Bank Angle In The Circuit

Shiny Side Up · Post by **Shiny Side Up** » Mon Jul 30, 2012 7:28 pm

Spending a whole lesson just in Attitudes and Movements and then practicing straight and level, climbs descents and turns until the student can accurately fly the aircraft is incredibly boring and tedious for the instructor

Which is why one gets worn out of doing ab initio stuff with students. Its especially frustrating when you get that odd guy who just doesn't seem to get it, and you're trying to explain why you're going to go do more straight and level, climbs, turns and descents for the next lesson and he's all "when am I going to solo?" One thing at a time grasshopper.

trey kule · Post by **trey kule** » Mon Jul 30, 2012 7:47 pm

First of all, I need a bit of clarification here...CS,in your original post are you suggesting that 60 degree banked turns can safely be done at low level or that people should be doing 60 degree banked turns in the circuit?

If the first, then what we are really talking about, despite the references and personal stories is simply being able to do a co-ordinated turn. It really is nothing more complicated than that. But , as it happens, many pilots, and particularly student pilots who are spending relatively more time in the circuit than the rest of us, may just not be able to do a coordinated turn that well, particularily is something catches their attention.. We are talking learners here, not experienced pilots. I simply see no reason for the average pilot to be making 60 degree banked turns at low altitude in the circuit.Personally, when I do see it, I consider them to be a bit of a showoff...even though they will sometimes try to rationalize it for one reason or another.

As to training. IMHO there is not only a rush to solo, but a rush to get into the circuit without the necessary learned skills (like how to make co-ordinated turns). Instructors, in general, do not recognize the importance of pre solo upper air work prior to entering the circuit. If the upper air work is done well, and the student is proficient, the time a spent doing circuits prior to solo is actually quite minimal. The circuit is not the place to be learning how to do a co-ordinated turn, and particularily for a student pilot, not steep turns at low level.. The FAA has two flight test items, a chandelle, and a lazy eight which are excellent learning tools if done as they are intended and not as air show items. But I have seen more than a few instructors who change the parameters of these exercises not to teach co-ordination, but to show off their awesome ability to do them far in excess of their intent. The rationale is always the same for increasing the challanges to the student...

And one of the challanges students face with steep turns (as they are identified) is that the wings produce less lift (vertical component for the nitpickers) and so the nose drops and what should have been a level of low rate of descent turn becomes the start of a spiral with increasing airspeed. The bank increases a bit over 60, descent rate increases, ground is coming up fast, and the student instinctively pulls back on the control column.......the result is not usually that pretty.

Steep turns have their place in training, and occassionally in normal flight operations. But the last thing we need is students, or pilots in general to be practicing them for proficiency is close to the ground..Leave that to the professionals and showboaters. I have no idea why some pilots seem to think that no matter what we have learned about flight training and TC specifies they always know a better way to do things... One of the posters made it quite clear with a TC post.

And to empahsize my point again. I see no need whatsoever in normal flight operations to be doing 60 degree banked turns in the circuit...You are simply reducing the margin of acceptable pilot error..and the average pilot does make the odd error.

There is an old saying that the world looks like it is full of nails to a man with a hammer. Instructors need to think more from the student's perspective, and sometimes a little less of their own background.

iflyforpie · Post by **iflyforpie** » Mon Jul 30, 2012 8:53 pm

I think that CS's point was that a 60 degree bank is safer than skidding at a low altitude.

That being said, needing to do a 60 degree bank in the circuit represents poor planning and judgement. I do a 1/2 mile offset for my downwind and only need to do a rate one... but I also distain square circuits.

CpnCrunch · Post by **CpnCrunch** » Mon Jul 30, 2012 9:04 pm

So why exactly is a 60 degree turn safer than a skidding turn? With the 60 degree level turn you have a much higher stall speed, and any stall will likely be unrecoverable at 500 feet AGL. Assuming as we are that it is a dumb/lazy pilot, the airspeed won't be high enough to maintain the necessary AoA (and will likely decay if the pilot isn't paying attention), and the result will be just as big of a smoking hole in the ground as if the lazy pilot did a skidding turn. You're somehow assuming that a pilot is dumb enough to do a skidding turn, but smart enough to do a 60 degree turn at higher-than-normal approach speed. Doesn't really make sense. Limiting bank angle to 30 degrees in the circuit and making all turns coordinated makes sense for the average pilot.

Colonel Sanders · Post by **Colonel Sanders** » Tue Jul 31, 2012 4:32 am

CS's point was that a 60 degree bank is safer than skidding at a low altitude

Exactly! Neither is a really good idea, but IMHO a slow
skidding turn is more dangerous than a momentary 60
degree banked turn in a descent with the ball either
centered or sideslipping.

needing to do a 60 degree bank in the circuit represents poor planning and judgement

When a circuit gets that screwed up, I would hope that
an overshoot would be considered.

