Zeppelin



A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. Zeppelin's ideas were first outlined in 1874 and formulated in detail in 1893. They were patented in Germany in 1895 and in the United States in 1899. After the outstanding success of the Zeppelin design, the term zeppelin in casual use came to refer to all rigid airships. Zeppelins were first flown commercially in 1910 by Deutsche Luftschiffahrts-AG (DELAG), the world's first airline in revenue service. By mid-1914, DELAG had carried over 34,000 passengers on over 1,500 flights. After the outbreak of World War I, the German military made extensive use of Zeppelins as bombers and scouts.

The World War I defeat of Germany in 1918 temporarily halted the airship business. But under the guidance of Hugo Eckener, the deceased Count's successor, civilian Zeppelins became popular again. In 1919 DELAG established scheduled daily services between Berlin, Munich, and Friedrichshafen. Their heyday was during the 1930s when the airships LZ 127 Graf Zeppelin and LZ 129 Hindenburg operated regular transatlantic flights from Germany to North America and Brazil. The Art Deco spire of the Empire State Building was originally, if impractically, designed to serve as a mooring mast for Zeppelins and other airships to dock at. The Hindenburg disaster in 1937, along with political and economic issues, hastened the demise of the Zeppelins.

Principal characteristics
The most important feature of Zeppelin's design was a rigid light-alloy skeleton, made of rings and longitudinal girders. The advantage of this design was that the aircraft could be much larger than non-rigid airships, which relied on a slight overpressure within the single pressure envelope to maintain their shape. The framework of most Zeppelins was made of duralumin.

The basic form of the first Zeppelins was a long cylinder with tapered ends and complex multi-plane fins. During World War I, as a result of improvements by the rival firm Schütte-Lanz Luftschiffbau, the design was changed to the more familiar streamlined shape and empennage of cruciform fins used by almost all later airships. Within this outer envelope, several separate balloons, also known as "cells" or "gasbags", contained the lighter-than-air gas (usually hydrogen, but helium in airships operated by America). For most rigid airships the gasbags were made of many sheets of goldbeater's skin from the intestines of cows. About 200,000 sheets were needed for a typical World War I Zeppelin. The sheets were joined together and folded into impermeable layers. Non-rigid airships often do not have multiple gas cells (though some Italian-built semi-rigid airships did).

Forward thrust was provided by several internal combustion engines, mounted in nacelles, or engine cars, attached to the structural skeleton. Some of these could provide reverse thrust for manoevering while mooring. A comparatively small compartment for passengers and crew was built into the bottom of the frame, but in large Zeppelins this was not the entire habitable space; they often carried crew or cargo internally for aerodynamic reasons.

The first generations


Count Ferdinand von Zeppelin's serious interest in airship development dates from 1884, when he was inspired by a recent lecture given by Heinrich von Stephan on the subject of "World Postal Services and Air Travel" to outline the basic principle of his later craft in a diary entry dated 25 March 1874. This describes a large rigidly-framed outer envelope containing a number of separate gasbags. He had previously encountered Union Army balloons in 1863, during the American Civil War, where he was a military observer.

Count Zeppelin began to seriously pursue his project after his early retirement from the military in 1890 at the age of 52. Convinced of the potential importance of aircraft designs, he started working on various designs in 1891, and had completed detailed designs by 1893 These were reviewed by an official committee in 1894, and were the subject of a patent granted on 31 August 1895, with Theodor Kober producing the technical plans.

Count Zeppelin's attempts to secure government funding for his project were unsuccessful, but a lecture given to the Union of German Engineers gained their support. Zeppelin also sought support from the industrialist Carl Berg, then engaged in construction work on the second airship design of David Schwarz. Berg was under contract not to supply alumnium to any other airship manufacturer, and subsequently made a payment to Schwartz's widow as compensation for breaking this agreement. Schwarz's design was fundamentally different from Zeppelin's, crucially lacking the use of separate gasbags inside a rigid envelope and in December 1897 Zeppelin stated that the Schwarz design could not be developed. Sean Dooley speculates on the indirect benefits Zeppelin gained from Carl Berg and Schwarz's work. In 1899, Zeppelin started constructing his first airship to his own designs.

One unusual idea, which never saw service, was the ability to connect several independent airship elements like train wagons; indeed, the patent title called the design Lenkbarer Luftfahrzug (steerable air train).

In 1898, he founded the Gesellschaft zur Förderung der Luftschiffahrt (Society for the Promotion of Airship Flight), contributing more than half of its 800,000 Mark share capital himself. He assigned the technical implementation to the engineer Theodor Kober and later to Ludwig Dürr.

Construction of the first Zeppelin began in 1899 in a floating assembly hall in the Bay of Manzell on Lake Constance, Friedrichshafen. This was intended to facilitate the difficult launching procedure, as the hall could easily be aligned with the wind. The prototype airship LZ 1 (LZ for Luftschiff Zeppelin, or "Airship Zeppelin") had a length of 128 m, was driven by two 14.2 hp Daimler engines and was controlled in pitch by moving a weight between its two nacelles.

The first Zeppelin flight took place on 2 July 1900 over Lake Constance (the Bodensee). Upon repair, it proved its potential in two subsequent flights on 17 October and 24 October 1900 beating the 6 m/s velocity record of the French airship La France. Despite this performance, the shareholders declined to invest more money, and so the company was liquidated, with Count von Zeppelin purchasing the ship and equipment. The Count wished to continue experimenting, but he eventually dismantled the ship in 1901.

Donations, the profits of a special lottery, some public funding, a mortgage of Count von Zeppelin's wife's estate and a 100,000 Mark contribution by Count von Zeppelin himself allowed the construction of LZ 2, which took off one single time, on 17 January 1906. After both engines failed, it made a forced landing in the Allgäu mountains, where the anchored ship was subsequently damaged beyond repair by a storm.

Incorporating all usable parts of LZ 2, the successor LZ 3 became the first truly successful Zeppelin. This renewed the interest of the German military, but a condition of purchase of an airship was a 24 hour endurance trial. This was beyond the capabilities of LZ 3, leading Zeppelin to construct his fourth design, the LZ 4. While attempting to fulfill this requirement, the LZ 4 had to make an intermediate landing at Echterdingen near Stuttgart. During the stop, a storm tore the airship away from its anchorage on the afternoon of 5 August 1908. She crashed into a tree, caught fire, and quickly burnt out. No one was seriously injured. This accident would have finished Zeppelin's experiments, but his flights had generated huge public interest and a sense of national pride regarding his work, and spontaneous donations from the public began pouring in, eventually totalling  6,096,555 Marks. This enabled the Count to found the Luftschiffbau Zeppelin GmbH (Airship Construction Zeppelin Ltd.) and the Zeppelin Foundation.

