to be performed up to eight times an hour. Both the rudder and elevator were aerodynamically balanced, and the type had no fixed tail surfaces. This combination rendered the Eindecker very responsive to pitch and yaw. For an inexperienced pilot, the extreme sensitivity of the elevators made level flight difficult; German ace Leutnant Kurt Wintgens, who along with Leutnant Parschau was the primary Fliegertruppe pilot responsible for bringing the first armed Fokker monoplanes into active service during the spring and summer of 1915, once stated "lightning is a straight line compared with the barogram of the first solo". The roll response of the Eindecker, on the other hand, was poor. This is often blamed on the use of wing-warping rather than ailerons - although the monoplanes of the time, even when fitted with ailerons, often had unpredictable or unresponsive roll control due to the flexibility of their externally braced wings. Engine installations and associated changes The main difference between the E.I and E.II was the engine - the former having the seven-cylinder 60 kW (80 hp) Oberursel U.0 rotary engine which was essentially a direct copy of the French-made 60 kW (80 hp) Gnome Lambda seven-cylinder rotary engine, while the latter had the nine-cylinder 75 kW (100 hp) Oberursel U I, a direct copy of the 75 kW (100 hp) Gnome Monosoupape Type 9-B2 rotary. The larger diameter of the E.II's nine-cylinder rotary mandated raising the upper nose paneling to match the larger-diameter cowl the U.I required — this also caused the outer edges of the upper nose paneling to overhang the fuselage's upper longerons, making it necessary to add "soffit"-like surfaces, projecting outwards and upwards from the upper longerons' forwardmost length behind the cowl to fully enclose the nose once more on all E.II and E.III aircraft. The "soffit"-like surfaces were eventually created from upward extensions of the sheetmetal panels on the sides of the forward fuselage, by the time the E.III was in full production. Production of the types, built in parallel, depended on engine availability. Many E.IIs were either completed as E.IIIs or upgraded to E.III standard when returned for repair. The definitive version of the Eindecker was the Fokker E.III, which used a slightly narrower-chord (1.80 meter, or 71 inch) wing than earlier versions. Boelcke's Feldflieger Abteilung 62 began operating the E.III towards the end of 1915. A few E.IIIs were experimentally armed with two 7.92