Jan Peter Apel

Aviation safety 

In 2008, a Tiger-Moth biplane crashed in Australia with a Sky Walker on the wing. In climb shortly after takeoff, the engine failed and the pilot made a sharp 180 degree inversion turn that resulted in a steep orbit incline that hit the ground and ended in a total crash. Both, pilot and Sky Walker dead. You see it in www.youtube.com/watch?v=DFWMBT1zDlI&feature=related).
The reason for this is to be sought with great certainty in the problem of curves in the wind, which is still largely unknown in aviation.

An airplane moves in and against the air, which itself is inactive. It requires a minimum speed against the air in order not to fall down. With that, the air, through which an airplane flies, is definitely the basis of flying, since without it, it does not work. This means that the air is the natural, the correct coordinate system, ie the sole reference point for the natural phenomenon of flying.

Whether steadily straighton  or on circular orbits, each aircraft must move with its own speed against the air given by its construction. Moves the air, in which the plane flies, against the ground, as we say wind, then the coordinate system of flying is moving with the wind.

In straight flight, no matter in which direction, no deviation from the flight in stagnant air is detectable and there is also no. If the aircraft flies in a circle in the air, which is moving in relation to the ground, it must neverthelass have the maintain its speed in relation to the air.

However, pilots do not perceive any differences in circular flight, which they would have to iron out. But these are there, are only unconsciously compensated by tax rashes, without asking of why. Such rashes are indeed necessary by many other small-scale air movements. A pilot never knows how the air he flies through is moving. He can not know that either.As a glider instructor, I first came across the problem of wind when, on several days of strong wind, I noticed successively during several training flights that every time in the landing curve, ie when driving against the wind, an increase in speed had to be avoided or air brakes had to be actived. It felt like a climb by thermals, that did not exist that day. The same process also took place when the landing curve was closer or farther away from the runway, so it was not stationary.

In flight bends, two separate independently physical processes exist side by side:

1) An aircraft must maintain a constant air speed in the air coordinate system.
2) In order to do this, it has to become slower in the Earth coordinate system, that is, slower in the headwind and faster in the tailwind in relation to the ground.

To become faster and slower to the ground, an airplane must change its kinetic  pulse of mass times its velocity in relation to the ground. To accelerate the plane, it needs energy (engine power or loss of height). The slowing is possible through air brakes or altitude gain.
If a plane with constant drive power flies in a full circle in the air, it will periodically change its height while maintaining the speed by pulling and poshing the elevator. This does not bother a pilot, he does not realize it consciously, unless it happens close to the ground. And there lurks the danger.
Namely, if the circumstances are such that there is strong wind and in addition a small curve radius is flown and also near the ground, then this happens as with the Tiger Moth.

For the flight practice the following arised:

The loss of speed through turns from the opposite into the tailwind becomes as dangerous at additionally low altitudes with narrow radii as in the disaster in Australia. A second such case in Germany (the passengers had already waved to those waiting at the edge of the square) had cost four lives.
The plane crashed into the ground after the return curve, because it was too low. The result of the reviewers: pilot error. Of course, but, the pilot could not know as the one in the Tiger-Moth, that driving into the companion wind at tight curve radii meant enormous speed / altitude losses.

When gliding / paragliding on a slope, it is forbidden to curve in the directioen to the slope. Of course, the ban comes only from experience, because that there is a problem when curving in the Mitwind, was and is unknown until today.
For large aircraft such events do not happen, even because the airspeed is greater in relation to the wind speed and they do not fly tight turns.

Pilots must learn that turns into the tailwind cause height / velocity losses. Specifically, after starting up in case of unsuccessful touchdown gaining height enough once again and then to complete the new round course at rest with not too small curve radii or to land straight on by emergency after engine failure. The pilot in the Tiger Moth was already lost immediately after the 180 degree turning curve, from which point there was nothing to save for lack of altitude.

The calculation of the height loss when turning out of the headwind into the tailwind

Changes in energy due to changes in velocity do not happen linearly but quadratically. Therefore, a change may not be considered on its own, but always the difference from the state before to after.

The fall height required for a certain speed from the potential energy is calculated by the basic formula of the free fall v = root of 2 * g * h. It is not necessary to calculate the energy itself.
The required height h then results by the square of the basic speed divided by 2 * g, ie by about 20.
Airplane speed against the air 30 m / s (108 km / h), wind speed 10 m / s (36 km / h).
In the headwind, the plane has 20 m / s ground speed, that is 20 squared divided by 20 equally coincidentally even 20 m as an equivalent potential altitude. It would reach this speed from zero speed.

During flying with the wind, the aircraft must reach a speed of 40 m / s. The equivalent potential energy is then equals 40 squared by 20 equal to 80 m height. From this height, it would fall to a speed from zero to 40 m / s.

To get from 20 m / s speed over ground in the headwind to 40 m / s in the tailwind, the aircraft requires a loss of altitude of 80 m - 20 m equal to 60 meters in height!

Do add to that in the 180 degree curve is flown uncleanly, so that the airplane also loses kinetic energy in this curve, the height loss increases much more. The result of the above calculation is thus a minimum height loss value. The mathematics for the process of wind curves after its physical clarification is therefore limited only to good mental arithmetic.

What does this theory prove in practice?