Before World War I
Before World War I, a total of 21 Zeppelin airships (LZ 5 to LZ 25) were manufactured. In 1909 LZ 6 became the first Zeppelin used for commercial passenger transport. The world's first airline, the newly founded DELAG, bought seven Zeppelins by 1914. The airships were given names in addition to their production numbers, four of which were LZ 8 Deutschland II (1911), LZ 11 Viktoria Luise (1912), LZ 13 Hansa (1912) and LZ 17 Sachsen (1913). Seven of the 27 were destroyed in accidents, mostly while being moved into their halls. There were no casualties. One of them was LZ 7 Deutschland, which made its maiden voyage on 19 June 1910. On 28 June it began a pleasure trip to make Zeppelins more popular. Among those aboard were 19 journalists, two of whom were reporters of well-known British newspapers. LZ 7 crashed in bad weather at Mount Limberg near Bad Iburg in Lower Saxony, its hull getting stuck in trees. The crew then let down a ladder to allow all the passengers to leave the ship. One crew member was slightly injured on leaving the craft.

The German Army and Navy purchased 14 Zeppelins, who labeled their airships Z 1/2/... and L 1/2/..., respectively. During the war, the Army changed their scheme twice: following Z XII, they switched to using LZ numbers, later adding 30 to obscure the total production. When World War I broke out, the military also took over the three remaining DELAG ships. By this time, it had already decommissioned three other Zeppelins (LZ 3 "Z 1" included). Before the war the Army had lost three zeppelins to accidents, in which two people had died. The Navy lost two, both in 1913: a storm forced Navy Zeppelin LZ 14 or "L 1" down into the North Sea, drowning 14; LZ 18 or "L 2" burst into flames following an engine explosion, killing the entire crew. These accidents deprived the Navy of a large number of experienced personnel.

By 1914, state-of-the-art Zeppelins had lengths of 150 to 160 m and volumes of 22,000–25,000 m3, enabling them to carry loads of around 9000 kg. They were typically powered by three Maybach engines of around 400 to 550 hp each, reaching speeds of up to 80 km/h.

During World War I
The German airships were operated by both the Army and Navy as two entirely separate divisions. Over the course of World War I, the Zeppelins were mainly used in reconnaissance missions for the Navy. Bombing missions, especially those targeting London, captured the public's imagination, but, in the end, proved to have only psychological value, and were not a military success. These were executed by both Navy and Army aircraft.

1914–1918 naval patrols
The main use of the airship was in reconnaissance over the North Sea and the Baltic, where the endurance of the airship led German warships to a number of Allied vessels. Zeppelin patrolling had priority over any other airship activity. The majority of airships manufactured were commissioned by the Navy. During the war almost 1,000 patrols were made over the North Sea alone, compared to about 50 strategic bombing raids. The German Navy had some 15 Zeppelins in commission in 1915 and was able to have two or more patrolling continuously at any one time, almost regardless of weather. They prevented British ships from approaching Germany, spotted when and where the British were laying mines and later aided in the destruction of those mines. Zeppelins would sometimes land on the sea next to a minesweeper, bring aboard an officer and show him the mines' locations. Before the widespread availability of incendiary ammunition made commerce raiding too risky, they would also land or hover close to a merchant ship suspected of carrying contraband, order all ship's hands to leave in boats, then inspect the ship, and either destroy it or take it back to Germany as a prize.

1915 bombing raids
At the beginning of the conflict the German command had high hopes for the airships, which were considerably more capable than contemporary light fixed-wing machines&nbsp: they were almost as fast, could carry machine guns (even multiple ones), and enormously greater bomb-load range and endurance. Contrary to previous belief, it was not easy to ignite the hydrogen using standard bullets and shrapnel. Only with the invention of incendiary ammunition later in the war could the Allies start to exploit the Zeppelin's great vulnerability to fire.

At the beginning of the war, Captain Ernst A. Lehmann and Baron Gemmingen, Count Zeppelin's nephew, developed an observation car for use by Zeppelin dirigibles. The car was equipped with a wicker chair, chart table, electric lamp, and compass, with telephone line and lightning conductor part of the holding cable. The car's observer would relay navigation and bomb dropping orders to the Zeppelin flying within and above the clouds to avoid precise location by ground artillery units.

From 1915, a number of Zeppelin raids were conducted. The majority were against Britain, leading the way in bombing techniques and also forcing the British military to bolster its air defences. The possibility of airship raids was approved by the Kaiser on 19 January 1915, although he excluded London as a target and further demanded that no attacks be made on historic, government buildings or museums. The night time raids were intended to target only military sites on the east coast and around the Thames estuary, but after blackouts became widespread, many bombs fell at random on East Anglia.

The first attack was planned for 13 January 1915. Four Zeppelins were launched but bad weather forced all the airships to abandon the raid. The first successful raid was on the night of 19–20 January 1915, in which two Zeppelins, L.3 and L.4, were directed towards the Humber but, diverted by strong winds, dropped twenty-four 50 kg high explosive bombs and ineffective 3 kg incendiaries on Great Yarmouth, Sheringham, King's Lynn and the surrounding villages. In all, four people were killed and 16 were injured. Monetary damage was estimated at £7,740.

