American Zeppelins

US Navy sailors could only lust after the Zeppelins’ long range fleet scouting (photos), credited with saving the German Fleet at Jutland. Dr. R. K. Smith wrote, “The Germans first exploited their Zeppelins as a reconnaissance vehicle… and there were experiments to carry airplanes as a ‘built-in’ fighter escort, and an effort to develop a remote-controlled glider bomb which would provide a limited standoff capability.” (lower right, both on LZ-80, while other ships carried a “spy basket”).


America was the last major power to initiate work on a large airship, but early design efforts were quickly discarded when an exhausted Zeppelin literally fell into Allied hands. Brig. Gen. William “Billy” Mitchell wrote, “Several pilots from French squadrons in the vicinity had attacked the great ship on its way down and fired innumerable bullets into its envelope, many of them incendiary, but with little effect.” One source says the Zep crews then hastily fired flares into the airless hydrogen cells, which, lacking oxygen, snuffed their combustion. This allowed French troops to capture the L-49 (below) and its altitude- sick crew, intact and still partially buoyant.


French constructors reverse-engineered plans of that height-climber Zep (factory number LZ-96).  By 1919 Americans were adapting the plans and strengthening its lightweight structure. By 1922, the Americans had begun construction of their copy, originally designated DR-1, via pieces riveted at the Naval Aircraft Factory.

Following the loss of the R.38/ZR-2, the Allies allowed the US Navy to purchase a real Zeppelin. Signing a contract in June, 1922, construction began in Germany on build number LZ-126.

Meanwhile, following an admittedly fraudulent “demonstration” that tricked Congress into cutting funding for hydrogen-borne powered airship flight, inflation of the new ZR-1, which would become USS Shenandoah, awaited shipment of enough Bureau of Mines helium bottles. Dr. Richard K. Smith offered a sobering view of the realities of the change-over, “…it was the Shenandoah which taught the Navy and indirectly the world, that however “safe” helium was by virtue of its nonflammability, it was no panacea.  Indeed, helium created its own peculiar problems to afflict airship operations.” Peter Andrews would detail, “She had been designed for hydrogen, and although helium produced 92 percent of the lifting power of hydrogen, its use reduced the Shenandoah’s range by almost 40 percent, which effectively robbed the ship of its long-range reconnaissance capability.”

ZR-1 finally launched in September, 1923. (Surviving motion pictures are included on the DVD The American Zeppelins.) Her early operations – including a daring flight to the St. Louis Air Races in October – repeatedly found the ship delayed, waiting for the helium to cool down – superheat was now a larger problem. Lifting gas naturally had to be vented for landing. Author R. K. Smith explained, “As an airship burns off fuel it becomes lighter and wants to climb higher. Ordinarily, [lifting] gas would be valved to correct the situation. But the Americans were obliged to devise a system to generate ballast to replace the weight of the fuel. The Navy developed a means of condensing water vapor by [cooling the hot] exhaust gases of the airship’s engines, which more than replaced the weight of the fuel consumed. However, the weight of this water recovery apparatus was substantial, its aerodynamic drag was phenomenal, and its maintenance was a constant headache.” (Photo: final version of the water-recovery condenser stack on ZR-1 engine car #2.) British author Teed had only seen such equipment in use in the ZR-1 at the time he wrote “…this means a double reduction in the efficiency of an airship.”

Meanwhile, Zeppelin constructors drug their feet on what was assumed to be their last job, finally delivering LZ-126 to Lakehurst in October, 1924. 1&3Propped up from the floor and hung from the hangar rafters, ZR-3’s hydrogen was vented through the roof. But there was only enough helium for one rigid. Both ships had to be suspended from the hangar and propped on lumber to transfer ZR-1’s gas to ZR-3, which was then flown to Washington and christened USS Los Angeles. 

Suddenly the airship that had crossed the Atlantic could not go back, even with the favorable prevailing wind. Airship guru Charles P. Burgess explained the harsh realities of the problem in his 1927 book AIRSHIP DESIGN. “It is common practice in America to take the unit lifts of hydrogen and helium as .068 and .060 lb/ft3 in the standard atmosphere at sea level. Both units are conservative. From these figures, 11.8% of the gross lift is lost by the lift of helium instead of hydrogen; but the percentage of losses of the useful and military or commercial load are much greater because the weight of the ship empty is a fixed quantity, and the absolute losses of gross and useful lifts are therefore equal.” In the example given, a mathematical formula proves that the airship’s useful load is decreased by 31%, and the loss of commercial load is an astonishing 59%!

Those figures came before the weight of the now-necessary water recovery apparatus was figured in. Robinson and Keller wrote of it, “While the theory was simple, the practice was not, and some of the problems were never solved.” Naturally the engines lost efficiency due to back pressure, and the radiators had to be bypassed for full power – just when fuel weight was disappearing at the greatest rate. The power-robbing hardware hanging out in the slipstream increased aerodynamic drag. Units added to ZR-3 were found to increase drag anywhere from 5% to an astonishing 10%. Since the units once froze and became useless, extra tonnage of anti-freeze had to be carried, and as Robinson and Keller reported, “…extensive corrosion of the keel girders caused by the use of calcium chloride antifreeze in the ballast bags… Subsequently, alcohol was the preferred anti-freeze despite the greater expense.”

USS Los Angeles proved to be consuming the helium almost as fast as it could be bottled and shipped from Texas. On 8 June, for example, 125,000 cubic feet of helium – enough to inflate the J-1 blimp, had it been in service – was vented away to allow a landing. Following a few month’s flights of the “German jewel”, the two-ship process was repeated and ZR-1 reclaimed the remaining helium – as well its original condensers, since only one set had been made. There had been serious planning to borrow helium from the Army and marshal other resources for a flight to the North Pole, but comparatively little actual scouting in Fleet exercises.

