# Tag Info

23

Here is one reason. It once was common for suspension wires to be flattened rather than circular in cross-section, to reduce drag. those wires were then aligned with the airflow past the wing and fuselage in cruise. However, any time that airflow was not aligned with the wires, they would present an angle of attack to the slipstream and generate lift, which ...

18

As Ron Beyer pointed out in a comment, your instructor was showing you a forward slip - a pretty standard maneuver for light aircraft. A spin would involve full rudder and a stalled wing, which usually means pulling the yoke or stick back a lot. That's why overshooting the base-to-final turn can be dangerous - you likely already have a lot of rudder in and ...

15

Source: Wikipedia. Origin of the theory Klaus Holighaus, one of the famous glider pilots of the 70s, and himself a glider designer at Schempp-Hirth, is at the origin of a controversy when he recommended not to turn with the ball centered, and especially when climbing in thermals. Mr Holighaus did see two problems with the perfectly coordinated turn: It ...

10

I've found some useful research here: E.C. Polhamus. Some factors affecting the variation of pitching moment with sideslip of aircraft configurations. Technical report, NACA T.N. 4016, 1958. The image shows the situation for high angles of $\beta$: At large angles of sideslip with swept horizontal tails, the loading will probably not be antisymmetrical ...

9

The turn and slip instruments are combined for convenience and by convention more than anything else, slip is important whether you are in a turn or not. When you slip it means one wing is more directly pointed into the airflow, which increases lift for that wing in comparison to the other. At a high angle of attack, for instance a climb and close to stall ...

8

(Source) Here's a representative image of the variation in lift coefficient with respect to angle of attack. The same airfoil is considered in a "clean" configuration, with a deflected flap, and then with both flap and slat (you can ignore the last, which is the uppermost example). You can see that, with deflected flap (or, shall we say, rudder) the lift ...

7

It is the same thing that makes you slide sideways in your seat going around a corner in your car. Or the same thing that would cause you to slide sideways the other way if you were driving straight ahead on a side hill. Don't overthink it... the ball simply responds to the same forces you feel. ADDENDUM: “I agree the comparisons are spot on if you are only ...

6

The use of asymmetric thrust when landing a twin in a crosswind effectively accomplishes the same thing that rudder input does. It induces a yawing moment about the aircraft’s vertical axis, the same as pushing on the rudder pedals does. It helps to alleviate excess rudder pressure on the flight controls during the approach, making it a little more ...

6

I just want to go back to the OP's concern that rudder one way and aileron the other way is related to a spin - it's my understanding that this is a cross-controlled situation, and that is something that can't be ignored, so (again, I'm saying this from an armchair not-even-a-pilot standpoint) it will influence what you have to think about doing at the same ...

6

The basic problem is that sideslip induces a cross flow over the fuselage that can increase the local negative AOA and flow disruptions beyond that already caused by the turbulence and downwash being generated by the flaps. The stabilizer surface on the "lee" side of this cross flow may get enough flow disruption to be felt in the elevator, maybe ...

5

1. Answer to original OP In a stable airmass, the amount of sideslip/skid indication is irrespective of the wind strength and orientation; it is a function of the relative velocity of the airplane against the airflow only (stable winds are referenced to ground). That is, with all engines operating and rudder centered (assuming no inherent asymmetry), then ...

5

1. Preamble The ball reacts to the body force (or acceleration), with the exact same working principle as a bubble level. In airplane frame, the force is expressed as: $$Y+mg\cos{\theta}\sin{\phi}=m(\dot{v}+ru-pw)$$ where $Y$ is all external side forces minus gravitational component, $m$ is airplane mass, $g$ is gravitational acceleration, $\theta$ is ...

4

To answer what you wrote: $c_{n_q}$ is the yawing moment induced by a pitching motion. In a conventional, symmetric configuration this is zero for the airframe and has a small value for propeller aircraft, depending on the rotation direction of the propeller. If the tractor propeller is spinning clockwise (when seen by the pilot), a positive pitch motion $q$ ...

4

The sideslip to pitch coupling is a result of the canted tail rotor and the asymmetry of the main rotor downwash. The tail rotor thrust pushes the tail to the right and upward (pitch down). The main rotor downwash across the tail boom also generates a pitch up motion. The 'static' position of the stabilator is set (stab range is 10 deg up to 45 deg down ...

4

Slipping an aircraft is mostly perfectly safe. I say mostly because there are exceptions: Some aircraft operator's manuals explicitly forbid slipping. This might be because of the general handling or aerodynamic characteristics of the aircraft. There are other reasons outside of handling why slipping is dangerous to some types of aircraft. For example ...