The Kaiser allowed the bombing of London docks from February 1915, but no raids took place on London until May. The first two London raids failed owing to poor weather – L.8 crashed near Ghent on 26 February and a four airship raid by the Army ran into fog on 17 March and was abandoned. One Army airship was damaged on landing and three more were lost in the next few weeks. With two Navy raids failing due to bad weather on 14 and 15 April, it was decided to hold off further action until the more capable P-class Zeppelins were in service. The Army received its P-class Zeppelins first and undertook the first raids. Erich Linnarz commanded LZ.38 on a raid over Ipswich on 29–30 April and again on 9–10 May, attacking Southend; LZ.38 also attacked Dover and Ramsgate on 16–17 May, before returning to bomb Southend on 26–27 May. These four raids killed six people and injured six, causing property damage estimated at £16,898. Twice Royal Naval Air Service (RNAS) aircraft tried to intercept LZ 38 but on both occasions the zeppelin was either able to outclimb the aircraft or was already at too great an altitude for the aircraft to intercept – the BE2 took some 50 minutes to climb to 10000 ft. The Kaiser extended the, so far theoretical, ambit of the London raids in May 1915, allowing attacks anywhere east of the Tower of London. On 31 May, Captain Linnarz again commanded LZ.38 on the first London raid; LZ.37 was also to be part of the raid but suffered structural damage early on and returned to Namur. Flying from Evere LZ.38 crossed the English coast near Margate at 21:42 before turning west once over Southend. London police were warned of an incoming raid around 23:00; a few minutes later small incendiaries began to fall. The devices were a simple metal canister filled with a mix of thermite, tar, and benzol; the exterior was wrapped in tarred rope and a simple fuse was fitted. In total some 120 devices were dropped, totalling 3000 lb, including 91 incendiaries, 28 bombs and two "grenades". Seven people were killed, 35 were injured; 41 fires were started, burning out seven properties, damage was asessed at £18,596. The RNAS had 15 aircraft in the air, but only one even sighted the Zeppelin; no ground-based guns fired and no searchlights found the airship. This marked failure by the capital's defences led to the British government implementing strong press restrictions on the reporting of air raids.

The Naval airships also tried to raid London. L.10 attempted to reach the city on 4 June; strong winds led the commander to misjudge his position and the bombs were dropped on Gravesend. L.9 was also diverted by the weather on 6–7 June, attacking Hull instead of London and causing considerable damage. On the same night an Army raid of three Zeppelins also failed because of the weather; in an added blow, as the airship returned to Evere they coincided with a counter-raid by RNAS aircraft flying from Furnes, Belgium. LZ.38 was destroyed on the ground while LZ.37 was intercepted in the air by R. A. J. Warneford in his Morane Parasol, he dropped six 20 lb Hales bombs on the zeppelin which caught fire and crashed into the convent school of Sint-Amandsberg. Two nuns were killed and all but one of the Zeppelin's crew also died. Flight S/L Warneford was awarded the Victoria Cross for his achievement. As a further consequence of the raid both the Army and Navy withdrew from their bases in Belgium; the vulnerability of such sites was now clear.

The short summer nights discouraged further raids for some months, after an ineffective attack by L.10 on Tyneside on 15–16 June. In the same period the remaining Army Zeppelins were re-assigned to the Russian Front. The Navy returned to raids on Britain in August. On 9–10 August, four Zeppelins were directed against London; none reached their target and one, L.12, was damaged by ground fire while near Dover and ditched into the sea off Zeebrugge. Despite eight attacks by RNAS aircraft the airship was towed into Ostend where it was abandoned and later dismantled. The four-Zeppelin raid was repeated on 12–13 August; again only one airship made landfall, L.10 dropped its bombs on Harwich. A third four-Zeppelin raid again tried to reach London on 17–18 August, two turned back with mechanical problems, one bombed Ashford, Kent on 10 August in the belief it was Woolwich, but L.10 became the first Navy airship to reach London. L.10 was also misnavigated, mistaking the reservoirs of the Lea Valley for the Thames, and consequently dropping the bombs on Walthamstow and Leytonstone. 10 people were killed, 48 injured, property damage was estimated at £30,750 by the London Fire Brigade. A number of guns fired at L.10 and a few aircraft were launched (two Caudron G.3s crashed on landing after their search), but the Zeppelin suffered no damage in the raid (L.10 was destroyed a little over two weeks later in a thunderstorm over the North Sea; it crashed off Cuxhaven and the entire crew was killed).

Two Army Zeppelins successfully bombed London on 7–8 September, SL.2 dropped bombs on the Isle of Dogs, Deptford, Greenwich and Woolwich. LZ.74 was forced to drop weight on its approach and scattered 39 bombs over Cheshunt, before heading on to London and dropped devices on Bermondsey, Rotherhithe and New Cross. Eighteen people were killed and 28 injured, property damage totalled £9,616. Fog and mist prevented any aircraft being launched, but a number of anti-aircraft guns fired at LZ.74 with no effect.

Although these raids had no significant military impact, the psychological effect was considerable. The poet D.H. Lawrence described the raid in a letter to Lady Ottoline Morrell: "Then we saw the Zeppelin above us, just ahead, amid a gleaming of clouds: high up, like a bright golden finger, quite small (...) Then there was flashes near the ground &mdash; and the shaking noise. It was like Milton &mdash; then there was war in heaven. (...) I cannot get over it, that the moon is not Queen of the sky by night, and the stars the lesser lights. It seems the Zeppelin is in the zenith of the night, golden like a moon, having taken control of the sky; and the bursting shells are the lesser lights."

The Navy attempted to follow up the Army's success the following night. Three Zeppelins were directed against London and one against an ironworks at Skinningrove. L.11 turned back early with engine trouble; L.14 suffered the same problem while over Norfolk, its bombs were dropped on East Dereham and the Zeppelin returned home. L.13 reached London, approaching over Golders Green, Kapitänleutnant Heinrich Mathy began bombing around 22:40. Amongst the bomb-load was a 300 kg device, the largest yet carried by a significant margin. It exploded on Bartholomew Close, did much property damage, gouged a crater eight feet deep and killed two men. The Zeppelin was repeatedly caught by searchlights and all 12 anti-aircraft emplacements in London were active – but every shell exploded too low and the falling shrapnel caused both damage and alarm on the ground. Three aircraft were in the air. None even saw the Zeppelin; one crashed on landing killing the pilot. The raid took 22 lives and injured 87. The wavering line of destruction through central London caused damage estimated at £530,787.

After three more raids were scattered by the weather a five-Zeppelin raid was launched by the Navy on 13 October, the "Theatreland Raid." Arriving over the Norfolk coast around 18:30 the Zeppelins encountered new ground defences installed since the September raid under the guidance of Sir Percy Scott. These new gun sites proved ineffectual. Indeed a 13-pounder near Broxbourne was actually put out of action by three bombs dropped from L.15. L.15 continued on to London and began bombing over Charing Cross, the first bombs striking the Lyceum Theatre and the corner of Exeter and Wellington Streets, killing 17 and injuring 20. Further bombs were dropped on Holborn, as the airship neared Moorgate it was engaged by a new 75 mm gun sited at the Honourable Artillery Company. L.15 quickly recognised this new threat and dumped ballast, dropped only three more bombs (one landing on Aldgate High Street causing much damage) before departing, having suffered some engine damage from the shells. L.13 dropped its bombs around Guildford and later near Woolwich. L.14 dropped bombs on Otterpool Army Camp, killing 14 soldiers and injuring 12, and later bombed Tonbridge and East Croydon. Both the other Zeppelins, L.16 and L.11, were even further off course, L.16 dropped up to 50 bombs on Hertford and L.11 scattered a few bombs over Norfolk before heading home. In total, 71 people were killed and 128 injured. This was the last raid of 1915, as bad weather coincided with the new moon in both November and December 1915, and continued into January 1916.

