Jump to content
Buckaroo

Climbing at -6 degrees vs 0 degrees?

Recommended Posts

I really haven't yet traveled far so higher altitude levels and climb times haven't yet concerned me. 

With this in mind I'm wondering if one wants to climb say from 6000 feet on a cross country to say 10,500 is it wise to retract the 6 degree to 0 for more efficient climb numbers? 

This could be a vy vs vx question I guess!! 

Today at zero flaps she performed brilliantly compared to -6 in a short run! 

Makes sense zero flaps equals more lift tha n minus 6 due to flap lift equations but also zero is more drag! ?

 

Share this post


Link to post
Share on other sites

neg six gives best rate of climb not zero. once clear of obstacles, clean up.

more flaps = more drag and less rate of climb.  I fly in 14,000' mountains 3 times a week and from experience I can tell you that going down to zero if you are going to fail to out climb something works and going down to 15 if it gets drastic works more.  the reason it works is you slow down and balloon up then climb at a steeper angle but lower speed.

using zero for your normal climb outs is less efficient

 

 

Share this post


Link to post
Share on other sites
On 8/20/2017 at 10:33 PM, Roger Lee said:

I disagree. 

 

We know your fond of Newton and will agree that our flaps increase lift when deflected downward from their highest setting.

We know from 10 years of talking that you agree that increasing lift by necessity increases drag (induced drag)

We can certainly agree that our 912 have a limited amount of power available for climbing, something like 93hp or less at altitude.

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

Using the above premise: At negative flap setting the amount of available power used to produce lift = to the weight of the airplane is the same as at zero flaps, the weight does not change the power required does  change.

Remaining power is available for climb and because the zero flap setting requires more of it to offset the additional drag of zero flaps deployed the zero flap setting has less power reamaing for climb compared to the negative six setting.

 

 

 

 

Share this post


Link to post
Share on other sites

This is Taboose pass, 11,500.  I used it yesterday to exit the Sierra in order to capture this photo.  It took me just over 10 minutes to climb to 13,000'  at a TAS of 100kts.

There is one benefit to doing the climb at zero instead of reflex flaps, it takes longer and you have more time to watch the scenery go by.

Baxter Pass to Taboose Pass.jpg

Share this post


Link to post
Share on other sites

Awesome photo Ed.  You're fortunate to be able to experience this and viewing your pictures helps me to understand why you take a high risk to do so.  You could tell me that it was a shot from Mars or the moon and I'd believe it.  A place that a flatlander like me will never go.

FWIW, Phil attended the Page event last year, flying from our home base here in Michigan.  He found that it was best to go to zero flaps to gain altitude in the mountains on his way to and from Page.

Share this post


Link to post
Share on other sites
24 minutes ago, Runtoeat said:

Awesome photo Ed.  You're fortunate to be able to experience this and viewing your pictures helps me to understand why you take a high risk to do so.  You could tell me that it was a shot from Mars or the moon and I'd believe it.  A place that a flatlander like me will never go.

FWIW, Phil attended the Page event last year, flying from our home base here in Michigan.  He found that it was best to go to zero flaps to gain altitude in the mountains on his way to and from Page.

Dick,

Here's the crux of this argument: Adding flaps reduces the L/D ratio and increases the power required to climb.

How would you explain Phil's finding? He needed some of the available power to offset the extra drag produced at zero and it took away from power available to climb.  If Phil is right then this logic is wrong. I have hundreds of such flights so what makes Phil's flight determinative? 

The authors below agree:

"Extending the flaps will decrease the climb performance as L/D ratio is reduced and the power required increased. The best rate-of-climb and angle-of-climb is always reached with flaps up. Hence the need to retract flaps after a go-around if there are obstacles in the climb out path."  http://www.experimentalaircraft.info/flight-planning/aircraft-climb-performance.php

"Flaps reduce aircraft stalling speed by increasing lift and it enables you to lift-off at a lower airspeed. Resulting in a shorter ground run. It also reduces the rate of climb (and angle) due to a somewhat higher drag."  http://www.experimentalaircraft.info/flight-planning/aircraft-performance-5.php

"The flap setting also affects the climb gradient. Increasing the flap angle increases the drag, and so reduces the climb gradient for a given aircraft mass. If there are obstacles to be considered in the takeoff flight path, the flap setting that gives the shortest takeoff distance may not give the required climb gradient for obstacle clearance."  http://www.skybrary.aero/index.php/AP4ATCO_-_Factors_Affecting_Aircraft_Performance_During_Takeoff_and_Climb

