Features of Aircraft in WWI

by

Hans Appel

1/16 © Hans Appel, 13-07-19

Features of a fighter aircraftThe 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 seriesThe 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 oflater, 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.

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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.

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The De Havilland DH-2The 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 devicewas 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 17The 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 thatalso has a "V" shape.This means that the pilot has a great view downwards.

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The first Nieuport fighter aircraft had some structural problems with the lower wing that tendedto 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 aircraftAlbatros 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 ofhis 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.

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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.

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Fokker Dr-IThe 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 atthe 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.

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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 CamelThe 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.

“Streamlined” tension wires were used for the first time, which were designed by the Royal Aircraft Factory in Farnborough. The advantage of these tension wires over the round wires was a factor of 10 in reducing air resistance!The excellent maneuverability, the mobility, of the Sopwith Camel had to do with a good load & balance.The main weights such as pilot, engine, machine guns and fuel were concentrated in one place. The result was that the position of the pilot could not be envied. His feet were under therear part of the engine, his legs were under the machine guns, and the fuel tank was right behind his back. So in an accident the chances of survival of the pilot were under great pressure.

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The Sopwith Camel was a great weapon in the hands of a skilled pilot. The plane had remarkable control features.The combination of the aerodynamic properties of the aircraft, together with the torque (torsional torque) and the gyroscopic properties of the heavy rotary engine, made the aircraft extremely maneuverable.

But these things were also the cause of a number of peculiar, characteristic operating characteristics.The strange way in which the controls should be treated in the left and right turns was the cause of many accidents.At a left turn the nose of the aircraft was forced up (by the gyroscopic torque of the engine), while at a right turn the nose was pushed down.As a result, with a sharp turn to the left, in addition to moving the stick to the left, a large amount of left foot rudder (rudder) was also required and a moderate back stick had to be given.If one gave too much back stick, the plane stalled immediately and it started to spin (toll flight or vrille).

At a right turn the stick was moved to the right and a moderate amount of left rudder had to begiven, while the stick had to be pulled completely backwards.It may be clear that an inexperienced pilot could quickly become confused with these peculiar operating characteristics.That is why the Sopwith Camel is called the most hated and also the most loved device of theFirst World War.

SPAD XIIISPAD is an acronym for the French company: Societé pour Aviation et les Derieves, which was led by Louis Blériot.

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The SPAD XIII was a somewhat "squat" but elegant aircraft that was flown by, among others, the Americans deployed in the First World War (including the American ace Captain Edward V. (Eddy) Rickenbacker).

A recess was made in the upper wing so that the pilot had a very good view upwards. The design was a double bay airplane.The cockpit was placed directly behind the engine so that the pilot's feet and lower legs were in a kind of aluminum pipe under the engine.The landing gear was far in front of the center of gravity of the aircraft. This was to prevent nose landings.The ailerons of the aircraft were mounted on the upper wing.

The SPAD XIII can also be easily recognized by a typical round radiator that was installed in front of the Hispano-Suiza V8 engine and whose “shutters” (shutters) could be operated manually by the pilot.Furthermore, long exhaust pipes were installed on each side of the hull. The pilots made use of those exhausts by grabbing those exhausts with their thick gloves during the flight to warm their cold hands.

The SPAD XIII was the fastest and most robust aircraft of its time.In a steep dive that was sustained for a long time, there were no problems with the mechanical structure of the aircraft, that was quite special for that time.

Fokker D-VIIThe Fokker D-VII looked like a somewhat angular plane with an inline engine that had a radiator in the nose.Fokker used a technology that was advanced at that time with regard to the wings. They wereself-supporting, thick wings that were braced inside the wing.The thick wings were responsible for many of the excellent flight characteristics of this aircraft.

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The ailerons were of the horn-balanced type (elephant ears), the stabilizer and rudder were also made like this.Despite the fact that the performance was not exceptional, the flight characteristics were excellent. The aircraft responded quickly and accurately. The operation of the controls was light. There were no "strange" features that should be taken into account during driving, such as with the Sopwith Camel.

The Fokker D-VII is the only aircraft that is specifically named in the truce declaration. Which says something about the excellent qualities of this aircraft.

The Sopwith DolphinA very good example of experimenting with airplanes during the First World War is the Sopwith Dolphin.If you look closely at this design you will immediately see that it is not your average biplane aircraft.

The first thing you notice is that the upper wing is behind the lower wing. We call it that the wings have a "negative stagger" (an opposite zigzag arrangement). This was done to give thepilot a completely unobstructed view.

Furthermore, the pilot was immediately behind the Hispano-Suiza engine with his feet on the handlebar, directly under the crankshaft of the engine.The fuel tank was directly behind the pilot.The pilot's head protruded through an opening in the upper wing, above the aircraft.

