Spin (aerodynamics)

Spin (English spin, double vrille, also in German-speaking Switzerland Vrille ) is a flight condition in which the flying object moves according to a one-sided stall on an airfoil in a steep spiral respectively helix around the vertical axis towards the floor.

There are strong indications that the crash of the gliding pioneer Otto Lilienthal in 1896, the first spin accident in the history of modern aviation was.

Introducing some spinning

A plane gets into a tailspin when at a large angle of attack, the flow on one side breaks off to a supporting surface. This breaks the lift together on this wing, while the resistance increases sharply, making this surface tilts down and the aircraft begins to be similar corkscrew turn down. The flow at the inner wing remains demolished, while it may at least partially still be present on the outer wings to the airplane type or tear completely. But in any case the angle of attack of the wing and thus also its air resistance is different, whereby the outer blade to a certain extent in a circular path around the inner flies around. Even if the rate of descent when spin is high, the actual flight speed as well as the g - loads remain low due to the high flow resistance.

The stall is not dependent on the speed, but the angle of incidence. Only the constant buoyancy condition provides a relation between speed and angle of attack, therefore, is usually spoken of in terms of the normal flight of the ( 1g ) stall speed.

When aerobatic flying the spin is introduced intentionally, by increasing constantly at a low airspeed the angle of attack by further pulling the elevator and initiates a rotation about the vertical axis by deflection of the rudder, whereby the flow is brought to tear off one side.

The standard method for introducing Spin Recovery

The spin can be initiated by the surface load is increased by drawing, whereby the critical angle of attack is achieved at higher speeds even at high speed. This situation can occur in steep turns ( usually unintentionally ). In aerobatics it is aware by sudden pull caused ( flick roll ), but this is because of the high spin around the longitudinal axis of considerable demands on the torsional strength of the hull and is therefore not allowed with each aircraft.

Discharging Spin Recovery

Prescribe licensing regulations that the spin at each plane - unless loading and center of gravity are within the permissible limits - can be terminated at any time by using the standard method must.

The standard method for discharging Spin recovery is defined according to JAR as follows:

The order ( first page then elevator) is important, otherwise the rudder is shadowed by the elevator, which can delay the discharging, or even completely prevent. The listed under point 4 pause between pages and elevator is in the jars so not included (2006 ). But it is important as a premature and / or excessive pressures due to the aforementioned shading instead of Ausleitens can trigger an "accelerated spin", which are no longer directly, but only through the prior restoration of "normal" Spin Recovery discharged by pulling can. Presumably, many spin accidents, especially those in which the aircraft was tailspin at low altitude, due to the fact that the pilot pushed too early in the hustle and bustle.

Been rooms only and has other Ausleitverfahren described ( is known, for example, " Mueller- Beggs "). But this all does not work for all airplane types or in all spin states. (What Incidentally, Eric Müller himself, the inventor obgenannter method, in his textbook " Flight Unlimited " stressed. )

The standard method works for all aircraft that have been approved in accordance with JAR. However, it is clearly formulated only at first glance, upon closer examination, many questions remain open. How long will the break be? How far the stick is to subside? There are approved in accordance with JAR aircraft, which can be correlated only with fully depressed height control from a spin. Others, however, suggest at fully depressed level control seamlessly into inverted spin to retablieren instead, so that with them the stick should be relaxed only to the neutral position. While still others retablieren while pressing the height control, but only after a delay of several revolutions while they go with drawn immediately from the height control tailspin. It is therefore in spite of the defined standard method absolutely necessary to read the flight manual and to know the Ausleitmethode described therein. This applies even in airplane types that are authorized under older standards. This retablieren not by the standard method under certain circumstances. Some aircraft types can be produced by accelerating, better flow against rowing again or better Dredge. This is counteracted by the acceleration so that often the fuel supply to the engine is interrupted.

Flat spin

Depending on the slope of the airplane's longitudinal axis distinguishes between steep (or normal ) spin and flat spins. In some sources is called (usually 45 ° or 60 °) as the boundary between the two states a certain pitch. But this is wrong. [ Evidence ?] Firstly commute many aircraft during some spinning more or less around the transverse axis so that the specification of a certain inclination angle from the outset is pointless. In addition, the main difference is not in a certain angle of inclination, but in the flow conditions at the rudder.

In the normal ( steep ) spin is located on the rudder during some spinning always flow. The spin can be discharged properly at any time by a resolute action of the rudder (see "Standard Method " above). In a flat spin which is not the case. Device an aircraft due to incorrect loading ( center of gravity too far back ) into a flat spin, so there is often no way to auszuleiten this. First you should try to use a jerky Press to increase the pitch until it stops to get back into the normal spin. It should also have been cases where it is supposed to be the pilot managed to finish the flat spin through unbuckle and shifting the center of gravity forward, but the success of this desperation by no means guaranteed.

In aerobatics a flat spin can be generated at the propeller-driven aircraft with the help of the power setting and the effected thereby different gyroscopic effect of the engine influences the spin position and so also with a correct focus. This then goes back into a tailspin as soon as the power is withdrawn. Some glider patterns can be brought about, which can also be canceled by appropriate aileron again using appropriate aileron a flat spin. Here, a pilot must know exactly how his plane behaves with the current load but.

The authorization provisions regarding Trudel behavior imply that an aircraft must not get into a flat spin by itself when properly loaded.

Spiral dive

Not to be confused with the spin, the spiral dive. Again, the airplane will turn on a narrow vertical downward spiral, but in contrast to spin lies with the spiral dive the flow at both wings, whereby the large flow resistance of the " gestallten " inner wing is eliminated and the speed and the g - load very fast increase. Spiral dive must be terminated immediately, otherwise the stress limits of the aircraft ( high g - load, exceeding the speed limit ) and also by the pilot ( loss of consciousness due to high g - load) exceeded very quickly.

Some aircraft go, especially when loaded in the front focal area, by itself after a short time from a tailspin into a spiral dive over. An attentive pilot noted that but immediately, as the two flight modes feel completely different. When you spin the acceleration is to the side opposite the rotation palpable, almost vertical effective on the seat during a spiral dive. Because of the risk of transition into a spiral dive is also now explicitly discouraged from using in an unwanted test flight in a cloud the spin as a rescue operation as the has been recommended in the older literature to some extent.

Etymology

Spin The word is attested since the 18th century. Its origin is unclear. There had of course nothing to do with aviation, but meant generally " slow and uneven roll" or " to give yourself fall turning slowly ." Such as autumn leaves fall and swirl without safe destination from the trees. This general meaning is still alive in the word " roll in " on. Spin itself no longer exists in this general sense today, scenic, it is still used for dice, leaning against the " trudelnde " movement of the dice.

Apart from this scenic special case, the word " spin " today used with the meaning described above only as a well-defined technical term of aviation. In particular, an aircraft is not " tailspin " for any loss of control, as you read it often. Most is by the stall (aircraft too slow, the pilot does not want down and pulling back on the elevator involuntarily ) before a stall and the plane drops like a stone to the ground.

Theory

A physical theory of Spin recovery was first formulated by Frederick Lindemann (1886-1957) during World War II. Lindemann was a member of the Royal Flying Corps and verified his theory in successful self- test.

Since then, many other books have been written on the subject. However, the spin depends on so many parameters and the possible processes are so diverse that there is no final, all possible modes comprehensive theory.