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

[Ed Cesnalis]

4 hours ago, Tom Baker said:

... from a standing stop to 500 AGL it took the same amount of time from brake release to 500 feet with both flap settings. The amount of time from ground break to 500 feet was less with 0° flaps. The distance from brake release was greater with 0° flaps. The difference between the two was greater than the difference between take off distances. There for the distance from ground break to 500 AGL was greater for 0° flaps compared to 15° flaps. This would seem to indicate that the angle is slightly less, but at a greater rate for 0° flaps

Climbing to 500' AGL only speaks to rate not angle.

Including ground roll blends 2 angles and can't determine climb if angle is steeper by itself.

Take off roll for zero is much longer so even though the climb at zero can be steeper it might not be steep enough due to the starting point farther down the runway.

All in all we are not close to comparing apples to apples when you add in ground rolls.

[WmInce]

47 minutes ago, Ed Cesnalis said:

Bill,

Yes that's what I meant.

Vx doesn't enter into this discussion though, the diagram is correct.

I think the diagram is misleading.

Since clearing obstacles after takeoff was used in the example, Vx would have been a better parameter.

Who authored that diagram?

[Ed Cesnalis]

Please consider the subject of the thread.

The intent is to show that zero flaps climbs steeper than 15* flaps even if 15 is needed for obstacle clearance.

If you expect to see a Vx comparison it will be confusing.

[Roger Lee]

"The intent is to show that zero flaps climbs steeper than 15* flaps even if 15 is needed for obstacle clearance"

I am always higher at the end of the runway using 15 vs zero flaps. So were the other 7 CT's at my field. The guys that used zero flaps got to the end of the runway sooner, but were lower. I don't often believe what I read and like to do my own research and testing. Many times I find Mfg's wrong.

This debate has been coming up about every 6 - 8 months for the last 11 years. It has never been agreed upon, it usually goes for many pages of post and will come up again in several months.

It almost doesn't make any difference because each pilot picks the flap setting he or she likes for their own reason and sticks with it. Most all use either zero or 15 for normal take offs  and each has a reason why they like their way.

[Ed Cesnalis]

1 hour ago, Roger Lee said:

"The intent is to show that zero flaps climbs steeper than 15* flaps even if 15 is needed for obstacle clearance"

I am always higher at the end of the runway using 15 vs zero flaps. So were the other 7 CT's at my field. The guys that used zero flaps got to the end of the runway sooner, but were lower. I don't often believe what I read and like to do my own research and testing. Many times I find Mfg's wrong.

This debate has been coming up about every 6 - 8 months for the last 11 years. It has never been agreed upon, it usually goes for many pages of post and will come up again in several months.

It almost doesn't make any difference because each pilot picks the flap setting he or she likes for their own reason and sticks with it. Most all use either zero or 15 for normal take offs  and each has a reason why they like their way.

You have misunderstood, this is not the old debate that has come up before at all.

[JLang]

8 hours ago, Ed Cesnalis said:

Please consider the subject of the thread.

The intent is to show that zero flaps climbs steeper than 15* flaps even if 15 is needed for obstacle clearance.

If you expect to see a Vx comparison it will be confusing.

"Climbs steeper," or clearing an obstacle, means angle, not rate.  Therefore Vx, not Vy.

This goes back to my skepticism in this and the other related thread regarding the contention that best angle will always be with least flaps on all aircraft, even those with negative flaps like the CT.  Towards the goal of reaching best angle (not rate), at some configuration change that results in less drag, the accompanying decrease in lift and increasing ground speed -- which reduces best angle, everything else being equal -- leads to worse (shallower) climb angle.

[WmInce]

8 hours ago, Ed Cesnalis said:

Please consider the subject of the thread.

The intent is to show that zero flaps climbs steeper than 15* flaps even if 15 is needed for obstacle clearance.

If you expect to see a Vx comparison it will be confusing.

Consideration is duly noted.

