Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Mon, 31 May 2004 16:38:36 -0400
Message-ID: <redirect-98342@logan.com>
From: "Dan Schaefer" <dfs155@adelphia.net>
Subject: Re: lnc2 flaps
MIME-Version: 1.0
Content-Type: text/plain;
	charset="Windows-1252"
Content-Transfer-Encoding: 7bit

Per Gerard's question about the flap actuation:

Can't comment on the need for bushings since I have an early 235 version and
I think the flap mechanism on later models was changed. However, I believe
the same (or similar) actuator was used (magnetically operated limit
switches).

Early on, I had some trouble with the actuator getting beyond the up-limit
switch allowing the motor to drive the to the mechanical stops, resulting in
the mechanism jamming in the reflex position. This happened several times,
most of which was caught during the pre-flight check - but not every time
(makes for an exciting landing if your intended runway is on the short side!
Because of this, by the way, I occasionally practice approach and landing
with the flaps in reflex - just in case - since anything can fail).

Each time, after disconnecting the actuator from the flap lever to get
things un-jammed, I found that the switch was OK. Long story short, I found
that if I let go of the flap switch just before the actuator was stopped by
the limit switch, the motor could coast just enough to go past the point
where the limit sw. should have stopped it. I believe the magnetized portion
of the feed-back rod is quite narrow and, in the right circumstances can get
past the limit switch.

In flight, and particularly during the initial flight test period, this
would happen when I "milked" the flaps into reflex, trying to find the best
amount of reflex. I never had a jam when I just held the flap switch until
the limit switch stopped the motor.

As an aside, I didn't like this and designed a separate flap drive limiting
device that is not affected by motor "coast". It also allows selecting any
amount of flaps without looking out at the wing to see where the  flaps are
(really helps on a go-around). Pretty easy to build and I think the plans
are in Marv's archives.

Dan Schaefer