Hot air airship

Hot air airship with advertising over Cologne

Hot-air airships are airships that get their static buoyancy from the difference in density between hot and cold air. They were derived from the technology of hot air balloons .

History of the hot air airships

The first hot-air airships, whose buoyancy is generated exclusively by heating the carrying volume, appeared with the renaissance of the hot-air balloon in the 1970s. The company Cameron Balloons in England offered the first hot air airships for sale from the mid-1970s, alongside classic hot air balloons. These early hot air airships were essentially elongated hot air balloons. Shape and stability were only achieved through the static pressure of the hot air inside the envelope. As with the balloon, the burner system was attached below the shell, which was open at the bottom.

At the end of the 1970s, the English company Thunder & Colt brought the first overpressure hot air airship onto the market, which was technically superior to the Cameron type. In this development, the envelope pressure is increased and stabilized with the help of a fan . The burner worked inside the now completely closed shell. The number of airships sold worldwide by both English types by the turn of the millennium is estimated at around 100.

Cameron Balloons in Bristol followed suit in the mid-1980s with the introduction of their own overprint type of similar construction. Since the mid-1990s, Lindstrand Balloons has also been represented on the market with its own type of overpressure airship.

There was still great potential for development in the 1990s. Up until the early 1990s, no manufacturer had undertaken basic scientific research in the strictly classical sense. The development work was limited to the purely practice-oriented experimentation and the technical implementation of the subjective flight experiences of a few pilots.

One to two-seat overpressure types with a volume of 1500 to 3000 m³ prevailed. The engine output varied between 18 and 37 kilowatts (25–50 hp). The achievable speeds were around 18 to 28 km / h (10–15 kn). The flight times of the production models are one to one and a half hours. Depending on the suitability of the airfield and the professionalism of the respective team, these hot-air airships on the market can be used with ground winds of 6 to a maximum of 8 knots ( wind force 2). Conventional hot air airships are therefore a bit more sensitive to weather than hot air balloons and have a similar operational profile as the so-called special shape balloons (balloons with envelopes in a special shape).

Thunder & Colt was bought by Cameron Balloons in 1995 .

Development in Germany

A hot air airship as an advertising medium over Hamburg

GEFA-FLUG GmbH, based in Aachen , has been involved in the development and use of lighter-than-air vehicles since the mid-1970s and, since 1980, in the development of hot-air flight systems, which has since been used in various projects in around twenty countries used for scientific and commercial purposes. The highlights of the technical development to date are a two-seater airship construction developed together with Thunder & Colt in 1996, as well as a high-performance four-seater hot-air airship, which was approved as a model by the German Federal Aviation Office (LBA) at the end of 1999 according to the known strict and internationally valid criteria . By the beginning of 2002, GEFA-FLUG had manufactured a total of 25 such aircraft.

In addition to aerodynamic investigations in the wind tunnel and the scientific investigation of purely aerostatic issues by means of measurement flights with temperature sensors on board and their computer-aided evaluation, cover fabrics were examined and seam techniques developed further. Another focus of development was the attempt to improve general maneuverability by means of a pneumatic rudder control in order to reduce the physical workload of the pilot and his crew. In particular, the newly designed airship had to meet the requirements of the North Rhine-Westphalia technology project :

The specifications of the NRW technology project hot-air airship (1994–1999) were:

• Type certification by the Federal Aviation Office
• Carrying capacity for four people
• Upgrade and flight use up to 12 knots of ground wind
• Airspeed increased to over 20 knots
• Improvement in general maneuverability
• Reduction and simplification of the operating elements (under ergonomic aspects)
• Increase in flight times to more than two hours
• Crew including pilot not larger than four people
• only one towing vehicle with a trailer is required to transport the crew and aircraft
• massive increase in the service life of the shell materials to 400 to 500 hours.