However, steepness implies grade. There is a difference between climb rate and climb angle (or the climb grade.)

Which one are you trying to make your point with?

Ed, for a 2nd time, where did that diagram come from?

[Tom Baker]

10 hours ago, Ed Cesnalis said:

Climbing to 500' AGL only speaks to rate not angle.

Including ground roll blends 2 angles and can't determine climb if angle is steeper by itself.

Take off roll for zero is much longer so even though the climb at zero can be steeper it might not be steep enough due to the starting point farther down the runway.

All in all we are not close to comparing apples to apples when you add in ground rolls.

Ed, go back and read my findings again. I addressed the difference in distance from a standing start and also point of lift off. The point I reached 500 AGL with zero flaps was farther than with 15° flaps, with the distance being greater than just the additional take off roll. The extra distance traveled was almost double the additional take off roll. That equates to a shallower angle for 0° flaps, but a better rate.

I will never argue that 0° flaps will give a better rate, but for the CT it seems that with 15° flaps the reduction in rate is offset by a greater reduction in forward speed. This equates to a steeper climb angle.

[WmInce]

8 hours ago, Roger Lee said:

Most all use either zero or 15 for normal take offs and each has a reason why they like their way.

I prefer takeoffs using flaps 15° until 500' above field elevation.

[WmInce]

40 minutes ago, Tom Baker said:

I will never argue that 15° flaps will give a better rate, but for the CT it seems that with 15° flaps the reduction in rate is offset by a greater reduction in forward speed. This equates to a steeper climb angle.

Tom,

Is that a typo?

Don't you mean the better RATE is with flaps 0°?

[Tom Baker]

4 minutes ago, WmInce said:

Tom,

Is that a typo?

Don't you mean the better RATE is with flaps 0°?

Oops! corrected my post.

[WmInce]

45 minutes ago, Tom Baker said:

I will never argue that 0° flaps will give a better rate, but for the CT it seems that with 15° flaps the reduction in rate is offset by a greater reduction in forward speed. This equates to a steeper climb angle.

I would substitute "forward speed" with ground covered.

 

[FlyingMonkey]

The issue is that at 0° flaps, you are flying faster and covering ground faster, and at -6° you are flying faster still, eating up precious distance to the obstacle at a higher rate, so your climb rate MUST be higher than at 15° in order to clear it.  It's hard to know in advance if the increased climb at lower flap settings is enough to offset the shorter time period to reach the obstacle, especially in short field operations involving tall obstacles.    

As an example, let's say you can get climb rates of 1000fpm at 0° flaps at 70kt, and 850fpm at 15° flaps at 60kt.  Let's also assume the takeoff roll at 0° is about 700ft and the roll at 15° flaps is 500ft (these are close to what I've observed at my typical DA).  We will also assume that there is a period of acceleration after breaking ground to get to climb speed, where the airplane climbs at an average of half speed, that lasts three seconds in both cases, with a speed of 55kt for both airplanes during that period to make the math easy.

Now take these numbers to a 1500ft airstrip with an obstacle at the departure end:

At 0° flaps, the airplane has 800ft of runway left when it breaks ground.  Three seconds of climb is at half climb rate as it accelerates from 55kt, so it climbs 500fpm ( 8.3 feet per second) x 3sec = 24.9ft, then with 721ft remaining, an additional 4.4sec x 1000fpm (16.6fps) =  73.0ft, for a total height at the obstacle of 97.9ft.

at 15° flaps, the airplane has 1000ft of runway left when it breaks ground.  Three seconds of climb is at half climb rate as it accelerates from 55kt, so it climbs 425fpm ( 7.0 feet per second) x 3sec = 21ft, then an additional 7.1sec x 850fpm (14.1fps) =  100.1ft, for a total height at the obstacle of 121.1ft.

