Hi Don,
Comments interspersed below:
On Feb 27, 2009, at 18:33, n2808h wrote:
Greetings all,
Ever since I've owned my 415C I've tried to get the tail up to the
recommended height. I started right after I bought the plane by having
the A&P at the time do the sleeve or shim upgrade (I can't think of
the correct description but I got the entire package and paperwork
from Lee when he was running Skyport)...and I had them replace the
existing Bellville springs with new rubber donuts. That got me close,
maybe 1 inch or so low. Now, seven years later, is currently 3" below
the recommended height from the top of the vert. stab to the ground.
The "recommended height" is a red herring because of the variation in
nose strut/fork/wheel size-length combinations. It is NOT "one size
fits all".
The plane is set up correctly when the aluminum sill one each side of
the cockpit is LEVEL from side to side and fore-aft.
It has an old style, double fork nose gear (not sure what that means
but it what the current A&P said).
The "old style, double fork nose gear" would have the close-fitting fork
fitted to Ercoupes serials 1 through 186. Your airframe should be
Serial
No. 3433, which is much later to have the "early" fork which had a Hayes
5.00 x 4 two-bearing wheel fitted.
If you have a 5" nose wheel and tire and a double fork, then you either
have the Univair double fork assembly U415-34310-1A shown on page 21
of the Parts Catalog, or the Forney-Alon-M10 double fork shown in the
various Parts Catalogs and the Univair catalog.
The Univair fork should not cause a tail low problem because it uses
taxi spring U415-34104. Because this fork was originally intended for
use
as a "steel gear" conversion that originally had a 4" wheel and tire,
the
taxi spring is shorter to compensate for the greater height of the 5"
wheel
and tire.
The A&P measured the entire donut
stack and compared it to another Coupe he is working on an it is 1/4"
shorter.
This does not make sense. The "height" of the taxi absorber stack
assembly is absolutely fixed when the retaining clip is installed. For
this reason I must "recant" my earlier belief that Bellevilles somehow
raised the tail.
If rubber donuts are new (not "new-old" stock), it requires some method
of mechanical compression to hold everything so the retaining clip can
be installed (and when pressure is released, there should be no vertical
"looseness".
The Belleville installation kit includes six aluminum washer spacers,
part number F-33254. These are used "as necessary so that there is
a maximum of 1/16" vertical free movement in the stack (and if it were
my plane, I would add another spacer if I had that 1/16" stack slop).
My question is this. Do most of you have Bellville springs or donuts?
I don't mind putting donuts in periodically but my concern is whether
even new donuts will get me the correct tail-up attitude that I want.
The donuts are by far the most common. New donuts with spacers as
described should resolve your problem.
Can I find Bellville's out there? Are Bellville's the only real
solution?
Yes, Bellevilles are available; but they are NOT a solution for your
problem as described.
I live in Colorado and fly out of an airport the Eastern Slope of the
Rocky Mtns. and the wind ALWAYS blows here. I landed last night in a
quartering x-wind 14knts peak gusts to 21knts. Those conditions may be
old-hat to a long-time 'Coupe driver, but they had my complete and
undivided attention. 08H did its thing, touching down in a crab at
about 60 mph, and I did my thing by relaxing control on the yoke as it
swung around and started tracking straight.
That's the right technique.
I always add a little forward yoke to firmly plant the nose wheel and
then
I'm driving it, but I'm thinking to myself that I've got to get this
fixed.
Don
08H
If you gradually slow the plane to minimum speed and full back yoke in
the crabbed flare before touchdown, the plane will stay down once down.
That said, anyone who continues to fly a bird with a genuine "low tail"
problem is accepting increased risk in high crosswind operations and
sooner or later may be called upon to "pay the piper".
Understand, I'm not a mechanic; but I've done all this (under
supervision,
of course)
William R. Bayne
.____|-(o)-|____.
(Copyright 2009)