The way to the goal:

• Scientific studies on aerodynamic and thermodynamic parameters of hot air airship hulls etc. a. in the wind tunnel , through computer simulations and through the determination of data through measurement flights
• Investigations on the positional stability and increase of the maneuverability of hot air airships in the wind tunnel
• Investigations of different cover materials, their material behavior under flight conditions, as well as investigations on aging processes of the cover material and the seams.
• Optimization of the sewing and seam techniques under the aspect of higher safety and improved service life
• Weight optimization on the overall shell and nacelle system through material analyzes
• Flight test program for the purpose of determining various parameters relating to positional stability and temperature distribution
• Backflow and implementation of the knowledge gained in series production
• Development of internationally valid building regulations with the Federal Aviation Office
• Establishing a flight test program for type certification
• Creation of a training concept for pilots with the Federal Minister of Transport
• Establishing criteria for licensed examiners with the Luftfahrt-Bundesamt
• Certification of GEFA-FLUG according to JAR 21 as a development, manufacturing and maintenance company by the Federal Aviation Office

Areas of application

Hot air airships serve a niche market. In addition to the relative lack of awareness of the possibilities available, the main obstacles to greater use are the still low technical performance of these aircraft, which has a negative impact on economic efficiency in the great sensitivity to weather.

Aerial advertising

Most of the hot-air airships are used in the classic area of ​​application, air advertising . The general conditions of use are similar to those of hot air balloons. Due to the motor drive, an airship, unlike a balloon, can stay longer over a previously selected location. Hot air airships, like hot air balloons, are sensitive to thermals and are therefore used in the months with high sunshine (April to September) preferably in the first hours after sunrise and in the last hours before sunset , because then the air is due to weak or missing thermals is the calmest.

With its flight time profile, the following types of use are available for aerial advertising: Attending major events of all kinds that last into the evening hours, such as open-air concerts, folk festivals and sporting events . In addition, work in the vicinity of motorways , motorway junctions and metropolitan areas in the early morning and evening rush hour . In winter, a visit to popular and media-rich winter sports events with flights along ski slopes or jumps rounds off the scenario. In the areas of application shown here, the hot air airship is considerably superior to the hot air balloon in terms of advertising value, since its flight route can be largely planned and it is not a plaything of the air like the uncontrollable balloon.

Hot-air airships are often used as camera platforms by television broadcasters and photojournalists. Instead of a fee for the flight time, broadcasting time is often agreed with the display of the airship through a second camera on the ground - an "intelligent" variant of product placement , as can of course also be achieved with the gas airship.

Another advantage of the hot air airship compared to the gas airship is the fact that almost all flight operations have a take-off and landing site in the immediate vicinity of the event to be attended. In this way, the viewers become active participants in the events around the airship, which in turn increases its advertising value.

Air sports

Hot air airships are similar in many ways to the classic hot air balloon. The real difference compared to the hot air balloon is the drive that gives the hot air airship its maneuverability. However, this maneuverability is also influenced by the respective weather conditions . It was obvious that these new types of aircraft would also be used for competitions and record-breaking purposes. However, it took about 15 years before the first official World Cup was held in Luxembourg in 1988 .

Hot-air airship competitions consist of distance and triangular drives over land, slalom courses , demonstration of general maneuverability, precision tasks with centimeter-accurate dropping of markers and pylon races with a “flying start”. What is demanding in these competitions is the mix of the individual tasks set by an international jury for the day-to-day task, the pilots are challenged to the utmost both mentally and physically.

Six world championships had taken place in Europe up to 2004 . The first non-European world championship was held in Canada in September 1998 . The 10th World Championship will take place February 15-22, 2018 in the Tegernsee Valley; A total of 10 teams from Lithuania, Poland, Sweden, Switzerland, USA and Germany (with 5 entries) take part. In 2015 the first German championship (officially: "Open German Airship Championship") also took place in the Tegernsee valley. There were also several European championships and some airship festivals as well as unofficial competitions.

A German airship race took place on August 20, 2005 in Bad Homburg vor der Höhe on the occasion of the 95th anniversary of the first German airship parade. Seven hot air airships took part. First was Karl-Heinz Krug, second place went to Tanja Witte, third was Helmut Seitz.

