During a recent airplane owners’ gathering in Florida, I did a short poll of the audience on basic aerodynamics. One result reflected a common pattern: pilots fear banking past 30 degrees (especially in the pattern)! Pilots at all levels erroneously believe 45-degree bank turn has much more “aerodynamic threat” (raises the stall speed much higher) than is actually the case. 70% of the pilots here thought a 45 degree turn added >40% to the stall speed (that is more than double the actual answer of 19%). And since most pilots fear banking and maneuvering in general, they are not confident enough for safe aircraft control. Generally, gentle and trimmed is a great idea for passengers and daily comfort, but timid piloting makes flying unsafe for many important reasons.
Like continual use of autopilot, super-gentle timid flying makes a pilot unwilling and unable to take accurate and decisive control when necessary (unpracticed skills are unavailable). Secondly, timidity in turning leads to pilots “turning the plane flat”- skidding the plane with rudder. This is much more dangerous than coordinated banking, and the real threat in the 
base to final phase of flight. A timid pilot’s brain is saying “danger: low and slow, don’t bank too much” due to a gross misunderstanding of the real threat (skidding). The third problem with timid piloting adds more “airspeed buffer” and flies way too fast in the pattern. This leads to being unable to slow down and stabilize the final approach for a normal landing. All the accumulated energy gained through 
aerodynamic ignorance creates a much more dangerous landing. Most high-performance pilots fly final much too fast into the landing leading to porpoising and prop strikes. A too-fast approach also leads to landing long and LOC on the runway. These are usually not fatal but regularly wreck expensive planes. 1.4 Vso on base to final yields almost 20% margin above stall even with a 45% bank (which is admittedly excessive). But most (timid) pilots get uncomfortable with even 30% of bank angle in the pattern.
Here is one more related point. Historic pitch/power dogma might lead to all kinds of pilot actions (depending on initial training) to attempt a correction in airspeed. Some pilots might simply add power (and often too much) to recapture lost airspeed. In a left-hand pattern the resulting uncompensated yaw might cause a further skidding force. A more nuanced approach to energy management (see new AFH Chapter 4 on energy management) would recommend a little power and a lower nose attitude (unload) and yield a better result. Practicing Envelope Extension Maneuvers at altitude makes a more confident and knowledgeable pilot. Fly SAFE out there (and often)!
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David, do you listen to my lectures to my students and then come here to post? (Just kidding. It is interesting how your posts on a topic seem to come right on the heels of one of my ground school sessions.)
All kidding aside, you are spot-on, as usual. I had two CFI students day before yesterday. They come for spin training and I use the time to not only cover the aerodynamic aspects of the spin, but general aerodynamics and aircraft behavior. I try to point out that, “It’s not about the spin.” It is about understanding what leads up to a spin and avoiding/recovering BEFORE we need our spin training. (Spins we do for fun.)
We desperately need to put a stake in the heart of, “Stall speed increases with bank angle,” and replace it with, “Stall speed increases with wing loading.” We also need to replace, “The elevator controls pitch,” with, “The elevator controls angle-of-attack.”
Time to tout Rich Stowell’s “Learn to Turn” again. It is at the heart of all of this.
Also, on your point of flying approaches too fast, time to emphasize how to calculate Vref (approach speed) from current weight, max gross weight, and published stall speed at max gross weight (the way the POH is written). Most CFIs have never seen this and most pilots are totally unaware, unless they fly heavy iron where the FMS calculates it for them and then puts a bug on the airspeed tape. Pilots are often surprised by doing the calculation and then finding that the correct approach speed is some 10% less than the number published in the POH.
Here’s the formula: Vref = 1.3 * Vs0 * SQRT( GW/MGW )
Vref = proper approach speed
Vs0 = published stall speed in the landing configuration at max gross weight
SQRT = square root of what’s in the parantheses
GW = current aircraft gross weight
MGW = aircraft max gross weight
The funny thing is, this can be used to correct nearly all the V-speeds for current gross weight. This is also really useful to explain why Va changes with GW.