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The pilots made use of those outlets by grasping the outlets with their thick gloves during the flight to warm their cold hands. After all, with every 1,000-foot height gain, the temperature decreases by 2ºC.So at around 15,000 feet, where air fights generally took place, that was a difference of -30ºC with the ground temperature.

All in all, the aviator had an unenviable position.If the aircraft were to make a "nose landing" (which was certainly a regular occurrence at that time), it would have to retract its head quickly because otherwise the entire weight of the aircraft would rest on the unfortunate one.If that had succeeded, it would be a maze of tension wires and struts and a fuel tank that could explode at any moment.

Return of the monoplaneTowards the end of the First World War, in June 1918, the German Air Force launched a competition to obtain a monoplane fighter aircraft. Fokker scored a contract for 400 aircraft with the Fokker D-VIII, while Junkers was allowed to build its J-1, an all-metal aircraft.

Fokker D-VIIIThe Fokker D-VIII was a parasol configuration. Characteristic of this configuration is that the wing is constructed above the pilot so that an unobstructed view to the ground is created.The disadvantage of this configuration is that the required trusses (stiffening beams) that are required and that produce a lot of aerodynamic resistance.

The wing is relatively thick so that the struts for reinforcement are included in the wing. The wing was tapered and made entirely of plywood.This type of wing was applied to many aircraft produced by Fokker in the years following the war.

The hull was made of metal tubes that were covered with fabric.The engine was from an Oberursel rotary engine of only 110 hp.Moreover, the flight characteristics were of a very good quality. The climbing capacity was phenomenal for that time and was achieved by applying the "thick", tapered wing.

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With the first 20 aircraft supplied, the German Air Force was involved in the way the wings were supported. They wanted "old" methods to be applied, such as those used with traditionalwings. As a result, the wings broke due to torsion.When Fokker was allowed to use the originally designed method, this problem was solved.

Junkers J-1 and D-1The Junkers J-1 bi-plane and the D-1 monoplane were a very modern design with thick, fully self-supporting wings.With the D-1 monoplane, the wings were attached to the bottom of the hull. The wings tapered, from front to back with 17%, from body to the tip with 12%.

The most striking thing about these aircraft is that they are made entirely of metal.Corrugated, riveted, metal alloy plates were used.The durability of the metal construction was a huge improvement over the fabric-covered aircraft.

The fabric upholstery quickly degenerated under the influence of the weather, the sun and thedifferences in air pressure.The wood used did not escape rot and the release of the wood layers that made up the plywood.

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The Junkers J-1 bi-plane was equipped with a photo camera and radio transmitter as standard.These aircraft were initially armored with 5 mm steel plates, but during production the thickness was reduced to 3.5 mm.This was necessary to limit the weight of the plane.The runway length required to start was much larger than with the aircraft made of wood and fabric cover. And since there were not enough large airports at the front, this concession was made.

The pilots were happy with the armor present.The J-1 was used tactically to support the infantry (the PBI, Poor Bloody Infantry) and to attack ground targets.Pilotes returned from their mission with dozens of hits of ground fire, but the J-1 seemed indestructible.

An otherwise salient detail is the pilot's seat. At first glance, it looks comfortable, even with armrests. But this seat was the main 120-liter fuel tank.In addition, there was a kind of slit in the chair was used for operation of the elevator!

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Attachments

Ascent rate of various aircraft from the first World WarVertically the height and horizontally the required time in minutes.

Time required in minutes --------- →

It can be seen that the Fokker E-III took about half an hour to reach 10,000 Ft and the Fokker D-VIII climbed to 20,000 ft in less than 20 minutes.And that outlines, among other things, the progress of the aircraft in 3 to 4 years.

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Zero-lift drag coefficient

CD, 0 = CD - CD, i

CD, 0 = zero-lift drag coefficient

CD = total drag coefficient for a combination of power, speed and height

CD, i = induced drag coefficient with the same flight conditions as total drag coefficient

The zero-lift drag coefficient is a dimensionless number that varies with every aircraft. The smaller this number is, the "aerodynamically cleaner" is the aircraft.For the Fokker E-III yacht aircraft this number was 0.0771

Drag area fThe "drag area f" is the product of CD, 0 (zero-lift day coefficient) and the surface of the wing. This number is interesting because it indicates the ratio between the zero drag coefficient anda plate that has the same parameters. The ideal ratio is 1.0. For the Fokker E-III yacht aircraft, this number was 12.61

Maximum lift-drag ratio (L / D) maxThe value of the maximum lift-drag ratio (L / D) max is the aerodynamic efficiency at cruising speed. The amount of power required to maintain a given mass in the air and is proportional to the number of miles per pound of fuel with a specific propulsion system and aircraft weight. The higher the (L / D) max number, the higher the efficiency at cruising speed.

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