Spin Recovery - Cross Controls and Angle of Attack
Remember those wonderful days when you knew everything at the old age of fifteen? I think I passed through that "era" when I was just learning to fly.
I was absolutely sure as long as the nose of my venerable Cessna 120 Trainer was pointed down below the horizon and my indicated airspeed was 70 mph I was as safe from stalling as anything in the world! Yes Sir! I knew it all! So confident I would prove it!
My Dad turned to Bob Nichols, then the Manager at Gaylord, Michigans local airport located about 75 miles South of Mackinaw City. ( Now there is a hugh suspension bridge that connects Michigans Lower Peninsula with the Upper Peninsula)
"Is it time Bob?" my venerable Dad inquired of Bob. "Yes it is, Perry!" he replied.
Supremely confident of my flying knowledge we went through the customary exterior Pre-Flight, climbed into the Cessna 120, and after the normal in-the-cockpit check-off fired her up and proceeded to taxi to the take-off runway.
After the take-off I proceeded to climb the Cessna to five thousand feet in a series of climbing turns. In the practice area Bob Nichols told me to turn on carburetor heat (This plane is considered an antique now - just as I am!) slow the plane to 70 mph (like in a landing mode). I did just that!
Checking with this lanky know-it-all that all was comfortable and well Bob inquired again that a plane wouldn't stall as long as the airspeed was well above the stall speed of the Cessna and the nose was below the horizon.
I replied, in my cock-sure clipped English of a Michigander, "Can't stall when were in this attitude!"
Bob calmly told me to tighten my seat belt and put in full right airleron and full left rudder. I just got out the word "See" when the plane was heading downward in a snap-stall spin (straight down)!!
Since I never experienced a spin before he calmly told me to stop the rotation, above my screams, first and then apply forward pressure on the yolk until the aircraft leveled out and cruising speed was achieved. The previous information keeps the plane from entering a secondary stall. Then, and only then relax the forward pressure on the yolk and slowly apply power while turning off the carburetor heat. Needless to say I was impressed. A small change in my informational database was altered - for my own good!
Wolfgang, from Stick and Rudder, explains "Angle of Attack" well and that was what I exceeded when I "Crossed Controls" in the Cessna 120. When the angle of attack is exceeded the plane enters a stall that can rapidly turn into a fatal spin if done at approach to landing altitudes.
Safety hint? If you encounter cross winds while landing make a co-ordinated turn into the wind to correct for drift from the runway. Straighten out with rudder control and slight wing-drop into the wind just as you are about to touch down. Happy Flying from a know-it-all!
Be sure to check with your own instructor and follow his advice. Things may have changed somewhat over the years. I am an old not so bold pilot now!
Jim
Here is a brief paragraph of rudder control.
Aircraft rudders
The tail of a Martin B-57E with rudder deflected to starboard. On an aircraft, the rudder is called a "control surface" along with the rudder-like elevator (attached to horizontal tail structure) and ailerons (attached to the wings) that control pitch and roll. The rudder is usually attached to the fin (or vertical stabilizer) which allows the pilot to control yaw in the vertical axis, i.e. change the horizontal direction in which the nose is pointing. The rudder's direction is manipulated with the movement of foot pedals by the pilot.
In practice, both aileron and rudder control input are used together to turn an aircraft, the ailerons imparting roll, the rudder imparting yaw, and also compensating for a phenomenon called adverse yaw.
Adverse yaw is readily seen if the most simple type of ailerons alone are used for a turn. The downward moving aileron acts like a flap, generating more lift for one wing, and therefore more drag (though since the 1930s, many aircraft have used frise ailerons or differential ailerons, which compensate for the adverse yaw and require little or no rudder input in regular turns).
Initially, this drag yaws the aircraft in the direction opposite to the desired course. A rudder alone will turn a conventional fixed wing aircraft, but much more slowly than if ailerons are also used in conjunction.
Use of rudder and ailerons together produces co-ordinated turns, in which the longitudinal axis of the aircraft is in line with the arc of the turn, neither slipping (under-ruddered), nor skidding (over-ruddered). Improperly ruddered turns at low speed can precipitate a spin which can be dangerous at low altitudes. This can be clearly seen in the crash of United Airlines Flight 585 and USAir Flight 427, where the aircraft experienced a rudder hard-over at a low altitude.
Sometimes pilots may intentionally operate the rudder and ailerons in opposite directions in a maneuver called a forward slip. This may be done to overcome crosswinds and keep the fuselage in line with the runway, or to more rapidly lose altitude by increasing drag, or both. The pilots of the Air Canada Flight 143 used a similar technique to land the plane as it was too high above the glideslope.
Any aircraft rudder is subject to considerable forces that determine its position via a force or torque balance equation. In extreme cases these forces can lead to loss of rudder control or even destruction of the rudder. (The same principles also apply to water vessels, of course, but it is more important for aircraft because they have lower engineering margins.) The largest achievable angle of a rudder in flight is called its blowdown limit; it is achieved when the force from the air or blowdown equals the maximum available hydraulic pressure.
