CAUTION: DO NOT EXCEED NORMAL BAROMETER OPERATING RANGE OF 28.10-31.00 IN. HG (952-1049 MB). EXCEEDING RANGE MAY CAUSE MALFUNCTION OF PRESSURIZATION SYSTEM.
5) Open landing gear lights circuit breaker and check that outflow valve goes to full open within 1 minute as observed on the VALVE position indicator.
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6) Set CABIN PRESS BARO-SET counter to 0.3 in. Hg (10 mb) above field pressure and check that outflow valve goes to full close within 1 minute as observed on the VALVE position indicator.
7) Set CABIN PRESS BARO-SET counter to 0.3 in. Hg (10 mb) below field pressure and check that outflow valve goes to full open within 1 minute as observed on the VALVE position indicator.
(f) Check isobaric pressure reference. 1) Set FLT ALT control to 28,000 feet. 2) Set LAND ALT control to 5000 feet. 3) Check that CABIN PRESS BARO-SET counter is set at 29.00 inches of mercury and that outflow valve is open. 4) Assure that at least 2 minutes have passed since the LANDING GEAR LIGHTS circuit breaker was opened. Activate vacuum source to increase altitude at a rate of 2000 +300 ft/min. Stabilize at 4.0 +0.5 in. Hg differential pressure from ambient and hold for at least 1 minute.
5) Release vacuum at a rate of 2000 +300 ft/min and check that OFF SCHD DESCENT light comes on within 1 minute and then goes off after the pressure signal has returned to ambient.
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6) Slowly increase the barometric correction at a rate not exceeding 0.30 inch of mercury/minute while observing the VALVE position indicator. When outflow valve starts to close, stop changing barometric setting unless a small additional increase is required to completely close the outflow valve.
NOTE: Step 6) above is a setup step to just close the valve. When completed, a slight decrease in the correction will start the outflow valve toward open.
7) Increase LAND ALT setting to 5100 feet and check that outflow valve remains closed. 8) Increase LAND ALT setting to 5700 feet and check that outflow valve goes to
open. 9) Close landing gear lights circuit breaker. 10) On airplanes with one CABIN pressure fitting on front of controller;
a) With analog air data computer: 1 Actuate and hold the ALT SLEW switch on the No. 1 air data computer for at least 5 seconds. b) With digital air data computer: 1 Position TEST SELECT switch on the No. 1 air data computer for at least 5 seconds. 2 Press and hold PUSH-TO-TEST switch for at least 5 seconds. c) Release the switch and check that OFF SCHED DESCENT light does not
come on. 11) Select AC MANUAL OPEN and ensure that outflow valve is open. 12) Determine if there is any further need for electrical power on airplane, if not,
remove external electrical power.
2. Pressure Controller Test Pin Function Test (Fig. 501)
A. General
(1) The tests described in the following paragraphs will isolate problems to the pressure controller, pressure control panel, outflow valve and barometric correction potentiometers, landing gear module and No. 1 air data computer (No. 2 air data computer on airplanes with SB 21-1119) including the airplane wiring.
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TEST JACK NO. FUNCTION EXAMINED (COMPONENT) MODE
CPC22 CPC21 AUTO STANDBY MAN AC MAN DC
A 1 CABIN RATE (SELECTOR PANEL) X
B 2 FLT ALT (SELECTOR PANEL) X
C 3 LAND ALT (SELECTOR PANEL) X
D 4 BARO CORRECT - AUTO MODE (AIRCRAFT COMP) X
E 5 CAB ALT (SELECTOR PANEL) X
F 6 BARO CORRECT - STANDBY MODE (AIRCRAFT COMP) X
G 7 FLT - GRD SWITCH (SELECTOR PANEL)+ AIR - GRD SAFETY SWITCH (AIRCRAFT COMPONENT) X X X X
H 8 NO. 1 AIR DATA COMPUTER ALTITUDE REF (AIRCRAFT COMPONENT) (MERCURE USES SERVO ALTIMETER) 1 2 3
J 9 AC ACTUATOR (OFV) BRAKE VOTLAGE (CONTROL/OFV) X X
K 10 AC ACTUATOR (OFV) CLUTCH VOLTAGE (CONTROL/OFV) X X X X
L 11 DC ACTUATOR (OFV) CLUTCH VOLTAGE (CONTROL/OFV) X X
M 12 AC ACTUATOR (OFV) MOTOR VOLTAGE (CONTROL/OFV) X X
N 13 GROUND X X X X
P 14 STANDBY RATE LIMITER
R 15 AUTO RATE LIMITER X
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