Military airship

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Italian airships bomb Turkish positions in Libya in 1911

Military airships were mainly used in the two world wars . Initially, these were used as bomb carriers for strategic air missions, later they were mainly used as maritime patrols and submarine hunters . In the early days of the Cold War, they should as part of the early warning system of the United States with their radar before approaching Soviet ICBMs warn.

The largest operator of military airships was the US Navy . In addition to the five rigid airships , it operated over 200 impact airships . However, their airship program ended in 1962. The tasks of the airships were taken over by the increasingly powerful helicopters , airplanes and satellites .

Beginnings

Especially before and during the First World War there were the military units of field airmen . They operated tethered balloons for reconnaissance and carried this name because balloonists were also known as aeronauts, especially in the early days of aviation.

At the outbreak of World War I, the Russian Air Force (founded in 1912) had 12 airships, Germany 11 (including 7 rigid airships and the naval zeppelin LZ 24 ), Great Britain 6, France 4 and Austria-Hungary 1.

First World War

A British airship escorts German warships after the end of the war

The outbreak of World War I (1914–1918) brought about great technical advances . At that time, almost all leading nations had airships in service in the navies . Only Germany also used it overland with the army. The nightly bombing raids on London spread fear and terror among the population.

Great Britain had, among other things, impact airships that could stay in the air for up to 22 hours for coastal protection and convoy escort (“ Coastal Class ”). Of the model "Sea Scout Zero" (SSZ), the successor to the "Sea Scout Pusher" (SSP), which was introduced in 1916, and was primarily used for sea surveillance and submarine searches, 66 were built by the end of the war. Each cost only about £ 4,000 to £ 5,000. The British also incorporated their six impact airships assigned to the army into the navy when war broke out. A total of around 200 non-rigid airships were in service during the war, working successfully primarily for maritime surveillance and as escorts for merchant ship convoys. The following sentence has come down to us from the British Admiral Lord Beatty , which he spoke shortly after the Battle of Skagerrak (May 31 to June 1, 1916)

This is a model of a British North Sea class blimp
R23 airship with the Sopwith Camel suspended

"The enemy still has the monopoly of the best air scouting on good weather, when one Zeppelin can do as much as five or six cruisers."

"The enemy still has the monopoly of the best aerial reconnaissance in good weather, where a zeppelin can do as much as five or six cruisers."

This finding was reflected in practice. Most British blimps were about 50 m long, so this value increased to 80 m for the North Sea class introduced in 1917. But it was not until the end of the war that the British had six larger rigid airships of the R23 class at their disposal, which roughly resembled the zeppelins of the O-cash register at the beginning of the war.

Four “ Sea Scout ” ships were sold to Russia under this name. There they were given the designation Chernomor 1-4

The United States had made in the period 1919 to 1933 a total of 31 blimps and a semi-rigid airship for the Army in the service, after which all ships were in the Navy. Italy's 18 army ships (so-called keel airships ) fought almost exclusively in the navy.

Military airships in Germany

The naval airship L 50 in front of the hall in Ahlhorn.

The military leadership of the German Reich initially had high hopes for the airships. They appeared as a kind of miracle weapon: Compared to contemporary aircraft that were still at the beginning of their development, they reached greater heights, were almost as fast, could be more heavily armed with their much larger payload and loaded with more bombs, could last much longer Stay air and had a much greater range .

During the war, therefore, the development of the Zeppelin military airships was strongly promoted. In addition, impact airships of the Parseval type and, above all, rigid airships of the Schütte-Lanz type were used. They were very innovative, from which the zeppelins also benefited, but their performance was limited due to their wooden framework. It was not until the end of the war that they, like the zeppelins, were built from a frame made of duralumin .

The airships were used for aerial reconnaissance and / or for air attacks (= bombing).

Technical advantage

The German airships had a barograph in addition to the technical navigation equipment , the army airships later also had a scouting cage that could be lowered with a winch so that the ship could sail above the cloud cover, while a lowered observer below the ship could use an on-board telephone to navigate the invisible from the ground Ship took over. This invention was soon left out because it was too heavy. For external communication, the ships usually carried a radio telegraph with a towed antenna. All deployment data were documented in the log book. In addition to the engine control, the height control was carried out by dropping ballast or releasing gas. In addition, the ships had holding ropes and regular anchors for landing, locking or train transport from the ground. Crew and equipment were housed in gondolas under the gas body, the separate motorized gondolas were accessible from 1915 by ladders through a corridor in the airship body, the hull of the rigid airship with its subdivided gas cells was accessible so that necessary repairs to gas cells, outer skin or engines during the flight could be made. The gondolas were equipped with machine guns, and there was also a machine gun stand on the deck (top) for defense against air attacks from above.