First of all by the me known six dead. To discover the big wake vortices behind planes, more people had to die until schoolmaster finally accepted this new knowledges 

Second, an attempt, made by each pilot. When the wind is strong, fly so high that you no longer notice the curve offset from the ground, so you think that you are only part of the air. Fly full circles with meticulous attention to constant speed. It will be observed, that is to push on one semicircle and pull on the other. The height becomes smaller on the pushed semicircle and larger on the pulled one. On the pushed half side you find yourself in the tailwind, on the pulled in the headwind. This takes place unchanged even above the clouds!


About Windkurven there is in Germany an article by J. J. Buchholz and Joerg Russow from 1991. They describe mathematically the geometric path of an aircraft in the coordinate system of the solid ground as the sum of the circular motion of the aircraft in the air and the movement of the air. As expected, the corresponding cycloid trajectory over ground arises whith different aircraft speeds over ground.
Non-mathematically, they describe, that an aircraft must accelerate and decelerate above ground to reach these different speeds, and even that these accelerations in the aircraft are not measurable. As far as that it is verifable.

What incomprehensible is, is, that an aircraft would put back this cycloid path at the same height. This is assumed by the authors as an assumption and subsequently tried to justify. The author Russow is not a pilot, By Buchholz I have no information.

For the changes of the speeds of an aircraft by needed changes of their energies,  which unfortunately does not relate to the air but to the Earth's surface, they describes in terms of content, that an aircraft in a circular flight in the area against the wind releases energy into the air, which then brings it back to accelerate in tailwind again with the following words: "The energy must therefore be exchanged with the air flowing around the aircraft."

The authors correctly recognize, that the kinetic energy of an aircraft arises from its speed relative to the Earth's surface, while the speed of the aircraft required for flight must be in relation to the air. But, to accelerate an aircraft to ground requires an external energy input: either higher engine power or consumption of potential energy, ie altitude. That an airplane can deposit energy in one place in the air and then pick it up at another place is an adventurous fantasy. That something like this is even invented by academics is a sign, that technical teaching is still ignorant of the true physics of flying.

The authors continue write correctly that accelerating the aircraft over ground can not be measured by an accelerometer. But, accelerations due to external forces are always measurable!. When driving power is increased, forward acceleration is also measurable in an aircraft engine. However, if an aircraft is accelerated by loss of height, that is, by potential energy, the forward acceleration is actually not measurable. It is a gravitational fall that an accelerometer can not detect. Glider always accelerated by gravitay. When driving in the headwind it rises (see Albatros), when driving into the tailwind it falls. And in an powered airplane, it's the same thing. A pilot can not know when and where and how much gas he must give, unless he flies by the altimeter.
An accelerometer in a glider will never be able to show acceleration forward. To the rear but very well, even permanently by the external force of the air drag, which slows down a free falling on the inclined plane of the flight path. In stationary vertical plummet down the deceleration would be 1g due to this drag force.
The authors write on the same topic also, that the lift force vector in the circular area against the wind tilts back umd in a tailwind forward. Such a skewed lift vector can only arise, if a special view is used, namely one with a wrong coordinate system. For flying, however, for the air forces only the coordinate system of the air must be used and for the kinetic accelerations of the aircraft mass the coordinate system of the earth. All other coordinate systems are prohibited!
"You can see it that way, too" is the biggest mistake, that can ever be made in physics. It is to find out how a natural event must be seen. It must be found the "natural coordinate system", that's that, with which the nature sees itself. For flying it is the air ambient air, which is unaffected by the flight 
Technology does not care about any physical rules, ie rules of nature. It can do so, because its success sanctify all means, whether with right or wrong or no theory, everything works, unfortunately.
That's why technology has nothing to do with physics. Technicians sometimes do not know or understand the associated physics. An aircraft designer really does not care why a plane flies! The main thing is, it is flying.

In all of this, there is also an indefiniteness (lack of explicit definition) in the terminology of aerodynamics, which even exists in the higher doctrine. Lift is not an independent force, but only the vertical component of the vector of the total air force. In vertical plummet is, for example, only the drag of an aircraft is the lift
. By definition, the lift vector can not change its direction, it is defined for just the single direction of the vertical! And the vector of the total air force is never tilted forward, it would make a plane to a perpeduum mobile, you could omitting the drive.

What the two authors write about energy flows between aircraft and air is sheer nonsense. There is only one flow of energy from an aircraft to the air, with which it is air moving downwards in order to stay up with the resulting recoil force. In a helicopter this vertical energy flow is directly in front, its wings are the rotor blades. That is why there is no dependence on speed over ground.

The truth:

An aircraft with constant engine power, when driving into the tail wind, becomes faster only by the conversion of potential kinetic energy, which makes a loss of height inevitable. When turning into the headwind, kinetic energy is shifted to potential energy and the aircraft becomes faster in relation to the airBy turning into the headwind an albatross wins height. But it has the advantage that he does not have to go back into the tailwind, so keeps this height

First, it must be found out physically (without mathematics!) which cause-and-effect processes exist for wind curves. Only then can mathematics be used. Mathematics is told by physics what and how it has to calculate, not vice versa.

Over all, however, is the practice, in physical terms the experiment. And there an aircraft needs, when turning out of the headwind, a boost to higher speed compared to the ground, which can be given it only by external energy supply. Air crafts can taken power, glider can taken energy only from the height. Any theory, that denies that, leads to more deaths.