Prevent LOC-I; Please Train Turning Stalls!

We had great attendance for our national LiveStream with Patty Wagstaff and Rich Stowell; thank-you all for watching. You can watch (and share) it [here] Once again, however, I am amazed at the number of pilots (and CFIs) who have limited understanding of the aerodynamics of turns. Pilots on some deep level seem misunderstand and fear banking. We need to elevate our game to avoid LOC-I accidents. Training turning stalls (at a safe altitude please) is an effective way to build confidence and understanding.

In a stable, coordinated turn (level, climbing or descending), the lift on the wings is equal! Obviously, there was unequal lift while rolling the plane into the turn, but when it is established and coordinated, lift on the wings is equal. If you reduce power and decellerate to a stall, it’s no big deal, the nose falls away from the lift vector. For the CFI this is a very powerful and useful demonstration (and an effective teachable moment). I guarantee your student (who should already be comfortable with level stalls to be ready for this) will grab the seat and expect a spin (even though you already explained it all). This is a misunderstanding due to the flight attitude. The usual airplane reaction to this stall is a mushing motion away from the lift vector. Most pilots are surprised at the lack of a sharp stall break and fail to even identify the stalled condition!

Remember; the turning stall maneuver is also available to be tested on both the Private and Commercial flight tests. I also have had flight test applicants refuse to slip to land because it’s “dangerous” (and yes…that’s also on the FAA test) so I wrote this article to clear up this misunderstanding.


Here is some more stall information from SAFE member Robert Reser; “How To Fly A Plane”

—INADVERTENT STALL

Stalling an aircraft requires pitching the nose to the critical angle-of-attack. Remember, exceeding the critical angle-of-attack is when stall occurs. The aircraft being pitched to an attitude that reaches the critical angle-of-attack causes the stall! There are only two possible ways to cause the nose to reach the critical angle-of-attack in a positive stable aircraft.

  1. Pulling and holding the elevator aft…the pilot causes stall.
  2. In descent trimming nose up to a very slow indicated-airspeed at reduced power, then increasing power causing thrust component-lift which could add back enough pitch trim effect to reach the critical angle-of-attack…the pilot causes stall.

There are only two ways an aircraft can pitch to the critical angle-of-attack. One is for the pilot to pull and hold the elevator aft. The second is for the pilot to input a large nose up elevator trim when at a low thrust setting then add lots of thrust…again pilot induced.

It might be easier to understand if the pilot realizes the only thing the elevator ever does is allow change of indicated air-speed with angle-of-attack change. Also when operating at reduced thrust of descent, any increase of thrust increases angle-of-attack until in level or climbing flight.

It is difficult to see that in minimum indicated-airspeed descending flight, adding power can cause stall. The fact remains it can happen. In descent, there is a substantial reduction of thrust component-lift normally contributing to angle-of-attack. To compensate, and for maintaining the slowed constant indicated-airspeed, added aft-elevator control and/or nose-up elevator trim maintains the desired angle-of-attack.

If a slowed, hands-off level flight is operating at 12-degrees angle-of-attack, the corresponding thrust component-lift is contributing as much as 6-degrees to that angle.

Reducing to idle thrust removes 4-5 degrees of that angle-of-attack contributed by thrust component-lift, so allows acceleration. It requires adding aft-elevator or additional nose-up elevator trim to maintain the original constant indicated-airspeed in this descent.

Now the stabilizer is contributing 10-11 degrees of the angle-of-attack. Adding back the thrust toward a level sustaining setting is adding nose-up pitch to the trim as much as 8-10 degrees, so without forward elevator input can cause immediate stall.

—LOW INDICATED-AIRSPEED AND APPROACH STALL

All low indicated-airspeed maneuvering flight is subject to inadvertent stall. A turn when in a slow indicated-airspeed situation if requiring added power, while already holding the control wheel aft for altitude control, can potentially cause immediate stall.

When in a descending steep turn at reduced thrust with the elevator trimmed for very slow indicated-airspeed flight, the aircraft can be at a 12 to 14-degree angle-of-attack. Added thrust for reducing descent rate or leveling will cause considerable thrust component-lift, adding as much as a 6 to 10-degrees angle-of-attack…immediate stall…it requires coordinated forward elevator control to avoid attaining critical angle-of-attack.

A common condition where this occurs is the base to final VFR approach when overshooting the extended centerline. A pilot already in the trimmed, low-powered, landing configured slow-flight tends to increase the bank attitude and simultaneously pull the elevator attempting to correct back toward the extended centerline.

The increased bank reduces vertical lift and any added aft elevator causes more slowing from the added angle-of-attack plus increased “g” force. At this point, a power increase adding those 4-5 degrees to the angle-of-attack may cause immediate low altitude stall with no altitude for recovery.

Low altitude, slow indicated-airspeed flight maneuvering must be with minimum or no manual aft elevator input. There must be anticipation of applying forward elevator prior to or while adding thrust in this condition.

A pilot must understand how thrust component-lift affects flight. All flight instruction of normal level turns should be without elevator input but with coordination of added thrust for its thrust component-lift.

Descending turns use gravity component-thrust so for constant indicated-airspeed must increase descent rate during the turn. It is impossible visually ascertaining a steep nose-up attitude when descending but anytime using aft elevator, the increased angle-of-attack reduces indicated-airspeed.

In slow indicated-airspeed maneuvering, always expect stall indication and if occurring, immediate forward elevator toward zero “g” with coordinated rudder and aileron leveling the wings for maximum vertical lifting.

In all flight, always trim to a hands-off condition with aircraft controls. “You will be surprised how the airplane just wants to do its thing without all the fussing with the control wheel”.

—TAKEOFF AND GO-AROUND STALL

Takeoff and go-arounds are situations where slow indicated-airspeeds are transitioning into both increasing indicated-airspeed and altitude. Without using hands-off techniques for flight, a pilot will be manually holding aft elevator control for angle-of-attack. Inadvertent increased aft elevator input can easily lead to stall.

With the go-arounds, there is transition from trimmed slow indicated-airspeed descent to leveling for acceleration and then climb. In this case the added thrust alone adds back nose up pitch increasing the aircraft angle-of-attack trim to level flight and then any excess thrust continues pitching to a climb angle with increased altitude. Any added manual aft elevator initially added to stop descent can lead to stall.

These situations require specific training in awareness of what is happening and again knowing hands-off flight control techniques. A go-around should allow acceleration while leveling and then climb. The aircraft is already flying; it seldom requires immediately jamming lots of thrust.

In all cases, a trimmed hands-off aircraft cannot stall. The elevator sets angle-of-attack and only if at a descending power setting will that change and then with thrust change. Just don’t pull the control wheel!

For a free .pdf version of Bob’s book, “How to Fly Airplanes” e-book send an e-mail to Bob with “e-book” as subject!


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Author: David St. George

Master CFI, 141Chief Instructor, FAA DPE, ATP (ME/SE)

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