Innovative “Zack” Lansdowne made the best of the situation by carefully managing gas availability and flight schedules. Without the press catching on, longer missions were begun in darkness by using all the available helium at the moment – not enough to lift a typical fuel load – and walking the ship to the tower mast. After the rising sun warmed the helium, its expansion allowed additional supplies and required fuel to be taken aboard. Launch would be made before clouds gathered.

By the late summer of 1925, ZR-3 was still propped up and hanging awaiting gas, while ZR-1 was seeping helium so badly it would have soon exceeded available replenishment – without one bottle set aside for ZR-3.  (At the low point not even one ASW blimp could be inflated.) The helium-only policy forced the airshipmen into a no-win situation: since there was no war, and since Congress had cut funding for it, they could not return to full performance with hydrogen. The pure helium-only policy was without exception – even when there was not enough to make the airship airworthy. In desperation to keep flying on even a limited schedule, “jam-pot” covers were used to cap the worst seeping valves – the ones that were at least reachable – the leaky overpressure safety valves.

Zeppelin Captain-instructor Anton Heinen, hero of the breakaway flight, as Stan Washburn explained, “bluntly announced that such a move was insane and likened securing the gas valves on the Shenandoah to tying down the safety valves on a steam boiler. He then advised the Navy Department he would not fly aboard the Shenandoah with the emergency valves tightly secured.”

Leadership scheduled more flights, but not to a Fleet exercise, but instead a public visibility flight in September. ZR-1 encountered a most violent Ohio storm in which “…the ship was pushed above its pressure height in the up-draft…”  The helium cells expanded normally as in any ascent, but the safety valves had been closed off. Unable to vent, “internal pressure broke the structure into three sections which crashed down separately…”  Men in the car, at the break junction and in the engine cars, were lost. Many men were saved by hanging on to other individually buoyant pieces until they settled. Unlike R.38 / ZR-2, whose break exposed gasoline spraying from the broken fuel line at the point severed and sparking electrical cables were still connected to a running generator, there was, thankfully, no fire.

In the aftermath, “… a Navy spokesman said the disaster was an act of God.”  Anton Heinen refused to parrot the helium propaganda. Interviewed, “… he brought out the directive from Washington ordering that the valves be sealed to prevent leakage of expensive helium and his written refusal to comply.”  Pointing out the structure failed right where the valves had been capped,  he emphasized publicly, “Those valves were put there for a purpose!”   However, at the time, the wisdom of the necessities of helium operations was not supposed to be questioned publicly.  Heinen told the New York Times, “I could have taken the Los Angeles filled with hydrogen on that same morning and followed in the wake of the Shenandoah and brought her through without the slightest danger… [Shenandoah’s] alterations were designed as a measure of economy to save helium. It was poor economy for it wasted the most precious material aboard – 14 human lives.”  A loose cannon on the deck, as a “…result – Heinen was fired.”

It was not public knowledge the British had purposely overpressurized the cells of R 32 during its being dismantled, which verified the rigid’s structure would be compromised without functional cell safety valves. Though never admitted aloud or in print, destructive testing of ZR-3 just prior to WWII also verified Heinen’s assessment. No apology to the ZR-1 victim’s families has ever been made for the helium-only policy that forced the airshipmen into rendering their airship unairworthy.

While it is not a substitute for a complete history, we have created a half-hour video covering the ZR-1 history.

Waiting almost a year for enough helium to be accumulated, ZR-3 resumed flights in April, 1926.  In spite of meager helium allotments and aging, leaky cells, no safety valves were ever again capped off.  Several flights were made for calibrating radio stations as well as fostering interest in rigid airships. On 27 January 1928, ZR-3 “landed” aboard the aircraft carrier USS Saratoga for practice refueling and crew exchange (right; motion pictures are in the DVD The American Zeppelins). She was used in the development of the stub mooring and mobile mooring masts. ZR-3’s overhauled but still leaky cells challenged a regular flight schedule as the original Petrolia natural gas filed ran dry of helium. Congress authorized sums to develop the only other rich field, hundreds of miles away, centered around Amarillo, Texas.   Rosendahl summarized, “…LOS ANGELES… contributed very extensively to general airship progress during her intermittently active 15-year existence.”

While it is not intended as a complete history, a short video about ZR-3 is offered:


After the original German, and later British, and even US Army blimps’ airplane carrying experiments, a “trapeze” was installed aside the ZR-3’s keel in December 1928. ZR-3 began experimenting with launching and retrieving airplanes while in flight. A hook-on and release were demonstrated at the National Air Races held in Cleveland, Ohio, in September, 1929. Three N2Y-1 trainers and the XF9C-1 rejected fighter airplane were given “skyhooks” and tested, but a plan to add more airplane handling equipment along the ZR-3 keel was shelved for economy reasons.  Likewise the airship herself was decommissioned 30 JUN 32, operating two helium rigids at the same time was out of the question.

For those interested in the complete history, click on the paly icon > for a one-minute clip from our DVD “The American Zeppelins.” (Sound on. Karl Kalbaugh, narrator.) The entire series is offered on our Youtube channel.

Ever since ZR-1’s control and engine cars fell loose, the Navy’s Bureau of Aeronautics had envisioned interior fireproofed engine rooms and an hull-integrated command car. Since Bu Aer Design #60 evolved steadily through the later 1920s, it is difficult to pinpoint precisely when seaplane-carrying capability was added to the wish list. It is clear, however, the earliest designs were modified to add airplanes, rather than being originally laid out as a mobile aircraft base.

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