CFI task: Flight at minimum controllable airspeed (slow flight)

This thread got me playing around with MCA in the Chief on Saturday. We were floating around, fully controllable at 42 mph and about 5 mph ground speed.
 
The examiners in my area like to see between 60 and 65 in a 172 or warrior. More than likely they don't want the maneuver to get out of hand on the check ride.

Personally I demonstrate it and have the student perform the maneuver with the horn going on and off. Just so they can get a feel for the practical application of the aerodynamic factors. However I tell them to try and use the speeds that the examiners prefer if they are out on their own doing the maneuver until they build up their experience and comfort with that type of flying after they have successfully completed their check ride.
 
LearDriver said:
The examiners in my area like to see between 60 and 65 in a 172 or warrior. More than likely they don't want the maneuver to get out of hand on the check ride.

Personally I demonstrate it and have the student perform the maneuver with the horn going on and off. Just so they can get a feel for the practical application of the aerodynamic factors. However I tell them to try and use the speeds that the examiners prefer if they are out on their own doing the maneuver until they build up their experience and comfort with that type of flying after they have successfully completed their check ride.
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55 indicated is completely doable in the Cherokee - at least the one I'm flying with students... and down here one ought to have the horn or light going off the whole time with at least some of the examiners.

Ryan
 
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My primary CFI pounded into me that slow flight was SLOW flight. His favorite thing for me to do was point into a nice steady wind, get the stall horn blaring, made me hold the plane at the bottom of the ASI and then look outside the plane. If we were actually going backwards, he was satisfied!!! My right leg sometimes started to get the shakes from holding the rudder down hard for that whole time. The recovery also taught me alot about how lowering the nose and controlling the power setting got you back to level flight with minimum loss of altitude. I thank him every time I fly for kicking my ass in that plane...
 
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bbchien said:
Since we are talking about beyond the PTS, I consider "riding the buffet" a mastery maneuver, e.g, at the commercial level. One rides the buffet wtih the RUDDER. Here we allow for the wing pickup with rudder in which we are a smidge unco-ordinated, right at the brink of stall.

When the wing drops, you ARE in stall. This is definitely not part of the PVT PTS. But to master the Stall recovery to Comm standards, it's much easier to do if you are comfortable with riding the buffet with RUDDER.
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Interesting. I recall (it was about 9 1/2 years ago) when I took my PP check ride the DPE wanted recovery from a full stall, with a 20 degree banked turn (power on). I hadn't ever done one other than with wings level, and knew that the 172 liked to drop the left (?) wing in a stall, so I turned right (she didn't say which way), let it stall and drop the wing, caught it at wings level with the rudder and recovered from the stall. Wasn't really much of an issue. Oh, and this was with my CFI in the back seat. Poor guy had to sit back there and keep his mouth shut. :D
 
Tim,

I think Henning has this right on.

In the past Slow Flight had been taught as slowing the aircraft down and flying at speeds slower than cruise (like you might do while extending a downwind for a period of time)

The current definition of slow flight is: Flight at an airspeed where any increase in angle of attack, increase in load factor, or reduction in power will result in an immediate stall. Basically MCA.

To that end I teach slow flight with the horn continually on. I'll allow the bottom of the white arc (flaps extended) +5 knots. The student learns how to control the aircraft while maintaining altitude. They also really see the loss of the vertical component of lift as they begin their shallow banked turns. This will require the addition of power, if done correctly. If anyone claims you don't need any more power - then you're not in slow flight - because you don't have any more AOA to give up to the manuever.

It's really a good lesson, and something I focus on alot during our training.

Hope this helps
 
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Commander Dave said:
In the past Slow Flight had been taught as slowing the aircraft down and flying at speeds slower than cruise (like you might do while extending a downwind for a period of time)
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That definition (1.15 Vs0, or something like that) was in effect only briefly (like 4-5 years) from the late 90's through about 6 years ago. Before that, it was the same as it is now (just above a stall) from at least the late 60's until they made that change to like 1.15 Vs0 in the late 90's (that change being rescinded around 2004).
 
