Low altitude steep descending turns...

2Airtime2

2Airtime2

Pre-takeoff checklist
Joined
Nov 5, 2015
Messages
197
Location
Raleigh, NC
Display Name
Display name:
Cherokee 180c
I'm training in a c172 and am in the process of buying a Cherokee 180.

When turning in the pattern, usually to final, sometimes the wind is such that I want/need to turn steeper. When around 75 kts how close are you getting to a stall condition at 30 degrees, at 45 degrees, at 60 degrees?

Am I correct that the slower you are going and the steeper you turn the higher the stall speed (plane stalls more easily) ?

Someone tell the difference in stall speed in the above scenarios when descending vs. holding altitude. I think if you are turning steep and descending the stall speed is lower (safer) than if you were holding altitude. Is that correct?

Which has a greater angle of attack? Steep altitude holding turns or steep descending turns?
 
Last edited:
You are asking the right questions and you really should discuss them with your flight instructor and do some practice at altitude to see what it takes to stall it with the conditions you describe.

It sounds like you've got most of the concepts in mind but haven't reached the point of grasping them fully. One big point you may be missing is good ole force of gravity. Question for you: can you stall a wing at zero "g"?
 
Play with it at altitude, just remember to keep the ball centered, or flying with a relaxed back you should feel any side loading.

It also depends on how much power you're bringing into the turn, stol kit, weight and turbulence.
 
Clark1961 said:
You are asking the right questions
I know the inside wing will be closer to a stall condition. If I'm in a low altitude steep turn I want to know how close I am to dropping that wing.

Question for you: can you stall a wing at zero "g"?
Click to expand...
Hey buddy, I'll be the one asking the questions in my thread. :D

Lol. I don't know but I suspect the answer is no. A stall is when the wing quits generating lift. Lift is not needed if you are in a 0 g environment. Wait a second. When you are descending you are approaching 0g, correct? It sounds like you made me think of the correct answer. The lower the g's, the safer it is to turn since the harder it will be for the wing to stall.

Am I close to the correct track?
 
2Airtime2 said:
Which has a greater angle of attack? Steep altitude holding turns or steep descending turns?
Click to expand...

Steep turns trying to maintain altitude have a higher angle of attack than steep descending turns.

Think of it this way: The angle of attack has nothing to do with the bank of the aircraft. It has to do with the angle that the wing is in relation to the air it is moving through. So you are increasing the angle of attack when you increase the elevator back pressure to maintain altitude in the steep turn.
 
Fearless Tower said:
Steep turns trying to maintain altitude have a higher angle of attack than steep descending turns.

Think of it this way: The angle of attack has nothing to do with the bank of the aircraft. It has to do with the angle that the wing is in relation to the air it is moving through. So you are increasing the angle of attack when you increase the elevator back pressure to maintain altitude in the steep turn.
Click to expand...

This is what I thought but I didn't know exactly why. Thank you. So steep descending turns can be done relatively safely. This is good since they are exciting and fun.

My questions (obviously) stem from not wanting to stall at 500' agl.

:)
 
my instructor said "no more than normal rate turns in the pattern" I think it is a good rule to live by
 
I do agree with that and want to be as safe a pilot as possible. I think fully understanding the capabilities/mannerisms of the aircraft will help with that.

I've read some pilots say they prefer a tight pattern. Seems to me a tight pattern involves steeper turns so I want to know what's safe and what isn't.
 
2Airtime2 said:
Hey buddy, I'll be the one asking the questions in my thread. :D

Lol. I don't know but I suspect the answer is no. A stall is when the wing quits generating lift. Lift is not needed if you are in a 0 g environment. Wait a second. When you are descending you are approaching 0g, correct? It sounds like you made me think of the correct answer. The lower the g's, the safer it is to turn since the harder it will be for the wing to stall.

Am I close to the correct track?
Click to expand...

First wrong statement. A stall is NOT when the wing quit's generating lift. A stall occurs at the point where the critical angle of attack is exceeded. This is the point where further increase in angle of attack does not result in an increase in lift. In fact, the lift vs. angle curve is fairly symmetrical arouind this point.

Second wrong statement: A descent is NOT approaching zero g. It's not even, other than transiently, less than 1G. A steady rate of descent is a 1G operation. Any how, the number of G's has nothing to do with stalling. ANGLE OF ATTACK is the only thing that causes stalls.
 
2Airtime2 said:
I've read some pilots say they prefer a tight pattern. Seems to me a tight pattern involves steeper turns so I want to know what's safe and what isn't.
Click to expand...
People that fly tighter patterns are typically descending while turning.

I fly a pretty tight pattern in my biplane, but from the point abeam the touchdown area on downwind, I am in a continuous descent.
 
Ok, first of all you really never need to bank more than 30° in the pattern. It's a good rule to follow and the mark of a good pilot.

