1811D INSTRUCTION MANUAL
56-101-00164 Rev. F
SECTION 3
Apr / 19 / 13
Page 14 of 38
B. Static Pretest
(1) Open CROSSBLEED valve (#3) fully.
(2) Open VACUUM valve (#5) to bring altimeter to 20,000 ft. Close valve and monitor
the airspeed for one (1) minute. (Airspeed should not fall more than 2 knots.)
Record leak rate.
Note: If necessary, pump additional vacuum.
(3) Open PRESSURE VENT (#2) valve to return the altimeter to ambient pressure.
Caution: Opening the VACUUM VENT valve (#4) could cause damage to the
Airspeed indicator.
C. Applying a Leak Correction
(1) If the leak rate does not exceed 2 knots or 100 ft in 1 minute, determine the actual
aircraft system leak rate by adding the observed rate obtained from a previous
aircraft leak test to the recorded rate.
D. Instrument Calibration Correction
Before attempting calibration tests of aircraft instruments, ensure that instrument
correction card calibration dates are within the approved recertification periods.
Note: Calibration cards are based on tests performed with instruments vertically
mounted (i.e., face up) and at a 75° F (24° C) temperature. A slope of more than
30° from level, and/or a temperature difference of more than
15° F (
8° C),
could affect the precise calibration accuracy.
E. External Pressure and Vacuum
To use the external pressure and vacuum source, remove the vented plugs from ports
(#J) and (#K). Install the appropriate connecting fittings and connect them to pressure
and vacuum sources. Raise the PRESSURE PUMP handle (#A) before applying
external pressure. (The pump handle will rise when external pressure is applied.)
Caution: Do not exceed 20 psi external pressure.