在不正常程序 CAB PRESS MAN CTL FAULT 中，提到了“automatic protection function”，但是在系统章节中并没有任何描述。
对此，空客回复如下：
For A350, the manual mode is smart. The unit for MAN mode is called "semi-automatic control unit" (SACU).
It contains protection functions, for instance:
- Against excessive differential pressure
- Against excessive cabin altitude
- Against pressurization with unsafe (not closed and secured) aircraft door; this function is called "prevention of pressurization".
The monitoring of the complete Cabin Pressure Control System allows to identify if the manual mode (within the SACU) has activated the prevention of pressurization erroneously; this is done by comparing the discrete coming from Door and Slide Control System (DSCS) to SACU with the status on AFDX. If the discrete to SACU is erroneous (meaning for instance broken wire), the monitoring detects that SACU has identified erroneously that the doors are not closed and secured and MAN CTL fault is triggered.
所以，半自动模式也有一些保护，可以避免过度压差、过高的客舱高度、以及在门没关好或者锁好的情况下增压。