Why do HAL planes crash so often

To what extent do bionic inventions improve modern aviation?

Table of Contents

1 Introduction

2. Drag and flow forces acting during flight

3. The flight of birds and its explorers
3.1 Leonardo da Vinci - ahead of its time?
3.2 Otto Lilienthal - The Aviation Pioneer

4. Natural role models and how they influence aviation
4.1 Bird wings and aircraft wings
4.2 The jet propulsion - locomotion using the recoil principle
4.3 The stall - why do planes crash?
4.4 Thumb wing of birds
4.5 The hand wings of the birds - winglets
4.6 The seeds of the maple tree - propellers in aviation

5. The technical improvement of military vehicles through bionics
5.1 The seeds of the zanonia plant - B-2 Spirit
5.2 The swift - the delta plane

6. Other forms of flying machines
6.1 The dragonfly as a model for the helicopter
6.2 The body shape of the penguins - unmanned zeppelins

7. Experiment to study the utility of winglets

8. Conclusion on the question

9. List of sources
9.1 Primary literature
9.2 Secondary literature
9.3 Internet addresses
8.4 Additional sources

10. List of figures

11. Appendices

1 Introduction

When huge planes weighing hundreds of tons rise into the air, I often ask myself: How is that possible? Apparently I was and am not alone with this question. Even the forefathers of aviation, Otto Lilienthal and Leonardo da Vinci, were enthusiastic about free flight and laid the foundation for modern aviation with their knowledge. But where did they get this knowledge from when there were no airworthy devices or even only records of them?

They made use of nature and found, above all, in birds, but also other animals and plants, everything that was necessary to enable humans to fly. This is called bionics in aviation. It was still a long way from this knowledge to modern aviation, but today we can already marvel at aircraft that are packed with new technology. They cover longer distances than would have been imaginable 50 years ago and, despite the high speeds, are statistically the safest means of transport.

But what has changed in these years and to what extent does nature have to do with these changes / inventions? I would like to find out in this work and, if possible, also point out further possibilities for improvement. Nature can certainly continue to inspire us, because the proverbial “end of the flagpole” in terms of efficiency, safety and, above all, environmental protection is still a long way off.

In my pre-scientific methodology, I would like to address a special invention that has only reached aviation in recent years. I plan to use a meaningful experiment to highlight the difference between missiles with and without "winglets" (further information in text 3.5) and thus to be able to draw conclusions about the usefulness of bionic inventions. Further information about winglets in general can be found in point 3.5.

So what does bionics bring us? How can we continue to drive developments in aviation? And what is the difference with and without winglets? Let's find out!

2. Drag and flow forces acting during flight

The basic principle of bird flight and flight in general is based on the fact that the Total air force FL counteracts the weight force. This is made up of two different forces.

So that the one can arise, the wings (wings) must have a special shape in the profile. On the one hand, it must be arched upwards and, on the other hand, similar to a horizontal teardrop shape, it must be thick in profile at the front and taper to a point at the back. These asymmetrical airfoils now have to be surrounded by air in order to generate the first force dynamic buoyancy to generate. The difference to a symmetrical profile is very simple. With the symmetrical wing profile, the air is divided, but flows around the wing at the same speed above and below.

Editor's note: This image has been removed for copyright reasons.

Figure not included in this excerpt

Figure 1: The asymmetrical wing profile and the forces acting

This is different with the asymmetrical wing profile. Here, the air on the top has to travel a further distance in the same time, so it flows faster. On the underside, the air flows more slowly because the path is shorter. This creates a negative pressure (suction) over the wing and an overpressure (air cushion) under the wing. If a certain speed is now reached and the air flows around the wing with this, an air cushion is created under the wing and a suction over the wing. These air cushions in connection with the suction provide the necessary lift that allows an airplane or bird to take off from the ground. This upward force is the dynamic lift force FA.