Yes, we certainly have the same focus Brian, the need for confident, positive A/C control! This requires good academic understanding and also practice outside the comfort zone (both unfortunately rare). I like Kershner’s rule of thumb on V speeds. Adjust speeds by half of your differential from max. gross (e.g. if you are 20% below max gross, reduce your V speeds by half of this percentage – and it leaves a margin). With smart phones though, it is easy to calculate the exact square route of the ratio.
New data reveals that 97% of stall/spin accidents occur at pattern altitude or below so “spin recovery” is almost a moot point. Instead, a focus on all the causal factors (startle, ignorance, and sloppy flying) that lead to spin might be the best focus to improve safety?
“We desperately need to put a stake in the heart of, “Stall speed increases with bank angle,””
Hi Brian. I think that would be a mistake. If the typical light GA airplane is operated at recommended speed, the bank angle alone is normally not a big threat. But with some other types, bank angle is extremely critical. I remember the emphasis on that in a Lear ground school. It was emphasized we had to be certain not to pass a certain bank angle and it wasn’t very much. And look what has happened just recently – a Lear at Teterboro, another one at San Diego, and the Challenger at Truckee. All three were circling to land.
Warren, I appreciate your point but I think you are confusing a couple of concepts. My comment, that stall speed varies with G-loading rather than with bank angle, is 100% correct. You can prove that by rolling an aircraft through 360º without stalling. Obviously we can pass through 90º without stalling. That doesn’t mean that we don’t have other constraints we have to deal with.
If you think about the scenario you mention, you have a circling approach to a landing. Here we are constrained by distance from the runway as well has arriving at the runway with the proper amount of energy so we can round-out and touch down. It is a balance between having enough energy to make the turn tight enough but not too much energy in the final round-out. The faster the airplane, the more challenging this becomes and the more precisely the pilot must fly the profile. Regardless, this does not change the truth of my comment.
I suspect that, if the pilots involved were trained early on to understand the relationships between stall speed, G-loading, lift, energy, and turn radius, those accidents would not have happened. As Dirty Harry put it, “A man’s got to know his limitations.” In this case those limitations are dictated by the laws of Physics.
Lear accidents have consistently demonstrated their unforgiving low-speed control. But remember, the Lear 25/35 is also equipped with a unique “spoileron system” (for low speed control w/flaps set) This system has often been found to be inop. (or poorly rigged) in some of these accident planes (and not commonly cited in the causal factors).
Good rule of thumb, David. Like you said, with nearly all phones also being a calculator, doing the calculation is pretty easy.
As an example, Mooneys are especially prone to porpoising. (We call it “the Mooney Bounce.”) If the pilots tries to force the airplane on the runway too soon it will touch down on the nose wheel. Mooney recognized that 40 years ago and began to add an “approach speed vs. gross weight” table to their landing performance chart. Most Mooney pilots I encounter are unaware that it is there or its significance.
The way to avoid startle response or “freeze up” is to actually experience the event and recover from it multiple times. Pushing our aircraft to the aerodynamic limit repeatedly in a safe and controlled environment will pay dividends if and when it happens accidentally. “We must keep people away from stalls,” is absolutely the wrong answer. We need to make them aware of all the sensations and behavior of the aircraft as it approaches and exceeds critical AoA so that they can recognize and respond rather than startle and freeze, or even put in the wrong control inputs.
As an aside, when doing spin training in an aerobatic aircraft, it is a good time to demonstrate that an airplane can have its nose well above the horizon and not stall, or well below the horizon and stall. I use a hammerhead turn to demonstrate how we can fly vertically upward with the airspeed decaying below “stall speed” without the wing being stalled. When I kick over into the vertical down-line, I pull hard on the stick to stall the wing and show the airplane being stalled (stall warning on, buffet, uncommanded roll) even though the nose is pointed straight at the earth. It is an eye-opener for most CFI candidates.
Thanks for another great missive. I have to run as I have an aerobatic student coming. Have a great weekend.
👍
Brian a corollary to the elevator controls angle of attack is therefore elevator controls stall not bank,
Exactly, Gennaro. One of the questions I ask of CFI students and clients during a flight review is, “What makes the airplane stall?” After getting many answers involving critical angle of attack, I point out that, “It is the pilot pulling on the stick or yoke.”
