PDA

View Full Version : master FCC in 737NG


alistomalibu
16th Jul 2009, 19:00
Hi

My question: What will the autopilot do in this following scenario?
Pilotīs VHF NAV are the same (example 116.5) but courses are different. The captain selected a 340 course and the First officer selected 010. If flying outbound, which radial will follow the VOR LOC mode when engaged? 340 or 010?

Please read the following information. (It helped me but I dont finish to understand it very well...)
The master FCC is indicated by illumination of the respective Master (MA) F/D Indicator Light. The master FCC is determined as follows :
- With neither A/P engaged in CMD, the FCC for the first F/D turned on is the master.
- With one or both A/Ps engaged in CMD, the FCC for the first A/P in CMD is the master FCC, regardless of which F/D is turned on first.

Normally, FCC A drives the Captain's command bars and FCC B drives the First Officer's command bars. With both F/D switches ON, the logic for both pilot's F/D modes are controlled by the master FCC and both ADIs or PFDs show the same mode status. If both pilot's VHF NAV frequencies
and/or courses have not been set the same, their F/D commands may not agree.

Thanks
Alejandro
Argentina

Rainboe
16th Jul 2009, 19:59
1- With one or both A/Ps engaged in CMD, the FCC for the first A/P in CMD is the master FCC, regardless of which F/D is turned on first.

2-Normally, FCC A drives the Captain's command bars and FCC B drives the First Officer's command bars.

Don't get confused between turning on the autopilot and turning on either F/D switch. The best way to not get confused is, as far as possible, have the same selected on both VORs and radial settings.

To think all those 'instant electronics and autoflight experts' in the 737 Turkish AMS thread knew so much better how Boeing should design the complete autoflight/autoland system too!

RAT 5
17th Jul 2009, 21:48
Malibu, I have only tried this in a B733, but I have no reason to think it would be diffeent in an NG:

Left CRS set 340, RHS CRS set 010. Engage A/P A and it will fly the CRS of LHS; engage A/P B and it will fly CRS of RHS. I don't get confused with which was master FCC or which was selected first\, or which is master FD or A/P. This is what the a/c does.

Indeed it was demonstrated by a TC on and approach where LNAV was not an option due to a -300 being non GPS for approach navigation accuracy. Fly inbd a VOR on radial ABC; fly otbd on radial DEF: intercept radial XYZ from another VOR; then intercept LOC.
Method: PF flying with own side A/P engaged; PF select VOR 1 on NAV PF and radial ABC; overhead VOR reselect radial DEF. On NAV PNF select VOR 2 & radial XYZ. When radial XYZ is alive select the opposite A/P, i.e. the PNF side; PF selects ILS freq on his Nav and INBD CRS. At LOC alive reselect PF A/P and ILS CRS. This avoids going via HDG SEL as VOR/LOC stays engaged all the time.
I'm noy advocating this as an SOP. It was a demo of how the system could be used and showed the function of the MASTER side.

BOAC
18th Jul 2009, 07:50
Alejandro - Rat 5 has given you the answer.in paragraph 2.

The technique described by Rat5 for 'complicated' raw data patterns works well and I have used it several times.

Do not be concerned over different radials set on each side. Indeed if you are making a 'raw data' postion check that is most probably exactly what you will have. If the F/Director bars are confusing you, either just ignore them (as PNF you do not need them) or turn yours off. It is, of course, important as always to know what you are doing and with what and that your colleague knows what you are doing too!.

alistomalibu
18th Jul 2009, 15:48
Thanks Rainboe, RAT 5 and BOAC
Very interesting answers