When a bird or airplane moves through the air, the second force arises from which the Total air force composed. Isaac Newton already proved with Newton's third law that every force acting on a body produces an equally large but opposing force. In this case the forward force is that of the drive. The opposite works against this Drag force FW. The air resistance partially slows down any movement in one direction. Since the airplanes and birds have to use a lot of energy to overcome the air resistance, fuselage and wing shapes developed in the course of evolution, which only cause a low air resistance. This means that you can fly much more efficiently.

All in all, it can be said that every wing around which air flows, creates two forces. On the one hand the dynamic lift force FA, as well as the Drag force FW. Both together, make the Total air force FL represent.1

Figure not included in this excerpt

3. The flight of birds and its explorers

The flight of birds is the first thing that comes to mind when we think about natural role models in aviation. Since it is also the largest research area in bionic aviation, many inventions have been derived from this class. This is why it is by far the most important area to understand how bionics has improved our aviation. In addition, there are some individuals who have dedicated their lives to researching this class of animals and its unusual characteristics. The two most important people in this context, one could say the forefathers of aviation, are Otto Lilienthal and Leonardo da Vinci. They and their services are presented in the following sections.

3.1 Leonardo da Vinci - ahead of its time?

Before the first flying machines could be invented, humans first needed knowledge about locomotion in the air and the forces involved. Leonardo da Vinci was the first person who recognized this problem and worked not only practically, but above all scientifically. He realized that the flight of birds was the most important source of information for this area of ​​locomotion. So in 1505, at the age of 53, he began his studies of birds. In the same year, a summary of his findings was published in his book “Codex about bird flight”, in which he also provided theoretical knowledge for the practical implementation of flight machines. He then developed and constructed various flying machines himself, such as the propeller or the ornithopter. They were based on many different flight techniques, e.g. the propeller worked according to the principle of helical lift or the ornithopter according to the principle of flapping wings. Unfortunately, none of da Vinci's flying machines were airworthy. There was simply a lack of the necessary technology that would provide enough strength and buoyancy, as a person can hardly lift his own body weight and a glider that usually weighs around 18kg in the air. That is why Leonardo da Vinci is usually described as "ahead of its time". The fact that he was the first person to collect scientific knowledge and to venture his first attempts at the construction of flying machines, despite this failure, can be described as the forefather of bionics in aviation.2

3.2 Otto Lilienthal - The Aviation Pioneer

Otto Lilienthal is considered the aviation pioneer in general. He was the first person who could achieve a reasonably stable and long flight with the prototype of an airplane. He was born in the small town of Anklam in 1848. He was a trained mechanical engineer and therefore founded his own factory in 1981, which dealt with the manufacture of steam engines and steam boilers.

He has been dealing with the basics of flying since he was 19. What was new at the time was that, unlike his predecessors, he did not concentrate primarily on trying out flying machines, but rather focused on the theory of flight in the first few years. Experiments on small models alternated with theoretical knowledge. In the course of these discoveries, he was particularly fascinated by one class of animals, the birds. He examined the flight of birds with scientific accuracy by not only observing but also taking numerous measurements. He wanted to gain knowledge about aerodynamics through them in order to be able to use them later profitably in his flying machines. His work “The flight of birds as the basis of the art of flying”, published in 1889, summarized all of his observations and measurements on bird flight and its aerodynamic properties. His work is still considered the standard work of the editor's note: This image has been removed for copyright reasons.

Figure not included in this excerpt

Figure 2: Otto Lilienthal's first flight bird flight research.

After Otto Lilienthal had dealt with the theory of flight for about 20 years, he jumped from a hill for the first time in 1890 with a self-made flying machine. In the following year he flew a distance of 25 m for the first time and landed comparatively gently. This flight of seconds is considered to be the first human flight with a flying machine. The Derwitz Apparatus, the name of the first flying apparatus used, was followed by 16 more, all of which Lilienthal developed and tested in-house.