There were 20 raids in 1915, in which 37 tons of bombs were dropped, killing 181 people and injuring 455.

1916 raids
British ground defences were divided between the Royal Navy and the British Army at first, before the Army took full control in February 1916, and a variety of sub 4-inch (less than 102 mm) calibre guns were converted to anti-aircraft use. Searchlights were introduced, initially manned by police. By mid-1916, there were 271 anti-aircraft guns and 258 searchlights across England.

Aerial defences against Zeppelins were haphazard, and divided between the RNAS and the Royal Flying Corps (RFC), with the Navy engaging enemy airships approaching the coast while the RFC took responsibility once the enemy had crossed the coastline. Initially the War Office believed that the Zeppelins used a layer of inert gas to protect themselves from incendiary bullets, and discouraged the use of such ammunition in favour of bombs. The initial trials of incendiary bullets in mid-1915 were unimpressive. Incendiary ammunition also underwent several separate development tracks. The first bullet was designed by John Pomery, but by mid-1916, the RFC also had Brock, Buckingham and "Sparklet" incendiary cartridges. Ten home defence squadrons were organised from February 1916, with London's defences assigned to No. 19 RAS at Sutton's Farm and Hainault Farm (renamed No. 39 (Home Defence) Squadron in April 1916, who were also allocated North Weald Bassett airfield in August 1916). The actual number of aircraft varied: in February there were only eight squadrons and less than half the number of aircraft expected, and by June the number of squadrons had been cut to six and only No. 39 Squadron was at full strength and equipped with newer aircraft – BE12s with interrupter gear and Lewis guns firing a mix of explosive, incendiary and tracer rounds.

Raids continued in 1916. In December 1915, new Q-class airships were delivered to both the German Army and Navy as well as additional P-class Zeppelins. The Q-class simply added two more gas cells to the P-class, lengthening the airship to 585 ft, adding 100000 cuft of gas, and improving both ceiling and bomb-load.

The first raid of 1916 was organised by the German Navy. Nine Zeppelins were sent to Liverpool over the night of 31 January – 1 February. A combination of poor weather, difficult navigation and mechanical problems scattered the aircraft across the English Midlands and several towns were bombed. A total of 61 people were reported killed and 101 injured by the raid. Fifteen of these fatalities occurred in the town of Tipton.

Despite ground fog, 22 aircraft were launched to find the Zeppelins but none succeeded. In attempting to land in the poor conditions, 16 aircraft suffered various degrees of damage and two pilots were killed. One airship, the L.19, crashed in the North Sea because of engine failure and damage from Dutch ground–fire; all 16 crew were lost. Further raids were curtailed by an extended period of poor weather and also by the withdrawal of the majority of Naval Zeppelins in an attempt to identify and resolve the recurrent mechanical failures. Three P-class Zeppelins did attack Hull on 5–6 March, causing significant property damage.

On 28–29 July, the first "Super Zeppelin", the 650 ft M-class L.31, appeared in English skies. Powered by six engines and capable of operating at 13000 ft, (with another 5000 ft to its maximum ceiling), while carrying up to four tons of bombs. Part of a 10-Zeppelin raid that achieved very little, four returned home early and the rest wandered over a fog-shrouded landscape before giving up. Adverse weather dispersed the next raid on 30–31 July and again on 2–3 August. On 8–9 August, two M-class Zeppelins were part of a nine airship raid that did much damage to Hull. The sixth successful London raid was on 24–25 August 13 Navy Zeppelins were launched and Heinrich Mathy's L.31 reached London, flying above low cloud, 36 bombs were dropped in 10 minutes on West Ferry Road, Deptford Dry Dock, the station at Norway Street and homes in Greenwich, Eltham and Plumstead. Nine people were killed, 40 injured and £130,000 of damage was caused. L.31 suffered no damage in the attack but several weeks of repair-work was needed following a rough landing.

The biggest raid so far was launched on 2–3 September when 12 German Navy airships and four rigid airships from the German Army took part. A combination of rain and snowstorms scattered the airship while they were still over the North Sea. None of the naval airships reached London. Only the army's LZ.98 and the newly commissioned Schütte-Lanz SL.11 achieved their objective. SL.11 came in over Foulness with the intention of looping around and attacking the capital from the northwest. The airship dropped a few bombs over London Colney and South Mimms. At about 01:50 it was picked up by a searchlight over Hornsey and subjected to an intense but ineffective barrage. Sl.11 was lost in cloud over Wood Green but rediscovered by the searchlights at Waltham Abbey as it bombed Ponders End. At around 02:15, one of the three aircraft in the sky that night finally came into range – a BE2c piloted by Lt. William Leefe Robinson flying from Suttons Farm. Robinson fired three drums of ammunition from his Lewis gun, one on each of three passes. After emptying the third drum, the airship began burning from the stern and was quickly enveloped in flames. It fell to the ground near Cuffley. There were no survivors. Four naval Zeppelins which had regrouped over Hertfordshire saw the fate of SL.11 and quietly slipped away. For the first rigid airship downed on British soil and the first 'night fighter' victory Leefe Robinson received the Victoria Cross. The pieces of SL.11 were gathered up and sold by the Red Cross to raise money for wounded soldiers.

The loss of SL.11 ended the German Army's interest in raids on Britain. The German Navy remained aggressive and a 12-Zeppelin raid was launched on 23–24 September. Eight older airships, including Zeppelin L.22, bombed targets in the Midlands and Northeast, while four M-class Zeppelins (L.30, L.31, L.32, and L.33) attacked London. L.30 did not even cross the coast, dropping its bombs at sea.

L.22 approached Sheffield, dropping its bomb load on Burngreave, Attercliffe and Darnall, all suburbs of Sheffield, killing 28 people and injuring a further 19. Sheffield's defenses were few and disorganized, so L.22 returned to its base without incident.