"No conventional airplane will climb more rapidly with the flaps extended than it does with them retracted."  http://commons.erau.edu/cgi/viewcontent.cgi?article=1026&context=jaaer

Share this post


Link to post
Share on other sites

Speed or climb - same logic

Start with speed. We all know that best speed comes with negative flaps.  More speed requires more power and the available power in our budget is that which is not needed to offset the 1,320lbs(max) of lift.  All power available beyond what is needed to offset weight can be accessed by keeping your nose level and setting the throttle to wide open.

You have budgeted all needed power for lift and the balance for additional speed.

Same with climb. To have the maximum amount of your total power available for climb you have to minimize that amount used for lift that is a fixed amount determined by your weight. Reducing flaps increases your L/D.

Share this post


Link to post
Share on other sites

I tend to agree with Ed on this. For a flat lander the need to switch to 0° flaps comes from not planning far enough ahead, and needing a steeper climb angle to clear the obstacle. 0° flaps gives the appearance of better climb, because you are going up at a steeper angle. The problem is a steeper angle does not necessarily mean you have the best rate.

Share this post


Link to post
Share on other sites

Thanks for the links and the information.  My statement about Phil's flap setting was not meant to mean 0 flaps as being the best choice for gaining altitude.  As I recall, Phil was not interested in gaining altitude but was just trying to be comfortable during portions of his trip when at higher altitudes.  I believe he mentioned to me that he went from -6 to 0 just to drop his nose a little to gain a better view and to take away the glare from the sun.  I recall him also telling me that the reduction in airspeed wasn't that great and the small reduction was worth the added terrain visibility and reduced sun glare.  This discussion has been enlightening for me.  Ed's links were educational and I learned more about best rates of climb when at the various flap settings and Vx and Vy speeds.  This post will prompt me to discuss this area with Phil which will be a good learning experience for me.

Share this post


Link to post
Share on other sites

FWIW, the CTLS POH does list both best rate and angle of climb (The CTSW only lists for 0 deg).  Rate(15): 740'/min.  Rate(0): 800'/min.  Rate(-6): 770'/min.  Also, both angle(15) and angle(0) are listed at 8:1. Angle(-6) is not given.

Even with that, it seems logical that best rate should be at -6.  This also matches my personal observation with my CTSW, though the difference between 0 and -6 seems small and it is difficult to get repeatable numbers just looking at the VSI.

Help me understand why best angle would be at -6.  Since higher speed is a negative, the climb rate at Vx would have to be significantly higher at -6 to make up for that higher speed just to result in the same angle.

Share this post


Link to post
Share on other sites
2 minutes ago, JLang said:

... Help me understand why best angle would be at -6.  Since higher speed is a negative, the climb rate at Vx would have to be significantly higher at -6 to make up for that higher speed just to result in the same angle.

Since higher speed is a negative, the climb rate at Vx would have to be significantly higher at -6 to make up for that higher speed just to result in the same angle.

That is true and the speed is higher yet because the result is a steeper angle.

 

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

Logic: If neg six minimizes power needed for lift and therefore maximizes the amount of power available to achieve max speed then neg six can do the same thing for climb (rate or angle)  You can choose among the three (max speed, best climb rate, best climb angle) with your stabilator trim.

Share this post


Link to post
Share on other sites
1 hour ago, Ed Cesnalis said:

Since higher speed is a negative, the climb rate at Vx would have to be significantly higher at -6 to make up for that higher speed just to result in the same angle.

That is true and the speed is higher yet because the result is a steeper angle.

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

Logic: If neg six minimizes power needed for lift and therefore maximizes the amount of power available to achieve max speed then neg six can do the same thing for climb (rate or angle)  You can choose among the three (max speed, best climb rate, best climb angle) with your stabilator trim.

Higher speed is definitely a negative for best angle.  The ideal is a helicopter taking off vertically, with zero forward speed.

Share this post


Link to post
Share on other sites

A couple of years ago I flew over the ND Badlands. I started out at 3500' on what was a 90 + degree day on the ground. I decided to climb to find the "air conditioning." That ended up being 7500'. I used the autopilot to set a climb and was almost immediately hit with the "more elevator" trim signal. I added trim until I began to lose significant airspeed. I then switched to 0 flaps and climbed well eventually leveling off at 7500 and returning to -6 in cooler air.