His flights got farther and farther, but the height of the jump became more and more dangerous. In 1893 he jumped from a 60m high hill with one of his newest devices and glided 250m through the air. In total, Lilienthal made about 2000 flight attempts in his life, sometimes jumping off a ramp up to 60 times in a day. He was also well aware of the risk involved in his plans and usually countered foot and arm injuries with a further improvement in the flight apparatus. These usually consisted of a network of willow branches covered with cotton. This made the flying machines very light, but still remained stable. He also experimented with movable wings and biplanes, but found that for the most part these were of no benefit. Lilienthal's four patented flying machines were mass-produced and sold. As an irony of fate, Lilienthal enclosed an instruction leaflet with each of the flying machines he sold, which pointed out the dangers of flying. These dangers of the flight attempts at that time became his own undoing when he was hit by a strong gust of wind on August 9, 1986 and crashed. He broke her cervical spine in a fall from 15m and succumbed to his injuries in the hospital one day later. However, his inventions lived on and are the basis of many modern aircraft today. Just like the knowledge of aerodynamics, which even today is still relevant and important for the improvement of aircraft.3

4. Natural role models and how they influence aviation

As already mentioned, modern aviation has made use of a number of models from nature. However, since there are extremely many examples of this, the following sections present some examples of inventions in aircraft construction based on models from nature and what influence these have on modern aviation.

4.1 Bird wings and aircraft wings

The wings are one of the most important parts of an airplane, as only these ensure that enough lift is generated so that the airplane can take off. For the development of today's wings, as we see them on airplanes, a model from nature was used, the bird's wings.

Otto Lilienthal was the first to recognize that wings should not be a straight board, but rather need a special shape that generates the necessary lift. He found what he was looking for in the birds, whose wings have a curved shape. With this knowledge, Otto Lilienthal was able to create the first curved wing. For more information about this shape and the forces involved, see point 2. With the help of this knowledge, Lilienthal carried out the first gliding flight and laid the foundation for later aircraft construction.

Birds can also control their wing curvature and thus always adapt their wings perfectly to the conditions and flight maneuvers, which the wings of most aircraft cannot yet technically implement. However, scientists from the DLR (German Aerospace Center) have been researching this improvement option for years, which is why a mechanism for changing the wing curvature could possibly also be used in conventional aircraft in the near future. 4th

4.2 The jet propulsion - locomotion using the recoil principle

Jet propulsion is one of the most important inventions in aviation. It ensures that aircraft of any kind can take off from the ground at all. Every aircraft needs a sufficiently high take-off speed to be able to generate the lift under the wing and the suction over the wing. With normal passenger aircraft such as the Airbus 350 or the Boeing 737, this take-off speed is approx. 300 km / h. After take-off, the speed increases from around 10,000 m to around 850 km / h until the cruising altitude is reached.4 This enormous speed is generated by the recoil principle used in the engines / jet drives.

Figure not included in this excerpt

Figure 3: Locomotion of a jellyfish

The recoil principle also comes from nature, but is not practiced by any flying animal. This time we have to look below the surface of the water to understand this propulsion system. The recoil principle, which is often used in the aerospace industry, was originally mainly used by jellyfish and squid. They suck water into the cavity formed by their body, then narrow the opening and press the water out with pressure. This causes them to jerk in the opposite direction of the expelled water. That is the recoil principle. It is based on the simple formula that is, the faster or larger the ejected mass, the higher the resulting momentum. This has the advantage that a relatively small mass (e.g. fuel in the form of kerosene) is sufficient to set a significantly larger mass (e.g. an airplane) in motion, provided that the smaller mass moves at a higher speed in the opposite direction . This also happens with the jet engine, as it sucks in ambient air at the front, then compresses it and mixes it with fuel and ultimately burns it in the combustion chamber. The extremely hot combustion gases now have a much higher volume and so shoot out of the rear of the engine. This triggers the impulse for the aircraft to move forward, which can also be calculated as long as one disregards the inertia. Due to the inertia, the aircraft naturally needs a long time to reach top speed. The aircraft can accelerate up to 300 km / h, then take off and accelerate further. Ultimately, the jet drive ensures the necessary speed for take-off, but also serves to maintain the cruising speed in the air and thus makes buoyancy possible in the first place

Figure not included in this excerpt

4.3 The stall - why do planes crash?

Normally, the curved shape of the wings generates enough lift above a certain speed to allow the aircraft to take off from the ground.

