Microcadam case study: rising high - Zeppelin Luftschifftechnik launches the new Zeppelin NT with Helix
Microcadam case study: rising high Zeppelin Luftschifftechnik launches the new Zeppelin NT with Helix
Keywords Airships,CAD, Zeppelin
Exactly 60 years since the last rigid airships were used for passenger services, Zeppelin Luftschifftechnik have developed the next generation airship the Zeppelin NT (new technology). The company is located at Lake Constance in Friedrichshafen,Southern Germany, exactly where the first generation of these huge aircraft started to fly. The Zeppelin NT LZN07 was first shown to the public on 23 April 1997 at the Aero aircraft trade show in Friedrichshafen. The first test flight took place at the beginning of September, and the official admission from the German aviation control authorities is scheduled for autumn 1998. Zeppelin have used the Helix Design System by CSC/Microcadam to develop the new Helix NT.
The history of rigid airships began in 1900, when Ferdinand Graf Zeppelin built his first 28hp motored aircraft, and started to fly from his workshop, which was located on Lake Constance at Manzell near Friedrichshafen. In 1908, the newly founded company "Luftschiffbau Zeppelin" started the commercial production of airships,mainly for luxury long distance passenger flights, but also for other purposes,e.g. military. At the peak of the evolution Zeppelin produced the giant LZ 129 and LZ 130. The tragic accident of LZ 129 Hindenburg on 6 May 1937 at Lakehurst, USA, ended this form of passenger transportation. LZ 127 and LZ 130 were used then for propaganda issues until 1939, when they were destroyed by SS troops. Various suppliers to Zeppelin were established in Friedrichshafen, for example the Zahnradfabrik Friedrichshafen (ZF), which is a widely known gearbox manufacturer, and the motor manufacturer Maybach, which is to date, in the large motor market, under the name of MTU. All of these companies produced military goods in the Second World War, and so were an extremely important goal for the allied bombers. As a result the production sites and the town of Friedrichshafen were totally destroyed in the course of the bombings.
In 1954, Luftschiffbau Zeppelin started sales and repairs for Caterpillar construction vehicles, which forms the largest sector of Zeppelins' revenue, of which Zeppelin delivers these machines to Germany, Austria and Czechia. In the following decades, additional business areas were developed, e.g. silo and machine manufacturing, and antenna technique. A technology company was also founded.
Today, the mother company Luftschiffbau Zeppelin, has revenues of 2.2 billion Mark and employs 3,200 people. The whole company, together with ZF, is owned by the Zeppelin Foundation administrated by the town of Friiedrichshafen.
In spite of Zeppelin working in many markets, the re-launch of the airship construction was always a dream for the company. As a result, a project team was founded in late 1989 to analyse the market opportunities and new uses for rigid aircraft. Zeppelin also carried out the initial technical investigations. The role of the passenger airships is largely dominated today by long-range aeroplanes which are able to fly non-stop, e.g. from Europe to South or North America. However, a new area of use for the Zeppelin is tourism due to its ability to fly very slowly and at low heights. At interesting sites, the Zeppelin can even stop completely in midair without making noise or vibrating. In research, the Zeppelin is perfect for air pollution measurement and surveillance. Additionally, the Zeppelin can be used as a flying camera platform at big events; a relay station; as a basis for infrared measurement and mapping; and as a command centre in the case of natural catastrophes.
Zeppelin's analyses showed that the market chances for airships were good and so the Zeppelin Luftschifftechnik GmbH was founded in 1993. Forty employees are working on the Zeppelin. Klaus Hagenlocher, who had been working as director of development for the mother company since 1972 and had started the project team, was nominated as director of the development and procurement of the new company:
It was always a dream of our company to build airships again, and so the project team was very happy when at last we got the go ahead for the new Zeppelin. It was very interesting to design a modern version of this old concept, using today's technology and materials.
The engineers designed a support structure which is much simpler than the old one. Instead of a complex aluminium structure, the Zeppelin NT uses a triangular structure. The triangular frame and the structure which supports the steering wings are made of carbon fibre, while the horizontal girders are aluminium. Pulling rods made from Aramid stiffen the structure. The hull is connected to the structure and helps to carry the load. The interior volume is filled with the non-burning helium gas. This makes accidents like the Hindenburg incident impossible, where the then-used hydrogen gas had exploded. Two flexible balloons in the interior can be filled with air to compensate pressure differences when the airship is rising or falling.
Overall, the new design has great advantages: the cost for the structure has decreased by a factor of ten, while the weight is 60 per cent lower than that of the old airships,increasing the payload at a given gas volume. A multitude of patents are securing the uniqueness of the Zeppelin NT.