Secondly, airplanes turn because of the back pressure (tail down force). That's what increases the angle of attack and causes curving flight. Straight and level is really a special case situation--there's a tail down force and angle of attack, but no turn results because gravity is constantly canceling the inherent curve the plane is trying to make (a loop). If there were no gravity during straight flight, there'd be no need for back pressure (tail down force), no angle of attack and no curving force. To curve, you need back pressure more than enough to counter gravity.

Canadians believe the angle of attack increases in a descending turn and vice-versa in a climb. In the US, we don't.

Stall speed increases in steeper turns because in order to achieve the tighter turn radius you have to increase the angle of attack. If you lessen the angle (of attack) to the point of zero 'g'--you won't turn anymore, thus defeating the purpose.

dtuuri
 
Last edited:
I wouldn't go that far.
 
dtuuri said:
Canadians believe the angle of attack increases in a descending turn and vice-versa in a climb. In the US, we don't.
Click to expand...

Curious, how do you know this? Is it written somewhere? :rolleyes:
 
dtuuri said:
Yes, in Canada.

dtuuri
Click to expand...

Yeah, you stated in Canada. But how do you know this? Is it written somewhere, or you heard it from someone, maybe a Canadian? IOW do you have a reference?
 
Last edited:
mscard88 said:
Yeah, you stated in Canada. But how do you know this? Is it written somewhere, or you heard ot from someone, maybe a Canadian? IOW do you have a reference?
Click to expand...

Not without researching it. Over the years I've simply noticed that they expound upon that idea, but we don't.

dtuuri
 
dtuuri said:
Not without researching it. Over the years I've simply noticed that they expound upon that idea, but we don't.

dtuuri
Click to expand...

I concur. I fly to/from Canada a lot, and every time I cross the border I need to make a slight trim change.
 
RotorDude said:
I concur. I fly to/from Canada a lot, and every time I cross the border I need to make a slight trim change.
Click to expand...

That is a direct result of the hot air from the French contingent that forces the airplane upward. Greater effect in eastern Canada than west.
 
dtuuri said:
Ok, first of all you really never need to bank more than 30° in the pattern. It's a good rule to follow and the mark of a good pilot.

Secondly, airplanes turn because of the back pressure (tail down force). That's what increases the angle of attack and causes curving flight. Straight and level is really a special case situation--there's a tail down force and angle of attack, but no turn results because gravity is constantly canceling the inherent curve the plane is trying to make (a loop). If there were no gravity during straight flight, there'd be no need for back pressure (tail down force), no angle of attack and no curving force. To curve, you need back pressure more than enough to counter gravity.

Canadians believe the angle of attack increases in a descending turn and vice-versa in a climb. In the US, we don't.

Stall speed increases in steeper turns because in order to achieve the tighter turn radius you have to increase the angle of attack. If you lessen the angle (of attack) to the point of zero 'g'--you won't turn anymore, thus defeating the purpose.

dtuuri
Click to expand...

I've certainly heard that adding back pressure causes turns, but I can turn an airplane with my hands in my lap. So, that's clearly an oversimplification. Not that it's a great idea in the pattern.

I'll agree with the trend -- more back pressure means a faster turn -- but your zero point is in the wrong place.
 
2Airtime2 said:
I do agree with that and want to be as safe a pilot as possible. I think fully understanding the capabilities/mannerisms of the aircraft will help with that.

I've read some pilots say they prefer a tight pattern. Seems to me a tight pattern involves steeper turns so I want to know what's safe and what isn't.
Click to expand...

As has already been said, you won't need more than a 30* bank in the pattern. If you need to fly the downwind in close your turns will remain the same while the straight lines between them get shorter. When asked to fly a tight pattern the key is to slow the plane. My home strip intimidates new and visiting pilots because the available pattern space is very compact and very busy. We still fly squared patterns and generally use 30* turns.

Old instructors used to do a landing drill that may help you. Abeam the threshold they'd pull power to idle and the pilot was expected to make a normal approach and landing. Energy management. That'll teach you about approach altitudes, speeds, and turns better than most drills.
 
MAKG1 said:
I've certainly heard that adding back pressure causes turns, but I can turn an airplane with my hands in my lap. So, that's clearly an oversimplification. Not that it's a great idea in the pattern.
Click to expand...
When I wrote "back pressure" I also put in parentheses (tail down force) to clarify that the amount of back pressure is a result of trim preference--it can be anything the pilot desires without affecting the result. You cannot turn without tail down force. The pilot's share of the force is adjustable.

MAKG1 said:
I'll agree with the trend -- more back pressure means a faster turn -- but your zero point is in the wrong place.
Click to expand...

:confused: "Zero point"? You cannot turn with zero 'g', but you can fall.

dtuuri
 
Last edited:
dtuuri said:
Ok, first of all you really never need to bank more than 30° in the pattern. It's a good rule to follow and the mark of a good pilot.

