Features of Aircraft in WWI by Hans Appel 1/16 © Hans Appel, 13-07-19 Features of a fighter aircraft The primary purpose of a fighter aircraft is to destroy another aircraft. This must be done in both an offensive and a defensive manner. These enemy aircraft can be fighter aircraft, but also bombers, patrol, reconnaissance and transport aircraft, or aircraft specifically designed for attacking ground targets. To be in a good position to perform its offensive tasks, the fighter pilot must be able to properly observe its prey. In the first World War that was always visual, optical. That is why when designing a fighter, a maximum view for the pilot was at the top of the wish list for the design. In addition to a good view, flight performance and maneuverability, plus having a stable gun platform are a necessity. And all this coupled with sufficiently powerful firearms to destroy the enemy, Regarding flight performance and maneuverability, the following parameters are important: • the correct speed under different flight conditions, • ascent rate, • height of the ceiling, • rolling speed, • turning circle, • climbing speed while turning a bend, • and range. The Fokker Eindecker series The Fokker Eindecker (=monoplane) was not particularly maneuverable or very fast, but he had the advantage of the presence of a machine gun that could shoot through the turning circle of the propeller. The machine gun was fixed and aimed by aiming the entire aircraft at the enemy. This Fokker became available in the summer of 1915. The Fokker E-I, E-II and E-III only had one machine gun, the E-IV had two and moreover this aircraft was larger and had more power available than the others. The E-I, E-II and E-III look like a fragile single-decker with many tension wires, many of which come together on a rack above the wing. The wing is remarkably thin, as with many designs in the first years of the war. It was assumed that thicker wings would provide a lot of air resistance. With the knowledge of later, a totally wrong starting point. But in those years the ratio of wing thickness to wing was 4% to 6%. Later the Germans used thicker wings with great success! The control mechanism of the Eindeckers was, even before 1914, very "old-fashioned". The aircraft was allowed to roll (lateral control) by applying the warping of the wings. The horizontal and vertical parts of the tail consisted of one piece. 2/16 © Hans Appel, 13-07-19 Frank Tallman, the author of the book "Flying the Old Planes" describes how to fly with the Fokker Eindeckers as follows: During the entire flight you have the feeling that when you let go of your stick or take your feet off the rudder control, the Eindecker immediately wants to roll or take a dip. While all moving parts are constantly vibrating and pulling, the pilot must constantly use hands and feet to keep things under control. By modern standards we would say that the aircraft is unpleasant to fly with and is not stable. Today, such an aircraft would not receive airworthiness approval. The construction of the hull was made of chromium-molybdenum tubes. The body and wings were covered with fabric and treated with special varnish to tighten the fabric and protect it from the weather. Rotational motors were used. With the E-III, for example, an Oberursel that delivered 100hp. To keep centrifugal forces under control, relatively low speeds of around 1200 to 1400 revolutions per minute were used. That is why four-blade propellers of large diameter were used. 3/16 © Hans Appel, 13-07-19 The De Havilland DH-2 The British did not have a synchronized machine gun. To solve this problem, they came up with a construction in which the engine, and therefore also the propeller, were placed behind the pilot. The aircraft was therefore equipped with a pusher. In this way, a free field of fire was obtained at the front of the aircraft. The De Havilland DH-2 is a good example of that British construction. The aircraft was a bi-plane, it had very thin non-tapered wings, with two sections marked out by struts. There was a small gondola (nacelle) that was incorporated in the lower wing. The plane was, as indicated earlier, equipped with a rotary push motor with a four-blade propeller. Both the upper and lower wings were fitted with ailerons. Incidentally, the control of the device was very sensitive, it tended to get into a spin. The device was able to climb faster than the Fokker E-series and it flew, despite the sensitive controls, more stable than the Fokker E-series planes. The Nieuport 17 The Nieuport 17 was an excellent bi-plane, with which the "aces" of that time won many victories. When the Nieuport 17 appeared on the battlefield, a synchronized machine gun was not yet available. That is why a Lewis Machine Gun was placed on the upper wing, so that the propeller could be fired over. Planes built later had a synchronized machine gun at their disposal. The Nieuport 17 is a "sesquiplane", a one-and-a-half wing, where the chord (cross-section) of the lower wing is much smaller than the upper wing. As a result, only one strut is required that also has a "V" shape. This means that the pilot has a great view downwards. 