Bank Angle In The Circuit (Pattern)
A pet peeve of mine for a very long time has been what
horrible nonsense flight instructors in
Decades ago, someone (long since retired, or probably dead) noticed that as bank angle increased, so did stall speed. So, to avoid stall/spin in the circuit, it was announced with near-religious fervor that henceforth minimum bank angle would be used in the circuit. Great celebrations followed, with banquets and awards, and not just the cheesy ribbons - I'm talking metal and wood trophies.
Tiny detail. It is only true that stall speed goes up with bank angle if you are pulling more and more G which is a result of a LEVEL turn with the BALL IN THE CENTER. This is a tremendously important assumption which is rarely true.
For example, I can safely turn base in almost any aircraft at 60 degrees of bank (ok, 59.99999999 degrees – keep it legal) at slow speed as long as the G is very light; the wing is not working, and hence has a low angle of attack) and especially if I sideslip.
Remember, slips (ball to INSIDE of turn) are good. Skids (ball to OUTSIDE of turn) are bad. I will frequently use a 90 degree sideslip on short final to dissipate excess energy (into what?) and my aircraft does NOT explode with infinite G as your ab initio instructor taught you, because the ball is NOT centered, and I am NOT maintaining altitude.
The above is really important to understand.
Anyways, I was flying with another victim of our flight training establishment recently. He would turn base with a very shallow bank angle as he was taught, but unconsciously, to speed up the turn, he would hoof the inside rudder (a skid) and then as the inside wing dropped due to loss of lift, try to pick it up with aileron creating more adverse yaw, which of course aggravates the incipient spin entry.
He really didn't want to enter a spin turning base or final. He was just doing what generations of unthinking flight instructors have parroted down through the decades - keep the bank angle low.
This is all so totally and completely wrong.
What matters in the turns is NOT keeping the bank angle low, but maintaining airspeed and keeping the ball centered.
I have a mantra for light trainers for maneuvering in turns after downwind, until wings-level on final:
80 AND BALL
If you maintain 80 mph with the ball centered, you can use 60 degrees of bank during turns onto base and final without stalling or spinning. Check your POH. This is helped immensely by the fact that you are NOT trying to maintain
altitude during these turns.
Most people are very very uncomfortable with excessive bank angle in the circuit - they will NOT willingly use even 60 degrees of bank.
But the good thing about bank angle is that YOU CAN SEE IT! You often can't see a nasty skid unconsciously caused by inside rudder - see Illusions Created by Drift.
So please, flight instructors, break the cycle. Stop teaching your students to fly dangerously and badly. Bank angle in the circuit is NOT evil - what's evil are skids at high angles of attack!
A skid is what happens when you try to turn an aircraft by not using bank - by yawing it flat, like how a car turns.
Yawing an aircraft flat at low speed and low altitude –
which is what the flight training establishment in
pilots, like Rob Holland.
What's important in a turn is actually angle of attack.
Don't stall the wings. In the absence of an angle of attack indicator - you really need two, one for each wing - you can avoid stalling in a turn by:
1) avoiding a skid (slips are good, skids are bad)
2) maintaining airspeed
3) keeping the G loading light
Notice that bank angle doesn't even make the top three.
Note that I will happily fly with 90 degrees of bank at zero airspeed without stalling the wings when I perform a hammerhead pivot!
Again, angle of bank is NOT evil. Understand the relative airflow over the wing and all will become clear!
The problem is people don't intentionally skid. They don't wake up in the morning and say, "When I turn base today, I'm gonna give it a bootful of inside rudder!"
The insidious thing is that people don't even know they are skidding. They just want to turn the aircraft, and since their instructor tells them they can't turn with bank, they subconsciously press on the inside rudder to increase the rate of turn. Then, the inside wing starts to lose lift because it has slowed down, so they then try to pick it up with aileron which creates adverse yaw which makes the problem worse.
Ah, the irony. Instructors try to have their students avoid stall/spin by keeping the bank angle down, and as a result make their students skid through their base and final turns. It would be funny if it wasn’t so horrifying.
Over and over and over and over I have had to explain to pilots that what they are doing is very dangerous: a flat turn at slow speed at low altitude. And, they don't even know that it's a very high risk maneuver - they are astonished to realize they are punching the inside rudder, and trying to pick up the resulting downgoing inner wing with aileron.