4

The DPE is correct, the airplane will drift in the direction of the wind. If you are piloting a boat across a river, and point the bow at the opposite side of the river with the rudder amidships then the boat will float in the direction of the current and stay where you pointed it. The boat is not going to turn upstream by itself because the water exerts ...

4

Yes. If you apply full rudder with no aileron, you initially just get a flat skid, but then differential lift starts to have an effect and the inside wing drops because that wing has slowed down, the fuselage is obstructing some of the flow on that side, and if there is wing dihedral, it creates a geometric angle of attack differential. One or more of these ...

4

What you've proposed is a reference frame translation of the aircraft velocity, so instead of the velocity referenced to East, North, and Up (ENU), it's referenced to the direction the aircraft is pointing. That gives you components of aircraft velocity along the nose, across the wing, and towards the ground. (You can find more details on these conversions ...

3

You would be risking your life. Cross controlled approaches should only be done well above stall speed and only after testing at a higher altitude. Increasing AOA will slow your plane down. If you recognize being high early in the pattern, you might be better off going ABOVE Vbg and slip, which makes the plane glide much less efficiently. Spoilers act in ...

3

Let's assume that to first approximation, a given rudder deflection (say, full deflection) creates a given slip angle of the fuselage. So for a given rudder deflection, don't you generate a lot more drag (and also sideforce- thus requiring a steeper bank angle if you wish to maintain a linear flight path) if you are flying at a HIGH airspeed than at a LOW ...

3

The "slip" part of the Turn and Slip Indicator (T/S) measures the lateral (transverse) acceleration of the airplane. When the slip indicator is centered, the pilot and passengers will feel gravity directly in-line with the seats; otherwise, they will feel a lateral sway, which doesn't provide the best ride experience, especially if martini spill is involved. ...

3

You drift downwind unless you turn into it. In a normal crosswind takeoff, say with the wind from the left, at rotation, you have left aileron to keep the left wing from lifting and right rudder to maintain runway heading during the rotation. You are taking off in a sideslip. As soon as you are clear, you center the controls to take out the sideslip while ...

3

In General Aviation light twins, when landing in heavy crosswinds, what are some considerations to using asymmetric (or Split) throttles to induce a sideslip, to align the fuselage with the ground track and the runway centerline instead of rudder? I was told that this technique allows the aircraft to track down the runway centerlines with ...

3

Relying on physics, causing a mass to execute a circular path requires a suitable centripetal force. In an airplane in a banked balanced turn, this comes from the inward component of lift due to the bank angle. However, if the turn is not properly co-ordinated, there can be additional contributions to the centripetal force from the power plant thrust no ...

3

No. Yaw, pitch and roll rates only describe the change in the orientation or attitude of the object relative to a frame of reference. Is it changing orientation to point further clockwise? or counter clockwise, or upwards/downwards, etc. Any acceleration is a measure of the change in the velocity of the object relative to the frame of reference in question. ...

3

When you see inclinometers placed at different locations like that it's for measuring level on the ground for fuel and center of gravity measurement or other leveling purposes. The one on the instrument panel works for measuring skids in flight because when you are skidding you are moving in an arc, or turning, to one degree or another, because the fuselage ...

3

It really depends on the aircraft. Some have plenty of rudder authority and sideslip very well, others are better at stall onset with still plenty of elevator and aileron authority. Now first to the term "mushing glide": This happens at very low speed when the airplane flies far at the backside of its envelope. Flow on the inner wing is already partly ...

3

You are confusing some of the directions. For a forward slip in the +y direction, you have to bank left. The lift and rudder vector should both point in the opposite direction. That would still leave a sideways component. However, the airframe will also generate some sideways lift! In fact, that is exactly the reason why you have to make some bank angle at ...

2

First, a clarification. The standard reference frame for and aircraft, w.r.t. a person sitting in the pilot seat, is: x axis positive ahead of the aircraft y axis positive in the right wing direction z axis positive towards down In addition, to be clear about the conventions used in the rest of this answer: positive roll is when the right wing is down ...

2

Loss of aerodynamic lift of the horizontal tailplane (downward force) causes the aircraft to pitch down. A disruption of airflow over the low pressure side of an airfoil has a greater effect on the airfoil's ability to create lift than a similar air flow disruption to the high pressure side of an airfoil. On a conventional tail, the wind shadow of the ...

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