Secondly, airplanes turn because of the back pressure (tail down force). That's what increases the angle of attack and causes curving flight. Straight and level is really a special case situation--there's a tail down force and angle of attack, but no turn results because gravity is constantly canceling the inherent curve the plane is trying to make (a loop). If there were no gravity during straight flight, there'd be no need for back pressure (tail down force), no angle of attack and no curving force. To curve, you need back pressure more than enough to counter gravity.

Canadians believe the angle of attack increases in a descending turn and vice-versa in a climb. In the US, we don't.

Stall speed increases in steeper turns because in order to achieve the tighter turn radius you have to increase the angle of attack. If you lessen the angle (of attack) to the point of zero 'g'--you won't turn anymore, thus defeating the purpose.

dtuuri
Click to expand...

How the heck is the OP gonna do a decent overhead with only 30 degrees of bank???
 
MAKG1 said:
I've certainly heard that adding back pressure causes turns, but I can turn an airplane with my hands in my lap.
Click to expand...

You can, but you won't maintain altitude (at least not for long) in that turn without either increasing back pressure, adjusting trim or adding power.
 
dtuuri said:
When I wrote "back pressure" I also put in parentheses (tail down force) to clarify that the amount of back pressure is a result of trim preference--it can be anything the pilot desires without affecting the result. You cannot turn without tail down force. The pilot's share of the force is adjustable.



:confused: "Zero point"? You cannot turn with zero 'g', but you can fall.

dtuuri
Click to expand...

You don't get zero G with zero back pressure.

And you can turn with a neutral elevator, at least in slow or fast cruise. You will lose altitude.

You can't fly at all without tail down force. What are you trying to say?

I thin a lot of these arguments go south because of implicit assumptions of level flight. Allowing descent changes things.
 
Last edited:
MAKG1 said:
You don't get zero G with zero back pressure.
Click to expand...
Depends on how you trimmed it, but there would be no point in trimming for zero 'g' and there may not be enough trim available to hold zero AoA anyway. Back pressure is just the chosen portion of the total down force on the tail. The rest goes unfelt.

MAKG1 said:
And you can turn with a neutral elevator, at least in slow or fast cruise.
Click to expand...
Again, there is an unfelt tail down force if you are turning with no perceptible back pressure.

MAKG1 said:
You can't fly at all without tail down force. What are you trying to say?
Click to expand...
That you can't turn if you aren't flying--you're falling. :)

dtuuri
 
MAKG1 said:
I thin a lot of these arguments go south because of implicit assumptions of level flight. Allowing descent changes things.
Click to expand...

So, assume we're talking gliders--they're always descending even when ascending.

dtuuri
 
To the OP, get your instructor to take you to a comfortable altitude and while using approach power and flaps do a 30, 45, and 60* turn and observe your rate of descent. The only way you'll arrest or control that rate is with power, just as you should already know from doing steeps or turns around a point. That's not a good idea for a low time pilot in an approach scenario. Ask to do 30* approach simulations at different speeds. That's easily done at lower altitudes where you have a ground reference. Your turn radius will be smaller when slower but get too slow and you'll need to add power again. It's a balancing act and conditions may warrant different actions. Learn to feel the airplane.
 
dtuuri said:
So, assume we're talking gliders--they're always descending even when ascending.

dtuuri
Click to expand...

Not always true. With enough starting airspeed (inertia), a glider can climb. A high performance/low drag one can do an entire aerobatic routine after a low pass over the runway.
 
2Airtime2 said:
I do agree with that and want to be as safe a pilot as possible. I think fully understanding the capabilities/mannerisms of the aircraft will help with that.

I've read some pilots say they prefer a tight pattern. Seems to me a tight pattern involves steeper turns so I want to know what's safe and what isn't.
Click to expand...
The idea behind a tight pattern is if your engine goes out while you are adjusting things for landing, you can still make the runway.

You can fly a tight pattern, basically a u turn to the runway and keep the turn at 30 degrees.
 
RotorDude said:
Not always true. With enough starting airspeed (inertia), a glider can climb. A high performance/low drag one can do an entire aerobatic routine after a low pass over the runway.
Click to expand...

Exactly, the thing people confuse all the time is ENERGY versus motion. A glider is always losing energy. It's not true that it's always descending in any sense (either aerodynamically or with respect to the ground).
 
flyingron said:
Exactly, the thing people confuse all the time is ENERGY versus motion. A glider is always losing energy. It's not true that it's always descending in any sense (either aerodynamically or with respect to the ground).
Click to expand...

To be exact, it's not true that "a glider is always losing energy."
Each time it finds lift -- and that could be thermal, ridge, wave or dynamic -- it gains energy. That's how it can go on long cross countries and stay in the air for many hours.
 
RotorDude said:
To be exact, it's not true that "a glider is always losing energy."
Each time it finds lift -- and that could be thermal, ridge, wave or dynamic -- it gains energy. That's how it can go on long cross countries and stay in the air for many hours.
Click to expand...

Good point.
 
You must log in or register to reply here.
Back
Top