TM 55-6610-247-40
Table 3-2. Scale Error Test
STANDARD
EQUIVALENT
SCALE ERROR
ALTITUDES
ATMOSPHERIC PRESSURE HG
TOLERANCE
PRESSURE MERCURY
FEET
MM
INCHES
FEET
0
760.0
29.92
*20
500
746.4
29.39
20
1,000
732.9
28.86
*20
1,500
719.7
28.33
25
2,000
706.6
27.82
*30
3,000
681.1
26.81
30
4,000
656.3
25.84
*35
5,000
632.4
24.89
40
6,000
609.0
23.98
*40
8,000
564.4
22.22
*60
10,000
522.6
20.58
*80
12,000
483.3
19.03
*90
14,000
446.4
17.57
*100
16,000
411.8
16.21
*110
18,000
379.4
14.94
*120
20,000
349.1
13.75
*130
22,000
320.8
12.63
*140
25,000
281.9
11.10
*155
30,000
225.6
8.88
*180
35,000
178.7
7.04
*350
point or points as listed in table 3-4 take two readings:
corrected by either of the methods described above,
first, before tapping instruments, and, second, after
diaphragm assembly must be replaced.
tapping it. Change in reading of pointers shall not
3-8. Friction Test.
exceed tolerances given in table 3- 4.
Test for friction as follows:
a. While holding pressure constant at any
Table 3-3. Hysteresis and After Effect
EQUIVALENT
PERMISSIBLE
STANDARD
ATMOSPHERIC
VARIATION
ALTITUDE
PRESSURE
FROM SCALE
TEST POINTS
IN FEET
(MM HG)
ERROR (FEET)
First Hysteresis
18,000
379.4
75
Test Point
Second Hysteresis
14,000
446.4
75
Test Point
After Effect
Local Pressure
30
b. While operating instrument at rate corresponding
(2) From 25,000 to 30,000 feet, movement of
pointer must be smooth although not necessarily regular
to an increase in altitude of approximately 3,000 feet per
when vibration is applied.
minute, a further check for friction is as follows:
(3) This test may be combined with test for scale
(1) From 0 to 25,000 feet, without vibration, pointer
error.
must not jump more than indicated tolerances given in
(4) If instrument fails to meet this test, it must be
disassembled and cleaned.
3-3
