TB 9-4920-457-24
(4) Tighten locking screw and replace black paper dot (R).
9. Vertical Speed Indicator
a. Performance Check
(1) Adjust TI vertical speed zero adjustment screw for 0 indication.
(2) Verify that PRESSURE CONTROL and VACUUM CONTROL valves are closed.
NOTE
As the vertical speed indicator case pressure equalizes with the
static system, the indicated rate will begin to decrease.
Continue to open VERTICAL SPEED control slowly until
indicator indicates 0, and then open fully.
(3) Observe vertical speed indicator and slowly open VERTICAL SPEED control
valve. Do not exceed full scale indication on vertical speed indicator.
(4) Slowly adjust VACUUM CONTROL until vertical speed indicator indicates 500 ft
per minute.
(5) When altimeter indicates (passes) 2000 ft, press LEAK CK pushbutton on
pneumatic pressure standard and enter 60 s. Record indication on pneumatic pressure
standard when check is completed.
(6) Slowly open VACUUM VENT valve until altimeter indicates less than 2000 ft,
then close.
NOTE
Start each of the following checks at approximately 2000 ft
indication on altimeter.
NOTE
The middle digit following the basic model number identifies the
vertical speed indicator installed in the TI. Table 5 lists
tolerances for each available model code. Select appropriate
(7) Repeat (5) and (6) above two times and average the three readings. Reset the
pneumatic pressure standard using the ESC key. The average reading will be within the
tolerance listed in table 5 for the applicable model code. Record TI error.
(8) Repeat (4) through (7) above for remaining vertical speed indications listed in
table 5 for the applicable model code. Record TI error at each indication.
