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Flap Vfe

Scotty G

Well Known Member
Hi guys,

I should take possession of my RV-8 in six days, and want to see what the brain trust has as background on this subject.

I’ve seen Vfe values of 87 MPH, and heard of some at higher air speeds. 87 seems low, but if that’s what it is; so be it.

Seeing how there is structure and metal parts involved, I’m sure Van’s engineers have performed the load calculations and then set Vfe at a nominal and safe value.

Have any of you performed load analysis and added structure to get the higher Vfe, or are these just WAGs?

Not looking to arbitrarily change or do anything, I’m just genuinely curious how some have set the higher Vfe.

Thanks in advance.
 
The VFE is 110 mph for half flaps and 100 mph for full flaps. I think the 87 number you have is in knots for full flaps.
 
Well, that certainly makes a lot more sense. Still curious if others have higher speeds, how they went about it.

And no, I’m not considering trying it, I’m genuinely curious.
 
I added hexagonal rods from the flap actuator assembly to the flaps as I thought this was a "weak link" in the system.

I used geometry to compare forward facing flat surface area of the flap at 10, 20, and 40 degrees to Vans Vfe at 40 degrees. This gave me a starting number for the roughly equivalent force at 10 degrees deflection. I did not consider any aerodynamic forces that might exist.

I added what I considered to be a reasonable buffer to this number and made that my 10 degree Vfe limitation. After almost 300 tach hours I have not seen any adverse indications.

I use my number for 10 degrees, Vans number for 40 degrees, something in between for 20 degrees.

I have not disclosed my number on purpose. It is for each to decide through analysis and test.
 
Gotta ask... higher Vfe... for what? To solve which problem?

PS
My pattern is flown clean, flaps being extended whilst on finals...
 
Flaps 0 - 100+ knots

Flaps 1/3 - 100-90 knots - downwind leg

Flaps 2/3 - 90-80 knots - base leg

Flaps Full - Below 87 knots (if needed) - short final

Has worked great for me for 800-ish hours. I added the hexagonal pushrods as well.
 
Have any of you performed load analysis and added structure to get the higher Vfe, or are these just WAGs?

We’ve gotten off topic, and some replies have moved outside the scope of the actual question.

Of course the flaps change how the wing caries the imposed loads. Of course the construction manual says that. Etc., etc., etc.

But back to the question. Who’s actually done the math? I’m intrigued and interested in how that data was calculated if you changed your Vfe and/or associated hardware. I’m not asking for Your Deep RV-8 Secrets, I’m just an airplane nerd and air racer that digs engineering and smart people.
 
Gotta ask... higher Vfe... for what? To solve which problem?

PS
My pattern is flown clean, flaps being extended whilst on finals...

I'm wth you DeeCee I don't touch the flaps till I'm on final and assured of making the airfield (not so much the Rwy) I like a clean machine till the last minute in case it all goes quiet:)
 
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