Mooney M20C - Weston-Garwin Altimeter Inspection; Inspection Step 1 & 2: Barometric Scale Setting; Inspection Step 3 & 4: Mechanism Movement Test

SUBJECT:
ALTIMETER
INSPECTION
MODELSPI~EC1TED:
~zoc,
S/N
670001-670135
~20E,
S/N
1177,
1199,
1217,
1268,
1273,
1277, 1281,
1283,
1286
thru
1288,
1290,
1292,
1293,
1295
thru
1308,
670001
thru
670062
~20F,
S/N
660001
ihru
660004,
670001
thru
670446
P122,
S/N
670001
and
670002
This
Bulletin
will also
apply
to
any
other
Mooney
airpla3le
for
which
a
Trleston-Garwin
Model
22-374
aftimeter
was
purchased
between
July
i,
1966
and
August
2,
1967.
~E
OF
COMPLIANCE:
Immedia’;ely,
this Service
Bulletin
is
mandatory.
INTRODUCTION=
Evidence has
been found that
an
accumulation
of tolerances
in
some
Weston-Garwin
Model
22-374
altimeters
can
cause
a
malfunction
of the
instrument.
Since
this
condition is
li~ely
to
exist
in all
airplanes
which
are
equipped
with
Model
22-374
altimeters,
this
Service
Bulletin
is
being
issued
to
require
testing
of
the
altimeter
and
replacement,
if
necessary,
on
several models
of
Mooney
airplanes.
II~STfLUCTIONS:
To
determine
if
the
Weston-Gar~Jin
Model
22-374
altimeters
are
operating
properly,
accomplish
the
following:
1)
Set
barometric
scale
or" altimeter
to
coincide
with
appropriate
field.
pressure
and
check
altimeter
reading.
It
should
agree
with
field
elevation
allowing
for
a
tolerance
of
plus
or
minus
100 feet.
2)
Set
barometric
scale
of
altimeter
to
29.92
inches
of
hg
(1013.3 mi77;hars)
and
observe
the altimeter
reading.
3)
Turn
the
bare
mechanism
so
as
to
move
the
scale
to
the
low
end
stop.
During
this
movement,
exert
slight
pressure
forward
and
aft
alternately
in
order
to
see
if
it
is
possible
to
cause
the
internal
mechanism
to
become
disen,oa,Ped.
The
disengagement
will
be
obvious
if the
pointer
hand fails
to rotate
as
the
knob
is turned.
4)
Turn
the knob
for bare
scale
soas
to
move
the scale
to
the
high
end
stop.
During
this
motion,
again
exert
pressure
by
alternately
pushing
and
pulling
slightly
and
watch
for
needle
slippage.