4/16 © Hans Appel, 13-07-19 The first Nieuport fighter aircraft had some structural problems with the lower wing that tended to twist at high speeds (for example, in a dive). Furthermore, the cover of the upper wing was released during a high-speed dive. However, these problems were quickly resolved. This aircraft was deployed with great success until well in 1917. Albatros fighter aircraft Albatros is a big name in the field of aircraft construction during the First World War. The Albatros D-III and D-V with their variants were incredibly successful fighter aircraft. These Albatros aircraft were in April 1917 due to their predominance on the allied planes the cause that this month went into history as "Bloody April". Manfred von Richthofen won most of his victories in Albatros fighters. The Albatros D-III aircraft were biplanes with "V" -shaped metal struts (just like we saw at the Nieuport). The lower wing exhibited structural problems when diving at high speed. The upper wing was equipped with ailerons. The Albatros D-III was equipped with a rudimentary form of "trim" system. To stay at a certain height without having to constantly pull or push the control stick, a "sliding collar" construction was made around the control stick with a tube anchored to the bottom plate of the cockpit. The pilot was able to secure things, freeing his hands to, for example, unblocking a jammed machine gun. The power came from a six-cylinder 160 hp Mercedes engine. 5/16 © Hans Appel, 13-07-19 There was an aerodynamically shaped cooling radiator on the upper wing. The aircraft was equipped with two synchronized machine guns. The hull was designed as a shell construction (monocoque). The outer shell was made of plywood that was kept in shape by joists (trusses). To obtain more stability in the length, a number of extra trusses were fitted over the length, which is why the Albatros D-III is called a "semi-monocoque" construction. 6/16 © Hans Appel, 13-07-19 Fokker Dr-I The Fokker Dr-I was a three-plane of which all three wings were self-supporting (cantilever). That is, the wings were supported but that was done inside the wing. There were struts between the wings but that was because the pilots felt safer, but those struts were structurally unnecessary. The wings of the Fokker Dr-I were very thick compared to the thin wings that were common at the time. It was initially not understood that thick wings with more profile can also generate more lift than their thin counterparts. At the University of Göttingen, research was carried out into the influence of wing thickness and Fokker was the first to use the so-called Göttingen 298 wing as support in his design for the Dr-I Furthermore, the wings were provided with "horns" (horn-balanced aileron or elephant ears). This was done to reduce the pivotal moments of the ailerons so that the pilot did not have to use as much force on the stick to initiate the roller movement. The Dr-I had the lowest zero-lift drag coefficient (0.0323) of all fighter aircraft from the First World War. This value was mainly due to the relatively small wing area of the Dr-I. In addition, the lack of struts and tension cables also had a major impact on this value. 7/16 © Hans Appel, 13-07-19 And finally there was the "thick" wing profile that was used. (The explanation of the zero-lift drag coefficient can be found at the end of this document) The speed of the Dr-I was certainly not impressive at 166 km/h, compared to other aircraft of that time, but the Dr-I had excellent climbing capacity and excellent maneuverability. The Sopwith Camel The Sopwith Camel was developed from the Sopwith Pup concept. It was the first English fighter with two forward-fired, synchronized machine guns. The streamlining caps over these two machine guns showed two "bumps", hence the name "Camel". What stands out with the Sopwith Camel is the flat upper wing. This was not based on aerodynamic principles, but was dictated only by the need to make production as simple as possible! The large V-position angle that the lower wing made was intended as compensation for the flat upper wing.