TM 55-6610-247-40
z. Changing length of calibration arm causes change
a plus error. turn screw out: to correct a
minus error, turn screw in. Each
in speed of rotation throughout range. Adjustment of
revolution of screw will correct an error
calibration arm speeds up or slows down mechanism
of approximately 80 feet.
throughout entire range. See figure 2-9.
NOTE
Check points listed in table 23 are
primary check points to be used during
position error adjustments.
x. Either change of diaphragm position or change in
length of calibration arm speeds up or slows down
mechanism with corresponding in crease or decrease in
rate of hand rotation between zero and maximum
altitude.
y. Shifting diaphragm position changes speed of
rotation at high altitudes more than at low altitudes.
Shifting diaphragm toward rocking shaft speeds tip
mechanism while shifting it away from rocking shaft
slows down mechanism. See figure 2-8.
Figure 2-9. Effect of Calibration Arm Movement
on Error-feet Range.
aa. By a combination of both adjustments. speed of
rotation can be selectivelv increased or decreased in low,
middle, or high altitude ranges.
ab. The following ratios may be applied when shifting
calibration arm or diaphragm in relation to correction
obtained in instrument indication. Ratios are approximate
but ",ill help in adjusting procedure. Figures for calibration
arm are based on a final change in reading of instrument
caused by turning drum of vernier calibration tool. part
no. TE 639, one segment. Figures for diaphragm are
based on a final change in reading of instrument for initial
change in reading. caused by moving diaphragm. Refer
Figure 2-8. Effect of Diaphragm Movement on
to table 2-4.
Error-feet Range.
Table 2-3. Check Points
STANDARD
EQUIVALENT
SCALE ERROR
ALTITUDES
ATMOSPHERIC PRESSURE
TOLERANCE
MERCURY
FEET
MM
INCHES
FEET
0
760.0
29.92
+20
5,000
632.4
24.89
+40
20,000
349.1
13.75
+130
35,000
178.7
7.04
+350
2-13
