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Ed Cesnalis

-6 has best ANGLE of climb - debate resolved IMO

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The concensus was argued for 15degrees being steepest like this:

  • 15degrees is steepest - 15degrees has the most excess power at its slow speed and excess power is used to achieve climb including steepest angle

The -6 argument:

  • -6degrees is steepest --6degrees has the most thrust available due to it being the lowest drag setting and available thrust is used to achieve climb including steepest angle

 

The Aerodynamic lesson below illuminated the correct terms, definitions and theory.

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I have never said that climb at 15° has more excess power. What have constantly said, unless I had a slip on the keyboard, was that excess power was not a factor in how steep a airplane climbs. What determines how steep an airplane climbs is a factor of forward speed compared to rate of climb.

Excess power effects rate of climb not angle of climb

Speed is controlled by angle of attack

Your chart is 100% correct, and what I am saying does not deviate from that. What your chart doesn't say is that in addition to having excess thrust for acceleration you must decrease the angle of attack for the velocity to increase.

Also you need to remember that when discussing aviation that acceleration does not necessarily mean an increase in forward velocity.  

 You seem to be seeing only what you want to see, and not what I typed.

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1 hour ago, Tom Baker said:

I have never said that climb at 15° has more excess power. What have constantly said, unless I had a slip on the keyboard, was that excess power was not a factor in how steep a airplane climbs. 

A number of people contributed to your side of this argument.  I couldn't attempt to compare the arguments simply as I did above and quote everyone precisely.

1 hour ago, Tom Baker said:

What determines how steep an airplane climbs is a factor of forward speed compared to rate of climb.

forward speed compared to rate of climb is a measurement of a resulting angle it doesn't determine anything it is a result. Think cause and effect.

1 hour ago, Tom Baker said:

Excess power effects rate of climb not angle of climb

1) excess power as you define it can't compare Vx performance at 2 flap settings.  You won't even address that and keep going back to it.

2)the idea the power does not effect the angle of climb is as foreign as you insisting that power doesn't effect speed.

115hp CT has a much faster top speed then an 80hp CT due to the power increase - period.  Power is used to increase speed on the takeoff roll without a change in angle of attack.

1 hour ago, Tom Baker said:

Your chart is 100% correct, and what I am saying does not deviate from that.

The chart says excess thrust can be used for speed or climb and you always say that excess power can only be used for climb not speed.

Both can't be right.

2 hours ago, Tom Baker said:

What your chart doesn't say is that in addition to having excess thrust for acceleration you must decrease the angle of attack for the velocity to increase. Also you need to remember that when discussing aviation that acceleration does not necessarily mean an increase in forward velocity.  

How does any of this explain the relative Vx perforance of -6 vs 15?  Your really loosing me here.

Consider that TA in our CTs is greatest at -6 and can be applied to climb or speed per the chart you agree with.  Its best at -6 because of lowest drag. This is a logical explanation that shows why best angle is at -6.

Your basis of 'excess power' isn't a fixed point and can't be used to compare the 2.  

I used to believe as you did until Fast Eddie challenged me.  I couldn't prove me point because both can't be true.  

Either dirty climbs steeper or clean climbs steeper. Both can't be true.

I try to see your logic but I know that power does effect speed.  It takes a plane with a lot of power to go really fast right?

100hp plane can't cruise fast it lacks the power.  300hp plane can cruise very fast, power does effect speed and climb including angle.

You can increase the angle a STOl plane can achieve by installing a more powerful motor.

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Ed, I have explained it several time, but you only seem to be seeing what you want in my post.

Lets start at the beginning and get this hammered out.

What is your definition of "STEEPER"?

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22 minutes ago, Tom Baker said:

Ed, I have explained it several time, but you only seem to be seeing what you want in my post.

Lets start at the beginning and get this hammered out.

What is your definition of "STEEPER"?

Sure Tom,

Steeper means a greater angle between 0 degrees and 90 degrees.

An example would be arriving at the departure end of the runway at pattern altitude takes a very steep climb.  

Noteworthy: we have a gauge VSI that reads out rate but none that tells us angle or steepness.  I can read my pitch attitude but of course not the same at all.

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2 hours ago, Ed Cesnalis said:

Pilot controls speed with pitch and power adjustments.

Can you change speed with pitch alone?

Can you change speed with power alone?

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18 minutes ago, Tom Baker said:

Can you change speed with pitch alone?

Most of the time my throttle is already wide open and pitch is my only option so I'll say yes.

19 minutes ago, Tom Baker said:

Can you change speed with power alone?