The air sports and all kinds of championships and meetings carry and contributed significantly to the development of hot-air airships. The same applies to the significantly increased skills of the pilots.

Environmental monitoring

A steadily growing market that can be served with the hot air airship is in environmental protection and environmental monitoring .

The use of balloons and airships for earth research and environmental observation has always been promoted and implemented. In the 1920s and 1930s there were some flight expeditions to explore the world. In 1926 and 1928 the polar trips of Amundsen and Nobile with the airships " Norge " and " Italia ", and in 1931 the multi-day polar research trip of the airship LZ 127 "Graf Zeppelin" under the direction of Dr. Hugo Eckener .

The advantages of airships and especially of hot air airships compared to "heavier than air" flight systems for observation tasks include: a .: to hover over a point as long as you like and to be able to make stopovers even on unprepared terrain, possibly with the collection of samples of all kinds.

In connection with the “tree raft” a French airship team did important work to document the tropical flora. A "tree raft" is a construction of pontoons and nets that is placed on the canopy of the tropical rainforest by the airship. A research team can collect plant samples there, which are then examined for their medical usability. In order to explore larger areas, the airship can also collect samples with a pontoon triangle - a miniature form of the tree raft - which is attached under the airship. Since 1986 there have been several expeditions that took place in Cameroon, French Guiana and Brazil.

Photographic documentation, for example of the two castles of Neuschwanstein , of river landscapes in research projects of the World Wide Fund for Nature (WWF) in Germany and Austria and similar projects of the Nature Conservation Union of Germany with sometimes quite elaborate documentation of floodplain areas and alluvial forests prove in a very impressive way the suitability of hot air -Airships for environmental monitoring or close-range measurement. The hot air airship often offers the best and often the only way to carry out scientific investigations from the air, which from the ground are either very time-consuming or sometimes even impossible. The use of “heavier than aircraft” is also ruled out here, since fixed-wing aircraft fly too fast and helicopters with their rotor downdraft disturb or even destroy the sensitive surfaces that are to be observed.

A very special kind of mission took place in March 1994 in the far north of Norway , in Vadsø , the landing station of the polar expeditions of Amundsen and Nobile in the 1920s. There, at the northernmost tip of Europe and thus far above the Arctic Circle on the Barents Sea , the "Adler Airship" as part of "Operation ARCTIC SKY '94" reminded of earlier airship expeditions in the Arctic with its flights on the historic anchor mast . The transport of an international special mail on board the "Adler Luftschiff" generated five-digit donations for the Pestalozzi Children's Village on Lake Constance through the sale of these letters .

Another large-scale mission took an airship team to Tanzania in the Serengeti in February 1998 . There they operated in the footsteps of father and son Grzimek , who at the end of the 1950s observed and analyzed the migration of the large herds of animals with a single-engine Dornier 27 . In 1998, the “Adler Luftschiff” was once again used as a camera platform for a film team from ARD and ARTE , in order to observe the migration of large herds from the air, as with the Grzimeks in the 1950s. "Serengeti will not die" was the name of the expedition in analogy to the world-famous Grzimeks film that was shot 40 years earlier and won an Oscar . A special post was also sent for this project, also with donations in the five-digit range. The film about this expedition was broadcast over twenty times on various German and international TV channels.

technology

Historically, a distinction is made between two designs that use natural or artificial overpressure.

Natural overpressure

Preparations for launching a hot air airship

On the one hand, there is the type that does not require artificial overpressure. It only gets its shape from the static pressure of the hot air in the envelope and from a apron that presses the airflow into the envelope. This conception is quite simple to manufacture and use, since all components are based very closely on the well-known hot air balloon. The burner system is located below the filling opening in an open gondola, which often resembles a balloon basket . However, due to the low overpressure in the envelope, the performance of these aircraft is very limited. Operations can only be carried out when there is (almost) no wind and only in gust-free air.

