Flaps to aid climbing - truth or fiction

[FastEddieB]

Your right, not 20kts but 10kts.  The point stands though, best rate at 15 is much steeper.

 

 

 

 

Curious - did you do the math on this? Seems like some trig would be involved comparing the lower climb rate at 15º with the percentage decrease in forward speed.

 

Interesting exercise, though if you wanted best angle, why not just use the published best angle?

[Roger Lee]

ED,

I agree those numbers are too low and I don't know anyone that uses those.

 

Eddie,

Those charts aren't up to date and lag behind real time testing. They are not representative of real world use. FD certainly needs to change these.

 

ED,

Most CT owners I know use 15 and take off and the other minority use zero.

Many use 15 at take off with 60 knots. At the end of a 6K ft. Runway I'm considerably higher with 15 over zero. Is usually use 70-80 knots in a Zero take off climb.

 

There is no way zero flaps will be higher at the end of the runway over zero flaps provided you do a normal take off

[Ed Cesnalis]

Curious - did you do the math on this? Seems like some trig would be involved comparing the lower climb rate at 15º with the percentage decrease in forward speed.

 

Interesting exercise, though if you wanted best angle, why not just use the published best angle?

 

I didn't do the math, I did a test flight instead. 

 

 

Beyond takeoff best angle is something I use out of necessity not  something I plan for.  I like to keep my speed up as a rule.

 

My most common departure from home, direction of flight is west and that requires climbing 3,000' min in the first 7 miles.  Most pilots use 5,000' - 9,000' but they have to circle first.

 

My departure usually includes climbing very near the terrain where there is generally lift.  When the lift isn't there at some point I have to either use a steep climb or turn away.  

 

I would rather circle than to use Vx beyond my initial climb to clear obstacles or to get to a height where I can return to the runway, that's when I retract and don't plan on needing 15 again until I'm slowing for landing.

[Ed Cesnalis]

There is no way zero flaps will be higher at the end of the runway over zero flaps provided you do a normal take off

 

 

Say what?

[Ed Cesnalis]

These are the climb numbers that work best for me.

 

Take off and initial climb to clear obstacles  1 notch of flaps and 68kts  

 

Climb to altitude steep = 85kts IAS

 

Cruise climb = > 100kts TAS

 

 

---------------------------------------------------------------

 

Safe CT take-off style for long runways prone to shear.

 

• Set nose down trim low so back-pressure is required.  ( I use the same setting that I use for approach at 55kts and 30 )
• Imediately after rotation as the mains rise begin to lower the nose and trim.
• Accelerate in ground effect prior to establishing climb at higher speed.  From in the cockpit it looks like a nose low helicopter departure.

[Tom Baker]

There is no way zero flaps will be higher at the end of the runway over zero flaps provided you do a normal take off

 

Roger, The airplane with 15° should be higher at the end of the runway, but the airplane with 0° flaps will get to the end of the runway faster. Even though they are not as high at the end of the runway, in most cases though the airplane with 0° flaps will reach the same altitude as the other airplane in less elapsed time.

[Roger Lee]

Hi Tom and maybe Eddie,

"but the airplane with 0° flaps will get to the end of the runway faster".

 

I thought this was what Eddie was talking about all this time.

 

I don't care about faster you're only talking a 1-2 seconds. It isn't a race. Getting there faster isn't safer. If someone cares about that 1 or maybe 2 seconds then they need a valium. You're going to get there soon enough and you aren't on a stopwatch and won't know the difference.

 

At the end of a 6K' runway I will be higher with 15 than the guy with zero and I will have left the runway at a lower speed and been in the air sooner. I don't see why anyone cares if they beat the 15 guy to the end of the runway. 

 

I care about a safe and high enough altitude to make a safe 180 turn, parachute pull and be in a landing configuration if things go south at 50' off the deck of the runway.   

 

If I take off at 15 doing 60 knots in climb and the engine quits at 50' off the deck I just need to lower the nose and land. I'm already set up. I keep this configuration until I hit a safe 180 degree turn safe altitude before making in flight changes. (usually, unless I'm doing special departure practices))

[Tom Baker]

Hi Tom and maybe Eddie,

"but the airplane with 0° flaps will get to the end of the runway faster".

 

I thought this was what Eddie was talking about all this time.