In fact, fighting from the air initially turned out to be difficult for the enemy, especially since the hydrogen gas was nowhere near as easy to ignite as is often assumed today; LZ 91 / "L 42" even survived two lightning strikes in the air in 1917 unharmed. Also, enemy aircraft did not initially have suitable, forward-firing interceptor weapons, so that the first successes in aerial combat against zeppelins were achieved by throwing bombs on them. The first "shot down" of this type was achieved on June 6, 1915 by the British pilot Reginald Alexander John Warneford , who set fire to the army airship LZ 37 over Ghent . For this he received the highest British medal , the Victoria Cross .

The Allies only achieved regular success after the introduction of incendiary ammunition in the spring of 1916. The first zeppelin to be shot down while burning was LZ 47 / "LZ 77" on February 21, 1916, the first day of the Battle of Verdun . “LZ 77” was launched from Namur Airport under the command of Major Horn and was shot down near Épinal during a war trip to Paris .

On 29./30. January the airship "LZ 79" under the command of the commander Major Geissert took off from Namur to Paris, dropped bombs there and was hit on the stern on the way back. The result was the stranding on the roofs of a village in southern Belgium (at that time a German position). All 12 crew members got away with the horror.

This crew later took over the airship "LZ 90", first under Commander Major Geissert, later under Commander Hptm. La Quiante and among other things carried out an attack run against London . There, because of the weather and because the commandant thought that the observation gondola , which was carried for the first time, would not bring anything, she simply dropped it over London.

Airships in action

German naval airship SL 8 of the Schütte-Lanz type over a ship of the line of the deep sea fleet , 1917

Despite their technical advantage over airplanes, many German airships were lost from the first days of the war. This was not least due to the fact that military strategists inexperienced in the technology entrusted them with tasks for which they were not suitable. Initially in broad daylight, the ships attacked heavily defended targets on the western front and were not infrequently brought to the ground by infantry fire, mostly because too much lifting gas was lost through the bullet-riddled shell.

Just two days after the start of the war, for example, LZ 21 / "Z VI" had to make an emergency landing near Bonn after a bombing of Liège due to heavy gas loss . In the same month two more zeppelins were shot down and LZ 23 / “Z VIII” fell temporarily into French hands. Particularly critical times outside of the actual mission were the gas filling as well as leaving the hall and landing, especially in gusty weather or in the dark.

The Imperial Navy only had the "L 3" , stationed in Hamburg-Fuhlsbüttel, because the double rotating hall in Nordholz near Cuxhaven was still under construction. The task of the naval airships was the reconnaissance and reconnaissance over the sea in the service of the deep sea fleet over the North Sea and Baltic Sea, but also search and recovery of missing seaplanes in cooperation with torpedo boats ordered by radio. The weather, and thus the meteorological service, had an impact, especially over sea, on operational planning, course determination and radio telegraphic connection ; Hugo Eckener , who acted as a trainer, enjoyed a special reputation in naval aviation and was called "Pope of airship" by the airships. Nordholz was the largest of the German airship bases. 42 of the Navy's 75 airships were stationed there. The area of ​​the base was 800 hectares in 1914 (1000 hectares from 1918). Among other things, it had a rotating airship hangar . In addition to Nordholz, the navy also had airship bases in Tondern , Kiel , Cuxhaven, Fuhlsbüttel , Hage , Wittmundhafen , Ahlhorn and Wildeshausen . The southernmost military airship port of the German armed forces was in Yambol / Bulgaria ; he too was entertained by the Navy.

At the beginning of the war, however, the army had the majority of the airships. The army airships proved themselves above all on the eastern front, later also together with naval airships in the southeast on the Black Sea and the Adriatic Sea . There they could bring their strength, strategic bombing and reconnaissance to full advantage. On the western front, on the other hand, due to the rigid fronts and the peculiarities involved, the airships were never the right means. Here they worked almost exclusively behind the actual battle lines and bombed supply routes and supply units; there were hardly any strategic bombing operations due to unfavorable weather conditions.

