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A DECISION made shortly after World War I likely delayed aircraft technology by more than several years. In its structure, power and utility, the German Zeppelin-Staaken E-4/20 was simply too far ahead of its time.
Even before World War I, Count Ferdinand von Zeppelin was impressed by Igor Sikorsky’s huge Bolshoi Baltsky (www.wp.me/p2ETap-oj). Initially, his company’s Reisen-Flugzeuge (“Giant Aircraft”) continued the biplane layout and wood/fabric construction of the period.
Not so the Staaken E-4/20: This 1920 design of Dr.-Ing. Adolf Rohrbach was a monoplane constructed entirely of duralumin. This age-hardened alloy of aluminum discovered in 1903 is now called 2000 Series aluminum.
Its fuselage accommodated pilot and co-pilot, radio operator, engineer and steward, plus up to 18 passengers. Amenities included a galley and toilet as well as full radio-telegraph communications, separate baggage and mail storage.
In the original design, the pilot and co-pilot resided in an open cockpit, the preferred layout of the era, better to sense conditions directly. The final Staaken had a slightly different fuselage profile and flight deck enclosed in Cellon windows.
Unlike most aircraft of the period, its cantilever wing required no external struts. The wing, of 101.7 ft. span, was covered with a thin duralumin skin and featured a single riveted box-spar of such size that a flight mechanic could tunnel through to reach any of the aircraft’s four engines.
The engines for the Staaken were also ahead of their time. In his Mb.IVa 6-cylinder powerplant, Karl Maybach traded away sea-level behavior for more critical high-altitude performance.
The Mb.IVa was oversized, at 23.1 liters, with a very high compression ratio, 6.1:1, for the era. It produced 245 hp at 6000 ft.—and had to be throttled back at lower altitudes.
Initial flight testing in late 1920 generally confirmed efficacy of the Staaken’s design. It reached a top speed of 143 mph, unprecedented for an aircraft of this size. However, contrary to hopes, it was unable to maintain flight on two engines, at least in part because of the turning moment of their widely spaced placement. An alternative design, which never came to pass, was a two-engine version with its engines more closely coupled.
From the magazine Flight, The Aircraft Engineer & Airships, Official Organ of the Royal Aero Club of the United Kingdom, March 17, 1921: “We do not know if the Inter-Allied Commission has passed this design, but for the sake of aviation in general it is to be hoped that the firm will be allowed to finish and test it, as it appears to incorporate ideas well worth trying out.”
This was not the case. In 1922, the Inter-Allied Commission ruled that the Staaken had military potential and thus violated WWI treaty stipulations. The aircraft could not be sold or even given away; it had to be scrapped. Its destruction took place—and aircraft technology paused—on November 21, 1922. ds
© Dennis Simanaitis, SimanaitisSays.com, 2013
Back office story: Too bad the Allied Control Commission was busy in 1922 with the E-4/20. In 1921 they missed, among many other things, some 84 new Krupp patents for artillery and munitions, including 14 for heavy cannon which could only be moved by rail. Also in 1922, they missed a new Krupp “branch office” in The Hague. They called it the “Engineering Office for Shipbuilding”, but it wasn’t engineering for ships, it was for boats . . . U-boats.