Ed Reavis/FRIEDRICHSHAFEN
Sixty-two years after the giant Zeppelin airship was engulfed in flames at Lakehurst, New Jersey, the legendary manufacturer has been reborn. The modern version of this great silver whale is as big as a Boeing 747, but only one-third the size of its pre-Second World War ancestors.
Since September 1997, Zeppelin-N07 has flown more than 400h of test flights. Based in Friedrichshafen on the north side of Lake Constance, where Count Zeppelin based production of his airship, the Zeppelin-NT Technics company believes strongly in the new aircraft's prospects.
"We are not here to recreate the past," says Zeppelin-NT chairman Bernd Sträter. "Our philosophy is that the Zeppelin tradition is an obligation to shape the future."
Sträter sees the Zeppelin-N07 attracting customers with performance requirements between those of conventional aircraft and helicopters. "All the cigar-shaped formations that you see as advertising carriers in the sky are so-called blimps", he says. "There haven't been any generations of rigid-frame airships since 1933. We have chosen the middle road - a combination of pressure and rigid aluminium construction with an internal triangle structure - new to Zeppelin construction."
The propulsion system, also new to Zeppelin, can be rotated to compensate for some of the deficits of normal airships. "We can take off and land vertically like a helicopter, which makes it markedly less susceptible to wind conditions than the old airships and existing blimps", says Sträter.
Setting the rules
Zeppelin had to define the certification rules with Germany's federal authorities for its new airship - it had to meet the criteria for passenger aircraft, unlike other airships.
Sträter sees three potential markets for the new Zeppelin: tourism (safaris, for example); providing a platform for covering events and spectacles and for missions such as environmental protection, atmospheric research, remote sensing and astronomy and civil and military surveillance.
Zeppelin claims the airship will prove an economic alternative for work requiring long duration, low speed, comfort and environmental compatibility - such as earth exploration, tropospheric research, pollution study, maritime patrol missions, coastal and border supervision and some commuter services.
Its competitive advantages include manoeuvrability and the location of engines and fuel tanks away from the cabin. A relatively high maximum speed allows operation in strong winds, while simplified take-off and landing procedures mean few groundcrew are needed, keeping costs down. Unlike the blimp, which collapses when it loses pressure, the Zeppelin can lose up to 80% of its hull pressure and retain its structural integrity. Its fins can continue to operate, and the cabin remains intact. The craft has a low environmental impact because it is quiet, has a noise- and vibration-free cabin and a low emission level.
Preliminary sales contracts for five airships have been signed, with Skyship Cruise, in Switzerland, Rheinische Luftschiffbetreibergessellschaft in Bonn, Transatlantische Luftschiffahrt in Munich and Ernstings Zeppelin in Münster/Osnabrück.
The Swiss are to receive the first two airships in the second quarter, getting first choice because of their forthcoming international exhibition, "Expo 01", for which they want to use the airships as advertising and passenger vehicles between exhibition sites. The Bonn company plans to use the Zeppelin for scientific and technical purposes. The airship can be fitted externally with measuring instrumentation.
Transatlantische Luftschiffahrt is interested in using the Zeppelin for tourist cruises and for advertising. Similarly, Ernstings Zeppelin wants the airship for comparable functions and for passenger services to the Hanover trade fair or to the North Sea Islands.
Zeppelin chose to sign preliminary contracts for the first year-and-half because the company did not want to bind itself to production until it was sure of market acceptance.
"Up to now we've built up 400 flight hours, we've passed our critical tests and we are working on fine tuning. This year, we plan to intensify our marketing on the civilian and military side and we already have contacts," says Sträter. He adds that several nations' armed forces have shown interest in the Zeppelin.
Zeppelin GmbH has an 8% stake in the company. Its major shareholders are Zeppelin Luftschiffbau, with 42% of the stock, and ZF Friedrichshafen - one of the world's largest gearbox producers, with DM11 billion ($5.5 billion) annual turnover - which has 41%. "Their participation makes it possible for us to use the synergy from these companies in marketing worldwide and we can profit immensely on the research and development side," Sträter says.
Sträter says Zeppelin has not received government funding, mainly because the company was not ready to publish its work - a requirement for new projects to be subsidised. Berlin has indicated, however, that Zeppelin would receive financial support within the framework for new projects, should it apply in the future.
Pilot requirements
Zeppelin-NT employs three pilots: chief pilot Scott Danneker, and Dominique Manire and Hans-Friedrich Fritz Gunther. The minimum requirement to become a certificated airship pilot is 50h for someone with no airship experience. "We don't believe it will take 50h to do the transitional training for someone who is a certified airship pilot. But we don't know yet because we haven't done it," Danneker says.
He says the thrust-vectoring system, which Zeppelin claims is unique, provides pilots with greater control, particularly at low speeds, than is possible with conventional airships. The system consists of three Textron Lycoming piston engines with swivelling propellers, two mounted in front and one aft - but away from the airship hull. This configuration is possible because of the N07's semi-rigid construction. Unlike blimps or dirigibles, in which the engines can be used only for forward drive or slowing down, the N07's are used for lateral movement as well. The aft engine is used for pitch and yaw and those in the front for height control, particularly during docking and landing.
One result of increased pilot control is that the Zeppelin-N07 needs only a small groundcrew to secure the airship to the mast. Danneker says longitudinal trimming "is accomplished using engine thrust by varying the vector angles on the forward engines and using the vertical portion of the tail thrust. Generally, what we use to bring the airship into a state of equal trim are the ballonets' [the gastight compartments inside the airship's envelope] air bags."
The inside of an airship is not exclusively filled with helium. If it were, it would expand as the airship rose and helium would have to be jettisoned. As the airship rises, the expanding helium forces the air out of the ballonets through valves. As it descends, the ballonets take in air. "We can maintain stable trim by taking air out of the forward ballonet and into the rear ballonet. We change the centre of mass with this operation. Although it's a rigid structure airship, it is still a pressure airship and pressure airships must have some kind of ballonet," says the chief pilot.
Danneker says the theoretical maximum operating altitude of the airship is about 10,000ft (3,050m) above ground level. Lift varies dramatically during operations from a high-altitude airport - for example, Denver, Colorado. "To reach 10,000ft above Denver, you will have to take off with both of those ballonets absolutely full. As altitude increases, they lose air, so that, by the time they have reached that altitude, they will be flat," he says.
Flying conditions
The Zeppelin-N07 is not certified to fly under icing conditions. But, adds Danneker, that does not pose much of a limitation. "Zeppelin-N07 operations are normally performed at around 1,000-2,000ft and there are seldom icy conditions at that height," he says. "Airships have handled icing in the past without any trouble," he adds. "But we intend to get the certification. When one thinks about it the entire airship is like a de-icing machine - you change the air pressure and the ice falls off.
"Flying the Zeppelin requires a lot more anticipation on the part of the pilot; he must fly it all the way down to the ground. No two approaches to landing are exactly the same." Danneker says that a pilot who has 40,000h in a 747, monitoring all the flightdecks, would not necessarily make a good airship pilot. Those who fare the best at the helm of an airship, the chief pilot says, are those pilots "with a lot of good stick and rudder background-pilots who really can control it".
Source: Flight International