Commander Dave said:
This will require the addition of power, if done correctly. If anyone claims you don't need any more power - then you're not in slow flight - because you don't have any more AOA to give up to the manuever.
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Not entirely true.....if you go back to page 2 of this thread and read what Ron and Kent had to say about the increase in airspeed needed to maintain level flight in a low say 10 degrees of bank turn, it is really very small. I can and have done level turns in slow flight with the stall horn sounding continuously without needing to add any power.
 
Fearless Tower said:
Not entirely true.....if you go back to page 2 of this thread and read what Ron and Kent had to say about the increase in airspeed needed to maintain level flight in a low say 10 degrees of bank turn, it is really very small. I can and have done level turns in slow flight with the stall horn sounding continuously without needing to add any power.
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Completely airplane dependent.
 
dmccormack said:
Completely airplane dependent.
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In theory, yes, but in practice, it doesn't matter what light SE airplane you're flying -- the increase in power required for 5 degrees of bank is insignificant (at least for the range of light singles I've flown, from CTSW, Luscombe, and J-3 Cub to 36 Bonanza, 210, and PA-32).
 
Ron Levy said:
In theory, yes, but in practice, it doesn't matter what light SE airplane you're flying -- the increase in power required for 5 degrees of bank is insignificant (at least for the range of light singles I've flown, from CTSW, Luscombe, and J-3 Cub to 36 Bonanza, 210, and PA-32).
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You added "5 degrees of bank" as a qualifier.

I was responding to "say 10 degree of bank turn."

Some airplanes will require additional power to maintain level and MCA when turning at 10-15 degrees. 5 degrees is barely perceptible and within the margin required to maintain wings level if the air is anything but smooth.
 
dmccormack said:
5 degrees is barely perceptible and within the margin required to maintain wings level if the air is anything but smooth.
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5 degrees is a standard rate turn for most light SE trainers at Vmca, and it is quite perceptible (both bank angle and turn rate). Even in light turbulence, it is easy to maintain, and can be held as an average value in greater turbulence than that -- even by a 20-hour Student Pilot.
 
dmccormack said:
You added "5 degrees of bank" as a qualifier.

I was responding to "say 10 degree of bank turn."
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Dan,

Go back and read my post that was being referred to. I did my calculations for 10 degrees of bank. The increase in stall speed is a fraction of a knot - So you can do that without adding power. Nobody is holding their airspeed THAT perfectly in slow flight that a fraction of a knot is going to make a difference.
 
flyingcheesehead said:
Dan,

Go back and read my post that was being referred to. I did my calculations for 10 degrees of bank. The increase in stall speed is a fraction of a knot - So you can do that without adding power. Nobody is holding their airspeed THAT perfectly in slow flight that a fraction of a knot is going to make a difference.
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Yes, you did. I wasn't replying to your post per se.

I was replying to the general notion that the MCA exercise can be done at a single power setting. During both my comemrcial and IR practicals, I was instructed to maintain MCA straight and in a "standard rate turn."

"Standard rate" is a function of airspeed, so at 50 knots the rule of thumb is to divide by 10 then add half (5+2.5 = 7).

Now, the difference between 12 and 10 and 7 degrees of bank is very hard to know without an attitude indicator, and even then it's a bit of a guess.

So I use the turn coordinator to achieve "standard rate" and -- interestingly enough -- so did the examiner.

Did I add power? Do I always add power once a bank is established?

I can't tell you absolutely for each airplane in each instance because my hand is on the throttle and the reactions are almost subconscious.

I also teach that way -- we're flying on the ragged edge and the slightest application of power and change of pitch may be required, but make the changes small enough to maintain the stall indication.