According to the math here, the pilot is better off selecting 15° flaps for takeoff and leaving that setting in until clearing the obstacle, which gives him an extra 23.2ft of clearance.  The additional 150fpm climb rate cannot overcome the disadvantage of faster airspeed gobbling up the runway.  In fact, using 55kt throughout the 3sec acceleration period for both flap settings probably disadvantages the 15° flaps airplane, since the 0° flaps airplane would in reality be traveling faster than 55kt for a good portion of that period.  

This is just the (simplified) math for one scenario, I'm not trying to say 15° flaps are the bees' knees for all situations, just that in the above scenario things seem to work to the advantage of the 15° flap setting.

[FlyingMonkey]

35 minutes ago, WmInce said:

I prefer takeoffs using flaps 15° until 500' above field elevation.

That's what I have been using as well.

[Tom Baker]

I use and teach 15° as well. I like the way the airplane feels coming off the ground better than with 0° flaps.

[Tom Baker]

1 hour ago, WmInce said:

I would substitute "forward speed" with ground covered.

 

I chose forward speed instead of  ground covered or ground speed because I was considering the difference in airspeed only. I think everyone knows that if you have a headwind the airplane climbs at a steeper angle.

[FlyingMonkey]

1 hour ago, Tom Baker said:

I use and teach 15° as well. I like the way the airplane feels coming off the ground better than with 0° flaps.

Agreed, when you are used to 15° flaps for takeoff the 0° setting makes it feel like the roll is forever and the airplane is stuck to the ground.

[WmInce]

19 minutes ago, FlyingMonkey said:

. . . when you are used to 15° flaps for takeoff the 0° setting makes it feel like the roll is forever and the airplane is stuck to the ground.

That calls for more positive (nose up) takeoff trim. Just a tad mind you.

[FlyingMonkey]

1 minute ago, WmInce said:

That calls for more positive (nose up) takeoff trim. Just a tad mind you.

Agreed.  But I'm more talking about the sensation of liftoff.  At 15° the airplane seems to quickly "leap" off the ground; at 0° is more just slowly lifts off, like it doesn't want to fly as readily.  I definitely learned about the trim required after my first couple of 0° takeoffs -- the nose definitely felt planted with insufficient trim set!

[Tom Baker]

Because of the landing gear the CTLS feels different on the ground than the SW, a little more stable in my opinion. To me the both airplanes just starts to feel unstable on the ground with the higher speed for rotation with 0° flaps.

[WmInce]

1 minute ago, Tom Baker said:

Because of the landing gear the CTLS feels different on the ground than the SW, a little more stable in my opinion. To me the both airplanes just starts to feel unstable on the ground with the higher speed for rotation with 0° flaps.

Agreed.

[FlyingMonkey]

19 minutes ago, Tom Baker said:

Because of the landing gear the CTLS feels different on the ground than the SW, a little more stable in my opinion. To me the both airplanes just starts to feel unstable on the ground with the higher speed for rotation with 0° flaps.

Definitely.  One reason I don't like landing at higher speeds.  It's just squirrelly.  Does the CTLS have a wider gear stance than the SW, or just better gear legs?

[WmInce]

1 hour ago, FlyingMonkey said:

Does the CTLS have a wider gear stance than the SW, or just better gear legs?

No idea on the wider wheel base.

Others can chime in, but I found the composite gear legs have more dampening (shock absorption) and are much quieter during braking.

The SW gear legs are much firmer. Seems like the only dampening effect is the air in the tires.

YMMV.

[Anticept]

I find the opposite, the SW is bouncy while the LS is firm.

[Tom Baker]

I find both to be stiff. The SW has more rebound than the LS. The main gear on the LS was moved back slightly compared to the SW to improve stability on the ground. 

An interesting bit of information about the gear on the CTLS. When they originally move the gear back the drawings were misread and the gear was moved back by the power of 10 on the first production airplanes. The airplanes didn't wont to rotate for take off.  They had to rework the main gear attachments on the first few before they left the factory. They also had to redo the molds.