Flight Loads on Flaps

[AlexPeterson]

I saw somewhere on a recent posting some discussion of forces needed to deploy flaps. I have HDPE tape on the flap skins where they rub the wing top skin, and there are clear witness marks showing where the flaps are during flight. Of course, on the ground with no loading, they are down a bit further than these marks indicate. What is amazing is how little force it takes at the trailing edge of the flap to "raise" them to their highest flight position. I'd estimate it might be 15 pounds per flap. I'll try to measure it with a fish scale next time I'm at the hangar.

Of course, some brave or crazy guy who has manual flaps could get some altitude, use a fish scale, and post the results! I can't imagine how we can build and fly these planes without this important data!

[Ron Lee]

Do you want the force needed to raise the manual flap to the first, second and third detents?

If so, I would suggest 100 mph for the first, 90 mph for the second and 85 mph for the third.

[Norman CYYJ]

You have to have a very strong arm to move the flaps at 100mph. I have found at that speed it takes two hands to lower them, mind you I am not that strong either.

[gasman]

I have two notches of flaps. First notch is at 100 mph down wind. The pull is about as hard as setting the E brake on a 70 VW. My flap handle is cut short, and lowered to the floor and left just high enough to get my fingers around it. Now I don't have to lift as far to set the flaps.
To extend to full flaps, I wait till I am on base and at 85 mph. I have altered my flap bracket so I don't push the button for the second and final notch of flaps. I can just reach and pull and it is done. BUT 85 IS THE MAGIC NUMBER.

I love these flaps and would not even think of going electric after reading about all of the problems that people have had................ well, maybe if I gained 75 pounds I might need to go electric. But for now, EL Manual!!

[rocketbob]

I love my manual flaps too. For kicks I have put some flap down in cruise to see what effects the trailing edge have on the trim of the airplane, maybe 5 degrees. I just held it there since there's no notch at that point. The airplane will pitch nose down slightly but it has suprisingly little affect on speed and trim. I'm guessing the trailing edge was down maybe an inch. I've also put flaps down at 120 and it takes a heck of a pull to do that. Much easier the slower you get.

I have done some tests and found the difference between half flap and full flap has a negligible effect on stall speed, 1-2 knots. The stall however is less abrupt. So I started landing with half flaps a few years ago and found that I consistently get better landings, especially three point. Landings seem just as short.

[Mel]

My flap handle is build like Gasman's except that I have 3 notches. I deploy to first notch (12 degrees) at 105-110 mph.
Specs call for up to 20 degrees at 110. Full deflection at 100.
I also agree with Bob in that the last notch has little effect on stall speed, but it does add drag, so I still use full flaps for short fields.

[Bob Axsom]

I owned a Piper Archer II with manual flaps for 22 years and I loved the operational flexibility they gave me but they were not an option on the standard quickbuilt RV-6A. I thought I would miss the ability to go to full flaps and slip through holes on circle to land instrument approaches like VOR-A to El Monte (EMT). In fact it has not proven to be a problem. When the plane slows to the top of the white arc on the airspeed indicator I depress the flap switch an glance at them out of the canopy and release the switch when they stop moving. The original flight testing by Van and countless over speed deployments of the flaps by the more than 2,248 RV-6 airplanes give me assurance that operation within the white arc will not cause a problem and the spring in the system is not a problem for me. All I want is the drag they provide at full deflection and every approach is a short approach where practical. I have stainless steel on the leading edge of the flaps and the trailing edge of the stainless steel exactly aligns with the trailing edge of the wing skin. There are no marks on the flaps aft of the stainless steel and flaps do not raise above the ailerons and wing tip line in flight. I am a little curious why this caused you concern. I know you have been flying your plane for quite a while - do you suspect an anomaly in your installation? I would imagine that there is more slack in the manual flap system like there is in my manual pitch trim system.

Bob Axsom

[AlexPeterson]

Originally Posted by Bob Axsom

I owned a Piper Archer II with manual flaps for 22 years and I loved the operational flexibility they gave me but they were not an option on the standard quickbuilt RV-6A. I thought I would miss the ability to go to full flaps and slip through holes on circle to land instrument approaches like VOR-A to El Monte (EMT). In fact it has not proven to be a problem. When the plane slows to the top of the white arc on the airspeed indicator I depress the flap switch an glance at them out of the canopy and release the switch when they stop moving. The original flight testing by Van and countless over speed deployments of the flaps by the more than 2,248 RV-6 airplanes give me assurance that operation within the white arc will not cause a problem and the spring in the system is not a problem for me. All I want is the drag they provide at full deflection and every approach is a short approach where practical. I have stainless steel on the leading edge of the flaps and the trailing edge of the stainless steel exactly aligns with the trailing edge of the wing skin. There are no marks on the flaps aft of the stainless steel and flaps do not raise above the ailerons and wing tip line in flight. I am a little curious why this caused you concern. I know you have been flying your plane for quite a while - do you suspect an anomaly in your installation? I would imagine that there is more slack in the manual flap system like there is in my manual pitch trim system.

Bob Axsom

Bob, were you referring to me? I have no anomolies, just an observation. BTW, just to be clear, I'm talking about how much deflection from full down flap position there is between static and flight loading. You should be able to see the same affect on yours. Lower the flaps completely, and look to see if you see witness scratches which show where the flaps generally are in flight when fully down.

[Bob Axsom]

OK that makes more sense to me but I have the same basic conclusion. I would certainly expect the flaps to yield to full down air loads at max flap speed.

Bob Axsom