L.31 approached London from the south, dropped a few bombs on Kenley and Mitcham and was picked up by a number of searchlights. Forty-one bombs were then dropped in rapid succession over Streatham, killing seven and wounding 27. More bombs were dropped on Brixton before crossing the river and dropping 10 bombs on Leyton, killing another eight people and injuring 30. L.31 then headed home. Also coming in from the south was L.32, running late due to engine problems, it dropped a few bombs on Sevenoaks and Swanley before crossing Purfleet at about 01:00. The Zeppelin then came under anti-aircraft fire as it dropped bombs on Aveley and South Ockendon. Shortly thereafter, at 01:10, a BE2c piloted by 2nd Lieutenant Frederick Sowrey engaged L.32. He fired three drums of incendiaries and succeeded in starting a blaze which quickly covered the entire airship. The Zeppelin crashed to earth at Snail's Hall Farm, Great Burstead. The entire crew was killed, with some, including the commander Oberleutnant-zur-See Werner Peterson, choosing to jump rather than burn to death.

L.33 dropped a few incendiaries over Upminster before losing its way and making a number of turns, heading over London and dropping bombs on Bromley at around midnight. As the bombs began to explode, the Zeppelin was hit by an anti-aircraft shell fired from the guns at either Beckton, Wanstead, or Victoria Park despite being at 13000 ft. Dropping bombs now to shed weight, a large number fell on homes in Botolph Road and Bow Road. As the airship headed towards Chelmsford it continued to lose height, coming under fire at Kelvedon Hatch and briefly exchanging fire with a BE2c. Despite the efforts of the crew, L.33 was forced to the ground at around 01:15 in a field close to New Hall Cottages, Little Wigborough. The Zeppelin was set alight and the crew headed south before being arrested at Peldon by the police. A close inspection of the wreckage enabled the British to understand where their own rigid airship designs had been deficient. Furthermore, one 250 hp engine recovered from the wreck subsequently substituted for two (of four) 180 hp engines on a Vickers-built machine, the hitherto underpowered R.9.

The next raid came on 1 October 1916. Eleven Zeppelins were launched at targets in the Midlands and at London. As usual weather played a major role and only L.31 under the experienced Heinrich Mathy, on his 15th raid, reached London. Approaching from Suffolk, L.31 was picked up by the searchlights at Kelvedon Hatch around 21:45; turning away, the airship detoured over Harlow, Stevenage and Hatfield before cutting its engines and drifting with the wind over Hertford. As the airship neared Cheshunt at about 23:20 the engines were restarted and the airship was quickly picked up by six searchlights. Three aircraft of No. 39 Squadron were in the air and closed on L.31. Mathy ordered the dumping of bombs, (50 fell on Cheshunt), in order to gain altitude. A BE2c piloted by 2nd lieutenant Wulstan Tempest engaged the Zeppelin around 23:50; three bursts were sufficient to set L.31 ablaze and it crashed near Potters Bar with all 19 crew dying – although again many decided to jump rather than burn (including Mathy, whose body was found near the wreckage, embedded some four inches in the softened earth). Tempest had had to dive out of the way of the stricken airship and, overwrought, had crashed on landing, suffering minor injuries.

With the next raid on 27–28 November, the Zeppelins avoided London for targets in the Midlands. But again the aircraft and the incendiary bullet proved lethal – L.34 was shot down over the mouth of the Tees and L.21 was attacked by two aircraft and crashed into the sea off Lowestoft. There were no further raids in 1916 although the Navy lost three more craft, all on 28 December – SL.12 was destroyed at Ahlhorn by strong winds after sustaining damage on a poor landing, and at Tondern L.24 crashed into the shed while landing and the resulting fire destroyed both L.24 and the adjacent L.17.

There were 23 airship raids in 1916 in which 125 tons of ordnance were dropped, killing 293 people and injuring 691.

1917 raids
Anti-aircraft defences were becoming tougher and new Zeppelins were introduced with an increased operating altitude of 16500 ft and a maximum ceiling of 21000 ft. The first S-class Zeppelins entered service in February 1917. They were largely a modification of the M-class, sacrificing weight for improved altitude. The surviving M-class Zeppelins were converted to S-class, notably by reducing the number of engines from six to five. To avoid searchlights, they flew above the clouds whenever possible, lowering an observer through them in a Spähkorb (observation gondola) to direct the bombing. The improved safety was counteracted by the extra strain on the airship crews who became more prone to altitude sickness and exposure to extreme cold and high altitude winds.

The first raid of 1917 did not occur until 16–17 March and the five high flying Zeppelins encountered very strong winds and none reached their targets. This experience was repeated on 23–24 May. Two days later 21 Gotha bombers attempted a daylight raid on London. They were halted by heavy cloud but the effort led the Kaiser to announce that airship raids on London were past; under pressure he later relented to allow Zeppelin attacks to continue under "favourable circumstances".

On 16–17 June, another Zeppelin raid was attempted, only two out of six Zeppelins reached England in the face of strong winds. L.42 bombed Ramsgate, hitting a munitions store. The month-old L.48, commanded by Korvettenkapitän Franz Eichler, but with Korvettenkapitän Viktor Schutze also on board, suffered from both engine problems and compass malfunction. It was forced to drop to 13000 ft where it was caught by four aircraft and destroyed, crashing near Theberton, Suffolk. This was the last Zeppelin raid to explicitly target London.

After ineffectual raids on the Midlands and other targets in the north of England on 21–22 August and 24–25 September, the last major Zeppelin raid was launched on 19–20 October with 13 airships headed for Sheffield, Manchester and Liverpool. Two Zeppelins did not launch and the remainder quickly found themselves badly affected by powerful headwinds which made navigation extremely difficult. L.45 was trying to reach Sheffield, instead it dropped bombs on Northampton and London. Undetected and with no warning its bombs did great damage – the first few fell on Hendon Aerodrome but the rest, dropped at random from 16000 ft, struck in Piccadilly, Camberwell and Hither Green. L.45 then reduced altitude to try to escape the winds but was forced back into the higher air currents by a BE2e. The airship then had mechanical failure in three engines and was pushed by the wind out over France, eventually coming down near Sisteron; it was set ablaze and the crew surrendered. L.44, L.49, and L.50 were also lost to anti-aircraft fire or the weather over France. L.55 was badly damaged on landing and later scrapped.

