Reduced Vertical Separation Minimum
(RVSM)
RVSM
Skin Waviness Inspection
Procedures
For Cessna Model 500/501 and
550/551 Citation Aircraft
Equipment Needed
The equipment needed to
complete the task
include:
Skin Waviness Inspection
Procedures Document Number
R34-0206
Skin Map Reference Bar –
With Base (part # KSR TOL
723)
Dial Indicator Depth Gauge
(part # Mitutoyo 547-217)
24 in. Flexible Steel Ruler
(various)
Grease Pencil or Dry Erase
Marker (various)
Establishing a Reference Grid
Draw a vertical line
through the upper and
lower static ports at least
6 inches above and
below
Locate a point midway
between the upper and
lower static ports and
mark
Determine the distance from
the center point of the static
ports to the skin overlay below
the static ports (approximately
3.25 in)
At a point about 12 inches
forward of the static ports,
measure up from the skin
overlay this same offset and
mark (approximately 3.25 in)
Using the 24 inch straight edge
and dry erase marker, draw a
horizontal line through the
centerline of the static ports
and the mark made from the
previous step being sure the
extend the line at least 14 in.
forward of the static port center
line and at least 4 in. aft.
Verify that the horizontal
line is parallel with the
skin overlay below and
that the line extends at
least 14 inches forward of
the ports and at least 4
inches aft as shown
Locate the double vertical
row of rivets approx. 3
inches aft of the static
ports
Locate a point just
forward of these rivets,
centered between these
and the rivet just forward
Measure the distance of
this point from the vertical
line drawn in step 1 and
record for next step
Measure aft from the top
and bottom of the vertical
line the same distance
and mark
Using the 24 inch straight
edge and the dry erase
marker, draw a vertical
line through these points
as shown in middle photo
When finished, your line
should resemble the one
shown in lower photo
At a point 15 inches
forward of the aft vertical
line just drawn, use the
straight edge and dry
erase marker to draw a
vertical reference line
This vertical reference
line should extend 8
inches above and below
the horizontal reference
line
The grid should now look
like the top photo
Next, for both vertical
reference lines (fore and
aft lines), mark each 1
inch increment (up to 7
inches above and below
the horizontal reference
line)
Both vertical reference lines
should now be incremented as
shown in top photo
Next step is to number the
increments
Positive numbers above the
horizontal reference line and
negative numbers below the
line as shown in lower photo
Verify the vertical lines are
parallel by measuring the
distance between the lines at
the positive and negative
seven inch mark (both should
measure 15 inches) before
continuing
Depth Gauge Setup
Start by adding the 2.5
inch extension and
reinstalling the plunger
end into the gauge,
ensure that the tip is
secured into place
Place the reference bar
on a flat smooth surface
and place the depth
gauge in the reference
bar track
Place the gauge near one
end of the reference bar
Zero the dial by pressing
ZERO/ABS, the gauge
should read 0.000
Confirm this zero (+/- 0.002)
at the opposite end of the
reference bar
Now check the function of
the dial depth gauge.
Ensure the gauge reads
negative numbers when
plunger is extended and
positive when retracted
(If not, press +/- button on gauge and
confirm proper sign, This should be
reconfirmed periodically during the
measurement process)
Skin Map Measurement
Begin by aligning the
reference bar with the +5
inch mark on the vertical
reference lines
While firmly holding the
reference bar in place,
stick the depth gauge
through the space in the
bar and align the gauge
at the 1 inch increment
Ensuring the depth gauge
is seated, now record the
measurement in table A1
Proceed to the 2 inch
increment on the bar and
record the measurement
Continue until all 13
increments are recorded
from bar
Now move reference bar
down to remaining vertical
reference lines and record
measurements in table A1
Additional Recording Methods
Measurements can also
be recorded by using a
Windows based computer
equipped with MS Excel
Plug the supplied depth
gauge cable assembly
shown in photos into a
USB port of the computer
Open the MS Excel
spreadsheet for RVSM
Waviness Recording
Additional Recording Methods
(cont.)
With the computer, select
the corresponding
spreadsheet cell for the
grid point to be recorded
Once the depth gauge is
firmly in place press the
DATA button on the depth
gauge accessory as
shown in photo
Verify measurement was
recorded in correct cell
Repeat procedures for
the rest of the grid points
Slope Calculation
Start at Horizontal Grid reference 5.0 and Reference Bar
Graduation 12.0, note the recorded measurement
Subtract this record measurement from the recorded
measurement to the left, in his case, Horizontal Grid
Reference 5.0 and Reference Bar Graduation 13.0
Enter the result in corresponding location in Table A2, in
this case, Horizontal Grid Reference 5.0 and Reference
Bar Graduation 12.0
Repeat steps 1-3 for the remaining Reference Bar
Graduations
Repeat steps 1-4 for the remaining Horizontal Grid
Reference rows down
Skin Overlay Measurements
Ensure the skin waviness
procedures are completed
Begin by using the 24 inch
ruler to mark (12) one inch
increments starting at the
aft vertical reference line
and going forward along
the aircraft skin overlay
When complete the
aircraft should resemble
the lower photo
Remove the 2.5 inch
plunger extension from
the gauge and reinstall
the tip, make sure the tip
is properly tightened to
the depth gauge
Verify that the plunger is
able to retract flush with
the blue base plate of the
depth gauge
If plunger fails to retract
fully into base plate as
shown in lower photo,
please perform base
plate adjustments in next
step
Depth Gauge Base Plate
Adjustment
Using the supplied hex
key, loosen the set screw
in the base plate and
adjust the depth until the
plunger is able to fully
retract into the gauge
base plate
Secure base plate by
retightening the set screw
and continue with skin
overlay procedures
Skin Overlay Procedures
Position the gauge near the
skin overlay mark such that
the plunger is depressed by
the upper fuselage skin
While holding the gauge in
place, zero the gauge by
pressing the ZERO/ABS
button
Now place the gauge base
plate on the upper fuselage
skin with the plunger next to
the skin overlay as shown in
lower photo (also see figure
5.2)
Start at the aft skin
overlay index mark (1
inch forward of aft vertical
reference line as shown
in top photo)
Record measurement
(gap between upper and
lower fuselage skin) onto
Figure A.1,
Now proceed to next
overlay index mark and
repeat until all 12 index
marks are measured and
recorded