With the advent of more powerful airships (type L 10), bombing raids against more distant targets, especially Great Britain, were carried out from the beginning of 1915. The first squadron attack by the four new zeppelins "L 10", "L 11", "L 12" and "L 13" on August 10, 1915, with the "L 45" being First Lieutenant Peterson, had a special meaning and a high surprise effect A heavily damaged ship with its stern on the water was only able to rescue it to the Belgian coast with great difficulty and under dramatic circumstances; the ship was destroyed in the rescue, Peterson and his crew were killed in a later attack on London with L 32.

By the spring of 1917, the army and navy jointly bombed areas in the greater London area . The threat to airships from fighter planes or anti-aircraft guns with incendiary ammunition increased massively in the spring of 1916. Since the “lifespan” of the airships was usually relatively short, innovations quickly caught on. At the forefront of development were the new super airships of the 55,000 cubic meter R-Class. The navy was preferably equipped with these airships. The army lacked the large airship hangars necessary for this . Retrofitting would have been much more difficult and expensive than with the Navy. At the same time, the large aircraft ("G-aircraft") and the giant aircraft ("R aircraft") came on. By March 1917 there was virtually parity in the number of bombs dropped, while costs were reduced at the same time.

The Supreme Army Command (OHL) or the new "Commanding General of the Air Force" ( Kogenluft ), Lieutenant General Ernst von Hoeppner , decided in the spring of 1917 to discontinue Army airship operations. The Navy also cut the number of its attacks to about half. The number of reconnaissance missions remained roughly the same, as the zeppelins were not replaced by airplanes here.

year Attack drives Reconnaissance trips
1914 - 58
1915 38 350
1916 123 312
1917 52 338
1918 18th 131

The Navy kept its airships in use until the end. Over the North Sea and the Baltic Sea , the zeppelins were able to fully exploit their endurance advantage in numerous long and sometimes very successful reconnaissance missions. They did a particularly good job tracking down enemy mine barriers and marking minefields with dropped buoys. In the winter of 1916, naval airships were also used to supply the German islands, cut off from the outside world by ice, with food. The naval airships, however, did not play a decisive role in the Battle of the Skagerrak . On May 31, 1916, they were unable to carry out their reconnaissance tasks because of bad weather.

The sinking of the German naval airship L 19 on February 2, 1916 in the North Sea. On the left, the English fishing steamer KING STEPHEN. Contemporary English illustration

Attack drives, especially against England , had only been carried out under cover of darkness since the end of 1914. This forced the opponents to further develop air defense and to use searchlights . There had already been air raids before the First World War (e.g. Tripoli 1911). There has been great controversy everywhere about the use of aerial bombs. There was also no agreement on the question between the German Kaiser and the OHL. So (as far as this was possible and selectable) only military targets were targeted, but the accuracy in the dark left a lot to be desired, since the airships only worked with dead reckoning and sextants for astronomical location determination.

From 1916 the new zeppelins could operate at greater heights, some of which (involuntarily) led them well over 7000 meters. In order to direct bombs dropped from clouds , observers were lowered into so-called scouting baskets on steel cables . However, the scouting basket and hawser were later left out because the commanders preferred to carry a corresponding amount of bombs or more ballast water or fuel with them. With increasing air defense, the airship attacks became more and more risky; But they also tied up numerous means of defense (aircraft, flak, headlights) of the enemy and thus withdrew them from the front. The night mission on 17/18 was particularly dramatic. October 1917: Of 17 ships starting around noon, two could not hold out because of strong cross winds, the remaining 15 reached England, where a strong north storm that set in at great heights drove some of the ships south and forced them to march back over the dangerous front lines in France. "L 44" was shot down while burning, "L 45" was driven off to the south of France and destroyed by its crew, "L 49" was captured by French armed forces on landing, "L 50" after the gondola was torn off on impact over the Alps into the Mediterranean Sea drifted off and the badly hit "L 55" irreparably damaged during the emergency landing in Thuringia.

In addition to the combat missions, accidents and air attacks in particular led to total losses. The most serious incident happened in Nordhorn on January 5, 1918, when an airship burned out during maintenance work in the hall from an unknown cause, causing the second ship in the hall to explode. Their severity captured the hall 800 m away with three airships, which was completely destroyed with a huge detonation. A British aircraft attack on the hangars in Tondern , launched by a carrier ship, destroyed the " L 54 " and "L 60" in the hangar there after it became apparent that the interceptors of the Schutzstaffel were banned from taking off due to work on the runway. The British aviators escaped unscathed to Denmark and destroyed their planes there.

