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Steve's Cessna 140 Lower Doorpost Cracks :-(
I was down at Rick's
hangar one day checking out his project, and he had this hangdog look on his
face. He had just found that he had cracks in the bottoms of both
doorposts in his 140 fuselage, which was already
apart for gear box repairs. This
was only going to add to the work he had to do to get it flying. I think
he was already sorry that he sold me his previous airplane (the yellow one), and
I'm sure this latest discovery only made him regret it more.
As we talked, I wondered out loud, half-joking, if I might have the same
cracks in my airplane, since they're very common to 140's. We decided to
go down to my hangar and see Rick grabbed his magnifying glass and
we went down to check. Sure enough, I looked and found that I had the same
cracks,
on
both
sides! As I announced this fact, I'm pretty sure that I detected a
slight smile on Rick's face.
These cracks are a common problem with Cessna 140's, but they seem to be ignored by most owners. It's hard to blame them, considering what a pain it is to do the repairs. The cracks start in a bending notch in the doorpost, below the floorboard, just above the area where the wing strut attaches, and travel about a half-inch until they reach a rivet hole (the "first rivet hole"). Most of the time they stop at this hole, but in a couple of cases I've seen, they continued through this hole on the way to the next, which is most of the way across the structure. Since the crack is in a part of the doorpost that is "sandwiched" in among four other layers of structure, there is no way to see if the crack has progressed beyond the first hole.
Although
there
is
no
Airworthiness
Directive
on
this
problem,
and
there
seems
to
be
no
known
case
of
any
airframe
failures
resulting
from
this
crack,
I
decided
to
go
ahead
and
do
the
"official"
repair
using
Cessna
service
kit
SK150-53.
This
kit
contains
a
drawing
and
a small
piece
of
aluminum,
a
replacement
for
what
I
call
the
"big
doubler"
that
extends
a
couple
of
inches
above
the
cracked
area
where
it
is
riveted
to
the
doorpost.
This
area
is
a
real
pain
to
repair
because
it
involves
double-flush
(flush
on
both
sides)
number
6
AD
rivets.
Below are some pictures taken during the repair of my airplane. They are a documentation of my own repairs so
others can see what was
involved.
Please
check
with
your
mechanic
and/or
IA
before
doing
anything
based
on
what
I
have
shown
here.
I
am
doing
this
work
under
the
supervision
of
an
experienced
A&P/IA,
and
other
experienced
individuals,
but
I
am
by
no
means
an
expert
and
this
page
should
not
be
construed
as
a "how-to"
on
doing
the
Cessna
140
lower
doorpost
crack
repair.
It's
for
information
only.
Click
on
the
thumbnails
below
for
larger
images,
or
view
as
a
slideshow
by
clicking
the
first
picture,
then
using
"Next"
and
"Previous"
links
at
the
top
of
the
page
to
move
around.
My Doorpost (start here) |
Rick's doorpost |
Rick's doorpost |
Rick's doorpost |
Rick's doorpost |
Rick's gearbox |
My doorpost crack |
Fuselage stand |
|
Wing support |
Jacking |
Wheel removal |
Axle removal |
Axle shims |
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