 

I don't care about faster you're only talking a 1-2 seconds. It isn't a race. Getting there faster isn't safer. If someone cares about that 1 or maybe 2 seconds then they need a valium. You're going to get there soon enough and you aren't on a stopwatch and won't know the difference.

 

At the end of a 6K' runway I will be higher with 15 than the guy with zero and I will have left the runway at a lower speed and been in the air sooner. I don't see why anyone cares if they beat the 15 guy to the end of the runway. 

 

I care about a safe and high enough altitude to make a safe 180 turn, parachute pull and be in a landing configuration if things go south at 50' off the deck of the runway.   

 

If I take off at 15 doing 60 knots in climb and the engine quits at 50' off the deck I just need to lower the nose and land. I'm already set up. I keep this configuration until I hit a safe 180 degree turn safe altitude before making in flight changes. (usually, unless I'm doing special departure practices))

 

The talk for the most part has been about rate of climb not angle of climb. I agree that it's not about who gets to the end of the runway the quickest, but it is also not about who is highest at the end of the runway. With safety in mind you want to get as high as you can in the shortest period of time, and not necessarily distance . If you take 2 CT's one with 0° and the other with 15° flaps and set them side by side for take off. When you get to the end of the runway with 15° flaps the other CT Should be ahead of you and also at a higher altitude, if everything else is equal.

[Roger Lee]

Hi Tom,

 

"If you take 2 CT's one with 0° and the other with 15° flaps and set them side by side for take off. When you get to the end of the runway with 15° flaps the other CT Should be ahead of you and also at a higher altitude, if everything else is equal."

 

Side by side is mine and most of the guys that I fly withs normal take off configuration the majority of the time. I rarely take off solo or fly solo.

 

This is why I don't have to look at those charts to know if they are right or wrong.

If a person only has a chart and no real time experience doing this on an everyday basis then the chart guy is behind the game and is trusting that someone published good numbers and that everyone will fly just like the test pilot did. That said many charts are calculations and extrapolations and not true full flight numbers under different conditions and or weights.

 

I fly at least 80% of all my flights with 2-4 others. We always take off side by side and fly side by side so I have a really good handle on this. I have always found that the guy using 15 flaps is higher at the end of the runway and if he is back it is such a small distance it wouldn't make any difference. 15 flaps is off the ground sooner. Some times the lead plane has 2 people and sometimes the wing man has two. The single guy is always off the ground first and always overtakes the plane with 2 people.

I have tried our formation flights in 15 and zero many times and many times when the lead is at zero I'm at 15 behind him. The first guy off the ground picks up speed faster. WSo if the 15 guy is wingman and off the ground sooner than the lead in zero I always have to pull back throttle or I pass him.  I would bet out of 1500 hrs. in the CT 9001000 hrs.  are in formation and all 2 person flights take off side by side.

 

15 flaps gives you the highest in the shortest time at take off.

 

 

 

 

 

[FastEddieB]

First, this was never about takeoff. It's been stipulated that flaps are used on takeoff to get the plane in the air and climbing sooner, resulting in more altitude gain over a given distance. This was about whether flaps could increase rate of climb - and, by implication, ceiling - at altitude.

 

Second, for me this thread is rapidly reaching a point of diminishing returns. We've gotten to the point of dismissing both texts on aerodynamics and published POH performance charts because they're "old". Hard to continue with reasoned debate once these sources are dismissed out of hand.

 

Look for maybe one final summary post from me on the topic. Or not - it may not be worth the effort.

[Roger Lee]

Hi Eddie,

 

"First, this was never about takeoff. It's been stipulated that flaps are used on takeoff to get the plane in the air and climbing sooner, resulting in more altitude gain over a given distance. This was about whether flaps could increase rate of climb - and, by implication, ceiling - at altitude."

 

 

Then I think you are debating on 2 different subjects. Some for the take off side of things and others in-flight at altitude. This may be why there is no good consensus. 

Looking back it isn't over clear at times.

 

I personally thought everyone was talking about two different things at times.

 

Both take off and then in-flight climb.

[Ed Cesnalis]

Eddie,

 

The charts have Vspeeds so out of range for my CTSW that I wouldn't rely on them.  My POH has things in it that aren't true but at least most speeds seem right.

