737 FCC
Hello colleagues
I have a question regarding the 737 FCC. Here goes: RHS FCC is master and A/P is connected. If HDG bug is turned, both F/D roll bars turn towards new heading. Fair enough. Next, RHS FCC is master and A/P is connected. RHS VHF panel has a localizer frequency selected and crs selector set to an inbound course. VORLOC is selected on the MCP. LHS VHF panel has a VOR frequency selected and CRS selector set to a 20 degree offset course from the localizer. Ok, the A/P will follow the localizer track, but the LHS F/D will show an offset, right? Even though RHS FCC is still master. The FCOM states: Rotate Captain’s course selector – provides selected course information to: • A FCC • No. 1 VHF NAV receiver • Captain’s course pointer and course deviation bar. Note: In VOR LOC or APP mode, the A A/P and Captain’s F/D use selected course and navigation data from the No. 1 VHF NAV receiver. Rotate First Officer’s course selector – provides selected course information to: • B FCC • No. 2 VHF NAV receiver • First Officer’s course pointer and course deviation bar. Note: In VOR LOC or APP mode, B A/P and First Officer’s F/D use selected course and navigation data from No. 2 VHF NAV receiver. It also states: F/D modes are controlled directly from the respective FCC under certain conditions. This independent F/D operation occurs when neither A/P is engaged in CMD, both F/D switches are ON and one of the following mode conditions exists: • APP mode engaged with LOC and G/S captured • GA mode engaged and below 400 feet RA • TO mode engaged and below 400 feet RA. Independent F/D operation is indicated by illumination of both MA lights. When independent operation terminates, the MA light extinguishes on the slaved side. So my question is: Why at all have a master FCC in F/D - operation at all? In situations where it seems we may have differing inputs on the left or right hand side (VORLOC/APP mode), the master function is from what I understand not applicable. I may be way off here, but any input is very welcome. Thanks :ok: |
The FCOM states that 'This independent F/D operation occurs when neither A/P is engaged in CMD'.
In the example you posted, you mentioned that the A/P is engaged so the LHS F/D is a slave of the RHS F/D. |
....and if the AP is in CMD in your example the FOs display will not show the FD bars because the ILS is not set.
|
Thanks for answering, but I'm afraid you're mistaken. Tested it in the simulator today. Only the RHS has MASTER-indication, but the LHS is NOT slaved. Read my first note from the FCOM:
Note: In VOR LOC or APP mode, the A A/P and Captain’s F/D use selected course and navigation data from the No. 1 VHF NAV receiver. So RHS show correct tracking, LHS shows an offset F/D. When A/P IS engaged I understand it's value, because you'd want to know what F/D-bars the A/P is following. On the other hand I'm not sure I get it if we were to have the same setup and the A/P's off. |
I'm assuming you had the B A/P engaged for your test run in the sim?
|
Both with the B A/P engaged-, and not engaged.
|
All times are GMT. The time now is 04:03. |
Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.