Vne/Va/Aircraft Mods

[Dale]

I'm flying a pair of Cessna P206s that have the Wing X STOL extended
wings. This mod adds about 18 inches to each wing at the tip. (And for
anyone thinking of STOL mods I highly recommend these..they reduce
takeoff roll 20-30%).

One mandate from the STC is that Vne is lowered to 189 MPH from the
usual 210 MPH. There is no change in Va however. I'm wondering why the
reduction in Vne? If it is a load factor issue why isn't Va also
lowered?

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

[Gerry Caron]

"Dale" > wrote in message
...
> I'm flying a pair of Cessna P206s that have the Wing X STOL extended
> wings. This mod adds about 18 inches to each wing at the tip. (And for
> anyone thinking of STOL mods I highly recommend these..they reduce
> takeoff roll 20-30%).
>
> One mandate from the STC is that Vne is lowered to 189 MPH from the
> usual 210 MPH. There is no change in Va however. I'm wondering why the
> reduction in Vne? If it is a load factor issue why isn't Va also
> lowered?
>

My guess is load factor is probably not the limiting factor, dynamic
pressure (Q) is. Above 189 mph, the sum of lift and drag is likely
approaching the structural limit of the extension. Whereas, at Va, the max
load factor can't generate enough Q to break the extensions.

Gerry

[john smith]

Gerry Caron wrote:
> My guess is load factor is probably not the limiting factor, dynamic
> pressure (Q) is. Above 189 mph, the sum of lift and drag is likely
> approaching the structural limit of the extension. Whereas, at Va, the max
> load factor can't generate enough Q to break the extensions.

That is the way it was described in a paper I downloaded last week.