I sometimes maintain a level pitch attitude and adjust my throttle setting to change my speed so I'll say yes again.

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6 minutes ago, Ed Cesnalis said:

Most of the time my throttle is already wide open and pitch is my only option so I'll say yes.

I sometimes maintain a level pitch attitude and adjust my throttle setting to change my speed so I'll say yes again.

You are OK on the first one, but I have some homework for you on the second one.                                                                           VVV This is the critical part VVV

The next time you are out flying set your throttle at 5000 RPM and trim for level flight. Make note of your airspeed. Now without adjusting trim or adding pressure on the control stick increase power to full throttle. Let things stabilize 30 seconds or so, and make note of your speed. Now reduce power to 4500RPM and let things stabilize. Make note of your speed.

Report back with your findings. I have done this 100's of times with students before, so I know what the results will be.

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52 minutes ago, Tom Baker said:

You are OK on the first one, but I have some homework for you on the second one.                                                                           VVV This is the critical part VVV

The next time you are out flying set your throttle at 5000 RPM and trim for level flight. Make note of your airspeed. Now without adjusting trim or adding pressure on the control stick increase power to full throttle. Let things stabilize 30 seconds or so, and make note of your speed. Now reduce power to 4500RPM and let things stabilize. Make note of your speed.

Report back with your findings. I have done this 100's of times with students before, so I know what the results will be.

I was going to qualify my response by saying you could argue that maintaining my level attitude is a pitch adjustment but I decided its not and didn't include it.

I don't need the homework I too know that maintaining my level attitude will likely take some active pressure and re-trim.  

I can change speed with power alone but I have to fly the plane, it will surely react at least momentarily. It might balloon or sink but I only fail your test if I change my pitch which I won't permit.  So my answer remains yes I can change my speed with power adjustment alone, a pitch and power adjustment isn't always necessary but pitch and power adjusted together generally gets a better result if you are good at controlling the plane.

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1 hour ago, Tom Baker said:

You are OK on the first one, but I have some homework for you on the second one.                                                                           VVV This is the critical part VVV

The next time you are out flying set your throttle at 5000 RPM and trim for level flight. Make note of your airspeed. Now without adjusting trim or adding pressure on the control stick increase power to full throttle. Let things stabilize 30 seconds or so, and make note of your speed. Now reduce power to 4500RPM and let things stabilize. Make note of your speed.

Report back with your findings. I have done this 100's of times with students before, so I know what the results will be.

I'll give you a more detailed answer so we can move this along.  Remember the objective is to demonstrate that -6 doesn't produce the steepest angle.

I would in fact be unable to adjust my speed with power alone and maintain my level flight because my new speed would result in a new deck angle and new angle of attack if I maintained level flight in stead of level pitch.  So I concede your point before you make it again, I can't change the speed and maintain my slope/climb/level and maintain my pitch.  That's why I said pitch and power adjustments, that's the advanced technique that allows you to avoid as much disruption.

Acknowledging the angle of attack adjustment does not negate the role power or thrust play in speed.  

I operate in a high altitude mountain environment and when I build or buy an airplane I carefully consider the amount of hp and the power to weight ratio.  I need sufficient power for the 3 things we are talking about

  1. Top speed
  2. Rate of climb
  3. Angle of climb 

Without enough horse power 1 or 2 or 3 of those will fall short of my needs.  To think power isn't related to speed is somewhere you can't get me to go without something new.

 

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My findings have always been if you change pitch alone your speed will change. If you change power alone the airplane will climb or descend while speed stays the same. 

 

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1 minute ago, Tom Baker said:

My findings have always been if you change pitch alone your speed will change. If you change power alone the airplane will climb or descend while speed stays the same. 

 

No argument there. Its a good reason to tell your students what you do.

However - try this perspective

  • We are cruising level in our CT and partial throttle and 75kts IAS  
  • We advance the throttle to full and accelerate to 110kts IAS but remain level.

That's a huge increase in speed that resulted from accessing something like 85hp instead of 45hp and we remained level but our angle of attack had to be adjusted.

That increase in speed is the result of the additional thrust.  The angle of attack adjustment was necessary to remain level was an adjustment made by the pilot to apply the additional power to speed instead of climb.  The pitch / angle of attack change was responsible only for the high speed being the result of the new power instead of climb being the result.

 

 

 

 

 

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5 minutes ago, Ed Cesnalis said:

No argument there. Its a good reason to tell your students what you do.

However - try this perspective

  • We are cruising level in our CT and partial throttle and 75kts IAS  
  • We advance the throttle to full and accelerate to 110kts IAS but remain level.