 

When it comes to aeronautical texts on aerodynamics, lots of guys don't really get it, for many not fun to read.

 

Personally I learned something on this thread.  Some of us have found flaps useful at times for clearing terrain which led to misunderstanding.  Now I believe that clean climbs at the best rate and has the highest ceilings.  When we use flaps to clear terrain its just a way of slowing down and finding a steep angle.

[FastEddieB]

Ed,

 

I'm glad, and it's a two way street.

 

I learned about negative flaps, about which I knew very little.

 

And it's possible to list a Vfe for a no-flap condition - which still seems oxymoronic!

 

And that some modern planes have far more comprehensive rate of climb charts than legacy planes ever had.

 

And that, at least according to Peter Garrison, it is at least theoretically possible for a very small flap setting to actually reduce drag (though I've not seen that confirmed anywhere else).

 

And I found a new, more modern compendium of basic aerodynamics for pilots.

 

No matter how long one has been at this game, there is still plenty of stuff to learn - as long as one approaches with an open mind.

[Mike Koerner]

Ed,

I don't know why my plane doesn't seem to get as hot as some of the others.

I certainly don't thermal out of the LA basin (my passengers and other airspace users would not appreciate that).

 

Eddie,

Thanks for sharing the CTLS POH data. I hadn't seen that. It certainly supports your initial contention that planes are designed for best rate of climb (and maximum L/D) at zero-degree flap settings.

However, my impression is that my plane climbs at a faster rate, greater angle, and to higher altitudes with 15-degree flaps rather than zero (or any other setting). Maybe this discrepancy is due to the difference in aircraft model (unfortunately, similar data has not been published for the CT2k). Maybe it has to do with the trim, flap adjustment or cg. location of my particular plane.

I'm sorry I don't have flight data to support my impression. Frankly, my claim should be discounted until I do.

 

Mike Koerner

[FastEddieB]

Mike,

 

That's a nice, healthy attitude. Skeptical, in the finest sense of the word.

 

I remain open to the possibility that some plane, somewhere, can actually climb to a higher altitude at a higher rate with flaps than without. But since that would violate at least the simplified version of aerodynamics that most of us as layman have, it would certainly be deserving of an explanation. I can think of at least two, which I think I've already mentioned:

 

1) The change in pitch caused by the flaps reduces form drag more than the increase in induced drag.

 

2) The airfoil design is sub-optimal, and partial flaps just "correct" it's shape to a more efficient airfoil overall.

 

None of the other explanations offered really seem feasible to me.

 

BTW, I got that data from an online CTLS POH I found online as a pdf. Should be easy to find via Google - if you want it and can't find it I can provide a link.

[Ed Cesnalis]

Eddie,

 

I challenged this once and you didn't respond.  It seems to be a major flaw in your theory.

 

• 1) The change in pitch caused by the flaps reduces form drag more than the increase in induced drag.

From your post #131 

1.  Flaps - and flaperons - deflected downward increase lift
2. Increasing lift, by necessity, increases induced drag.

See the conflict?

 

You arrive at a necessary increase in induced drag because flaps increase lift.

 

but.

 

lift = weight at either flap setting so the logic doesn't work.

[Mike Koerner]

Eddie,

I agree with your number 1.

I'm uncomfortable with the wording of number 2. For any wing, at any speed there is an optimal (highest Lift/Drag) flap position. But there is only one speed and flap position that gives the overall maximum L/D (though there is probably a wide range without much difference). I think, perhaps as a matter of consensus, aircraft manufactures refer to this maximum L/D flap setting as the zero flap position. If a plane climbs faster (and glides farther) at another flap setting, they may have misidentified the maximum L/D condition. But the wing may still be an "optimal design".

Recognize that it's very difficult to accurately measure aerodynamic performance.

Mike Koerner

[FastEddieB]

Ed,

 

I see your logic.

 

Try this, from Wikipedia:

 

"Flaps are a type of high-lift device used to increase the lift of an aircraft wing at a given airspeed. Flaps are usually mounted on the wing trailing edges of a fixed-wing aircraft. Flaps are used to lower the minimum speed at which the aircraft can be safely flown, and to increase the angle of descent for landing. Flaps also cause an increase in drag, so they are retracted when not needed.