Never push a bad approach into a bad flare. Never push
a bad flare into a bad touchdown. Never push a
bad touchdown into a bad rollout. There are some Porter
pilots that fly into CYTZ that should think about this.

If you are a really hot stick, yes you can recover. But
if you're such a good pilot, how did you get so screwed
up in the first place?

With the 60 degree level turn you have a much higher stall speed

Congratulations. You have entirely missed the entire point of
this thread. During a turn onto base and final, I hope you aren't
level. You should be descending. Also, you might need to sideslip
to lose altitude during one or both of these turns. A sideslip involves
more than normal bank, and top rudder with the ball falling to the
inside of the turn.

The effect of NOT trying to maintain altitude, and potentially
also doing a sideslip, means that you are not anywhere near
+2G as you assume, with the associated 41% increase in stall
speed. In fact, your G might be slightly less than +1G during
this maneuver, which means that your stall speed is in fact
slightly less than published Vs!

My objective in this thread is NOT to encourage student pilots
to explode with a 90 degree banked singularity in the circuit.

Rather, the objective of this thread is to get people thinking
about the dangers of slow, skidding turns which result from
well-intentioned efforts to reduce bank in the circuit.

I would also hope that people start to realize, as I have
described over and over and over and over and over again
in this thread, that bank angle itself is not evil. It is not
like HepC, HIV, herpes or even genital warts. It doesn't
even make the top three (see page one) in terms of
considerations for a safe turn in the circuit.

It's all about the angle of attack. Think about the relative
airflow over the wing! The wing has no eyeballs. It does
not get scared at 60 degrees of bank. It always responds
exactly the same way, as described by it's Cl and Cd curves.

Limiting bank angle to 30 degrees in the circuit

Sigh. No.

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, who's lives depend on
the correct functioning of the wing, are completely disinterested
in it, and instead focus on all sorts of psychological considerations.

Colonel Sanders · Post by **Colonel Sanders** » Tue Jul 31, 2012 5:33 am

According to the experts here, this is physically impossible:

I can assure you that it is not a fake. Skip Stewart knows
all about angle of attack.

My father used to be a flight instructor on the F-104 at Cold Lake. Because
he was an instructor, many people here will think he was not a very good
pilot compared to you. So be it.

When he was transitioning F-86 (Sabre) pilots to the F-104, he discovered
that they were all terrified to slow the -104 down, because of all the horror
stories they had heard about it.

Nonsense, my father would reply. Look at the equivalent angle of attack
indicator. He would pull the -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 -104 pivoted to a vertical downline. Throttle would stay
at idle, they would go supersonic in the vertical downline, then pull level
and throttle would go forward.

AOA is king. Nothing else matters to the wing.

PS Funny reading about the sportbike rider that was caught at 300 kph
on that nice straight road to Fort Mac. My father used to regularly fly it
at 600 knots and 10 feet. But he's not much of a pilot compared to you,
because amongst other things, he was a flight instructor.

Genetk44 · Post by **Genetk44** » Tue Jul 31, 2012 6:05 am

I love reading these types of threads....even though some of the physics and theory's are sometimes beyond my knowledge base I always seem to be able to learn something completely new and/or understand more clearly or forcefully something that could save my life. CS's last post just reinforced one of the things that really made an impression on me in Stick and Rudder.....AoA seems to really rule....now if my memory serves,i dont have the book in front of me,the author at one point says essentially that if you move the yoke forward and reduce the AoA you don't get in trouble.....pull the yoke back and bad things happen.....so I'm trying to visualize and have a question..... 60 degree bank and you realize your approach line-up is off....move the yoke slightly forward a bad thing??

trey kule · Post by **trey kule** » Tue Jul 31, 2012 6:11 am

According to the experts here, this is physically impossible:

I think you are maybe using the word "experts" in a rather unnecessary condescending manner, but sometimes the internet is not good at communication of meaning. In any event, I reread the whole thread.. I could not see anyone who posted this was physically impossible. Please direct me to the relevant posts.

I see that my original puzzlement was from the title thread and it was not your intention. Thanks for clarifying that.

CpnCrunch · Post by **CpnCrunch** » Tue Jul 31, 2012 7:20 am

With the 60 degree level turn you have a much higher stall speed
Congratulations. You have entirely missed the entire point of
this thread. During a turn onto base and final, I hope you aren't
level. You should be descending.

Nope, understood completely. I threw in the 'level' because I knew you would say that you're descending on final.

The point is that that when you enter the 60 degree turn, then you will have to pull the stick back to maintain your glideslope. If you're smart enough to do a safe 60 degree bank turn in the circuit, you're probably smart enough not to do a skidding turn as well.