However, this only happens up to an angle of approx. 15 ° to the incoming air. Draws editor's note:

Figure not included in this excerpt

Figure 4: Aerofoil stall If a pilot climbs his aircraft too steeply too quickly, the angle becomes too large and flow lines from the rear of the wing begin to loosen. This creates turbulence over the wing. Should that happen, the pilot has to react immediately and press down the nose of the aircraft, thus reducing the angle of attack again. The necessary buoyancy can then be built up again. However, if the angle of attack increases even further, the dangerous stall begins at around 18-20 °.This means that all of the air swirls on the top of a wing and negative pressure can no longer be generated. Since the suction above the wing makes up 70% of the lift, not enough lift can be generated by the air cushion under the wing. As a result, the wing loses its lift and can no longer keep the aircraft in the air. As a result, the plane falls "like a stone from the sky"5.

This dive is so uncontrolled that even an experienced pilot can only get the machine under control at high altitudes. If such a dangerous stall occurs during take-off or landing, the crash can hardly be averted. However, there are already a number of solutions from nature for this problem, which are explained in more detail in the following sections.6

4.4 Thumb wing of birds

Nowadays the planes are already sophisticated and powerful. Now, however, it is a matter of improving the existing techniques and making flying more efficient, but above all safer. The thumbs of the birds play a major role in this. The thumb wing is an area of ​​3-4 strong and wide feathers on the leading edge of the wing, just where the bird's thumb is. This helps the birds to prevent stalling when taking off and landing, whereby the wing is usually set relatively steeply. To do this, the thumb wing spreads away from the wing when the flow begins to break, creating an air channel at the leading edge of the wing. In this way, more air can flow from the underside between the wing and the thumb wing to the upper side and the negative pressure there is maintained.

Editor's note:

Figure not included in this excerpt

Figure 5: Thumb wings on a stork

Leonardo da Vinci already recognized this. However, 400 years should pass before the technical implementation. The development of the first slat was rather intuitive in the 1920s, as the design was only based on the assumptions of the designers. There has not yet been any evidence of the usefulness of such an additional door. The slat, like the thumbs of the birds, was designed to direct air from the underside upwards and to avoid stalling. However, it was not until later tests in wind tunnels that it became apparent how incredibly effective these slats were for the safety of the aircraft during take-off and landing.

Another advantage of the thumb wing is that it allows the birds to steer in a particularly energy-saving manner. To change the direction, it is sufficient to spread the thumb wing on one side, and the bird flies a curve. Airplanes cannot completely control their slats, but they can compensate for slight movements during a flight, which used to require complicated flight maneuvers. Ultimately, on this point, nature has once again helped us to make aviation safer and more comfortable for us

4.5 The hand wings of the birds - winglets

In recent years, both flight safety and the climate friendliness of flight have grown significantly. This is not least due to an invention that found its basic idea back in 1997, but has only been improved and used in the last 20 years.

[...]



1 Gründler, J.H. : Natural Sciences - From Flying, Berlin 1998, p. 7ff.

2 Prof. Dr. Bacon, T .: Leonardo da Vinci

3 Schautafeln / Otto Lilienthal Museum Anklam: no publisher given, visit on 13.09.19

4 Bürkle, A .: Aircraft take-off speed - what you need to know about the take-off process

5 Focus Online (Ed.): Aircraft stall - Why is the danger so great ?, 03/11/2019

6 Ibid. Last accessed: 13.09.19

End of the excerpt from 44 pages