Flaps for Take Off

A couple of questions that I cannot find on the site:
One is what static RPM should I expect out of my O 360-A1A, carb engine with a Sensenich fixed pitch prop from Vans. I had one fellow say 2100 was what he got but I would think it would be somewhere around 2250 +. I would appreiciate a few responses.
Also, some where I read some were using flaps for take off. If so is the take off distance much less, handleing qualities better than without, etc?
N542E is not flying yet but very close.
Thanks,
Ed Clegg
edwclg

Ed,
Normal static RPM should be around 2250-2300. Lower for a cruise prop and higher for a climb prop.
For short field take-off I recommend about 15 degrees of flap. The easy way to find this setting is to push the stick to one side and align the flaps with the "down" aileron. This is normally the best lift/drag ratio for the flaps.
I fly out of a 1500' strip in north Texas and 15 degrees of flaps produce a noticeably shorter take-off roll and better climb rate.

Short field technique is a moot point for RV's, but yes take-off distance is noticeably reduced and angle of climb increased. 15 degrees sounds right. I've only got 10 and 20 deg. notches. 20 degrees is much more effective, but you can feel the L/D ratio is not optimal. The high power-to-weight ratio of the RV-3 makes this negligible, though. Do it for fun, not 'cause you need to.

flaps for takeoff

Van recommends 10 deg flaps for takeoff, especially off grass or soft fields to get weight off gear sooner and added lift at slower liftoff speeds, plus better visibility over nose. Static rpm should be close to your opinion(2200-2250).

Static RPMs

Sensenich seems to think that the lower number for static rpm is normal.

Posted on the Sensenich BB - Wednesday, April 07, 2004 - 10:01 pm:

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Ed,

After visiting your booth at OSH several times in the last few years I finally decided it was time to buy when I found some very small cracks in my wood prop. I am now flying with the 72FM with 85" pitch on an RV-6, 0-360. The engine was bought new and now has 275 hours. The wheel pants are of the old style. Static rpm is about 2150 and at 8000' I can get 2710 rpm. The propeller is as smooth as the wood propeller (very smooth). I suppose this would be considered a cruise prop, but what really surprises me is how much better it performs on take off and initial climb--it makes me wonder if it should have more pitch? I am happy with it and do not intend to do any tweaking but am curious as to why I see more performance gain on take off and climb than in cruise. By the way, one of the hardest things about changing props was giving up the look of the wood prop, but the 72FM is growing on me and now I think it is just about as pretty. Thanks for a great product.

John Lane
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Posted on Thursday, April 08, 2004 - 08:23 am:

John,

Thanks for the kind words.

Your numbers (static and full throttle) are where most customers are comfortable. However, you may want something different. You can always have the pitch raised a bit more if you want to give up a little climb. We can discuss it in more detail later.

The metal prop should be more efficient then the wood. Structurally, the metal prop can be thinner. I'm sure you noticed that. However, I would guess that diameter may also be a factor here in the climb performance. Was your wooden prop shorter?

Ed----------------------------------

Static RPM

My static rpm is 2160. Sensenich cruise prop, 0-360.

edwclg said:

A couple of questions that I cannot find on the site:
...
Also, some where I read some were using flaps for take off. If so is the take off distance much less, handleing qualities better than without, etc?

Click to expand...

I use 1 notch of manual flap (15 deg) when taking off from grass as the ground roll is noticeably shorter. As I climb out at 120mph (fixed pitch on O-320) its easier to take off flaps up to make sure I don't forget to raise them, so from a 2000'+ hard runway I usually keep the flaps up.

Pete