When A220's PFCCs are all failed, the airplane enters direct law mode. In this mode, from description, pilots should manually control stabilizer trim. When this situation occurs, does pilot need to control stabilizer trim by controlling trim switches on the sidestick? Or is there any manual stab trim lever or wheel on board?

Plus, is there any feature that turns off speed trim bug or automatic stab trim in the simulator? (The model is CAE 7000xr)


1 Answer 1


The trim switches on the sidesticks are used during direct mode:

Sidestick pitch trim switch

The pitch trim is controlled by two pitch trim switches, one located on each sidestick:


In normal mode, the horizontal stabilizer position is determined by the FBW Control Laws (CLAWS). The autotrim function automatically off-loads the stabilizer, independent of the sidestick trim switches.

In direct mode, the pitch trim switches move the horizontal stabilizer directly.

(Bombardier CS300 / Airbus A220 FCOM 10-4: Flight Controls - Secondary Flight Controls)

There are no alternate switches on the pedestal (since the switches on the sidestick are already the alternate), nor is there a mechanical override in the cockpit, only 2 electrical motors:

Horizontal stabilizer

The horizontal stabilizer achieves the pitch trim function by varying its angle of incidence. A dual-channel Horizontal Stabilizer Trim Actuator (HSTA) moves the horizontal stabilizer. The HSTA includes two electrical motors, each controlled by a Motor Control Electronics (MCE) unit. The MCE receives commands from two REUs (AFT 1 REU and AFT 4 REU).

(Bombardier CS300 / Airbus A220 FCOM 10-4: Flight Controls - Secondary Flight Controls)

Note that depending on the type of direct mode, pitch trim speed may differ based on slat/flap position:

PFCC direct mode [...] The sidestick pitch trim switches control the horizontal stabilizer position directly as a function of the slat/flap position. [...]

REU direct mode [...] The pitch trim rate is a function of the slat/flap position, but is slower than PFCC direct mode. [...]

AFCU direct mode [...] The pitch trim is like PFCC direct mode regardless of slat/flap configuration.

(Bombardier CS300 / Airbus A220 FCOM 10-2: Flight Controls - FBW system operation - Direct Mode)

  • $\begingroup$ Thanks for detailed answering! Your description really helped me, have a good day! $\endgroup$
    – moon
    Commented Feb 23 at 2:07
  • $\begingroup$ And, could I ask you one more question? Where can I find my current flight track information on PFD's HSI and Map Display? Only Magenta circle is my current track information? $\endgroup$
    – moon
    Commented Feb 23 at 2:10
  • $\begingroup$ But, even that's correct, I couldn't find any cue in FCOM that magenta circle is current track ;( $\endgroup$
    – moon
    Commented Feb 23 at 2:11
  • $\begingroup$ @moon AFAIK the current track is not displayed on the PFD or map. Only current heading and desired track can be seen there. You can however see the current track in the IRS information (FMS -> POS -> IRS): "TRK/GS, indicates the aircraft track and groundspeed calculated by the IRS". $\endgroup$
    – Bianfable
    Commented Feb 23 at 9:10
  • $\begingroup$ Then how can I execute hand flying raw data ILS? without track information it sounds very hard in windy condition $\endgroup$
    – moon
    Commented Feb 23 at 11:41

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