For the development of mechanical and electrical components, Hagenlocher used MICRO CADAM, and in the last stages of the development process the Helix Design System was invented. In the Zeppelin company, Host CADAM was used up to the early 1990s, when the company switched to Microcadam. When Helix Design System was available in March 1997, CAD manager Karl-Dieter Hügle installed the Windows based 2D/3D system.
The hardware installation at Zeppelin Luftschifftechnik consists of 11 PC CAD workstations, which are equipped with 486 and Pentium processors, 16 Mbytes of RAM, and 20in monitors. The Windows-based computers are connected to the network with a Novell server,where a HP DesignJet 650 plotter is available. Hügle explains the relatively small RAM equipment:
16 Mbytes are more than enough to run Helix, which allows us to use older machines instead of having to upgrade the PCs frequently.
The 2.5D module of Helix has a particular advantage over other systems, says Hügle:
With this module it is possible to work as the engineer used to work on the drawing board with the crucial difference being that the system knows the context of the various views, although the view can be positioned freely on the drawing.
Another plus for Hügle is the integrated data management. Helix organises its drawings in a structure with a hierarchy of "groups" and "users". Hügle adds:
In the aircraft industry there is a standard for the naming of drawings called ATA-100. The ATA-code segments the whole aeroplane into assembly groups, and we are able to simulate this structure with the Helix data model.
Approved drawings are transferred to a server disk where the designers have read-only fights. So it is assured that drawings are not changed after the approval from the development director. Because most of the engineers working on the Zeppelin came from other aircraft manufacturers where MICRO CADAM is very widely used they were able to use the system without any learning curve.
Hügle came to Zeppelin in 1994, when MICRO CADAM was already in use:
When Helix was available in early 1997, we had already designed the supporting structure in MICRO CADAM. Despite that we re-modelled most of it in 3D with Helix and MICRO CADAM 3D. Actually, we found some errors in our designs, which otherwise would have been detected on the shopfloor, generating high cost and time losses. For example, it is very difficult to determine the exact length of the horizontal girders (Längsträger)in 2D. Even 2D CAD helps to detect errors earlier than on the drawing board, but with 3D this is most effective.
Illustrations for brochures were generated with Helix 3D too.
The Zeppelin is powered by two motors for about half of the length of the body, plus a motor at the stern,which drives a propeller facing behind plus a fixed propeller facing left. The two front propellers can be turned down, while the stem rotor turns can be turned down. With this arrangement, it is possible to steer the airship very precisely; e.g. it is possible to dock at the landing mast without the need for a large ground crew, which the older Zeppelins needed. So, this manoeuvre technology developed through long analyses with a radio-controlled ten metre model, is a major security factor. Three Lycoming motors, each 200hp, allow a maximum speed of 130km/h and a maximum flight time of 18 hours with full payload of nearly two tons. The steering follows the technique of the "fly-by-wire"systems used in modern aeroplanes.
Simple generation of manufacturing documents for the whole world
Manufacturing documents are generated from 3D models safely and easily which were then handed over to the suppliers. For example, the hull manufacturer which is located in the USA was supplied with data of the hull via the DXF and IGES interfaces of the Helix Design System. Hagenlocher claims:
This saved us a great deal of time, because duplication of development work was avoided.
The advantages of CAD use became very clear when the airship length had to be changed twice in the middle of the development process. Klaus Hagenlocher explains:
"Initially, we planned to produce a prototype first, which would have had 5,000 cubic metres of gas volume, carrying a pilot plus extensive measurement equipment. But as our market analyses showed that customers wanted a "real" product as soon as possible, we developed a 7,000 cubic metre version. Later when it became clearer that the Zeppelin NT would be used as a luxury device, we had to extend the airship a second time, now to 8,000 cubic metres. These changes meant that the whole support structure had to be amended, which would have involved starting from scratch when we used the drawing board."
With CAD, many parts which were already fully developed could be re-used. Despite this, stress analysis had to be done from scratch, which was not very time consuming as Helix data could be used as a basis for the FE analyses.
Following the first flight, the Zeppelin designers' work was not over. Especially in the process of the one-year-long test phase, design changes had to be done quickly to face any problems detected during practical use. Then, design and manufacturing speed was an issue, because the next test flights had to wait until the problem was fixed.
Klaus Hagenlocher of the development department:
In summer 1998 the first Zeppelin will get approval by the air control authorities. After that, we'll start with series production. At this moment, five airships have already been sold, and we have been inundated with orders. We are already planning a much longer version of the new Zeppelin, but first the series production of the LZ N07 has to be secured.