Yes, that is almost a too-simple answer but the truth runs very deep. How hard you can pull, and how many G you can pull, depends on airspeed. Go faster and you can pull harder. Available lift varies as the square of airspeed. Need to pull harder? Speed up. Need to speed up quickly? Add power and point the airplane down.
With the best intentions, I’ve heard CFI’s in pre/post flight lesson briefs advise students to keep the bank during base to final in the 20-30° range. In some cases, that’s only going to encourage the use of back pressure and/or inside rudder to reach an adequate rate of turn, either of which can result in loss of control. As you indicated, even a 45° bank has a good margin above stall speed. In terms of actual indicated airspeed, when the airplane is at the recommended base-to-final speed (near 70 in a Skyhawk), it will be around 25 kts above stall speed. Use back pressure instead of a little more bank and the margin immediately reduces.
Just like any other maneuver, banking properly at base to final to achieve a little extra turning performance in a safe manner needs to be discussed, demonstrated, and practiced. Use coordinated aileron and rudder and make sure the pitch reference (the spot on the glareshield directly in front of the pilot’s nose) does not move up toward the horizon and speed does not deteriorate. If that pitch reference maintains a steady gap below the horizon, the speed will stay stable, but with that said, train to be comfortable with nudging in additional power. If the CFI has never covered this and later warned to not exceed a too conservative bank, it can result in the student/pilot inadvertently taking some bad options.
Agreed Warren, eyes outside (directly ahead on roll) and correct pitch, coordinated turn – should all be practiced (and mastered) away from busy pattern distractions. There seems to be a tendency to “bank and pull” from level turns that needs direct intervention. Once properly trimmed, only slight pressure should be necessary for pitch during flap deployment. Every learner makes this whole process amazingly complicated until it becomes a habit. 🙂
Agreed but wanted to clarify that the training needs to occur also in the actual pattern. Remember the term ‘ground shyness’ that used to be in the Airplane Flying Handbook, the natural anxiety of banking at low altitude. That’s needs to be overcome also which I doubt can be done at altitude.
Response to Brian – there was no Reply button. “that stall speed varies with G-loading rather than with bank angle, is 100% correct. You can prove that by rolling an aircraft through 360º without stalling.” etc. No I think the pilot needs to watch the bank along with a number of other factors that you mention. True the airplane can be rolled without stalling in the sense of exceeding the critical angle of attack, but the aerobatic pilot increases kinetic energy and then uses some abnormal techniques momentarily to keep the airplane in the air. When the wing passes a certain bank, it is as good as stalled as when level with too much back pressure. How that all connects to and helps a regular pilot on approaches to avoid problems is pretty hard to see. I feel it is more helpful to talk about what to do or not do from the position of a normal approach at recommended speeds.
Thank you for your response Warren. As both an aerobatic and UPRT instructor, I can attest to the fact that, when I teach a ballistic or aileron roll, there is no increase in kinetic energy nor is there any abnormal technique involved other than rolling the aircraft in a coordinated fashion with the ball in the center. I suspect that you may be thinking of the slow-roll, which is NOT a coordinated maneuver. I am going to reiterate my statement because it IS 100% correct:
Stall speed does NOT increase with bank angle. Stall speed increases with G loading.
The constant speed level turn is a special case. Many people think that stall speed increases because of the bank but what is actually causing the increase in stall speed is pulling on the yoke to increase the angle of attack and achieve 2G of aircraft load. You can demonstrate this by putting the aircraft into a 60º steep turn and then increasing or decreasing the G loading. The only difference is whether you end up in an oblique climbing turn (increased G) or an oblique descending turn (decreased G). You will find that the speed where the aircraft stalls is purely a factor of the G loading applied.
I strongly recommend Rich Stowell’s “Learn to Turn” program. It addresses this issue better than I can here in this discussion.
Have a good week!