There were no more raids in 1917, although the airships were not abandoned but refitted with new, more powerful engines. The partly Zeppelin-built Zeppelin-Staaken R.VI Riesenflugzeug four-engined heavy bomber biplanes started raiding London on September 28, 1917, with only five of the eventual eighteen aircraft produced of the type making the raids. The Zeppelin-built heavy bombers' raids on the United Kingdom would not end until late May of 1918, with eleven raids conducted in total by the R.VI giants.

1918 raids
There were only four raids in 1918, all against targets in the Midlands and northern England. The final raid on 5 August 1918 involved four airships and resulted in the loss of L.70 and the death of its entire crew under the command of Fregattenkapitän Peter Strasser, head of the Imperial German Naval Airship Service and the Führer der Luftschiffe. Crossing the North Sea during daylight, the airship was intercepted by a Royal Air Force DH.4 biplane piloted by Major Egbert Cadbury, and shot down in flames.

On 10 March 1918 L59 attacked Naples after a 37 hours 10 min flight from Jamboli, 6350kg of bombs dropped.

On 5 January 1918, a fire at Ahlhorn destroyed four of the specialised double sheds along with four Zeppelins and one Schütte-Lanz. The British had begun bombing the Zeppelin production lines and their sheds in Cologne and Düsseldorf as early as September/October 1914. This was followed by the Cuxhaven Raid, which included Zeppelins as its targets, on Christmas Day 1914. In July 1918, the Tondern Raid conducted by the RNAS, destroyed two Zeppelins in their sheds.

Supply
In 1917, the German High Command made an attempt to deliver much needed supplies using a dirigible to Lettow-Vorbeck's East African Campaign in German East Africa. L.59 Zeppelin travelled over 6400 km in 95 hours, but in the end failed to deliver the supplies. The airship had been purpose-built and was intended to be broken up and used on arrival. It never attempted the mission again, and was converted into a bomber.

Technological progress
Strategic issues aside, Zeppelin technology improved considerably as a result of the increasing demands of warfare.

The pre-war M-class designs were quickly enlarged, first to the 530 ft long duralumin P-class, which increased gas capacity from 880000 cuft to 1130000 cuft, introduced a fully enclosed gondola, and extra engines. these modifications added 2000 ft to the maximum ceiling, over 10 mph to the top speed, and greatly increased crew comfort and hence endurance. Twenty-two P-class airships were ordered and the first, LZ.38, was delivered to the Army on 3 April 1915.

In 1916, the Zeppelin Company, having spawned several dependencies around Germany with shipyards closer to the fronts than Friedrichshafen, delivered airships of around 200 m (660 ft) in length (some even more) and with volumes of 56,000–69,000 m3. These M-class dirigibles could carry loads of three–four tons of bombs and reach speeds of up to 100 to 130 km/h using six Maybach engines of 260 hp each.

To avoid enemy defences such as British aircraft, guns and searchlights, Zeppelins became capable of much higher altitudes (up to 7600 m) and they also proved capable of long-range flights. For example, Zeppelin LZ104, based in Yambol, Bulgaria, was sent to reinforce troops in German East Africa (today the mainland of Tanzania) in November 1917. The ship did not arrive in time and had to return following reports of a German defeat by British troops, but it had traveled 6757 km in 95 hours and thus had broken a long-distance flight record.

A considerable, frequently overlooked, contribution to these technological advancements originated from Zeppelin's only serious competitor, the Mannheim-based Schütte-Lanz airship construction company. While their dirigibles never became comparably successful, Professor Schütte's more scientific approach to airship design led to a number of important innovations copied, over time, by the Zeppelin company. These included the streamlined hull shape, the simple yet functional cruciform fins (replacing the more complicated box-like arrangements of older Zeppelins), individual direct-drive engine cars, anti-aircraft machine-gun positions, and gas ventilation shafts which removed excess hydrogen.

End of the war
The German defeat in the war also marked the end of German military dirigibles, as the victorious Allies demanded a complete disarmament of German air forces and delivery of the remaining airships as reparations. Specifically, the Treaty of Versailles contained the following articles dealing explicitly with dirigibles:


 * Article 198:The armed forces of Germany must not include any military or naval air forces. [...] No dirigible shall be kept.
 * Article 202:On the coming into force of the present Treaty, all military and naval aeronautical material [...] must be delivered to the Governments of the Principal Allied and Associated Powers. [...] In particular, this material will include all items under the following heads which are or have been in use or were designed for warlike purposes:
 * [...]
 * Dirigibles able to take to the air, being manufactured, repaired or assembled.
 * Plant for the manufacture of hydrogen.
 * Dirigible sheds and shelters of every kind for aircraft.
 * Pending their delivery, dirigibles will, at the expense of Germany, be maintained inflated with hydrogen; the plant for the manufacture of hydrogen, as well as the sheds for dirigibles may at the discretion of the said Powers, be left to Germany until the time when the dirigibles are handed over. [...]

On 23 June 1919, a week before the treaty was signed, many war Zeppelin crews destroyed their airships in their halls in order to avoid delivery. In doing so, they followed the example of the German fleet which had been scuttled two days before in Scapa Flow. The remaining dirigibles were transferred to France, Italy, Britain, and Belgium in 1920.

A total of 84 Zeppelins were built during the war. Over 60 were lost, roughly evenly divided between accident and enemy action. 51 raids had been undertaken,in which 5,806 bombs were dropped, killing 557 people and injuring 1,358 while causing damage estimated at £1.5 million. It has been argued the raids were effective far beyond material damage in diverting and hampering wartime production, one estimate was that the due to the 1915–16 raids "one sixth of the total normal output of munitions was entirely lost."

Renaissance


Count von Zeppelin had died in 1917, before the end of the war. Dr. Hugo Eckener, a man who had long envisioned dirigibles as vessels of peace rather than of war, took command of the Zeppelin business. With the Treaty of Versailles having knocked out their competitor Schütte-Lanz, the Zeppelin company and DELAG hoped to resume civilian flights quickly. In fact, despite considerable difficulties, they completed two small Zeppelins: LZ 120 Bodensee, which first flew in August 1919 and in the following two years actually transported some 4,000 passengers; and LZ 121 Nordstern, which was envisaged being used on a regular route to Stockholm.



However, in 1921, the Allied Powers demanded these two Zeppelins be delivered as war reparations, as compensation for the dirigibles destroyed by their crews in 1919. Further Zeppelin projects could not be realized, partly because of Allied interdiction. This temporarily halted German Zeppelin aviation.

