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Aviation History
1995
1995 - 3456.PDF
'inrEH njAM framework inside a pressurised hull divided into discrete cells. The structure consists of three aluminium-alloy longerons running die lengdi of die craft, while die cross-section is supported by triangular carbonfibre-composite frames. This structure dius provides fixing points for die propulsion units away from the passenger gondola—previously an impossibility for blimps. It also provides strong anchor points, simplifying ground handling and anchoring procedures. According to Zeppelin, this primary struc ture accounts for only 12% of the total weight of the airship — less than half as much as on previous airship frames — and is much cheaper to produce. The carbonfibre-composite beams which make up the frames weigh just a little over 0.5 kg a metre, but an 11m strut can take a 2t compression load. Aluminium was selected for the longerons because it was easier to form the members to the required curvature of the airship's skin, and because the metal acts as a lightning conductor and has better deformation properties in the event of a crash. The hull itself is made of a high-strength low- permeability laminate, with the outermost layer made of Kevlar, which Zeppelin claims is highly resistant to ageing, allowing the airship to be per manently moored outside without the need to build large hangars. It is fastened to the primary structure along the longerons and inflated with helium at a low pressure of some 5bar (721b/in:i. Mooring is carried out using either a fixed or mobile mast, with a semi-automatic mast-cou pling procedure allowing the groundcrew to be kept down to three people. This compares with a typical groundcrew of 15 for a conventional blimp (and indeed, about 100 people for a pre- Second World War Zeppelin) and represents a 30% cut in direct operating costs per flying hour compared with competing airships, offset ting the higher cost of the rigid structure com pared with a blimp, claims Zeppelin. VECTORED THRUST The propulsion units are diree rotating vec- tored-thrust piston engines: one unit mounted on either side of the hull and one at the tail end, with an additional lateral-thrust fan mounted at the tail and driven by the rear engine. This arrangement allows for optimum manoeuvra bility in pitch and yaw, and true vertical take-off and landing capabilities even when the craft is 10% heavier than air. The manufacturer has selected 150kW (200hp) Lycoming IO360 engines to power the LZ N07. This airship's high manoeuvrability should allow it to operate in much higher winds than conventional blimps can. Zeppelin claims that its airship will be able to take off in 27kt (50km/h) winds, about twice the value for com parable blimps. The thrust-vectoring capability, along with fuel trim tanks, virtually eliminates the need for ballast management. Three large fins with aerodynamic control surfaces are mounted at the tail of the craft. The The destruction of the Graf Zeppelin in the Second World War was the final blow to airships control surfaces are controlled and co-ordinat ed with the thrust vectoring by a duplex digital fly-by-wire system, while the pilots steer the craft with sidesticks. At low speeds, the rear propeller is vectored downwards, triggering a switch which allows the pilot to control both propeller and lateral fan with the sidestick. This maintains pitch and yaw control at speeds too low for the aerody namic control surfaces to function. The pilots and passengers sit as usual in a carbonfibre-composite gondola slung under the hull, but, unlike in a blimp, they are com fortably removed from the noise of the engines. The LZ N07 gondola will be some 1 lm long. The attachments holding the gon dola to the frame are crucial: as in former times, a hard landing could mean scrapping the whole airship. The unit is therefore attached to the frame by a combination of cables and struts, which are designed to deform elastically above a given limit load. On the ground, the airship sits on tandem sets of landing gear — one leg supporting the gondola, one aft under the tail. The gear arrangement allows both vertical and short take-offs and landings. The technology incorporated into the new generation of Zeppelins makes an enormous difference in bulk compared with pre-war designs. The LZ NO7 will be 68.4m long, with a volume of 7,200m'. The future LZ N30 con cept, which could carry 84 passengers, is 110m long, with a 30,000m' volume. By comparison, the ill-fated Hindenburg, which carried 90 passengers and crew, was 245m long with a volume of 200,000m'. The LZ N07 is predicted to have a maximum take-off weight of 6,950kg, with a payload of 1,850kg. It will cruise at 60kt and will be capa ble of a maximum 75kt, with a ceiling of 2,500m (8,200ft) and a maximum flight time of 18h at 38kt. By comparison, the Westinghouse Skyship 600, which has a similar capacity, cruis es at 50kt and has a maximum speed of 60kt. Zeppelin's prototype NT airship is due to be completed by July 1996, with its first flight scheduled for early 1997, and certification pos sibly coming the following year. COMMERCIAL PRODUCTION The company expects to begin commercial pro duction in 1998, with an anticipated unit price of some DM10 million ($7 million). If success ful, LZ N07 will be followed by the 46-seat LZ Nl 7 — to be powered by three 300kW engines — and then eventually by the LZ N30. The manufacturer predicts that its NT air ships will be particularly suitable for applica tions such as maritime patrol, airborne remote sensing, environmental protection and tourism. Zeppelin says that its airships could allow many tasks relating to control of territorial waters to be carried out by a single vehicle. The company claims that its craft will be able to stay on-station longer than any other airborne plat form, and will be able to combine surveillance with on-die-spot interdiction. The craft is also potentially a usefully stable, vibration-free, platform for airborne sensors and scientific research equipment, as well as being able to observe and collect data from the air on phenomena such as environmental prob lems. As far as tourism goes, the company is counting on its name to draw the crowds, as much as the airship's capability to allow passen gers to enjoy a leisurely bird's-eye view in com fort and silence. Zeppelin thus sums up that its NT genera tion of rigid airships has "extremely promising market potential". The return of the company to airship manufacture has certainly stirred pub lic interest, but interest in airships has been stir ring for a long time without yet yielding a revival in substantial sales potential. It therefore remains to be seen whether the manufacturer's fortunes will now rise like a Zeppelin of old, or drop like a leaky one. • FLIGHT INTERNATIONAL 29 November - 5 December 1995 35
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