Cabin Pressurization Panel

Question 1

OFF SCHED DESCENT light

Answer 1

• aircraft has started descent at least 1,000 ft prior to reaching the altitude set in the FLT ALT window
• if the FLT ALT indicator is changed, the automatic abort capability to the original takeoff field elevation is cancelled

Question 2

ALTN light

Answer 2

• indicates pressurization system operating in alternate mode
• selected automatically or manually
• if the mode selector is in AUTO, illumination of both the ALTN and AUTO FAIL lights indicate a single controller failure and automatic transfer to the ALTN mode

Question 3

MANUAL light

Answer 3

• pressurization system operating in MANual mode, selected with the mode switch
• operate the outflow valve to maintain proper cabin altitude and cabin rate of change

Question 4

DIGITAL PRESS MODE SELECTOR
AUTO -
ALTN -
MAN -

Answer 4

AUTO
- automatic pressurization control (normal mode of operation) uses a DC motor
ALTN
- automatic pressurization control (alternate mode of operation) uses another DC motor
- second of two digital cabin pressure controllers, so auto mode has dual redundancy
- the green ALTN light illuminates if ALTN is selected
MAN
- overrides and bypasses the two cabin pressure controllers
- has its own valve motor system for triple redundant architecture
- 28v dc bat bus power source

Question 5

AUTO FAIL light

Answer 5

• illuminates if automatic pressurization system failure detected:
• indicates a single controller failure when ALTN light is also illuminated
• indicates a dual controller failure when illuminated alone
• MASTER CAUTION and AIR COND annunciator lights come on