 I am sorry I cannot recall either the DA or my rate of climb at the time.

Share this post


Link to post
Share on other sites
3 hours ago, Doug G. said:

A couple of years ago I flew over the ND Badlands. I started out at 3500' on what was a 90 + degree day on the ground. I decided to climb to find the "air conditioning." That ended up being 7500'. I used the autopilot to set a climb and was almost immediately hit with the "more elevator" trim signal. I added trim until I began to lose significant airspeed. I then switched to 0 flaps and climbed well eventually leveling off at 7500 and returning to -6 in cooler air.

 I am sorry I cannot recall either the DA or my rate of climb at the time.

For vertical axis control your AP is only able to raise or lower your pitch attitude. It's not very smart as you found out and once you are behind the power curve your AP has nothing left in its bag of tricks except to seek stall with  your help on the trim wheel.

You may be inferring that  you needed zero flaps to 'climb well' below 7500' on a hot day but that would be hard to accept.  My prop pitch is likely flatter than yours but I can still 'climb well' at 14,000' on any day.  

If your speed is decaying and your AP wants nose up trim then you should disengage.  Especially with this experience I would manually 'set your climb' and then engage your AP to maintain it.  That way you start off free of trim pressure as a side benefit.

 

 

 

Share this post


Link to post
Share on other sites

If I am going to be in a particular condition like a climb or descent for a while, and want to use the AP, I usually try to stabilize in that condition with minimum trim pressures, and then engage the AP.  As Ed mentioned, it's not too smart in some ways.  If there is going to be a large swing in airspeed or vertical speed (like leveling from a steep climb) I will often disengage the AP, get things set up for the new condition and let the speed stabilize, and then reengage the AP.  That way I take a little stress off the servos by making sure trim pressures are minimized for the new flight condition.  

Share this post


Link to post
Share on other sites

For those aircraft equipped with Skyview, engaging 'airspeed hold' (78 kts.) would work well. Of course, trimming the aircraft is a given.

In that mode, when the aircraft can no longer climb, that is the climb ceiling (at that specific airspeed) for a given flap position.

Share this post


Link to post
Share on other sites
1 hour ago, WmInce said:

For those aircraft equipped with Skyview, engaging 'airspeed hold' (78 kts.) would work well. Of course, trimming the aircraft is a given.

In that mode, when the aircraft can no longer climb, that is the climb ceiling (at that specific airspeed) for a given flap position.

My climb was varying from -800 to +1200 this morning without changing my pitch attitude or throttle or flaps.  Could be confusing to an AP trying to establish a climb ceiling. 

Days like today if you get into the big wave lift you can bust 18,000 with no way to avoid it.

Share this post


Link to post
Share on other sites

Under those conditions, I would avoid using the autopilot for climb. It would end up "chasing" selected vertical speed or selected airspeed. Best just to hand fly it.

Share this post


Link to post
Share on other sites
On 9/17/2017 at 6:12 PM, Ed Cesnalis said:

For vertical axis control your AP is only able to raise or lower your pitch attitude. It's not very smart as you found out and once you are behind the power curve your AP has nothing left in its bag of tricks except to seek stall with  your help on the trim wheel.

You may be inferring that  you needed zero flaps to 'climb well' below 7500' on a hot day but that would be hard to accept.  My prop pitch is likely flatter than yours but I can still 'climb well' at 14,000' on any day.  

If your speed is decaying and your AP wants nose up trim then you should disengage.  Especially with this experience I would manually 'set your climb' and then engage your AP to maintain it.  That way you start off free of trim pressure as a side benefit.

 

 

 

Exactly what I did, first, then after going to 0° flaps I re-engaged the ap. I did that because of a long ago comment by someone here who experienced something similar. I went to -6° flaps as I got closer to 7500' where it was considerably cooler.

So, 0° with autopilot climbed, with -6° it didn't. I don't know how else to interpret that. -6° gives me more speed in cruise. More speed in those conditions means less drag and therefore less lift, right? 