On August 5, 1918, the LZ 112 / "L 70" was shot down after an attack. The commander of the naval airship division, Frigate Captain Peter Strasser , was also on board (purely by chance) . After the bombing was over, L 70 had used its radio too intensively. It was eingepeilt and by a British fighter aircraft of type Airco DH4 shot down. After that, the naval airships were only used in long-range reconnaissance for the deep-sea fleet and for mine-hunting work or to secure mine-hunting associations.

Military record

A total of 88 Zeppelin military airships and 18 Schütte-Lanz airships were produced during the war . The airships dropped at least 456 tonnes of bombs (Army 166 t, Navy 277 t) on 51 attacks (mostly in the squadron) (according to the addition according to the lists of the Zeppelin and Schütte-Lanz airships ) and killed 557 people and injured 1,358 .

As "flying eyes", the naval airships alone completed around 1200 reconnaissance trips over the North Sea and the Skagerrak and 352 attack flights on Great Britain until 1918, under the leader of the airships, Frigate Captain Strasser .

In doing so, they gave the German fleet, which was generally inferior to the British, an information advantage. Because from a height of 500 meters an area of ​​22,000 square kilometers could be overlooked.

The lifespan of the combat airships was mostly short. About two thirds of all war airships were lost, about half due to enemy action and the rest due to accidents. The loss of life was rather small compared to other activities on the front lines; they amounted to 11% (79 men) in the army and 26.3% (389 men) in the navy.

The operational impact of the war airships was overall effective. Although the attacks caused only comparatively little damage, they spread disproportionately high levels of fear and terror among the enemy in the military and civilian population and tied up large amounts of resources essential to the war effort. The Entente Cordiale had to put down weapons, material and people in a ratio of almost 1 to 33 to combat the German military airships with around 5,000 men and an average of around 20–25 airships ready for action. Although other branches of arms, such as the naval forces, also adopted such binding strategies, the efficiency of the airships remained unmatched, even by the German submarines . In addition to the air raids on Great Britain since 1916, the main task of the airships was primarily to support German minesweeping forces in the North Sea. Here, in addition to monitoring the airspace of the sea area to be searched, the airships also provided effective help at certain points, as mine barriers (especially flat levels of sea mines) could be easily identified in calm weather from the increased visibility.

Even at the end of the war, the war zeppelins were cutting-edge technology in aviation . In this respect, it would be shortened to say that progress has “overtaken” them. Rather, the military, tactical and strategic requirements and, above all, practical constraints took their toll.

Technical balance

The large production volume and the increasing demands of the war effort led to a significant further development of the zeppelins. Towards the end of the war, the Zeppelin Society in Friedrichshafen and various other locations produced airships around 200 m in length and more. With volumes of typically 56,000–69,000 cubic meters, they could carry 40–50 tons of payload and, with five or six Maybach engines, each with around 191 kW (260 hp), could reach speeds of up to 100–130 km / h .

LZ 101 / "L 55" set an altitude record of 7600 m on October 20, 1917 to avoid enemy fire over the western front. LZ 104 / "L 59", in turn, the so-called "Africa airship", set a route record. On November 21, 1917, the German airship L 59 took off from Jamboli ( Bulgaria ) in the direction of East Africa . The commandant of the airship, Kapitänleutnant Ludwig Bockholt , had loaded ammunition, rifles and medical supplies for the protection force . After reaching its destination, the airship should be disarmed and used for tents and other equipment. After a radio message, the commander turned back halfway (see also German East Africa ). It covered 6757 km in 95 hours.

The longest continuous voyage in terms of time was made by LZ 90 / "L 120" under Captain Ernst A. Lehmann from July 26 to 31, 1917. The journey took 101 hours, and after landing the LZ 90 still had gasoline on board for a further 33 hours of travel. This endurance run over the Baltic Sea is partially viewed as a test drive for the Africa trip of the L 59.

The end of the war airships

The German defeat also meant the end of German war airships, because the victorious Allies demanded a complete disarmament of the German air forces. The Treaty of Versailles explicitly named the airships and, in Article 202, called for the surrender of all remaining airships, airship hangars and the German factory in which the lifting gas was produced as part of the reparation payments .