Really, I don't think it's any safer for the 'average' pilot (people like me) to be doing 60 degree turns in the circuit. I'm certainly not an 'expert', I'm just here to learn, and I don't think you're giving good advice to people like me.

Shiny Side Up · Post by **Shiny Side Up** » Tue Jul 31, 2012 7:53 am

iflyforpie wrote: but I also distain square circuits.

Thankfully the oval is also an aesthetically pleasing shape.

Colonel Sanders · Post by **Colonel Sanders** » Tue Jul 31, 2012 8:07 am

I don't think you're giving good advice

Congratulations, and welcome to the internet! Do remember
to take everything you read on the internet with a grain of salt.

In my case, I might specifically add that my advice is worth
precisely what you paid for it.

Regardless of people's feelings though, mathematics and physics
simply is. Little question for you:

If I turn base with 80 degrees of bank,
and I unload to zero G, what is my stall speed?

The above paragraph does not deal with people's feelings
or opinions about other people and what they say, or how
they feel about themselves. It is a simple matter of newtonian
physics which is well within the comprehension level of anyone
that passed high school physics. Anyone that considers being
by themselves in an airplane at any point in their life ought to
ponder and understand it.

trey kule · Post by **trey kule** » Tue Jul 31, 2012 8:20 am

First of all Crunch,,, I think the thread title was a bit confusing but CS made it quite clear his intent was not to promote doing 60 degree banked turns in the circuit..It confused me a bit, but he did clarify it. It is simply being able to do a co ordinated steep turn.

Now this...

The point is that that when you enter the 60 degree turn, then you will have to pull the stick back to maintain your glideslope. If you're smart enough to do a safe 60 degree bank turn in the circuit

Correct me if I am wrong, but I seem to recall having made a number of descending 60 degree turns without having to pull the stick back....or are you again alluding to a level turn...something you admitted you intentionally posted incorrectly for some reason or the other.
And exactly how does one maintain the "glideslope" by pulling the stick back in a turn? Did you mean glide path?
In any event both the glideslope, and a correct glide path are slanting downwards.

Rowdy Burns · Post by **Rowdy Burns** » Tue Jul 31, 2012 8:23 am

Colonel Sanders wrote:If I turn base with 80 degrees of bank,
and I unload to zero G, what is my stall speed?

0

CpnCrunch · Post by **CpnCrunch** » Tue Jul 31, 2012 8:52 am

I might not be an 'expert' around here like some other people, but I do know that you can do a 60 degree banked turn without increasing the load factor. However as I pointed out above, that will increase your sink rate / glidepath, which is likely not what you want to do. If it is, then fine

Here is an interesting video demonstrating my point:

http://www.youtube.com/watch?v=7nm_hoHh ... re=related

Clearly this cirrus pilot did a whole bunch of things wrong, but the conclusion of avweb is 'steep turns and high load factors in the pattern invite disaster...they should be avoided at all costs'.

So just to clarify: CS is saying that it's bad to teach students to limit bank angle to 30 degrees in the circuit. I'm saying it's a GOOD THING, because it would prevent accidents like the above. Certainly it's possible to do a safe 60 degree bank in the circuit if you know what you're doing, just as it's safe to do a skidding turn if you're well above stall speed. However for the average pilot who flies perhaps a few hours a year that's a recipe for disaster.

Bushav8er · Post by **Bushav8er** » Tue Jul 31, 2012 11:56 am

Excellent topic/post.

Right AOA is everything, it's to bad all aircraft don't have one.

Note to the youngers; going over 60 degrees of bank is an -

"aerobatic manoeuvre" - means a manoeuvre where a change in the attitude of an aircraft results in a bank angle greater than 60 degrees, an abnormal attitude or an abnormal acceleration not incidental to normal flying; (acrobatie aérienne)

You'll need a rating...like the Colonel

Colonel Sanders · Post by **Colonel Sanders** » Tue Jul 31, 2012 1:18 pm

Heh. Just to re-iterate, I'm really not trying to make people
use more than 60 degrees of bank in the circuit. I'm not trying
to hawk copies of the Watchtower, either. I'm just trying to
get people to think about basic aerodynamics; Why do you do
what you do? Why do you teach what you teach?

Next question:

I am turning downwind with 130 (no typo) degrees of bank. My
accelerometer is indicating precisely +1.0 G and the ball is in
the center. What is my stall speed?

Bonus question: if I stall, which way will the aircraft go?

old_man · Post by **old_man** » Tue Jul 31, 2012 1:45 pm

Edit: never mind, I messed that up. I am going to finish supper and then get to it.

