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Flaps for Takeoff

PeteP

Well Known Member
Curious to know how many 9 / 9A drivers use flaps for takeoff. If so how much flaps and what are you thoughts on takeoff flap usage.
 
Curious to know how many 9 / 9A drivers use flaps for takeoff. If so how much flaps and what are you thoughts on takeoff flap usage.
Do a search on this and you will find quite a bit of discussion on this. If you use flaps use 10 deg. But don't forget to retract them. :D
 
I don't usually use the flaps for takeoff at my home field but when i do use them i align the flap with the full down aileron. The plane jumps off the ground.

Russ
RV9-A N1909K
 
Only used on fields where I really want to get off the ground faster than normal (like gravel or muddy fields). Otherwise, no need.
 
opinions vary....

here's a previous thread by other curious folks... with some feedback from the airfoil guru.

http://www.vansairforce.com/community/showthread.php?t=66936&highlight=roncz+flap

I think that will work?

here's my data point; on the take-off roll, with a fixed pitch, my lyc. at 2150 rpm is only making about 85 hp....( I stand to be corrected) so it doesn't really 'leap' off the ground...kinda wallows a bit until speed builds.
but.....
with flaps at about 15, ( aileron down angle) it breaks ground cleanly, at a lower speed, and goes up like an elevator, in a flatter attitude, giving me a better view over the nose, and improved clearance over obstacles.
...a win-win in my opinion!
 
At 2150 rpm your Lyc should be generating about 85% rated power. For a 160hp 320, that would be 136hp rather than 85. Of course that would be at standard density, temperature, etc.
 
Almost never

I very seldom use flaps on take off, like others 10 max and only when there is a reason I need to do a harrier takeoff. :D
 
....



and only when there is a reason I need to do a harrier takeoff. :D

I like that quote Rick can I steal it? :D


On several (very rare)occasions I used full flaps on take off. OAT well below freezing, 10 gallons in the tanks. She jumped up indeed :D
 
Not in an RV, but I've found it desirable to make every takeoff a soft/short one. That way, when I've got to do a real one, it's routine and I know the distance to expect.

Dave
 
On several (very rare)occasions I used full flaps on take off. OAT well below freezing, 10 gallons in the tanks. She jumped up indeed :D
I would bet that you would get better performance in the same situation if you were to use 10 deg instead of FULL flaps. With full flaps the excess drag exceeds available excess lift generated by the flaps by a significant margin. Enough so that overcoming that drag is being done by shear brute force of the HP generated at the prop. 10 deg is a balance between drag and lift that gives the best lifting performance with the least amount of drag induced in a 'take off' setting.
 
I fly a 7 and not a 9 but have the same question. I find that if I use the flaps during a takeoff, I accelerate so fast that I can't retract tham fast enough to not overspeed them.

To complicate matters, I have the VP-X set to not allow the flaps to deploy above 100k and they will not retract above 100k either. Need to figure out how to change that. I want to be able to retract at any speed.
 
a fun discussion.....

I suppose if there were a POH that came with RV's, we'd STILL be having this discussion!:p
(I'm not a builder, and don't have plans nearby, so don't quote these numbers.!)
let's say the max flap is 30 degrees, some folks would say that half flaps is the only other setting worth worrying about ( it's not a 737 after all!)
IF we had some real wind tunnel test results, we might see that half flap ( 15-ish) just happens to roughly match the aileron down travel as a benchmark, and gives pretty close to best L/D.
Now, on take-off, there is a bit of ground effect, downwash or what-have-you occurring, so the airflow might be a bit different than a descent/approach.
Now, I still like to add 'one-notch' ( 10 degress) if I'm slowing to do some sightseeing at low altitude...does this make sense if 15 is the best L/D? Probably not, but it's partly a psychological thing I suppose.
 
I fly a 7 and not a 9 but have the same question. I find that if I use the flaps during a takeoff, I accelerate so fast that I can't retract tham fast enough to not overspeed them.

To complicate matters, I have the VP-X set to not allow the flaps to deploy above 100k and they will not retract above 100k either. Need to figure out how to change that. I want to be able to retract at any speed.

Not a good idea.

If you overspeed flaps, the preferred option is to leave them where they are, land and inspect. Moving them up or down risks further damage or worse. Imagine if you have buckled them and one retracts and the other doesn't.......
 
paul330,

Not sure overspending the flaps to the point where they would deform is ever a possibility the way I fly. A more realistic possibility is during takeoff, I hit the up button and as the flaps retract I hit 101k and everything stops even if they are almost completely up. (a VP-X thing) I need to slow down just as I am climbing away from the ground or point the nose higher to bleed off speed so I can complete the retract :D Why I don't normally use flaps on takeoff.
 
I like that quote Rick can I steal it? :D


On several (very rare)occasions I used full flaps on take off. OAT well below freezing, 10 gallons in the tanks. She jumped up indeed :D

I would do some stall testing with the flaps at half and full. I think you will find the only thing you gain is drag between the two. If you lost a engine at full flaps on takeoff it will be a difficult transition to avoid a stall.
I had some thoughts of having the flaps going to half with the flap switch and then have a speedbrake switch where I could modulate them from half to full since essentially all the flaps are in that range on a RV is speedbrakes.

George
 
I fly a 7 and not a 9 but have the same question. I find that if I use the flaps during a takeoff, I accelerate so fast that I can't retract tham fast enough to not overspeed them.
Pull the nose higher! Aren't you flying an air speed in this condition?

Related note. The simple flap RVs will climb very steeply and solidly with 20-25 degs flaps. Practice at altitude first.

Back to the -9 discussions.
 
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