Anyway, the point is this isn't an instrument exercise -- it's an airplane feel exercise. You need to be able to sense the edge through various inputs.
 
Fearless Tower said:
Not entirely true.....if you go back to page 2 of this thread and read what Ron and Kent had to say about the increase in airspeed needed to maintain level flight in a low say 10 degrees of bank turn, it is really very small. I can and have done level turns in slow flight with the stall horn sounding continuously without needing to add any power.
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I'm not trying to start a debate over this but...

Slow Flight defined as I had posted: "...where any increase in angle of attack, increase in load factor, or reduction in power will result in an immediate stall"

This leaves you not just with the stall horn sounding (where you may have additional AOA left - maybe 5 to 1o knots above the stall in some single engine aircraft) but instead places you just above the stall.

Sheer physics will show that if I require 100% of the developed lift to maintain straight and level flight, and then divide that 100% by any amount (as in horizontal component of lift to turn) then I will need to increase my total lift, or give up some altitude.

Two options, increase back pressure (but you can't because any increase in back pressure would have resulted in an immediate stall - therefore you weren't in slow flight) or increase airspeed (throttle)

I know we're splitting hairs here. However in the teaching realm, the lesson I want the student to come away with is, when I devote some of my lift towards the turn in slow flight, a little throttle is required to compensate for the addition of the horizontal component of lift.

My two cents...
 
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dmccormack said:
It is fun -- My ASI indicates mid 30s at the edge of stall. Very slow, rather steep, very cool. :thumbsup:
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Dan,

We operate a C172 with a STOL kit that allows for the same handling.

Had a photographer come out to the airport and asked if I could hold 50 knots. I said "sure, how about 30?"

:ihih:
 
Commander Dave said:
Dan,

We operate a C172 with a STOL kit that allows for the same handling.

Had a photographer come out to the airport and asked if I could hold 50 knots. I said "sure, how about 30?"

:ihih:
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That's fun!

:-)

I did a photo shoot solo a few weeks ago in the Chief low and slow, but I wish I had a pax on board to take the pics so I could fly really slow.
 
jesse said:
I'm no protractor but I can pretty easily spot the difference between 12 and 7 degrees.
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I said the difference between 5 and 7 and 12.

I own an airplane with no attitude instruments and can be close, but will not claim to know that I am in an "8 degree bank" as opposed to a 6 degree bank.

That's all.
 
dmccormack said:
Anyway, the point is this isn't an instrument exercise -- it's an airplane feel exercise. You need to be able to sense the edge through various inputs.
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This is the point that is mostly missed.

From what I can read here, and my experience with most pilots, everyone is wrapped up in 'verifiable' numbers, and sadly, most examiners encourage this behavior by expecting a 'solid' demonstration of a certain speed or warning device.

None of these indicators define the PTS definition of slow flight.

The training purpose of slow flight is to get the student to be able to 'feel' the edge of the stall.

The actual stall, or the final mushiness of the controls before the stall occurs, varies each day, or actually, by the hour, as gas is consumed, and the airplane weighs less.

Altitude, temperature, airspeed indicator accuracy, etc., etc., etc., all cause tiny changes in airspeed indications, and do not give the actual indication of an impending stall, as does the 'feel' of the controls just as the stall is about to happen.

The way I test for slow flight is, when the student says he has it slowed and trimmed and power set, I reach up and pull sharply back on the elevator for about an inch or two. If the airplane stalls, it was PTS slow flight. If the airplane does not stall with additional back pressure, it was not in PTS slow flight.

And I know some examiners will not want to go that slow. They are pilots who became instructors who did not learn the feel of real stalls, and do not teach it, nor test it.

But it is the essence of what we should teach: the intrinsic feeling in the controls which becomes an intrinsic feeling in our gut that tells us we are about to stall, no matter what the ASI or warning horn is doing or not doing.