Colonel Sanders · Post by **Colonel Sanders** » Tue Jul 31, 2012 2:43 pm

Don't feel bad. I couldn't find Edenvale in the CFS. Gotta
go practice the alphabet.

old_man · Post by **old_man** » Tue Jul 31, 2012 3:11 pm

Alright, is it as simple as your load factor is 1 in that case?

To be fair, it's a while since I have flown fixed wing and even longer since I did aerobatics. The most bank I ever stalled an aircraft with was 90 degrees.

And no, no one ever told me/taught me to do a skidding turn. Slipping turn to bleed off energy...sure but never a skidding turn.

DanWEC · Post by **DanWEC** » Tue Jul 31, 2012 5:56 pm

Colonel Sanders wrote: I am turning downwind with 130 (no typo) degrees of bank. My
accelerometer is indicating precisely +1.0 G and the ball is in
the center. What is my stall speed?

Bonus question: if I stall, which way will the aircraft go?

Ok I'll bite.. I'm no genius and I didn't overthink this, , but if you're pulling 1 G while in a coordinated maneuver, won't your stall speed just be the craft's Vs? As far as the wing is concerned is has a nominal AoA. It could care less what the hell direction it's going in, airflow is at that point equivalent to straight and level.... unless I'm very wrong. Also... you'd have to be going very, very fast with a pretty wide radius to have a coordinated 1 G turn at 130 degrees would you not?

As far as your bonus... wouldn't the nose drop directly towards the ground(so in a left hand turn, essentially yaw straight down to the left since you are almost at a knife edge with a proper forward C of G) into a typical spiral dive entry? That's basic stuff, unless I'm completely missing the point.

Anyhow... I think that saying a new pilot "can" rip a 59.9 degree bank in a circuit is a bit like telling a brand new 16 year old driver that they "can" drift a RWD car around a hairpin turn on a racetrack while they are still mastering where the windshield wiper switch is. Not "that" difficult, I can do it, but baby steps.....

From what I have seen, you're correct that (In my incredibly small sample group of 1...me) students don't get taught enough pushing the plane a bit more, but I could see that from a hypothetical instructors point of view, that you don't want to be pushing the odds and safety envelope every day by doing lots of spins and unusual attitude recoveries.... I couldn't wait to head out and do them on my own though.

That practice resulted in 4's in steep turns and related manouvers on the PPl and CPL tests. Now I want to do aerobatics.... coming soon.

Colonel Sanders · Post by **Colonel Sanders** » Tue Jul 31, 2012 6:14 pm

Doing well, but you need to think a bit more about
a positive G stall in a 130 degree banked turn, which
is actually 40 degrees past knife edge.

Take a model airplane, put it in that attitude, and
think about what effect lift (and the loss of it)
would have.

Another hint: in a vanilla upright positive G stall,
what does the nose of the aircraft do, relative to
you? Does it move up, closer to you, or down,
away from you?

DanWEC · Post by **DanWEC** » Tue Jul 31, 2012 7:58 pm

Nevermind, at that moment only my brain decided that knife edge was 180 and not 90. Information mistake.

To answer your question simply, the wing will stall in the direction that gravity is acting on it, whether it's the earth or centrifugal force creating it, it's all the same, as the function of lift is to counteract it.

Colonel Sanders · Post by **Colonel Sanders** » Tue Jul 31, 2012 8:32 pm

Food for thought:

DanWEC · Post by **DanWEC** » Tue Jul 31, 2012 9:04 pm

If that picture is real and not just rotated, then that shows the "gravity" I mentioned That the wing is feeling ( I should have been more clear and just said "force") resulting from centrifugal force.

cgzro · Post by **cgzro** » Tue Jul 31, 2012 10:57 pm

So why exactly is a 60 degree turn safer than a skidding turn? With the 60 degree level turn you have a much higher stall speed, and any stall will likely be unrecoverable at 500 feet AGL

A) Stalling in a skidding turn causes the already low wing to stall first putting you on your back very fast.

B) Stalling in a nicely co-ordinated turn of any angle of bank results in little to no roll either way.

C) Stalling in a slipping turn causes the high wing to stall first rolling you back through wings level.

B) and C) are easily recoverable without much in the way of special skills and minimum altitude loss by simply relaxing back pressure however if you do that with A) you will likely stop inverted after which some pilots haul the stick back or float off the seat and can't control the plane, grab the control column to stop themselves floating and pull it back.

B) and C) are safer than A) by a huge margin.

I don't think you're giving good advice

He is saying that given a choice between A) and B) you should pick B). That is 100% true, easily demonstrated and therefore perfectly correct advice. Naturally a well planned 30 degrees or so is preferable and won't scare your passangers but putting that rudder in to speed up the turn and keep the bank angle below 30 is dangerous and if you are intent on speeding up the turn for whatever reason increase the bank angle and stay co-ordinated instead.

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