Share this post


Link to post
Share on other sites

 

On 9/22/2017 at 3:51 PM, Doug G. said:

Exactly what I did, first, then after going to 0° flaps I re-engaged the ap. I did that because of a long ago comment by someone here who experienced something similar. I went to -6° flaps as I got closer to 7500' where it was considerably cooler.

So, 0° with autopilot climbed, with -6° it didn't. I don't know how else to interpret that. -6° gives me more speed in cruise. More speed in those conditions means less drag and therefore less lift, right? 

No, the amount of lift remains equal to the weight of the airplane. Drag changes while lift remains constant resulting in an improved L/D. You can use this additional performance for climb or lower the nose and use it for speed as you already do.

We flew home from Camarillo, CA this morning and stayed around ~12,500 for an hour and an hour climbing to and maintaining 10,000.  If I used your thinking and did the climbing at zero flaps I would add ten minutes to my flight time.

Kern River, Cruising above 12,000

Kern River.jpg

Capital Rock Sequoia National Park, beginning 400fpm climb to 12,500 - after we go by the crags.

Capital Rock.jpg

Bakersfield California from 10,000'.  Crossing valley to get from coastal mountains to Sierra Nevada

Bakersfield-3.jpg

Departing Camarillo, Initial climb 1,200fpm  degrading to 500fpm at 10,000 at 90kts IAS.

Camarillo.jpg

Share this post


Link to post
Share on other sites

"No, the amount of lift remains equal to the weight of the airplane. Drag changes while lift remains constant resulting in an improved L/D. You can use this additional performance for climb or lower the nose and use it for speed as you already do.

We flew home from Camarillo, CA this morning and stayed around ~12,500 for an hour and an hour climbing to and maintaining 10,000.  If I used your thinking and did the climbing at zero flaps I would add ten minutes to my flight time."

 

So, when I lower the flaps the lift and drag do not change?

That is not consistent with what I have learned either about flying or aerodynamics??

Flaps change the chord of the wing as well as the shape of the airfoil. More flaps = more power to maintain altitude. 

At -6° my speed increases from 0°. Why would that be?

Share this post


Link to post
Share on other sites
1 hour ago, Doug G. said:

"No, the amount of lift remains equal to the weight of the airplane. Drag changes while lift remains constant resulting in an improved L/D. You can use this additional performance for climb or lower the nose and use it for speed as you already do.

We flew home from Camarillo, CA this morning and stayed around ~12,500 for an hour and an hour climbing to and maintaining 10,000.  If I used your thinking and did the climbing at zero flaps I would add ten minutes to my flight time."

 

So, when I lower the flaps the lift and drag do not change?

That is not consistent with what I have learned either about flying or aerodynamics??

Flaps change the chord of the wing as well as the shape of the airfoil. More flaps = more power to maintain altitude. 

At -6° my speed increases from 0°. Why would that be?

Notice I say Drag Changes buy you repeat 'So ... drag do not change?'

When you lower your flaps both lift and drag do change momentarily. Upon stabilization lift will once again equal weight and drag will remain decreased. The result of the flap change will become an L/D change. A drag decrease with the same lift being produced. (fuel is being consumed when lowering flaps changing weight a negligible amount over a short time) 

This should be consistent with what you learned. Where is the conflict?

Even if flaps change the airfoil ( I don't accept that we don't have the laminar flow needed ) the weight remains constant so the lift cannot change.  After you lower flaps you would either be in a stead state level flight or a descent and in either case lift = weight.

As I said in the last post at  -6° you are producing less drag and the same lift as at zero because your are at the same weight and lift = weight. So now with less drag and same weight and power you do in fact go faster, or you could go faster while climbing, or your could climb and maintain the speed you had at zero.  What you do with the extra performance is dependent on where you set your pitch attitude.

Extra performance at -6° could be used for:

  • extra speed
  • extra climb (steep climb)
  • extra speed and climb (cruise climb)

 

 

 

Share this post


Link to post
Share on other sites

Yes, lift, drag, speed (or rather thrust), and AOA are all related, but your argument is semantic. You can use the lower drag to create more speed, or more lift, or both. There are, of course catalogs of wing designs that have different L/D ratios that have no relationship to weight at all. In fact the formula for calculating L/D does not involve weight. Once you add relative wind (by whatever method) you generate lift which is not related to weight.

Oh, and I did not say lift remained the same at 0° as at -6°.

How do you define the chord of a wing. Does it change when the flaps are lowered? 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×