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The best rate-of-climb and angle-of-climb is always reached with flaps up.


Ed Cesnalis

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9 minutes ago, Ed Cesnalis said:

Clearly FD numbers favor zero over reflex by a small amount on rate while reflex wins on angle.

They don't provide numbers in the chart for reflex flaps only 0° and 15°. In the numbers I ran 15° wins on angle, and 0° wins on rate. This goes with what my finding were when I did my limited flight testing.

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4 minutes ago, Ed Cesnalis said:

No, here I don't agree.  Your statement is wrong in that lift and drag are only lower when measured at the same true air speed but we don't fly or measure that way we use indicated airspeed and at that constant L&D don't change either quantity or ratio, why would they?

The wing 'doesn't care' about the true speed but only the amount of force that results from the air impact/flow.

 

Your original statement:  "Your assumption that drag is lower and lift is at a premium at altitude is probably wrong".  So either you don't agree that drag and lift are lower at higher DA, in conflict with every aerodynamics book ever published, or I'm misunderstanding what you are saying and we are in agreement.  I will let you decide which.   ;)

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2 minutes ago, Tom Baker said:

They don't provide numbers in the chart for reflex flaps only 0° and 15°. In the numbers I ran 15° wins on angle, and 0° wins on rate. This goes with what my finding were when I did my limited flight testing.

Thanks,

zero vs 15 is the one I have the best feel for because of hour 500' high ridge at the departure end.  Its hard to ignore that I get above it if I clean to neg six, I'm equal at zero and below at 15.

 

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9 minutes ago, FlyingMonkey said:

Your original statement:  "Your assumption that drag is lower and lift is at a premium at altitude is probably wrong".  So either you don't agree that drag and lift are lower at higher DA, in conflict with every aerodynamics book ever published, or I'm misunderstanding what you are saying and we are in agreement.  I will let you decide which.   ;)

I'll amend from wrong to confusing. We use indicated numbers to achieve no loss of lift or drag but an increase in true speed instead.  

If you compare at matching indicated numbers there is no loss and if you compare at true numbers there is a loss. If you don't specify its becomes confusing / ambiguous.

Where you crossed over into 'wrong' territory is where you reversed the relationship, I believe.

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13 minutes ago, Ed Cesnalis said:

I question FD's numbers, they certainly do no reflect my plane's performance trends accurately.

The numbers I posted were for the CTLS, and the testing I did was in the CTLS. You are free to disagree if you choose. I was merely posting a source that shows that not all airplanes climb at a steeper angle with less flaps like the post title claims.

One of the links you posted also supports that some aircraft have a better angle of climb with a small flap deflection. That is the reason they do not fully retract the flaps on a go around until the obstacle is cleared.

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6 minutes ago, Tom Baker said:

The numbers I posted were for the CTLS, and the testing I did was in the CTLS. You are free to disagree if you choose. I was merely posting a source that shows that not all airplanes climb at a steeper angle with less flaps like the post title claims.

One of the links you posted also supports that some aircraft have a better angle of climb with a small flap deflection. That is the reason they do not fully retract the flaps on a go around until the obstacle is cleared.

I appreciate it and I think that's the correct take away.  The concept in the thread title is quite useful to me and yet not a thousand percent true.

I do use flaps to get me over terrain more than once a week.  Flaps do work for obstacles absolutely but in many/most cases its because it slows us down and allows a steeper angle and not necessarily because there might be the steepest angle available at that setting.

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" I do use flaps to get me over terrain more than once a week.  Flaps do work for obstacles absolutely but in many/most cases its because it slows us down and allows a steeper angle and not necessarily because there might be the steepest angle available at that setting."

 

The world is coming to an end. <_<;):)

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11 hours ago, Roger Lee said:

At the end of my 6500' runway I want to be at 600' at the end or close to it so I could turn 180 degrees and land if when I do change flaps or change throttle something happens. It also gives me good chute deployment altitude. 15 flaps puts me there. Zero flaps gets me to the end of the runway faster, but only about 400' - 450'.

15 flaps gets me off the ground sooner and in 15 flaps at 60 knots if the engine quits I'm already in a landing configuration and all I have to do is lower the nose.

I had 8 CTSW's at my field and we always take off in twos. We split the runway. The guy in 15 always leaves the runway first and is higher by the end of the runway. The zero guy got to the end faster, but less altitude. This was real time flights for 10 years this way. If you haven't done flights in twos then it would be tough to debate otherwise because perception is never as good as the real deal..

Toss in aircraft gross weight for a flight and things change quick. Two vs one occupant. 1/2 tank vs full and baggage and density altitude.

When I'm at 9500'+ DA I would never use zero flaps.

With this one, I'm totally with Roger.

Flaps 15° and 60 kts until 500 feet.

It keeps things real simple.