That's a huge increase in speed that resulted from accessing something like 85hp instead of 45hp and we remained level but our angle of attack had to be adjusted.

That increase in speed is the result of the additional thrust.  The angle of attack adjustment was necessary to remain level was an adjustment made by the pilot to apply the additional power to speed instead of climb.  The pitch / angle of attack change was responsible only for the high speed being the result of the new power instead of climb being the result.

 

 

 

 

 

If you pitch for the same angle of attack without changing your power what will the speed be?

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39 minutes ago, Tom Baker said:

My findings have always been if you change pitch alone your speed will change. If you change power alone the airplane will climb or descend while speed stays the same. 

 

When the plane climbs or descends (assuming constant pitch attitude ) the relative wind picks up a vertical component which means a new angle of attack and new speed.

 

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1 minute ago, Tom Baker said:

If you pitch for the same angle of attack without changing your power what will the speed be?

If you don't change angle of attack speed won't change.  I've agreed with that already.

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If I don't take my car out of 1st gear it won't go 100mph.  Power is still what makes it go 100mph not the transmission.

Power makes my car go fast but only when its in its fastest gear.

Power makes my plane go fast but only when the angle of attack permits it.

 

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My tablet doesn't play well with the forum, so this will be my last post before tomorrow morning. 

I'll expand on your car analogy.  For your car to go 100 MPH there is only one specific RPM the wheels can be turning to achieve that speed. It doesn't matter if you are using power or rolling down hill, if the wheels are turning that RPM your speed will be 100 MPH.

For the airplane there is only one angle of attack that will allow it to fly 100 KTS. It doesn't matter if you are using power to maintain level flight, climbing, or no power and descending the angle of attack remains the same.

I will say as I have always said the above angle of attack will change slightly due to different weights or conditions.

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2 minutes ago, Tom Baker said:

My tablet doesn't play well with the forum, so this will be my last post before tomorrow morning. 

I'll expand on your car analogy.  For your car to go 100 MPH there is only one specific RPM the wheels can be turning to achieve that speed. It doesn't matter if you are using power or rolling down hill, if the wheels are turning that RPM your speed will be 100 MPH.

For the airplane there is only one angle of attack that will allow it to fly 100 KTS. It doesn't matter if you are using power to maintain level flight, climbing, or no power and descending the angle of attack remains the same.

I will say as I have always said the above angle of attack will change slightly due to different weights or conditions.

Okay,

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

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Ed,

It's not always aerodynamically "dirty" to have the flaps down at 15 degrees, and certainly not at zero. At low speeds those are the lowest drag (best L/D) flap positions. To climb steeply, you need low speed.

Please do not construe my lack of further discourse on this subject as concession. I'm merely trying to budget my time so as to concentrate my efforts on more constructive activities. In this case, cleaning out the cat box is the obvious choice.

Mike Koerner

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Ed,

Here's a few questions for ya'. No tricks intended.

When your aircraft is at approx. 1300 lbs., what is Vx airspeed at -6° flaps?

What is it at 0° flaps?

What is it at 15° flaps?

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46 minutes ago, WmInce said:

Ed,

Here's a few questions for ya'. No tricks intended.

When your aircraft is at approx. 1300 lbs., what is Vx airspeed at -6° flaps?

What is it at 0° flaps?

What is it at 15° flaps?

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

I know I seldom use Vx for -6.  

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6 hours ago, Mike Koerner said:

Ed,

It's not always aerodynamically "dirty" to have the flaps down at 15 degrees, and certainly not at zero. At low speeds those are the lowest drag (best L/D) flap positions. To climb steeply, you need low speed.

Please do not construe my lack of further discourse on this subject as concession. I'm merely trying to budget my time so as to concentrate my efforts on more constructive activities. In this case, cleaning out the cat box is the obvious choice.

Mike Koerner

Hi Mike,

You have mentioned this before and we are not in agreement here. - with all due respect.

Comparing the settings remember the L stays constant, lift is the same at any of these 3 settings but drag goes up as the flaps come down making the L/D worse every time you lower.

All you have to do to see that 15 and zero are not the lowest drag, best L/D positions is to set up a glide first with your field fixed in your windshield and then deploy the zero or 15 setting.  You will now be unable to make the field, happens every time.

Those settings have more drag that require more thrust. Thrust that would otherwise contribute to glide or climb.

Best,

Ed Cesnalis

BTW - Targets this morning are Mt Brewer and then on to Glacier Ridge.  Flew by with my girlfriend a few days ago but she was too freaked out to let me use the camera :) .  Going this morning with a 'no fear' assistant.

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