Eckener and his co-workers refused to give up and kept looking for investors and a way to circumvent Allied restrictions. Their opportunity came in 1924. The United States had started to experiment with rigid airships, constructing one of their own, the ZR-1 USS Shenandoah (see below), and ordering another from the UK when the British R38 (ZR-2) was cancelled. However, the R38 (based on the Zeppelin L70, ordered as ZR-2) broke apart and exploded during a test flight above the Humber on 23 August 1921, killing 44 crewmen.

Under these circumstances, Eckener managed to acquire an order for the next American dirigible. Of course, Germany had to pay the costs for this airship itself, as they were calculated against the war reparation accounts, but for the Zeppelin company, this was secondary. So engineer Dr. Dürr designed LZ 126, and using all the expertise accumulated over the years, the company finally achieved its best Zeppelin so far, which took off for a first test flight on 27 August 1924.

No insurance company was willing to issue a policy for the delivery to Lakehurst, which, of course, involved a transatlantic flight. Eckener, however, was so confident of the new ship that he was ready to risk the entire business capital, and on 12 October 07:30 local time, the Zeppelin took off for the US under his command. His faith was not disappointed, and the ship completed her 8050 km voyage without any difficulties in 81 hours and two minutes. American crowds enthusiastically celebrated the arrival, and President Calvin Coolidge invited Dr. Eckener and his crew to the White House, calling the new Zeppelin an "angel of peace".

Under its new designation the ZR-3 USS Los Angeles (the former LZ 126), became the most successful American airship. She operated reliably for eight years until she was retired in 1932 for economic reasons. She was dismantled in August 1940.

Golden age
With the delivery of LZ 126, the Zeppelin company had reasserted its lead in rigid airship construction, but it was not yet quite back in business. Acquiring the necessary funds for the next project proved a problem in the difficult economic situation of post-World-War-I Germany, and it took Eckener two years of lobbying and publicity work to secure the realization of LZ 127.

Another two years passed before 18 September 1928, when the new dirigible, christened Graf Zeppelin in honor of the Count, flew for the first time. With a total length of 236.6 m and a volume of 105,000 m3, she was the largest dirigible yet.

Eckener's initial concept was to use Graf Zeppelin for experimental and demonstration purposes to prepare the way for regular airship traveling, by carrying passengers and mail to cover the costs. In October 1928 the first long-range voyage brought her to Lakehurst, where Eckener and his crew were once more welcomed enthusiastically with confetti parades in New York and another invitation to the White House. Graf Zeppelin toured Germany and visited Italy, Palestine, and Spain. A second trip to the United States was aborted in France due to engine failure in May 1929.

In August 1929, LZ 127 departed for another daring enterprise: a circumnavigation of the globe. The growing popularity of the "giant of the air" made it easy for Eckener to find sponsors. One of these was the American press tycoon William Randolph Hearst, who requested the tour officially start in Lakehurst. As with the October 1928 flight to New York, Hearst had placed a reporter, Grace Marguerite Hay Drummond-Hay, on board who therefore became the first woman to circumnavigate the globe by air. From there, Graf Zeppelin flew to Friedrichshafen, then Tokyo, Los Angeles, and back to Lakehurst, in 21 days 5 hours and 31 minutes. Including the initial and final trips Friedrichshafen–Lakehurst and back, the dirigible traveled 49618 km.



In the following year, Graf Zeppelin undertook a number of trips around Europe, and following a successful tour to Recife, Brazil in May 1930, it was decided to open the first regular transatlantic airship line. This line operated between Frankfurt and Recife in 68 hours, and later, between Frankfurt and Rio de Janeiro, with a stop in Recife. Despite the beginning of the Great Depression and growing competition from fixed-wing aircraft, LZ 127 would transport an increasing volume of passengers and mail across the ocean every year until 1936. The ship pursued another spectacular venue in July 1931 with a research trip to the Arctic. This had already been a dream of Count von Zeppelin twenty years earlier, which could, however, not be realized at the time due to the outbreak of war.

Eckener intended to supplement the successful airship by another, similar Zeppelin, projected as LZ 128. However the disastrous accident of the British passenger airship R101 on 5 October 1930 led the Zeppelin company to reconsider the safety of hydrogen-filled vessels, and the design was abandoned in favour of a new project. LZ 129 would advance Zeppelin technology considerably, and was intended to be filled with inert helium.

Hindenburg, end of an era
Following 1933, the establishment of the Third Reich in Germany began to overshadow the Zeppelin business. The Nazis knew very well dirigibles would be useless in combat and thus chose to focus on heavier-than-air technology.

On the other hand, they were eager to exploit the popularity of the airships for propaganda. As Eckener refused to cooperate, Hermann Göring, the German Air minister, formed a new airline in 1935, the Deutsche Zeppelin-Reederei (DZR), which took over operation of airship flights. Zeppelins would now display the Nazi swastika on their fins and occasionally tour Germany to play march music and propaganda speeches for the people from the air.

On 4 March 1936, LZ 129 Hindenburg (named after former President of Germany Paul von Hindenburg by Eckener) made her first flight. The Hindenburg was the largest airship ever built. However, in the new political situation, Eckener had not obtained the helium to inflate it due to a military embargo; only the United States possessed the rare gas in usable quantities. So, in what ultimately proved a fatal decision, the Hindenburg was filled with flammable hydrogen. Apart from the propaganda missions, LZ 129 began to serve the transatlantic lines together with Graf Zeppelin.

On 6 May 1937, while landing in Lakehurst after a transatlantic flight, in front of thousands of spectators, the tail of the ship caught fire, and within seconds, the Hindenburg burst into flames, killing 35 of the 97 people on board and one member of the ground crew. The actual cause of the fire has not been definitively determined. Perhaps a combination of leaking hydrogen from a torn gas bag, and the vibrations caused by a swift rotation for a quicker landing started static electricity in the duralumin alloy skeleton. A flammable outer coating spread the fire from its starting point in the tail to engulf the entire airship in 34 seconds.

Despite the acknowledged danger, there remained a list of 400 people who still wanted to fly as Zeppelin passengers and had paid for the trip. Their money was refunded in 1940.

Graf Zeppelin completed more flights, though not for overseas commercial flights to the U.S., and was retired one month after the Hindenburg wreck and turned into a museum. Dr. Eckener kept trying to obtain helium gas for Hindenburg's sister ship, Graf Zeppelin II, but due to political bias against the airship's commercial use by the Nazi leadership, coupled with the inability to obtain helium gas in sufficient quantities due to an embargo by the United States, his efforts were in vain. The intended new flagship Zeppelin was completed in 1938 and, inflated with hydrogen, made some test flights (the first on 14 September), but never carried passengers. Another project, LZ 131, designed to be even larger than Hindenburg and Graf Zeppelin II, never progressed beyond the production of some single skeleton rings.