One week before the signing of the contract, on June 23, 1919, many war airships destroyed their zeppelins in their halls in order not to have to hand them over to the victorious powers. In doing so, they followed the example of the German deep-sea fleet , which had sunk itself in Scapa Flow two days earlier . The remaining zeppelins were transferred to France , Italy , England and Belgium in 1920 .

The British 23 class airships were scrapped in 1919.

Between the wars

The period between the two world wars was a heyday of rigid airships for airship travel. During this time the largest civil and military airships ever built were in operation. But it was also the time of the greatest disasters.

Some German airships had to be handed over to the military of the victors from the First World War, such as the Dixmude . But the construction details and dimensions of stranded zeppelins had already been adopted beforehand. The British R34 was the first airship to cross the Atlantic in both directions in July 1919 before it had to be written off after an accident in 1921. Her sister ship R33 was the "happiest" British airship, she was in service for almost 10 years before she was scrapped. The construction of both ships was based on the type R marine zeppelin L33. The same was true of the USS Shenandoah and the British R38 , based on one of the German lightweight height zeppelins. Both crashed due to structural overuse.

On February 21, 1922, the American airship Roma , built by Umberto Nobile in Italy, burned over Hampton , Virginia , after touching a power line, killing 34 people. After this and various other accidents in the early 1920s, the US Navy introduced helium as a lifting gas. At that time, only the USA was able to extract this gas from natural gas . The rigid airships "USS Shenandoah" and "USS Los Angeles" temporarily contained almost the entire world reserves of this noble gas. In addition, the US Navy operated the USS Patoka (AO-9), an airship mothership with anchor mast, in order to conduct experiments with its large rigid airships , some of which were themselves flying aircraft carriers .

ZR-3 lands on the aircraft carrier USS Saratoga
USS Akron launching an N2Y aircraft

U.S. Navy Rigid Airships:

In Great Britain, the disaster with the R38 was followed by a ten-year break in airship construction. This was followed by the R80 , R100 and R101 . After the R101 crashed, the two remaining ships were scrapped in 1931 and the British gave up building airships.

Germany was by the Treaty of Versailles severely limited and devoted himself exclusively civilian transport airships, except for the Zeppelin LZ 126, the American US for the navy was built and very successful there from 1924 to 1939 as ZR-3 "USS Los Angeles" service did . In 1920 DELAG carried out passenger trips with the airships LZ 120 and LZ 121 until the ships had to be handed in as reparations. The LZ 127 "Graf Zeppelin" was to become the most successful rigid airship of all time with world and polar trips. The military use of the German airships was limited to a few technical attempts, for example in radio technology. In this context, the 24th run of the LZ 130 "Graf Zeppelin II" in August 1939 became known as the "espionage run". There an attempt was made to obtain information about the English radar system. The Hindenburg disaster on May 6, 1937 in Lakehurst ended the era of passenger airships. The LZ 127 was decommissioned and only the LZ 130 continued to operate until August 20, 1939. Shortly after the beginning of the Second World War, Germany scrapped its remaining large airships LZ 127 and LZ 130 and the Americans their ZR-3 (LZ 126).

Second World War

K-Blimp in World War II

On December 7, 1941, the attack on Pearl Harbor , only 10 airships were in service in Lakehurst: G-1, K-2 to K-5, L-1 to L-3, TC-13 and TC-14

In the Second World War , airships were only used directly by the Allies , especially the USA. They carried out reconnaissance and rescue missions, escorted convoys to protect them from submarine attacks and sometimes even used depth charges against submarines. Around 89,000 ships were escorted by airships in American coastal waters alone. It is said that no ship was lost to enemy action in any convoy over which the airships were hovering. The airships were also used to clear minefields and help clear them. The backbone of US military aviation was 136 Goodyear K-class blimps .

The US Navy Blimps K-16 and K-58 were involved in the last known sinking of a German submarine ( U 853 ) on May 6, 1945. However, a German submarine also succeeded in "sinking" an American airship. On June 18, 1943, the American airship K-74 and the German submarine U 134 under Captain Hans-Gunther Brosin met off the coast of Florida. In the course of the battle, the airship was so badly damaged that it had to make an emergency landing on the water and be abandoned.

