RJGlidingClub.com

STALL

--In the training stall the nose always drops thus causing a misconception.

--It is possible for the wing to stall without the tail stalling first. Thus no
nose drop.

--A low airspeed high power situation can have the wing stalling with the
elevators still effective.

--The aircraft is stalling, falling and the nose has not fallen.

--The downwash of a high-wing aircraft is more effective than the
downwash of a low-wing aircraft.

--Therefore, the stall mush is more to be expected in high-wing aircraft.

--The extension of flaps in a high-wing plane increases the downwash and
causes the nose to pitch up.

--Studies show that the initial stall-shake of a high-wing aircraft occurs at
the rudder first then the elevator.

--An aircraft can get behind the power curve and locked into this stall and
be unable to lower the nose. (Behind the power curve)

--Close to the ground lowering the nose is not a viable option often on
landing or takeoff.

--Raising the nose only makes the situation worse the only options are
increase power and milk off flaps.

--The high power can over-power the pilot's ability to hold the nose down
due to flap or trim position.

--Low-powered aircraft in high-density altitude situations may not be able
to climb out of ground effect.

--The standard instructional procedure on takeoff is to have pilot lower
the nose to accelerate before climbing.

--In high density altitude situation do not rely on sense of speed for
anything. Use only indicated air speed.

-- Pitching up may be diametrically the wrong thing to do when you are
seeking the best climb attitude.

--When in doubt weight becomes a prime consideration. Unload, make
multiple trips or cancel.

stall
is a (usually undesired) condition in aerodynamics and aviation where there is a sudden loss of lift. In unaccelerated flight, a stall is usually associated with a certain airspeed below which the aircraft will not continue to fly. More rigorously defined, a stall occurs when the critical angle of attack is exceeded.

Increasing the angle of attack between an airfoil and the airflow causes the lift and drag produced to increase. This can continue until a point is reached where maximum lift is generated and this is known as the stall or stall angle. Any further increase in angle does not produce a corresponding increase in lift but will in fact lead to a sudden reduction in lift, a change in pitching moment or a wing drop. This is due to flow separation occurring on the upper surface of the airfoil.



This graph shows the typical behaviour of most airfoils:




Stalling an aeroplane

An aeroplane can be made to stall in any pitch attitude or bank angle or at any airspeed but is commonly practised by pilots reducing the speed to the stall speed, at a safe altitude. Stall speed varies on different airplanes and is represented by color codes on the air speed indicator. As the plane flies at this speed the angle of attack must be increased to prevent any loss of altitude or gain in airspeed (which corresponds to the stall angle described above). Any attempt to prevent the plane from descending by applying increasing up elevator control input or increasing the airspeed by use of the throttle will cause the airplane to stall. The pilot will notice the flight controls have become less responsive and may also notice some buffeting, an aerodynamic vibration caused by the airflow starting to detach from the wing surface.

In most light aircraft, as the stall is reached the aircraft will start to descend (because the wing is no longer producing enough lift to support the aeroplane's weight) and the nose will pitch down. Recovery from this stalled state usually involves the pilot decreasing the angle of attack and increasing the air speed, until smooth air flow over the wing is resumed. Normal flight can be resumed once recovery from the stall is complete. The maneuver is normally quite safe and if correctly handled leads to only a small loss in altitude. It is taught and practiced in order to help pilots recognize, avoid, and recover from stalling the airplane.

The most common stall-spin scenarios occur on takeoff (departure stall) and during landing (base to final turn). Stalls also occur during a go-around maneuver if the pilot does not properly respond to the out-of-trim situation resulting from the transition from low power setting to high power setting at low speed.

A special form of asymmetric stall in which the aircraft also rotates about its yaw axis is called a spin. A spin will occur if an aircraft is stalled and there is an asymmetric yawing moment applied to it. This yawing moment can be aerodynamic (sideslip angle, rudder, adverse yaw from the ailerons), thrust related (p-factor, one engine inoperative on a multi-engine non-centerline thrust aircraft), or from any number of possible sources of yaw.