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Roger and I will never agree on this issue.  Zero flaps is less drag on takeoff and I believe you will get higher faster and be able to glide farther for your altitude in the event of an engine failure. 

Try a glide from 500ft and 60 kts at flaps 15- see how far you go. Then try the same glide at 500ft, flaps zero and 90 kts. Flaps zero will win every time.  I know there are lots of other factors and I will not cover them all but the bottom line is more drag at flaps 15 than zero for takeoff. 

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1 hour ago, Duane Jefts said:

Roger and I will never agree on this issue.  Zero flaps is less drag on takeoff and I believe you will get higher faster and be able to glide farther for your altitude in the event of an engine failure. 

Try a glide from 500ft and 60 kts at flaps 15- see how far you go. Then try the same glide at 500ft, flaps zero and 90 kts. Flaps zero will win every time.  I know there are lots of other factors and I will not cover them all but the bottom line is more drag at flaps 15 than zero for takeoff. 

Roger and have had the same discussion, and I agree with what you are saying. If you use 15° flaps you are off the ground sooner, so you start your climb sooner. With 0° you have a longer ground roll, but then a better climb rate. My testing showed that from a standing stop to 500 AGL the time was the same for both flap settings. The difference was where you were from the starting point. 15° flaps might put you over the departure end of the runway, while 0° will put you just beyond the end. Anything less than a 500 foot climb I would give the advantage to 15° flaps, anything over 0° flaps. This is from a standing start.

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12 minutes ago, Roger Lee said:

I agree Tom.

I prefer a higher altitude by the end of the runway. If we are flying a mile out then I agree with zero flaps.

This thread is about a third choice, why keep bringing it back to the argument you are so tired of?

I would like to hear pros and cons of cleaning up early for the initial climb and how it works for others.

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The subject of this thread, relative to take offs is about climbing away clean after free of obstacles to realize better performance.

I usually depart niner which is downhill and cleaning up for the downhill departure feels very relaxed and high performance.

Departing two seven of course is up-hill and climb is needed not for obstacles but rising terrain.  In this direction the feeling isn't relaxed at all.

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What about what I mentioned a while back:  Take off at 15°, then switch to 0° ASAP for the climb.  That seems to satisfy the short takeoff roll and the better climb performance.  However, you still have to accelerate to an airspeed where at 0° you will beat the climb performance of 15°, where max climb occurs at a lower airspeed.

The more we talk through it, the more I'm in the 15° "set it and forget it" camp with Roger and Bill.  That's how I make 95% of my takeoffs now and it has worked great.  If there is doubt about clearing an obstacle at 15° all the way over it, you probably shouldn't be making the takeoff at any flap setting.  

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23 minutes ago, Ed Cesnalis said:

The subject of this thread, relative to take offs is about climbing away clean after free of obstacles to realize better performance.

I usually depart niner which is downhill and cleaning up for the downhill departure feels very relaxed and high performance.

Departing two seven of course is up-hill and climb is needed not for obstacles but rising terrain.  In this direction the feeling isn't relaxed at all.

The thread title also has best angle of climb, which indicates trying to clear an obstacle or gain the most altitude in the shortest distance. Maybe you should have made a better choice of titles.

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5 minutes ago, Tom Baker said:

The thread title also has best angle of climb, which indicates trying to clear an obstacle or gain the most altitude in the shortest distance. Maybe you should have made a better choice of titles.

 

Its a somewhat complex subject, I didn't get all points of consideration in the title its true. There are both take off terrain/obstacle clearance considerations as well as high terrain clearance and even most efficient climb to avoid over heating.

Its a useful subject to understand and one where many in the CT community seems to be on a different page.

 

 

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"At the end of my 6500' runway I want to be at 600' at the end or close to it so I could turn 180 degrees and land if when I do change flaps or change throttle something happens. It also gives me good chute deployment altitude. 15 flaps puts me there. Zero flaps gets me to the end of the runway faster, but only about 400' - 450'."

If you want the greatest altitude at some distance from the beginning of the takeoff roll, then you are correct, fly Vx (15 degrees of flaps at about 60 its for a CTsw).  But, if you want best altitude for chute deployment, fly Vy (0 degrees of flaps at 78 kts).  That is, assuming you want to get to chute altitude most quickly (i.e., shortest time).  But, one configuration can't achieve both goals simultaneously, which your statement seems to suggest.  Flying Vx will not get you to a particular altitude sooner (sooner by the clock, not by distance) than flying Vy.  

 

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A clean departure to the east from Mammoth Yosemite works very well.  The 7,000' runway is downhill and the terrain beyond descends.

It takes me less than 15 seconds from zero start with 15* until I'm 80kts and negative six.  It does eat up a lot of runway and by the departure end of this long runway I'm at the same point vertically but with 15-20 knots more speed.  

Makes no sense on short runways with obstacles but where there is room and wind shear it does allow you to get faster sooner.

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