Hi Carl,
The reason you didn't get the answer you wanted is because
there is no published specific limit to the turning radius. Back when
Erco was turning Ercoupes out, owners and pilots were expected
to have and use "common sense", but in my humble opinion Erco
should have provided a lot more "Ground Handling" information.
Per the Service Manual:
"To prevent control stops from being damaged, do not force the
wheel at too great an angle from side to side. Do not use tow bar
with a tractor. Do not two airplane with a rope unless airplane is
steered from the cockpit."
How great is "too great"? Not said. If you are using a tow bar by
hand, you can gently push the airplane backward and slowly tighten
the turn radius until a control stop is encountered limiting the
"maximum" angle in that direction. Now do the same (again
backwards) in the other direction. That's not much of an angle either
way, is it? Now that you know the angles for your bird, so what?
The control system in our Coupes is not as flexible and forgiving as
that on many planes. Control rods from the control column-to-nose
steering collar, control column-to-mast assembly (behind the
seat), bellcrank to aileron bellcranks, aileron bellcranks to ailerons,
rudder bellcrank to rudders and elevator arm to elevator are rigid,
unyielding connections with no play when new by design. Even
our elevator and rudder cables connecting the mast assembly to
the elevator and rudder bellcranks are highly tensioned.
Relatively little pressure on a tow bar is instantly amplified back
through the control system. Think "force multiplication"...a small
amount of movement of the nose wheel translates instantly to much
greater movement of ailerons and rudders. The next time you're
horsing your coupe into alignment with tie-downs, watch the rudders.
I have personally observed all too many coupes manhandled such
that I could hear the rudders slam back and forth from inner to outer
limit. That's why so many of our rudders make a crinkling sound inside
when firmly wiggled with thumb and index finger on preflight, revealing
existing damage that should be repaired. It's even easier to cause
damage without a towbar when throwing the plane around by its prop.
What I'm trying to convey is that the coupe control system can be
damaged in a variety of ways and places by poor ground handling
practices. It's not just "angle of turn". Beyond that, it's anybody's
guess
whether damage will be in the form of an unseen fracture of the steering
collar, the steering ball (hardened and relatively brittle), or one of
the
stops welded on the top of the control column being broken.
If either of the first two fail when a coupe with a single fork nose
wheel
support is landing, there is nothing to keep nose wheel from turning
sideways and flipping the plane. I would urge any new owner with a
single fork nose wheel support to install steering kit FMK 101 which
replaces the steering ball with a bolt and female rod end bearing. The
modification also requires replacement of the nose gear pushrod with
#51035 (415-C thru G and F-1) or 52479-9 (F-1A, A-2, A-2A and M10).
Cost of parts is something over $200 and well worth it as "insurance".
I would urge any new owner to get their steering collar inspected no
later than the next annual by flourescent penetrant for cracks and
discontinuities that cannot be detected by the naked eye. No one
knows what abuse this vital link has been subjected to in prior years.
Why not use a tractor? (or golf cart or pickup truck?) Because line
personnel cannot be trusted to use only the sensitive human hand
on the end of the tow bar. Such tow vehicles can easily turn more
tightly than a coupe, particularly in reverse; and the driver will
likely
be unaware of (and likely deny) any damage thus caused.
I don't think marks are the answer. Reasonable care and under-
standing are. It's next to impossible to get someone else to handle
your flying machine as you would (or should) handle it.
Best regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2009)
--
On Feb 8, 2009, at 22:50, profedihmc wrote:
I asked in an earlier post about the turning radius of a 415C
with a double fork Cleveland nose gear. I got several interesting
entries but there didn't seem to be a consensus. I cannot physically
lift the front end off the ground nor am I in the least way
mechanically inclined. Don't know what gene it is that men get who
are able to turn wrenches and swing hammers; all I know is that I
didn't get that one and I'm not afraid to admit it. I could write a
technical manual, mind you, but I'm just not a mechanic. Is there no
where to turn for an informed answer to that question concerning the
turning radius? I'm trying to prevent damage to the nose gear by
someone parking my plane using a tug. I need to mark the gear
somehow and having the radius would help me explain it to the local
mechanic so he could mark it for me.
Thanks!
"Couper" Carl LaVon
N415CB '46 ERCO 415C
