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Ed Cesnalis

-6 has best ANGLE of climb - debate resolved IMO

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9 hours ago, Ed Cesnalis said:

Okay,

I don't see how you are getting any closer to showing that dirty climbs steeper.

It is a long road, please bare with me.

Just like the car where there is only 1 RPM of tire rotation for every speed, in steady state flight there is only one angle of attack for each speed. For each speed there is only one power setting the will maintain altitude without climbing or descending. If you want to go faster you must change the angle of attack, and increase power to return to a steady state flight. I know in practice you increase power then change the angle of attack, but I want to show that it is the angle of attack that controls the speed not the power.

Excess or reserve power is the power that is left beyond what is needed to maintain level flight at the given speed. The power in reserve can be used for climb.

If you want to change speeds you choose a different angle of attack for the new speed and adjust power to maintain level flight, creating a different amount of reserve power to be used for climb.

So in steady state flight for every airspeed there is only one angle of attack. There is only one power setting that will maintain level flight for each airspeed. Any power left in reserve can be used for climbing.

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JLang   
6 hours ago, Ed Cesnalis said:

My POH has one Vx and does't identify which flaps.  

I know I seldom use Vx for -6.  

Comparing the settings remember the L stays constant

I have also stayed out of the fray due to time constraints, but I think here you proved the point made earlier: that you are confusing Vx and Vy.  You have stated that you use -6 to achieve best angle, and perform climbouts this way: take off with 15, then clean up and climb with -6 to achieve best angle.  How can you do this if you don't know Vx for -6, and "seldom use" it?  If you believe -6 achieves best angle, should you not also use Vx for -6 during your frequent canyon climb maneuvers?

Also, this point has been made before, but lift is NOT constant for all flap settings.

Question: why do flaps at 15 result in liftoff at lower speed than -6, or 0?

For your example with glide settings, what speeds are you using for -6, and 0, and 15?

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10 hours ago, Tom Baker said:

It is a long road, please bare with me.

Just like the car where there is only 1 RPM of tire rotation for every speed, in steady state flight there is only one angle of attack for each speed. For each speed there is only one power setting the will maintain altitude without climbing or descending. If you want to go faster you must change the angle of attack, and increase power to return to a steady state flight. I know in practice you increase power then change the angle of attack, but I want to show that it is the angle of attack that controls the speed not the power.

Excess or reserve power is the power that is left beyond what is needed to maintain level flight at the given speed. The power in reserve can be used for climb.

If you want to change speeds you choose a different angle of attack for the new speed and adjust power to maintain level flight, creating a different amount of reserve power to be used for climb.

So in steady state flight for every airspeed there is only one angle of attack. There is only one power setting that will maintain level flight for each airspeed. Any power left in reserve can be used for climbing.

Okay,

Now we are back to excess power (Not PA) can be used for climbing.

I'm  back to pointing out that excess power is not useful for showing which flap setting is capable of the steeper climb.

 

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10 hours ago, JLang said:

you proved the point made earlier: that you are confusing Vx and Vy

Perhaps you didn't read me correctly?

10 hours ago, JLang said:

You have stated that you use -6 to achieve best angle, and perform climbouts this way: take off with 15, then clean up and climb with -6 to achieve best angle.

I have been doing that routinely, obstacles haven't been an issue and I use absurdly long runways.

 

10 hours ago, JLang said:

How can you do this if you don't know Vx for -6, and "seldom use" it?  If you believe -6 achieves best angle, should you not also use Vx for -6 during your frequent canyon climb maneuvers?

I was contending that others seldom use it, I believe I am an exception because I am looking for best angle to clear terrain at -6 frequently.  I was shooting Mt Whitney and the southern Sierra this morning and used steepest angle at negative six several times.  I don't know Vx for any flap setting, my old CT provides few numbers.  I take my best guess at -6 just like I do at 15.

10 hours ago, JLang said:

Also, this point has been made before, but lift is NOT constant for all flap settings.

Actually it is.  Lift is precisely equal to current weight, changing flaps doesn't change weight and it doesn't change quantity of lift except momentarily before you are stabilized.

10 hours ago, JLang said:

Question: why do flaps at 15 result in liftoff at lower speed than -6, or 0?

Its due to the lower stall speed.

10 hours ago, JLang said:

For your example with glide settings, what speeds are you using for -6, and 0, and 15?

I see no point in gliding at 0, or 15 because -6 out performs every time.  

I fly at a lot of different weights so I find best glide visually and minimum sink by watching my VSI.

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13 hours ago, Ed Cesnalis said:

Okay,

Now we are back to excess power (Not PA) can be used for climbing.

I'm  back to pointing out that excess power is not useful for showing which flap setting is capable of the steeper climb.

