Stalling in the Traffic Pattern
From Plane and Pilot This is how it happens. The pilot turns base to final and notices a following wind is causing him to overshoot the centerline. He adds a little left uncoordinated rudder in an attempt to bring the nose of the aircraft back toward the runway. The aircraft rolls a bit to the left and he compensates by adding some right aileron to hold the 30-degree bank angle. The nose also drops slightly, so he compensates by pulling back a bit on the yoke or stick and adding a little power to maintain airspeed. Suddenly, the aircraft snap-rolls left to 150 degrees of bank. He instinctively pulls back on the yoke or stick to get the nose back to the horizon and, at the same time, uses aileron to turn the aircraft back to the right. Without warning, the airplane stalls, rolls inverted and spirals into the ground.…
From the Airplane Flying Handbook The aerodynamic effects of the uncoordinated, cross-control stall can surprise the unwary pilot because it can occur with very little warning and can be deadly if it occurs close to the ground. The nose may pitch down, the bank angle may suddenly change, and the airplane may continue to roll to an inverted position, which is usually the beginning of a spin. It is therefore essential for the pilot to follow the stall recovery procedure by reducing the AOA until the stall warning has been eliminated, then roll wings level using ailerons, and coordinate with rudder inputs before the airplane enters a spiral or spin.
A cross-control stall occurs when the critical AOA is exceeded with aileron pressure applied in one direction and rudder pressure in the opposite direction, causing uncoordinated flight. A skidding cross-control stall is most likely to occur in the traffic pattern during a poorly planned and executed base-to-final approach turn in which the airplane overshoots the runway centerline and the pilot attempts to correct back to centerline by increasing the bank angle, increasing back elevator pressure, and applying rudder in the direction of the turn (i.e., inside or bottom rudder pressure) to bring the nose around further to align it with the runway. The difference in lift between the inside and outside wing will increase, resulting in an unwanted increase in bank angle. At the same time, the nose of the airplane slices downward through the horizon. The natural reaction to this may be for the pilot to pull back on the elevator control, increasing the AOA toward critical. Should a stall be encountered with these inputs, the airplane may rapidly enter a spin. The safest action for an “overshoot” is to perform a go-around. At the relatively low altitude of a base-to-final approach turn, a pilot should be reluctant to use angles of bank beyond 30 degrees to correct back to runway centerline.
It is important for the pilot to understand that a stall is the result of exceeding the critical AOA, not of insufficient airspeed. The term “stalling speed” can be misleading, as this speed is often discussed when assuming 1G flight at a particular weight and configuration. Increased load factor directly affects stall speed (as well as do other factors such as gross weight, center of gravity, and flap setting). Therefore, it is possible to stall the wing at any airspeed, at any flight attitude, and at any power setting. For example, if a pilot maintains airspeed and rolls into a coordinated, level 60° banked turn, the load factor is 2Gs, and the airplane will stall at a speed that is 40 percent higher than the straight-and-level stall speed. In that 2G level turn, the pilot has to increase AOA to increase the lift required to maintain altitude.
When an airplane is banked, the total lift is comprised of a vertical component of lift and a horizontal component of lift. In order to not lose altitude, the pilot must increase the wing’s angle of attack (AOA) to ensure that the vertical component of lift is sufficient to maintain altitude. In a steep turn, the pilot will need to increase pitch with elevator back pressures that are greater than what has been previously utilized. Total lift must increase substantially to balance the load factor or G-force (G). The load factor is the vector resultant of gravity and centrifugal force. For example, in a level altitude, 45° banked turn, the resulting load factor is 1.4; in a level altitude, 60° banked turn, the resulting load factor is 2.0. To put this in perspective, with a load factor of 2.0, the effective weight of the aircraft will double. Pilots should realize load factors increase dramatically beyond 60°.
Avoiding Stall and Spin Accidents
Takeoffs and Landing: Base-to-Final Turn
Factoid: Base to final turn stalls account for 10% of all fatal maneuvering accidents.
Tip: If you are on downwind and find yourself being pushed toward the runway, your base leg will be need to be shorter to account for the wind.
Note: If you fly a slow airplane, like a Cherokee, and then switch to a faster airplane, like a Cessna 210, your turn will be wider because your airspeed will be faster. You’ll need to start your turn to final sooner than with a slower plane or you will overshoot the centerline.
Deadly Turn – Base Leg to Final Approach
Here’s some good information using diagrams—if you like that kind of thing.
Anatomy of a Cirrus Stall Accident
Tip: Steep banks and high load factors in the traffic pattern invite disaster.
Cirrus FATAL CRASH in Hobby-Houston!
This is the actual ATC tapes from a fatal stall-spin accident. The accident occurred after several landing attempts where the Cirrus overshot the runway. The lesson to be learned from this accident is that if things are going badly, ask for vectors away from the runway an deither go somewhere that isn’t as busy or clear your head and come back in fresh.
“Quit Stalling–or Spin In” 1945 US Navy Pilot Training Film
Case studies of lots of ways that Navy pilots found to spin in their airplanes—not just in the traffic pattern. These accidents demonstrate the adage that you can stall at any airspeed and any attitude.
Tip:
1. The steeper the bank or the sharper the pull-up—the higher the “G”.
2. The higher the “G” and the heavier the load, the higher the stalling speed.
3. Keep flying speed—always!
4. Never make steep turns at low altitudes.
Tip: Know how much airspeed you need to carry at every angle of bank then add a few knots for safety.
In most cases airspeed is a good substitute for angle of attack. If your airspeed is high your angle of attack is likely low. Keeping your airspeed in the green will keep your angle of attack below the stall angle. However, as we’ve seen in the previous video, that doesn’t apply with high or low pitch angles and steep bank angles—exactly the conditions pilots can inadvertently get into on turn to final.
Power Off Stall – Private Pilot
If you like classroom explanations of stalls, Cyndy Hollman does a good job explaining them.