I can't think of a better way to enter a spin. And I find it curious that so many people have no ostensible problem with entering spins at 500 AGL.
I guess the difference is that I think a slow, skidding flat turn is far worse than a coordinated (or slipping) steep turn with airspeed and no G load.
The Ball (inclinometer)
Centering the ball is nice because it is minimum drag. This allows you to get maximum climb rate, for example. Most people like to climb out in a sideslip after takeoff, using the side of the fuselage as a drag device to reduce the aircraft climb performance. Don't do that. Use right rudder to center the ball.
Centering the ball also feels good. Although cars turn flat, bicycles, motorcycles and airplanes incline during turns, so that all the forces are vertical. Maybe I'm getting old, but my back hurts after an hour of flying with the ball fully deflected. If you intend to ever fly anything with more than a few seats, you will give the people in back a wild ride with the ball sloshing back and forth.
Now onto turns. During a turn, the ball can be:
1) centered, which feels good with minimum drag, or
2) falling to the inside of the turn, which is a sideslip,
which creates drag and is a great way to lose energy, or
3) climbing to the outside of the turn, which is a skid which usually results from too much "inside" or “bottom” rudder application. This is dangerous if the speed bleeds off, because the inside wing is slowed down, produces less lift, and can even stall during a descending turn (e.g. onto final) which results you being upside down in a spin at 500 AGL, which you likely will not survive.
- ball centered is usually good. Minimum drag, good passenger comfort, and less likely to stall/spin (but NOT guaranteed not to spin)
- sideslip is good during turns. Creates drag if you are high. Can use to dissipate energy if you don't have flaps, or don't want to/can't deploy any more drag devices. Ball falls to inside of turn. Caused by application of “top” or “outside” rudder.
- skids are always bad. Don't do this. Danger of inside wing stalling. Ball goes to outside of turn. Caused by application of bottom or inside rudder, often to increase the turn rate with insufficient bank.
Maybe I'm living on another planet, but the above is not rocket science. It does not require the use of Kalman filters or Special Relativity and MUST be understood by anyone who ever wants to be the sole occupant of an airplane.
I do not understand why such simple, fundamental knowledge is not taught. Compared to all the nonsense that is thrown at student pilot, the basics of how an airplane turns should really be taught in the first few hours of dual.
Angle Of Attack
I really, really wish that more aircraft had AOA indicators, because that is what matters. Everything else is a proxy for AOA. You will notice that the USN, which does some pretty serious aviating, doesn't care about approach speed on a carrier landing - all aircraft are equipped with AOA indicators, and approach is flown at a specified AOA.
When I am flying, I don't care about pitch/bank attitude. I don't care about airspeed. I don't care where the ball is. I don't care about control deflection. I don't care about power setting.
The only thing I care about is AOA, because that's the only thing the wing cares about.
I find it astounding that so many people, whose lives depend on the correct functioning of the wing, are completely disinterested in it, and instead focus on all sorts of psychological considerations.
My father used to be a flight instructor on the F-104 at
Nonsense, my father would reply. Look at the equivalent angle of attack indicator. He would pull the F-104 vertical, and pull the throttle all the way back. Watch the AOA, as the airspeed falls to zero. Full rudder, hammerhead beautifully, with the AOA reading a nice number all the way through the maneuver as the F-104 pivoted to a vertical down line. Throttle would stay at idle, they would go supersonic in the vertical down line, then pull level and throttle would go forward.
AOA is king. Nothing else matters to the wing. If you don’t understand that, you should never be alone in an airplane.
Stall Speed In A Turn
Here’s a simple question for you. If I turn base with 80 degrees of bank, and I unload the wing to zero G, what is my stall speed?
Anyone that considers being by themselves in an airplane at any point in their life ought to ponder and understand it. And amazingly few do.
Answer: turning base with 80 degrees of bank, with zero G, my stall speed is ZERO. In ANY airplane.
Hopefully the above has made you question your assumptions, and what you have been told. You don’t have to accept what I type as gospel – that would be a very bad idea. Don’t accept what anyone tells you as gospel. I just want to get you thinking about and understanding what an airplane does in the air.