TB 9-4920-457-35
Table 4. Altimeter Accuracy Check - Continued
Test instrument
Pneumatic pressure standard indications
indications
(ft)1 2
(ft)
Min
Max
4000
3900
(3900)
[3930]
4100
(4100)
[4070]
5000
4900
(4900)
[4930]
5100
(5100)
[5070]
6000
5900
(5900)
[5930]
6100
(6100)
[6070]
8000
7850
(7825)
[7920]
8150
(8175)
[8080]
10,000
9850
(9825)
[9910]
10,150
(10,175)
[10,090]
12,000
11,800
(11,800)
[11,900]
12,200
(12,200)
[12,100]
14,000
13,800
(13,775)
[13,880]
14,200
(14,225)
[14,120]
16,0003
15,800
(15,760)
[15,860]
16,200
(16,240)
[16,140]
18,0003
17,800
(17,725)
[17,840]
18,200
(18,275)
[18,160]
20,0003
19,800
(19,700)
[19,820]
20,200
(20,300)
(20,180]
22,000
21,700
(21,660)
[21,800]
22,300
(22,340)
[22,200]
25,0003
24,700
(24,625)
[24,760]
25,300
(25,375)
[25,240]
30,000
29,700
(29,550)
[29,740]
30,300
(30,450)
[30,260]
35,000
34,700
(34,475)
[34,720]
35,300
(35,525)
[35,280]
40,000
(39,400)
[39,700]
(40,600)
[40,300]
45,000
(44,325)
[44,680]
(45,675)
[(45,320]
50,000
(49,250)
[49,660]
(50,750)
[50,340]
55,000
[54,640]
[55,360]
1Values
in parenthesis are for TIs with 50,000 ft altimeters.
2Values
in brackets are for TIs with 55,000 ft altimeters.
3Wait 5 minutes, then record pneumatic pressure standard indications at these points.
NOTE
No hysteresis check is specified for 55,000 ft altimeters.
(11) Slowly open VACUUM VENT valve until TI indicates 18,000 ft (25,000 ft for
50,000 ft altimeters). After 10 minutes pneumatic pressure standard indication will be
within 70 ft (150 ft for 50,000 ft altimeters) of indication recorded in (10) above for 18,000 ft
(25,000 ft for 50,000 ft altimeters).
(12) Slowly open VACUUM VENT valve until TI indicates 16,000 ft (20,000 ft for
50,000 ft altimeters). After 10 minutes pneumatic pressure standard indication will be
within 70 ft (150 ft for 50,000 ft altimeters) of indication recorded in (10) above for 16,000 ft
(20,000 ft for 50,000 ft altimeters).
(13) Slowly open VACUUM VENT valve until altimeter indicates lowest reading
with valve open completely. After 5 minutes altimeter will indicate within 50 ft (60 ft for
50,000 ft altimeters) of indication recorded in (8) above.
(14) If all indications are within tolerance, annotate correction chart and place in
holder on TI faceplate. The correction chart will show standard indications when TI
indicates nominal values.
7