 

Extending the wing flaps increases the camber or curvature of the wing, raising the maximum lift coefficient or the upper limit to the lift a wing can generate. This allows the aircraft to generate the required lift at a lower speed, reducing the stalling speed of the aircraft, and therefore also the minimum speed at which the aircraft will safely maintain flight. The increase in camber also increases the wing drag, which can be beneficial during approach and landing, because it slows the aircraft."

 

 

Yes, in level, unaccelerated flight the lift will always equal the weight - or, more precisely, the total up forces will equal the total down forces. But with flaps down, the wing will be at a higher AOA to compensate for the reduced speed. So, the lift has more of a rearward component, also known as induced drag.

 

So, rather than saying, "Flaps increase lift", I should have said "Flaps increase the maximum lift coefficient". But in my defense, I think you'll find "flaps increase lift" often used as a sort of shorthand.

[Ed Cesnalis]

I'll finish by saying its remarkable that the CT pilots that expressed an opinion all say that judging by experience 15* out climbs in every respect when theoretically it only out climbs in one respect - angle.

 

--------------------------

 

Last Last comment - When I find myself approaching the ridge and I don't quite have the climb to make it I'm still going to use zero and 15 settings for that bump to get me over.  Why would I do that now that I've learned there is no better climb available there?  Answer is because it works and it leaves me in a positive energy state.

 

As I approach the ridge I'm normally climbing at 100kts TAS so when it gets close, I would have energy for a zoom climb at the reflex setting but I would end up with speed decaying and a nose high attitude, better to turn away.

 

Same scenario but instead of the zoom or turning away I go for zero then 15 flaps.  As I select 15 the balloon is generally huge and problem solved.  I can utilyze this balloon without getting slow for this flap setting and my pitch attitude stays pretty level so if it doesn't work a descending turn away easily fixes everything with a minimum of drama.

 

You might say that I just climb too fast in the first place but that's by design.  Flying close to the terrain in the Eastern Sierra calls for energy in reserve.

[FastEddieB]

Last Last video:

 

 

Fast forward to about 5:30 for the part on flaps.

[Roger Lee]

I haven't seen you old school guys talk about Newton's Law for wing lift mainly just Bernoulli principle. I don't believe it's just lift vs drag and that singular theory seems to be outdated.

Air or wind impacts the bottom of the wing and pushes upward in simple terms. This would also help explain why 15 helps lift the plane upward and it makes no difference if you are in take off or in flight cruise mode.

 

 

This may help.

 

http://www.allstar.fiu.edu/aero/airflylvl3.htm

[ralarcon]

I haven't seen you old school guys talk about Newton's Law for wing lift mainly just Bernoulli principle. I don't believe it's just lift vs drag and that singular theory seems to be outdated.

Air or wind impacts the bottom of the wing and pushes upward in simple terms. This would also help explain why 15 helps lift the plane upward and it makes no difference if you are in take off or in flight cruise mode.

 

 

This may help.

 

http://www.allstar.fiu.edu/aero/airflylvl3.htm

I'm persuaded by your argument.

 

Cheers

[Roger Lee]

I haven't seen you old school guys talk about Newton's Law for wing lift mainly just Bernoulli principle. I don't believe it's just lift vs drag and that singular theory seems to be outdated.

Air or wind impacts the bottom of the wing and pushes upward in simple terms. This would also help explain why 15 helps lift the plane upward and it makes no difference if you are in take off or in flight cruise mode.

 

 

This may help.

 

http://www.allstar.fiu.edu/aero/airflylvl3.htm

 

 

Come on guys. Only Bernoulli quoters here. No one for Newton?????

How about both principles at work.  I am shocked that no one here talked about Newton and possible effects on 15 flaps in 9 pages.

You guys keep telling me you're old, don't force me to believe you.   

[Doug G.]

I think Newton is much older than Bernoulli. :-)

I did post that I have flown R/C that had a slab wing and was primarily impact lift. It is a combination. Just as you can't really say, "power for altitude, pitch for airspeed" there are always combinations of factors. It is not a simple system.

[Tom Baker]

I don't know if you are lumping me into the old school guy category, but I haven't said anything about either one. Frankly it doesn't really matter which method or methods of producing lift you subscribe to, wind tunnel test have proven time and again the when you increase lift drag also increases.

 

BTW, as an instructor I teach that both produce lift, because that is what the FAA teaches now.