David:
This particular set of comments, plus your article is a great foundation for a performance seminar or a very pithy webinar or two. I don’t recall this much meat in any CFI refresher I’ve attended. David, when are you planning to condense your very insightful essays into a book? I hope you include this discussion with Brian, Gennaro, and Warren verbatim. 🙂
Thank you for your comment. It is always nice to be appreciated.
Interestingly, none of this is new or news. Nearly everything in this discussion is covered in “Stick and Rudder”, by Wolfgang Langewiesche, written in 1944. When I learned to fly back in the ’60s, most flight instructors were military-trained and had flown propeller-driven aircraft in WW-II and Korea. These concepts were taught, however they were taught verbatim. Most of the instructors I had never explained WHY the airplane did what it did. As pilots we exist in a very conservative environment that does not reward questioning authority. (Sorry folks, I never bought into, “because I said so.”)
It wasn’t until I started flying aerobatics and truly began finding the edges of the envelope, that I began to link the “what” with the “why”. Upset recovery becomes a normal activity in the early days of learning aerobatics. I can’t tell you how many times I said to myself, “Oops, that didn’t work. OK, zero out AoA and wait until we have enough airspeed to maneuver again.”
What all this tells us is that we NEED to change how and what we teach, and that means we need to change how and what we teach CFI candidates. When I teach these concepts to a pilot, I make one pilot safer. When I teach these concepts to a CFI candidate I potentially end up making hundreds of pilots safer. One common comment I get from almost every CFI candidate who comes to me for spin training is, “Wow! No one EVER explained this stuff to me before. This makes it all clear!” The sad fact is that, by the time they get to me they already have several hundred hours of instruction received and probably they have worked with many other CFIs, and not one of them have ever heard things like, “The elevator controls AoA,” “Stall speed varies with load factor,” “Stick or yoke position tells you what your AoA is,” or, “When things are going wrong, the correct reflex is almost always to push on the stick or yoke to retain control of the aircraft.”
Oh, there is just so much to talk about when it comes to fixing the stick-and-rudder skills of pilots and CFIs. The answer isn’t more automation but rather more and better pilot skills. The one component that exists in every aircraft to deal with LOC is a pilot. We just need to ensure that component performs properly.
I hear that a lot, “Old Wolfgang had it all” but not really. The generalities were there but not much of the specific “how and why” (and certainly not the method of conveying this critical knowledge and skill). Rich Stowell has fleshed this out much better and modern educational practices transfer it better than the WWII “whack on the head with a chart” method (I too learned from a WWII aviator 50 years ago!)
Thanks for the kind words! Between charter, DPE and SAFE, that book will have to wait 🙂 Hopefully more webinar/video content in the next year!
Ha! Yeah, my glider instructor was a grizzled old Navy IP. His teaching method was a rolled up sectional on the back of my head. “Don’t WHACK do WHACK that WHACK!” As the WHACK rate decreased I knew I was doing better.
Ol’ Wolfgang had the information there for anyone to digest. Rich Stowell has done a masterful job updating it and making it far more consumable with “Learn to Turn”. Still, the information IS there in “Stick and Rudder”; it is just up to us as CFIs to make it available,
Because of its great popularity, I see Stick and Rudder as the number one reason that basic pilot skills and aircraft control are problematic. Stick and Rudder teaches to use power to control altitude (I’m talking specifically about approaches). That’s using a force that is normally horizontal, or slightly downward on approaches (on a Skyhawk probably a 500lb force), to control altitude – i.e. it will supposedly oppose a +2000lb downward force (gravity). I once was doing a Part-135 training flight with a job applicant in a Cherokee Six. We were red-over-red on final so he increased power. The only thing that changed was that the airspeed increased ten knots. We were still red-over-red. The power did exactly what it was designed to do – accelerate the airplane. The applicant just scratched his head saying I increased power and don’t understand why that didn’t correct the altitude.
The other problem is with the term ‘Region of Reversed Command’. Is it widely interpreted to mean that the elevator and throttle should be used in a reversed manner on approaches. Unless you are flying a V22 Osprey, the thrust line doesn’t change at any speed – the propeller or jet engine is in a fixed position. The lines of force don’t change at any speed in all normal maneuvers. What does change is drag. Below L/D Max, drag goes up and speed goes down – that is the Region of Reversed Command.
