Message-ID: <000d01c10f60$91424140$ae6b1b3f@F.Schaefer>
Reply-To: "dfs" <dfs@gateway.net>
Reply-To: lancair.list@olsusa.com
From: "dfs" <dfs@gateway.net>
To: "Lancair list" <lancair.list@olsusa.com>
Subject: LNC2 flap speeds
Date: Wed, 18 Jul 2001 01:06:35 -0700
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For reference, I have an early L235 with the upper-surface hinged flaps.

When Mike DeHate came to check me out when it was time to fly, he was
adamant that the flaps be in reflex any time my IAS was 160 MPH and above.
Don't remember reading this anywhere but if Mike said do it, that's good
enough for me.

In doing some research on the NLF series airfoils used on the LNC2's, it
turns out that they have quite a high pitching moment (tendency to twist
leading edge down) relative to more common airfoils. As I understand it, the
twisting stresses on the wing structure, due to this function, increase with
airspeed so there is some structural speed limit unless you do something to
alleviate the twisting forces. Reflexing the flaps does just this - at least
up to red-line.

Further, the high pitching moment forces you to use a lot of up elevator to
counter it creating a very high trim drag situation, which in turn, holds
your speed down. You should see the effects of this at the time you run the
flaps up to the reflex (cruise) position - if your airplane is like mine, I
have to put in a lot of down trim and the plane accelerates like it was
going down hill!

On deceleration for landing, I always leave the reflex in until I've slowed
below the 160 MPH mark, per Mike.

As an added bit of info, I've practiced landing while in reflex just in case
the flap system fails during cruise. If you haven't done this, you should
make sure you can handle the situation because there's no way to move the
flaps should you lose the flap motor or your electrics. You will land sorta
long and fast so stay away from short runways if such a failure develops.

Incidentally, from experience, let me warn you that if you're flying
formation with the other airplane in trail, you'd best alert your buddy that
you're going out of reflex because it's like throwing out an anchor and he
will certainly run up on you in a heart beat!

Cheers,

Dan Schaefer


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