Artificially generated overpressure

In order to increase general performance, the English company Thunder & Colt developed a hot-air airship with artificial positive pressure from the late 1970s. The overpressure was initially achieved by a fan mounted below the burner, and at a later point in time additionally by the drive propeller. In this type, the burner unit is located inside the now completely closed shell.

The envelope material, which was borrowed from the hot air balloon for both types of construction, did not allow any really high envelope pressures even with the first overpressure types, or the service life of the envelope was usually less than 100 flight hours. This only changed with the use of highly tear-resistant nylon fabrics with a silicone coating. The overpressure is up to 15 Pa, in comparison gas airships use an overpressure of around 500 Pa.

Drive and control

Two-stroke gasoline engines are used as the drive. Depending on the type of airship, they have an output of around 20 - 50 kW. The usual fuel supply is around 25 liters. Around 60 kg of propane gas are carried along for the gas burner to heat the air.

It is controlled by means of a rudder , the height control is implemented manually as with the hot air balloon via the frequency and duration of the operation of the mostly single-flame burner system. Like the shell, the elevator and rudder units are also purely pneumatic constructions and are arranged at the stern. The pressure required for the stability of the tail units is usually generated by part of the propeller air flow, which is fed to the tail units through an air scoop behind the drive propeller and creates an overpressure there. The tail units do not have any fixed components.

Hot-air airships have a take -off weight of up to around 900 kg.

gondola

The gondola usually consists of a rustproof tubular frame and aluminum and plastic cladding. It offers space for two or four people. Depending on the model, the seating arrangement is either side by side or in tandem . GEFA-FLUG also manufactured hot-air airship gondolas for six occupants.

Comparison with gas airships

The development, manufacture and also the operation of gas airships is very cost-intensive, which still rules out their use in many areas of aviation. Conventional gas airships are labor-intensive in operation and cause considerable costs, even if they are temporarily not in use. B. for accommodation and care in a hangar . Gas airships can only be operated profitably if they have a high number of flying hours over the year.

In all of these points, hot air airships have decisive advantages. When not in use they can e.g. B. be packed on a transport trailer and thus cause no further significant costs. The gas airship reaches its respective place of use only with considerable effort in terms of logistics (ground crew, anchor mast , planning costs , etc.) and exclusively by air. The hot-air airship, on the other hand, is inexpensively transported on the road in a trailer. Even today, gas airships of comparable size to hot air airships usually still have teams of 8 to 10 employees. Larger gas airships of older design even require up to 20 people.

The ground crew of a hot-air airship, on the other hand, gets by with three to four people, as these aircraft are only used in good weather and for a few hours and are repackaged after they have been used.

Apart from their lower performance, hot air airships can be used more flexibly than gas airships. This fact is particularly interesting when planning operations in distant countries, in which the gas airship either cannot be used at all or can only be used with an immense transfer effort.

A considerable disadvantage of the hot air airship compared to the gas airship is the physically required, considerably larger volume required to achieve comparable payloads . In comparison to heated air, helium has the usual temperatures of max. 127 ° C about three to three and a half times the lift. This fact can be compensated somewhat by the use of much lighter envelope materials and will be made even smaller by the massive further development of hot air airships (more tear-resistant materials and their higher temperature resistance). However, due to purely physical reasons, there will always be a considerable difference.

Also, hot air airships will never be as weatherproof as gas airships, because the large hot air airship hulls cannot be upgraded (inflated and heated) at higher wind speeds and turbulent air. Their operational limit is estimated at 12 to a maximum of 15 knots of ground wind, which, if at all, could only be overcome with considerable technological effort, a larger team and the associated greater financial effort. This, however, diminishes the actual advantage of the hot-air airship over the gas airship, namely that it is simple and inexpensive.

Some characteristic parameters for hot air airships are:

• Inexpensive to develop and manufacture, as technologically (still) quite simple
• Inexpensive to operate, especially for short-term, daily use
• low payload allows only short flight times; Flight missions therefore usually have a local to regional character
• Passenger transportation with previous construction (usually only 1 passenger) economically (for the time being) insignificant.