Hi Warren. I understand what you are saying and I am going to disagree with you maybe more than just a little.
First, the part where I agree with you. At the moment of power application the aircraft will begin to increase in speed. However, very shortly after that the nose will rise as the aircraft seeks to regain its trimmed airspeed. The aircraft will slow back down, but in a climb.
What is happening here is that the trim sets the “default” AoA of the wing. if the aircraft is faster than set by trim, the wing will generate more lift, causing the aircraft to pitch upward, at which point it will begin to slow again. Usually this results in a damped up/down oscillation known as a phugoid. We pilots help prevent the phugoid by “helping” the aircraft achieve the proper pitch attitude after a power change.
In most of our aircraft the aircraft will pitch until it comes into equilibrium again with all four forces balanced. If you have reduced power, that will be with the aircraft at an increased rate of descent. If you have increased power, that will be with the aircraft at an increased rate of ascent. So changing the power will result in the aircraft changing its rate-of-climb without a significant change in airspeed.
Another way to look at this is about energy gain and loss. If the power is set to a value greater than the rate at which the drag of the airframe loses or “bleeds” energy, the aircraft will climb. The extra power in excess of what is required to maintain level flight will be translated into a change in potential energy, i.e. energy of altitude, without a significant change in kinetic energy, i.e. energy of speed. If you change the AoA by applying forward pressure on the stick or yoke after a power change, the extra energy will go into kinetic energy of the airplane (speed) rather than climb.
None of this is dependent on whether the airplane is operating on the “front side of the curve” or “back side of the curve”, the latter also being referred to as the “area of reversed command”. The area of reversed command simply states that drag is rising faster than lift when you increase AoA that continuing to increase AoA requires greater power and hence, if power input is constant, increased rate of descent. If one flies by setting AoA to select the desired equilibrium airspeed, then power will control steady-state climb or descent, while AoA (elevator position) will set the steady-state airspeed.
Bottom line: pitch and power interact. You are going to change both at the samy time, typically speaking. Regardless, if you don’t change the trimmed AoA, the airspeed associated with that AoA will remain roughly the same and power will control climb or descent. That is what old Wolfgang was trying to tell us.
Relying on the trim to change the pitch is a sloppy way to control the airplane. You know there’s going to be lag and oscillation. At altitude, no big harm. But on approaches, no.
Warren, I appreciate your comments but I think you misunderstand me. I am not advocating flying the aircraft in pitch using trim. Trim sets the AoA that the aircraft will seek with no elevator input. It sets the IAS that the aircraft will seek. If you have trimmed the aircraft for 90KIAS and make a power change, the aircraft will seek to pitch up and climb if you increase power and pitch down and descend if you decrease power.
Perhaps you have heard the phrase, “Pitch plus power equals performance.” It is the characteristic of trim setting the no-input AoA that does this. Since we know that airspeed is a secondary indicator for AoA, we can “trim” for the airspeed we want the airplane to fly. So if I want my airplane to descend at 500fpm from cruise while remaining at cruise airspeed, I need only reduce the power. You are correct that the airplane will immediately begin to slow, but that will cause lift to decrease, causing the aircraft to begin accelerating toward the ground. As soon as it has regained its trimmed airspeed the forces will be back in equilibrium and the aircraft will again be steady state, but in a descent, at the rate determined by power setting.
Now, when I am maneuvering I make pitch and power corrections together. I know that making a change in elevator will result in a short-term climb or descent, but if I hold it, that will quickly result in a change in airspeed. I have found that, in all regions of flight, using power to control climb and descent, and trim to set my desired angle-of-attack (and hence airspeed) works better than anything else.
As a result of experimentation I fully understand that elevator and elevator trim sets AoA, and throttle sets how much energy I am putting back into the airplane and determines my available climb.
I cordially invite you to visit and fly with me. I think that by flying together I can help you understand how and why I fly the way I do. Maybe we can enlighten each other and both come out better for it.