Take some time. Spend 5 or 10 minutes in the stall region, going in and out of stalls during slow flight until you can hold it right above the stall by feel only.
 
dmccormack said:
I said the difference between 5 and 7 and 12.

I own an airplane with no attitude instruments and can be close, but will not claim to know that I am in an "8 degree bank" as opposed to a 6 degree bank.

That's all.
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If we're talking 6 vs 8, I'd buy that. But we're talking 5 vs 10 or more, and that's awfully big not to see, as is the doubled turn rate.
 
Ron Levy said:
If we're talking 6 vs 8, I'd buy that. But we're talking 5 vs 10 or more, and that's awfully big not to see, as is the doubled turn rate.
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I can't be sure of the difference between 5 and 7 degree bank.

I certainly know the difference between 5 and 15 degrees of bank.

But for the purposes of MCA, the actual number isn't important.

The exercise is supposed to test the ability to fly the airplane on the edge of stall -- the bottom end of the envelope. In every single I've flown this requires application of power to maintain altitude while in this attitude -- L/D and all that.

Any disturbance of this balance is supposed to result in stall-- reduced power, increased pitch, and at some point, bank.

Since I'm trading Vertical component of lift for horizontal -- except for the shallowest of banks -- this should require some change in pitch or power to maintain altitude.

Now -- we might be able to measure and extrapolate and come up with the millimeters in or out of the throttle for any given bank angle.

But that would take the focus away for the purpose of the exercise -- feel for the airplane.

So, I will continue to maintain that MCA requires hand on the throttle, with immediate adjustment to power and/or pitch to avoid stall, whether straight and level or banked.

:thumbsup:







.
 
dmccormack said:
So, I will continue to maintain that MCA requires hand on the throttle, with immediate adjustment to power and/or pitch to avoid stall, whether straight and level or banked.
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Me, too, but not because of any significant power change needed for five degrees of bank. Updrafts and downdrafts will be more of an issue than banks, and those will affect you regardless of bank angle.
 
dmccormack said:
Yes, you did. I wasn't replying to your post per se.

I was replying to the general notion that the MCA exercise can be done at a single power setting.
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And that's exactly what I addressed in my post.

Did I add power? Do I always add power once a bank is established?

I can't tell you absolutely for each airplane in each instance because my hand is on the throttle and the reactions are almost subconscious.
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But if you did have to add power, it's highly unlikely that the reason was because of your bank angle. You probably would have needed the extra power for the same reason in straight & level flight due to slight updrafts, downdrafts, etc.
 
Commander Dave said:
I'm not trying to start a debate over this but...

Slow Flight defined as I had posted: "...where any increase in angle of attack, increase in load factor, or reduction in power will result in an immediate stall"

This leaves you not just with the stall horn sounding (where you may have additional AOA left - maybe 5 to 1o knots above the stall in some single engine aircraft) but instead places you just above the stall.

Sheer physics will show that if I require 100% of the developed lift to maintain straight and level flight, and then divide that 100% by any amount (as in horizontal component of lift to turn) then I will need to increase my total lift, or give up some altitude.

Two options, increase back pressure (but you can't because any increase in back pressure would have resulted in an immediate stall - therefore you weren't in slow flight) or increase airspeed (throttle)

I know we're splitting hairs here. However in the teaching realm, the lesson I want the student to come away with is, when I devote some of my lift towards the turn in slow flight, a little throttle is required to compensate for the addition of the horizontal component of lift.
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"In theory, there's no difference between theory and practice. In practice, there is." -- unknown

In theory, you are correct - In practice, not so much.

Go back and read this post. A 10-degree bank in an airplane that stalls at 50 KCAS will result in the stall speed increasing by only 1/3 of a knot.

I guarantee that in stabilized MCA slow flight, you are not within 1/3 of a knot of the stall - You'd never be able to stabilize it that close to the stall. 1-2 knots, maybe - But then you're not in "theoretical" MCA flight, you're in "practical" MCA flight.