During the war, the USA provided the units (Airship Patrol Squadrons or Blimp Squadrons) ZP-11 (US Naval Air Station, South Weymouth / Massachusetts), ZP-12 Naval Air Station Lakehurst , ZP-15, ZP-21, ZP-22, ZP-23, ZP-24, ZP-31, ZP-32 ( US Naval Air Station Moffett Field / California) and ZP-33 (Naval Air Station Tillamook / Oregon), ZP-41, ZP-42 and ZP-51 on. ZP-52 was renamed ZP-41 after one month. The Squadron ZP-14 was deployed in the Mediterranean and had the main base Port-Lyautey in French Morocco / Africa

The Soviet Union also used a few airships within its territory (see: Russian Airship , Pobeda ).

Cold War

ZPG-2 airship during an anti-submarine exercise in 1958

After the Second World War, the USA used impact airships for submarine hunting, sea surveillance and rescue operations at sea until 1962 and was the leading nation in the use of airships. Even the largest impact airships of the 20th century of the type ZPG-3W had the task of warning the USA of approaching ICBMs by means of a radar antenna built into the hull during the Cold War in the early 1960s . 4 ships of this type were built by Goodyear .

US Navy types (incomplete):

  • ZP4K (later ZSG-4)
  • ZP5K (later ZS2G-1)
  • ZPG-2 and ZPG-2W
  • ZPG-3W

However, the airship program ended in 1962.

The NASP program

In the 1980s, the US Navy carried out the so-called NASP program ( US Navy Airship Program ). The aim was to develop an early warning airship which, in contrast to ship radar, could also detect fast, very low approaching cruise missiles in good time. Goodyear's contribution , or after the sale of Loral Defense Systems , was based on the design of the AEW airship type ZPG-3W, which had been manufactured for the US Navy at the end of the 1950s, and brought the first turboprop airship, the Spirit , as a test vehicle of Akron . However, the order went to Westinghouse Airship Industries , which then also developed a technology platform with the Sentinel 1000 . A dummy was built from the gondola of the originally planned Sentinel 5000 radar carrier . The program was canceled in 1996 after budget cuts.

present

The United States Department of Homeland Security uses impact airships for surveillance tasks. In other countries, too, airships are increasingly taking on such tasks in the course of counter-terrorism, but mostly on behalf of the local police. The military itself continues to show interest in airship technology; Lockheed Martin launched the P-791 in 2006, a test vehicle for a transport airship.

Unmanned airships are also the subject of research. They can be used as high-flying reconnaissance drones. The use of high-altitude platforms for military communication is also being investigated.

Other Projects

See also

literature

  • On German airship travel in the First World War, cf. (limited use) Horst Julius Freiherr Treusch von Buttlar-Brandenfels , u. a. Unknown facts about airships, their warfare and their losses , in the naval airship against England (Berlin: Eckart. 1917), airship attacks on England (Berlin: Mittler. 1918), zeppelins against England (Leipzig: v. Hase & Koehler. 1931)
  • Douglas H. Robinson: German Navy Airships 1912-1918. ES Mittler & Sohn, Hamburg / Berlin / Bonn 2005. ISBN 3-8132-0786-2 .
  • Paul Schmalenbach: The German naval airships. Becoming - working - after-effect. Koehlers Verlagsgesellschaft mbH, Herford 1977. ISBN 3-7822-0130-2 .

Web links

Individual evidence

  1. ↑ On the fate of the individual zeppelins, cf. Lemma List of all Zeppelins
  2. ↑ Kite Balloons to Airships ... the Navy's Lighter-than-Air Experience; (Edition on 75 Years of US Navy Aviation); Published by the Deputy Chief of Naval Operations (Air Warfare) and the Commander, Naval Air Systems Command, Washington, DC, Edited by Roy A. Grossnick, Designed by Charles Cooney, US Government Printing Office: 1983-187-029; Page 39
  3. ^ Blimp Squadron Eleven Chronology; Diary of the US Naval Unit ZP-14; online as PDF ( memento of the original from October 9, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. last accessed on October 9, 2016 @1@ 2Template: Webachiv / IABot / www.warwingsart.com
  4. ↑ a b US Navy considers AEW airship options in Flight International ; Issue of November 29, 1986 page 12; online as PDF ; accessed on December 31, 2016
  5. ^ A b US Navy awards NASP contract in Flight International , June 20, 1987 issue; Page 29; online as PDF ; accessed on December 31, 2016
  6. ↑ http://airshipsonline.com/airships/Sentinel_5000/index.html accessed on January 3, 2017
  7. ↑ Peter Kleinheins: The large zeppelins. The history of airship construction. 3. Edition. Springer, Berlin, Heidelberg, New York 2005, ISBN 3-540-21170-5, Chapter 17; Page 261