 

I just want to make sure that we are on the same page. In level flight there is only one angle of attack for each speed, and only one power setting for the airplane to maintain level flight at that speed. And any available thrust not used for level flight can be used for climb. If you are not in agreement with these basics then we need go no further.

My next question to you is simple. What is the standard measurement used to measure climb in a aircraft?

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1 hour ago, Tom Baker said:

My next question to you is simple. What is the standard measurement used to measure climb in a aircraft?

What do you mean by 'standard'?  You are asking for a single measurement yet we measure climb 2 ways, for rate we use 'feet per minute' (in the US at least) and for angle I don't know of a commonly used 'measurement'.  

Degrees is commonly used for glidepath so I think degrees might be the answer here, I don't know.

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WmInce   
2 hours ago, Tom Baker said:

What is the standard measurement used to measure climb in a aircraft?

Vertical speed, as measured by feet per minute.

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40 minutes ago, Ed Cesnalis said:

What do you mean by 'standard'?  You are asking for a single measurement yet we measure climb 2 ways, for rate we use 'feet per minute' (in the US at least) and for angle I don't know of a commonly used 'measurement'.  

Degrees is commonly used for glidepath so I think degrees might be the answer here, I don't know.

It wasn't intended to be a trick question. The answer is feet per minute. I don't think I have ever flown a airplane that can actually measures angle of climb or descent.

And are you in agreement with the statement in my earlier post?

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WmInce   
1 minute ago, Tom Baker said:

I don't think I have ever flown a airplane that can actually measures angle of climb or descent.

They do exist, I have flown several, but they are expensive pieces of equipment.

  • Upvote 1

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2 minutes ago, WmInce said:

They do exist, I have flown several, but they are expensive pieces of equipment.

I had no doubt that it did exist in the military or commercial air transport, but I have never flown anything like that. 

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4 minutes ago, Tom Baker said:

It wasn't intended to be a trick question. The answer is feet per minute. I don't think I have ever flown a airplane that can actually measures angle of climb or descent.

And are you in agreement with the statement in my earlier post?

ft/min for rate ft(vert)/ft(horiz) or degrees for angle.

I agree with your statement.  I also agree that 'excess power' can be used for additional speed in lieu of climb and when used for climb it can be used to pursue said climb at various speeds or angles.

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11 minutes ago, Ed Cesnalis said:

ft/min for rate ft(vert)/ft(horiz) or degrees for angle.

I agree with your statement.  I also agree that 'excess power' can be used for additional speed in lieu of climb and when used for climb it can be used to pursue said climb at various speeds or angles.

You keep trying to derail where I am going by adding irrelevant additional information. Additional speed comes from the decrease in angle of attack. The excess power that you had at the old speed can be used to maintain altitude at the new speed. I know in practice we do the reverse by adding power first to accelerate, but the acceleration in speed doesn't happen until the angle of attack is reduced. Remember acceleration doesn't always mean a change in speed, it could mean a increase in climb rate.

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Would you agree with the statement that the best rate of climb speed will be the speed at which the airplane can maintain level flight at the lowest power setting, because you have the most reserve power available for climb?

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WmInce   
41 minutes ago, Tom Baker said:

Would you agree with the statement that the best rate of climb speed will be the speed at which the airplane can maintain level flight at the lowest power setting, because you have the most reserve power available for climb?

Wouldn't that be at the critical AOA?

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42 minutes ago, WmInce said:

Wouldn't that be at the critical AOA?

I have always heard that critical AoA is the point where the wing stalls. As you start slowing down the power required to maintain level flight reduces to a certain point, then it starts to go back up again.

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WmInce   
42 minutes ago, Tom Baker said:

I have always heard that critical AoA is the point where the wing stalls. As you start slowing down the power required to maintain level flight reduces to a certain point, then it starts to go back up again.

That's true. I should have said "just before critical AOA is reached."

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3 hours ago, Tom Baker said:

You keep trying to derail where I am going by adding irrelevant additional information. Additional speed comes from the decrease in angle of attack. The excess power that you had at the old speed can be used to maintain altitude at the new speed. I know in practice we do the reverse by adding power first to accelerate, but the acceleration in speed doesn't happen until the angle of attack is reduced. Remember acceleration doesn't always mean a change in speed, it could mean a increase in climb rate.

I'm not trying to derail but like stay on a track. 

This is a major point of contention not irrelevant.  I agree if I use 'available power' for additional speed that you will then term that consumed power something else, diminishing or totally consuming 'available power'

Can you agree that this is quite different from the term commonly taught in aeronautics TA which represents for our purposes the power available from the propeller driven by the Rotax 912ULS with airframe costs like drag already subtracted? Its noteworthy that after I use TA for additional climb or speed that unlike your 'available power' it doesn't go away allowing for a comparison between flap settings.  