To understand why it is that you can't have stabilized slow flight that's literally right on the edge of the stall, you need to realize that the stall isn't something that happens all at once. Most modern airplanes incorporate some washout in their wing, and we're not flying through an ideal air mass (only a theoretical airplane can do so. ;)).

So no matter what airplane you're flying, different parts of the wing will stall at different speeds, and they'll come in and out of the stall at the same speed. That is probably at least partially the reason for the buffet that happens before the stall.

Go out in an airplane, and slow it down as slowly as you possibly can - 1 knot per 5-10 seconds would be great (but good luck actually achieving that). Look at what speed you first feel the buffet, and what speed the wing actually stalls. It'll probably take several times through the exercise to find the right numbers, but you'll see that the process of stalling probably takes 2-5 knots.

Thus, the 1/3 knot difference in stall speed that happens due to the 10-degree bank is insignificant in comparison. Any power changes you make in this process are more likely to be due to non-ideal factors in the air mass you're flying through rather than the tiny increase in load factor for such a small bank angle.

There's a place for teaching theory, but you also need to teach that theory and practice are different, and why. :yes:
 
flyingcheesehead said:
"In theory, there's no difference between theory and practice. In practice, there is." -- unknown

In theory, you are correct - In practice, not so much.

Go back and read this post. A 10-degree bank in an airplane that stalls at 50 KCAS will result in the stall speed increasing by only 1/3 of a knot.

I guarantee that in stabilized MCA slow flight, you are not within 1/3 of a knot of the stall - You'd never be able to stabilize it that close to the stall. 1-2 knots, maybe - But then you're not in "theoretical" MCA flight, you're in "practical" MCA flight.
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Are you calculating only load factor?
 
flyingcheesehead said:
What else would result in an increase in stall speed due solely to a changing bank angle?
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Is load factor the only delta between straight and level and turning flight?

What about increased induced drag on the high wing?

Isn't there form drag imposed by the rudder required to counter adverse yaw?
 
dmccormack said:
Is load factor the only delta between straight and level and turning flight?

What about increased induced drag on the high wing?

Isn't there form drag imposed by the rudder required to counter adverse yaw?
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:idea:which would also vary with which direction you're turning!:hairraise::cryin::D
 
flyingcheesehead said:
"In theory, there's no difference between theory and practice. In practice, there is." -- unknown

In theory, you are correct - In practice, not so much.

Go back and read this post. A 10-degree bank in an airplane that stalls at 50 KCAS will result in the stall speed increasing by only 1/3 of a knot.

I guarantee that in stabilized MCA slow flight, you are not within 1/3 of a knot of the stall - You'd never be able to stabilize it that close to the stall. 1-2 knots, maybe - But then you're not in "theoretical" MCA flight, you're in "practical" MCA flight.

To understand why it is that you can't have stabilized slow flight that's literally right on the edge of the stall, you need to realize that the stall isn't something that happens all at once. Most modern airplanes incorporate some washout in their wing, and we're not flying through an ideal air mass (only a theoretical airplane can do so.
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Why this is still continuing I'm not sure.

I never said the increase in bank angle (increasing load factor) is the reason for the application of power. True, at low bank angles the increase in stall speed is minimal.

The point of the maneuver (at the stage where we make turns in Slow Flight) IMHO is to teach the loss of lift due to the Horizontal Component taking away from the Vertical Component of Lift. I'll say this again, if truly at the edge of a stall (varying portions of the wing stalling independently aside) any loss of the Vertical Component (which is keeping you at your altitude) will result in a loss of altitude.

How do you propose we maintain that altitude???

I know of only two choices:

1) More back pressure (Elevator) - to increase lift

However we already said for this exercise we are to be at the edge of the stall where ANY increase in back pressure (Angle of Attack) will result in an IMMEDIATE stall - So that one's out.

2) Increase Power

In the scenario I presented this is the only option as I see it.
 
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