, let alone published anywhere, researchers would never find anything about this in the archives. Why? Like their failed hook-on experiments in 1937, it was not made part of their record.  These distinctly unique fabric elements were discovered by Dr. Addison Bain’s direction of testing of an LZ-130 fabric sample kindly supplied by “Zeppelin Collector” editor Cheryl Ganz, in comparison to actual LZ-129 fabric samples collected by Hepburn Walker, Jr. from where the ship fell.)

scannen0005The next step was a brilliant, two-solutions-in-one masterpiece. The aluminum pigmenting was revised to bronze-aluminum, which paid its weight penalty by adding both fire resistance and conductivity. Bronze won’t burn even bathed in a pure oxygen environment, and its low electrical resistance made the resultant mixture less likely to hold a charge. Next, to insure the covering would be a complete electrical circuit to the girders, graphite was added to the ramie fastening cord to electrically bond the newly conductive covering to the framework. (This also has not been found anywhere in the archives, but was seen by Harold Dick.) Now the newly fire-resistant and conductive covering could never develop a difference of potential between skin and frame. Nature electrically igniting the new covering would have been effectively impossible. Noting the graphite impregnation of the ramie cord, Goodyear liaison engineer Harold Dick reported, “Many changes were made to reduce static buildup.” Bauer and Duggan further detailed, “…the electrical conductivity of the hull was increased and a possible reduction in this was controlled through the installation of appropriate measuring equipment…”

20150626_112515The diesel engine’s electron-rich exhaust, however, was not so easily remedied. Every Zep with external power cars since World War One had been the more efficient pusher configuration. Completely redesigning the power cars to tractor, i.e. forward mounted propellers, was the first step toward addressing this problem.

03a-ansicht-von-oben-hutzenIt 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. It was thought the unnoticed invisible flames 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.

Meyer wrote, “Not only did the inert gas cause a 7 percent loss in buoyancy, it also required about six tons of additional operating equipment. Most of the [required] savings in weight had to come off the net payload of the airship.” It is likely we shall never know the width and breadth of the intensified efforts that were made available to overcome the enormous obstacles of operating a Zeppelin with payload-slashing American helium. Chapters of a skmbt_22316112202370-copybook have been (and an entire website should be) dedicated to the LZ-130’s transformation as the best talent in the airship community, backed by considerable resources, tackled the formidable challenges of helium operations’ new realities. First, a method of moving vast quantities of helium overseas would have to be engineered and built. The BoM agreed to sell helium, but as with Goodyear’s blimp operations, one had to bring one’s own containers. A typical “K” bottle held less than 100 cubic meters, demand quickly overwhelming even the great stacks of Army-Navy bottles manifolded together. Since it took four of the largest railroad-based compressed helium tank cars just to inflate a WWII “M” type blimp, it was not going to be practical to construct a merchant ship capable of carrying enough of those. Clearly higher pressure and greater capacity was needed if a ocean-going freighters were going to carry useful amounts of the rare Texas gas. A new, larger and tougher dessau-copybottle (photo) was designed and manufactured in large quantities. The specially modified freighter Dessau was loaded with these new bottles (photo) and sailed into the port of Galveston to unload them and await the first helium fill.  This effort represents the largest investment in moving pressurized helium overseas in history, dwarfing the US support of WWII blimp operations in South America and the Mediterranean. Nothing like it was ever before, or will ever be attempted again. Moving quantities of more than 10 million cubic feet of the rare gas overseas was not practical until the 1960s with the perfection of 4-walled dewars that could keep it liquid for long voyages.

skmbt_22316112202370The next outlay of funds built the facilities to receive, purify and store the precious gas (photo). Hefty spending on this highly visible infrastructure earned the ire of those less favored in the socialist regime.  As the bottles were stacked and manifolded together, anyone with knowledge of how much helium could be produced with the Fort Worth plant operating at full capacity was thankful no American rigids had to be filled at the same time. In fact, if there was to be enough to fill the LZ-130, full production was going to have to start filling those bottles pretty soon… but the Americans did not seem to be in any hurry.

zz-farbbild-07Meanwhile, LZ-130 had been designed to take advantage of some new interior arrangements.  After the helium edict, what passenger facilities had been built were pulled.  As Dörr wrote in 1938, “The framework which was already assembled has remained unchanged in its configuration. But the facilities for the passengers had been removed, where they already were in place. The arrangement of the rooms was changed in regard of their position to each other, and at the same time the facilities were reduced to a number of only 40 passengers. Thus and by some less visible measures, it was possible to reduce the weight of the hull. This was of importance in respect to the intended use of helium as the lifting agent, because this gas is much heavier than hydrogen, what adds up to a loss of 20 tons considering the size of the ship.”

zz-farbbild-08Dörr continued, “The installations in the lower gangway as well as the arrangement and the distribution of the load (fuel, water tanks, etc.) were slightly adjusted to the new conditions compared to the Hindenburg. The electric power plant was positioned close to the passenger facilities, because this offered some advantages; it was also slightly modified if compared with the Hindenburg.” 

fried-hangar-ext-copyAlthough the hangar lengthening had been planned before the accident, now there was the need to build the larger airship LZ-131 just to carry as many passengers and as much freight has LZ-129 had done. Hugo Eckener released a presentation in which he re-worked the books to put a happy face on the profit and loss of helium-only operations. Amid the helium resource expenditure, work on lengthening the hangar pressed on in conjunction with the first rivets being squeezed on LZ-131 “Super-Zep” girders. With hoped-for profit or just taxpayer subsidy, after missing two seasons, the Zep liners were slated to be finally coming back.

Read on to The Zeppelin Rebirth: 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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