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  #1  
Old 09-27-2012, 05:09 AM
drmax drmax is offline
 
Join Date: Apr 2006
Location: Martinsville, IN
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Default using 20 degrees flap for departure

Hello. My runway has a slight raise in it at about 900 ft. I lift off, solo at 60, come off the ground a bit, then settle back down a bit due to the hump, which is a little "unsettling". This is with 10 degrees. Going the other way is about 1200 feet before the raise, and is non issue. I don't want this to happen on a windy crosswind day, especially with passenger. I have not experimented with 20 degrees flaps as of yet. I'm 160 lyc fixed pitch metal.
Surfaceasphaltt. Your advice please. DM

Last edited by drmax : 09-27-2012 at 05:13 AM.
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  #2  
Old 09-27-2012, 06:19 AM
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jmbrwn jmbrwn is offline
 
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I would suggest trying 15 degrees of flaps first and see how that works. I use this off our 2400' grass strip with a 150hp Lyc fixed pitch, and seems to work well. I have no data to back it up, but 20 degrees seems like more drag than lift...my opinion only.
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  #3  
Old 09-27-2012, 06:46 AM
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blueflyer blueflyer is offline
 
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maybe try short field t/o procedure to get airborne before the "bump" in the runway.
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  #4  
Old 09-27-2012, 06:50 AM
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N941WR N941WR is offline
 
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Two options, the first is don't climb after you lift off. Fly it in ground effect, and inch off the ground, until 65, then rotate and accelerate to your desired climb speed. That won't take very long or take up more room.

As for the flap setting, I lower the aileron and drop to flaps to match them. That gives you 15* +/- which works out to about 1/2 flaps in the -9.
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Last edited by N941WR : 09-27-2012 at 07:49 AM.
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  #5  
Old 09-27-2012, 06:54 AM
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try lifting off at 65. this may give you more ummph so you dont settle back down. follow the hump in ground effect.
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  #6  
Old 09-27-2012, 07:13 AM
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Mel Mel is offline
 
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As has been stated above, 15° is optimum for max lift and min drag. I've done experiments with all flap settings and 15° works out best.

The aileron "down" travel is set to 15° for this reason. It also makes it convenient to set the flaps if you have electric. Just align the flaps with the "down" aileron and you're set to go.

I actually use 13°, but that's because my manual flaps have 13, 26, and 39° notches.
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  #7  
Old 09-27-2012, 07:24 AM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by Mel View Post
As has been stated above, 15? is optimum for max lift and min drag. I've done experiments with all flap settings and 15? works out best.

The aileron "down" travel is set to 15? for this reason. It also makes it convenient to set the flaps if you have electric. Just align the flaps with the "down" aileron and you're set to go.

I actually use 13?, but that's because my manual flaps have 13, 26, and 39? notches.
This is the proper way to set your flaps, it will help you pop off the ground a little quicker. But be advised it will also retard acceleration once you leave the ground. As soon as you are a few feet above the ground begin retracting the flaps so the plane can accelerate promptly.
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  #8  
Old 09-27-2012, 07:48 AM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Sam Buchanan View Post
This is the proper way to set your flaps, it will help you pop off the ground a little quicker. But be advised it will also retard acceleration once you leave the ground. As soon as you are a few feet above the ground begin retracting the flaps so the plane can accelerate promptly.
I disagree with this.

Don't be in a hurry to retract the flaps. Let the plane accelerate with the flaps down so you don't settle back on the ground. Once you have established a positive climb rate, well above the flaps up stall speed, then the flaps should be retracted and either Vx or Vy established, depending on the conditions/needs.
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  #9  
Old 09-27-2012, 07:55 AM
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Sam Buchanan Sam Buchanan is offline
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Quote:
Originally Posted by Sam Buchanan View Post
This is the proper way to set your flaps, it will help you pop off the ground a little quicker. But be advised it will also retard acceleration once you leave the ground. As soon as you are a few feet above the ground begin retracting the flaps so the plane can accelerate promptly.
Quote:
Originally Posted by N941WR View Post
I disagree with this.

Don't be in a hurry to retract the flaps. Let the plane accelerate with the flaps down so you don't settle back on the ground. Once you have established a positive climb rate, well above the flaps up stall speed, then the flaps should be retracted and either Vx or Vy established, depending on the conditions/needs.
Bill, I don't think we disagree.

My RV-6 (and I suspect most RV's) will establish a positive climb rate above stall speed a few feet above the ground.
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  #10  
Old 09-27-2012, 08:01 AM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Sam Buchanan View Post
Bill, I don't think we disagree.

My RV-6 (and I suspect most RV's) will establish a positive climb rate above stall speed a few feet above the ground.
Yep, I agree. Even when I had the small (135 hp) engine in my -9, it would jump off the ground and rotate to a positve rate of climb very quickly. With the 180+ HP engine, it just does it faster.
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