Training and pilot license

At least 6 hours of flight and journeys are necessary to acquire a flight license for hot air airships in Germany . The prerequisite for retraining on hot air airships is the existence of a hot air balloon pilot license with sufficient flight experience.

Not only the pilot needs training, also the ground crew. The training also includes these questions. Every pilot is recommended to bring his own crew to the training course. The training also covers the topics of maintenance and care, as well as fundamental questions relating to the repair of the entire system.

Outlook and development tendencies

At the moment (as of January 1, 2008) there are three officially licensed companies worldwide that manufacture hot air airships, the English providers Cameron Balloons / Thunder & Colt, Lindstrand Balloons and the German GEFA-FLUG. It is the small niche market , which is still relatively limited in terms of weather, the necessary and high level of specialist knowledge, but also the relative lack of awareness of the hot-air airship flight system, which stands in the way of widespread use. In addition, it must be taken into account that the operation of hot air airships also requires some financial outlay.

Whether there will be larger types in addition to the four-seater hot-air airships described here in the future depends on the development of the market for the types currently available.

Further development impulses come, for example, from the improvement of maneuverability, accompanied by a reduction in thermal sensitivity . The greatest potential lies in the further development of the cover materials, which are even lighter and stronger, allow higher temperatures for increased buoyancy and have a longer service life. An increase in the internal pressure allows higher travel speeds than with the materials currently used.

GEFA-FLUG and Festo , a manufacturer of pneumatic components, are jointly considering introducing a considerable amount of pneumatic control elements in order to increase both maneuverability and ease of use for the pilot. Various manufacturers are working on what is known as a “ pneumatic muscle ” that could be used in several places.

The improvement of the hot-air airships increases performance on the one hand, but also reduces the gap in the area of ​​application compared to the gas airship on the other. However, at least for the foreseeable future, they will not really compete with one another, but rather complement one another due to their different technology and application profiles.

The development potential of the hot-air airship is rated higher than that of the gas airship, which has a history of more than 150 years and is characterized by a. is also at a much higher level of development for military purposes and is therefore only being further developed in smaller steps. However, the physically determined difference between the different densities of heated air and helium as the carrier gas will remain.

Manufacturers and models

(Selection, according to manufacturer)

• Augur Aerostatic Systems Inc. ( RosAeroSystems -Russia)
  • AV-1R (two-seater in cooperation with the Czech company Kubicek, sro)
  • Au-29 (single seat)
• Boland Balloon (USA)
  • Model A-3 and A-5
• Cameron Balloons
  • AS80GD
  • AS105GD
  • AS105MKII
  • AS120MKII
• GEFA FLIGHT
  • AS 105 GD (two or four seats)
  • AS 105 GD / 6 (six seats)
• Kubicek AV-1, built in 1997 by Kubicek Balloons / Czech Republic for a customer in Moscow / Russia
• Lindstrand Hot Air Balloons Ltd
  • HS110

Web links

• www.gefa-flug.de GEFA-Flug (manufacturer and operator, German)
• www.geo-dieluftwerker.de geo - Die Luftwerker (currently (autumn 2016) the only maintenance company for hot-air airships in Germany)
• www.events-online24.de Air sports activities throughout Germany (operator, German)
• www.cameronballoons.com Cameron Ballons (manufacturer)
• www.lindstrand.co.uk Lindstrand Hot Air Balloons Ltd (Manufacturer)
• www.myairship.com/hotship/index.html (manufacturer)

Individual evidence

1. ↑ http://www.mein-tegernsee.de/wp-content/uploads/2018/01/Luftschiff-Weltmeisterschaft-Tegernsee-2018.pdf
2. ↑ http://www.airship-cup.de/
3. ↑ Report on the airship expedition to Tanzania (English) ( Memento of the original from January 22, 2010 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.