TA provides an instant illumination that -6 has more thrust available than 15 that can be used for climbing including at Vx speed.

The term available power only drags us into mud as far as I can see.

Not derailing just pointing out where I see clarity.

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Ed,

If I say excess power or reserve power I am saying the same thing you are saying when you say available power. It is the power that is left over beyond what is needed to  overcome drag and provide the lift needed for level flight.

If you chose to change speed, then the amount of available power will be different at the new speed.

Using this power to change speeds is irrelevant in regards to a discussion on climb.

8 hours ago, Tom Baker said:

Would you agree with the statement that the best rate of climb speed will be the speed at which the airplane can maintain level flight at the lowest power setting, because you have the most reserve power available for climb?

You never did answer this question. 

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3 hours ago, Tom Baker said:

If I say excess power or reserve power I am saying the same thing you are saying when you say available power. It is the power that is left over beyond what is needed to  overcome drag and provide the lift needed for level flight.

Really?  

They ARE NOT THE SAME - YOU EVEN HAVE AVAILABLE POWER WRONG!!!!!!!!!!!!!!!!!!!!!!!!

Sorry but I have said it over and over and over and you haven't heard me yet.

TA is commonly taught and it doesn't mean what you just said it means.

Available Power is sometimes taught along with TA and it doesn't define like you do.

Here are definitions on flash cards - tell me you see they are not the same as yours, okay?Capture.PNG.ac41106ce080f639da8845fd2a01cd4f.PNG

Capture1.PNG.45ab84941ca2f7cec349a2ac7910310e.PNG

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@Tom Baker Here's why the definitions taught are useful:

Quote

Thrust available, denoted by TA, is the thrust provided by the power plant of the airplane. Unlike the thrust required TR which has almost everything to do with the airframe (including the weight) of the airplane and virtually nothing to do with the power plant, the thrust available TA has almost everything to do with the power plant and virtually nothing to do with the airframe.

See how useful this is?

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@Tom Baker

I have now seen your definition used on Aeronautic lessons as well.  Using it means conclusions can be arrived at but relative flap performance doesn't seem to be one of them. 

The TA definition seems to be far more mainstream and it does lead to a conclusion about relative performance at various flap settings.

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@Tom Baker

I have yet to see where you are going with your excess power definition.  Here is a comparison of the 2:

  • Commonly used TA and TR - results in more thrust available and therefore more power available at -6. More power at -6 available for speed or climb, rate or angle.
  • Less commonly use 'Excess power' - results in more power available available as speed reduces.  The conclusion is the most power is available at the lowest speed which might be true for angle but not for rate or speed.

The top speed difference between -6 and 15 is huge because the drag difference is huge.  This same delta, more TA (power available from engine) and less TR (drag from air frame) exists for climb again give -6 a huge advantage.

 

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Ed, you have jumped around using the terms thrust and power. They are 2 different things in respect to climb. Just like torque and horsepower are different in a car.
 
Your claim has been that a airplane will have the best rate of climb at -6 because it has less drag, and more power available for climb. I have always said that is correct.
 
Since the speed for best rate of climb has the lowest drag, wouldn't any change from that speed have more drag? Isn't Vx always a slower speed than Vy, except when you reach the absolute ceiling for the airplane? If Vx is slower than Vy and you have more drag, doesn't it stand to reason that climbing at Vx is not dependent on having the least amount of drag and the most available power?
 
Angle of climb is dependent on available thrust not power. Would you agree that you have more thrust available at a slower speed? When you are climbing at VX your rate of climb will always be less than when climbing at Vy because you have less power available. Even though you have a lower rate of climb doesn't mean you can't have a steeper angle.

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20 minutes ago, Tom Baker said:

Ed, you have jumped around using the terms thrust and power. They are 2 different things in respect to climb. Just like torque and horsepower are different in a car.

I understand that to get to power from thrust you have to apply time, for our purposes this hasn't been a meaningful distinction at least yet.

 

21 minutes ago, Tom Baker said:

Your claim has been that a airplane will have the best rate of climb at -6 because it has less drag, and more power available for climb. I have always said that is correct.

Common ground - cool

 

21 minutes ago, Tom Baker said:

Since the speed for best rate of climb has the lowest drag, wouldn't any change from that speed have more drag? Isn't Vx always a slower speed than Vy, except when you reach the absolute ceiling for the airplane? If Vx is slower than Vy and you have more drag, doesn't it stand to reason that climbing at Vx is not dependent on having the least amount of drag and the most available power?

No that doesn't stand to reason.  The fact the Vx is slower than Vy for either flap setting doesn't change the fact that improving Vx requires either more thrust or less thrust required.

Steep climb performance means a high rate of velocity that includes a large vertical component.  Obviously that vertical component is very power dependent.

 

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