The career of Graf Zeppelin II was not over. She was assigned to the Luftwaffe and made about 30 test flights prior to the beginning of World War II. Most of those test flights were carried out near the Polish border, first in the Sudeten mountains region of Silesia, then in the Baltic Sea region. During one such flight LZ 130 crossed the Polish border near the Hel Peninsula, where she was intercepted by a Polish Lublin R-XIII aircraft from Puck naval airbase and forced to leave Polish airspace. During this time, LZ 130 was used as an electronic scouting airframe and was equipped with various telemetric equipment. From May to August 1939, she performed flights near the coastline of Great Britain in an attempt to determine whether the 100-metre towers erected from Portsmouth to Scapa Flow were used for aircraft radio localization. Photography, radio wave interception, magnetic and radio frequency analysis were unable to detect operational British Chain Home radar due to searching in the wrong frequency range. The frequencies searched were too high, an assumption based on the Germans' own radar systems. The mistaken conclusion was the British towers were not connected with radar operations, but formed a network of naval radio communications and rescue.

After the German invasion of Poland started the Second World War on 1 September, the Luftwaffe ordered LZ 127 and LZ 130 moved to a large Zeppelin hangar in Frankfurt, where the skeleton of LZ 131 was also located. In March 1940 Göring ordered the destruction of the remaining airships and the Duralumin fed into the Nazi war industry. In May a fire broke out in the Zeppelin facility, which destroyed most of the remaining parts. The rest of the parts and materials were soon scrapped, with almost no trace of the German "giants of the air" remaining by the end of the year.

Non-German Zeppelin-type airships
Airships using the Zeppelin construction method are sometimes referred to as zeppelins even if they had no connection with the Zeppelin business. Several airships of this kind were built in the USA and Britain in the 1920s and 1930s, mostly imitating original Zeppelin designs derived from crashed or captured German World War I airships.

The British R33 and R34, for example, were near identical copies of the German L-33, which crashed virtually intact in Essex on 24 September 1916. Despite being almost three years out of date by the time they were launched in 1919, these sister ships were two of the most successful in British service. On 2 July 1919, R34 began the first return crossing of the Atlantic by aircraft. She landed at Mineola, Long Island on 6 July 1919 after 108 hours in the air. The return crossing commenced on 8 July because of concerns about mooring the ship in the open, and took 75 hours. Their success led to proposals for a fleet of airships to link far-flung British colonies, but unfortunately post-war economic conditions resulted in most airships being scrapped and trained personnel dispersed, until design and construction of the R100 and R101 commenced in 1925 as part of the Imperial Airship Scheme.

Another example was the first American-built rigid dirigible ZR-1 USS Shenandoah, launched in September 1923, while the USS Los Angeles (ZR-3) was still under construction. The ship was christened on 20 August in Lakehurst, New Jersey and was the first to be inflated with helium, which was still so rare at the time that Shenandoah contained most of the world's reserves. When Los Angeles was delivered, she was at first filled with helium borrowed from ZR-1. Other airships were the USS Akron (ZRS-4) and the USS Macon (ZRS-5).

Cultural influences
Zeppelins have been an inspiration to music, cinematography and literature. In 1934, the calypsonian Attila the Hun recorded "Graf Zeppelin", commemorating the airship's visit to Trinidad. In the American science fiction series, Fringe, Zeppelins are a notable historical idiosyncrasy that helps differentiate the series' two parallel universes, also used in Doctor Who in the episodes The Rise of the Cybermen and The Age of Steel when the TARDIS crashes in an alternate reality where Britain is a 'people's republic' and Pete Tyler, Rose Tyler's father, is alive and is in fact a wealthy inventor. They are also seen in the alternate reality 1939 plot line in the film Sky Captain and the World of Tomorrow, and have an iconic association with the Steampunk subcultural movement in broader terms.

In 1968, English rock band Led Zeppelin chose their name after Keith Moon, drummer of The Who, told guitarist Jimmy Page that his idea to create a band would "go down like a lead zeppelin." Page's manager Peter Grant suggested changing the spelling of "Lead" to "Led" to avoid mispronunciation. For the group's self-titled debut album, Page suggested the group use a picture of the Hindenburg crashing in New Jersey in 1937, much to Frau Eva Von Zeppelin’s disgust. Von Zeppelin tried to sue the group for using the name Zeppelin, but the case was eventually dismissed.

Modern era
Since the 1990s Zeppelin Luftschifftechnik, a daughter enterprise of the Zeppelin conglomerate that built the original German Zeppelins, has been developing Zeppelin "New Technology" (NT) airships. These vessels are semi-rigids based partly on internal pressure, partly on a frame.

The Airship Ventures company operated zeppelin passenger travel to California from October 2008 to November 2012 with one of these Zeppelin NT airships.

In May 2011, Goodyear announced that they will be replacing their fleet of blimps with Zeppelin NTs. This will be resurrecting their partnership that ended over 70 years ago. They will also be building the airships in America.

Danish Post & Tele Museum Zeppelin articles

 * "Zeppelin Exhibition – An online exhibition about Zeppelins." Post & Tele Museum, Denmark.
 * "Zeppelin Exhibition – An online exhibition about Zeppelins." Post & Tele Museum, Denmark.
 * "Zeppelin Exhibition – An online exhibition about Zeppelins." Post & Tele Museum, Denmark.
 * "Zeppelin Exhibition – An online exhibition about Zeppelins." Post & Tele Museum, Denmark.
 * "Zeppelin Exhibition – An online exhibition about Zeppelins." Post & Tele Museum, Denmark.
 * "Zeppelin Exhibition – An online exhibition about Zeppelins." Post & Tele Museum, Denmark.

Patents

 * , "Navigable balloon". 14 March 1899. Ferdinand Graf Zeppelin.
 * , "Method of destroying aircraft", Filed 11 April 1916. Joseph A. Steinmetz
 * , "Light weight girder". Filed 28 June 1920. Karl Arnstein.
 * , "Airship". Filed 19 August 1922; Issued 20 November 1923. Julius Erhardt
 * , "Rigid airship with separate gas cells". Filed 27 November 1922; Issued August 1929. Hugo Eckener