FMC professors wanted

[EHM-1001 Robert]

Hi folks,

I know I could find answers in some manuals, but I think those are not cover "real" situations. I really need some strong help from FMC professionals, on "real" happenings and procedures, because I am having a lot of problems to solve them.

Basic setup:
Lets take the PMDG 744, and let take her to an Online flight, because these things probably will not happen with you, with Offline ATC control. So... we have a flight plan, between 2 destinations, the flightplan is entered into FMC. The flightplan includes runway for departure, and possible runway for arrival. For this, we have a possible STAR, either selected from the FMC database, either manually programmed as waypoints & altitude restrictions. We are on our way, and flying with LNAV + VNAV + CTR A/P...

Situation 0: Uncontrolled, fully FMC landing.
I always miss the descent, or the final approach somehow. If nothing interrupts your FMC flightplan, how do you make a nice approach ? How do you let FMC do its job, and put the plane down ?

Situation 1: I need to make a detour.
How should I enter a new waypoint that is not on my way, Should I simply insert it to the plan, and remove the "route disconnection" ? How should I delete a waypoint from my current flightplan ?

Situation 2: I need to make a holding, but do not have time to bother with FMC.
How should I get back the control from FMC, and fly "manually" the holding ? And after that, how should I precisely give back the controls to FMC to continue the route ?

Situation 3: The controller gives me vectors instead of STAR.
This happens usually when a CTR position do not want to bother with STARs and quickly give you vectors. How should you disable the FMC and get back the controls with simple A/P commands ? (quite similar to previous situation)

Situation 4: You need to make a manual landing.
How can you prepare the ILS freq, the bearing, and everything that is important to a manual landing, if FMC still keeps everything under control in the background (freqs, runway data...) while it is turned off ?

Situation 5: After a vectorial approach, you need to make a CATIII landing.
After some tricks "manually" with A/P how do you give back the controls to FMC, for a smooth autoland ?

IF you can, please write the answers detailed...I am really struggling with these FMC & A/P cooperative work i nthe cockpit.

Thank you in advance !

[EHM-1617 Iain]

FMC freaks?? I prefer the term 'nerds'.

0: On a Boeing FMC, the VNAV altitude is constrained by the altitude in the MCP. During climb, VNAV will climb no
higher than the MCP level. For example, the FMC calculates a continuous climb, but the SID tells you to stop at 6000'. You put 6000 in the MCP. When you engage VNAV, the FMC will automatically level off at 6000 and engage ALT mode. To pass control back to the FMC, select a higher alt in the MCP and reselect VNAV. Similarly, on descent, after inputting all that parameters into the FMC, it will calculate the ideal T/D point. Before this point, select your initial descent altitude in the FMC, and leave VNAV engaged. When reaching the T/D, VNAV will begin the descent, but it will level out and engage ALT when you reach the MCP alt.

The FMC will not land the plane. It will fly a non-precision approach. For the aircraft to land itself, you need to use (ideally) all 3 autopilots and APP mode. The FMC (coupled to an engaged autopilot in LNAV and VNAV) will follow the magenta line, and pitch the nose up or down to reach the VNAV track, and adjust the thrust to stay on speed, although you can swap the pitch and thrust roles on descent using the VNAV SPEED descent.

1: To make a detour, use the LEGS page. Type the waypoint name in the scratchpad. Click the left LSK next to the waypoint to insert the detour before. Leave the DISCO if you are not sure where you will be going after that, otherwise 'close the disco'. To delete a waypoint:

For example your route is BPK CLN REDFA. Then you are told to shortcut direct from BPK to REDFA. Press the LSK next to REDFA to put it in the scratchpad. Then press the LSK next to CLN to  move it to there. Close the DISCO if one appears. Now CLN has gone from the list.

2: Using the FMC is a lot faster than working it out manually. Press the HOLD key, select the waypoint to hold at, adjust the settings, and LNAV will do the rest.

3: Simply use HDG mode rather than LNAV. The FMC will tell you when you are abeam the previously planned waypoints, should you be interested. To go direct to a waypoint, put it in the scratchpad on the LEGS page, and then press LSK1L.

4: Turning the FMC off would not be a good idea. The FMC will continue to work as normal. If you are not using LNAV or VNAV, then the FMC will not affect the flight directors or the autopilot. Select your runway as usual, and the ILS information will appear on the INIT REF page. Flying the plane manually with the flight directors is good fun and practice.

5: You don't hand control back to the FMC for an autolanding. An autolanding is NOT made in LNAV and VNAV modes, but in SPEED and APP modes with all A/Ps on CMD. On the intercept leg for the ILS, with LNAV and ALT mode or VNAV engaged, press LOC. Wait for LOC capture. Press APP. Check the PFD for annunciations. When you get G/S capture, engage all autopilots and configure for landing.

EDIT: I am now officially very tired so any errors in this post are  to be accredited to more cups of coffee than you can count on your fingers and too many hours in front of a screen.

You could try the FMC manual, or the PMDG Ops Wiki.

I hope I helped a bit. Good luck on the big iron.

[EHM-1947 Miko]

I can't add much to Iain's remarks - they are perfect - perhaps a little help as to the logical aspect of that all:

When I startet with FMC-Flying I also thougt that the FMC is the most important and dominant Instrument for navigating an aircraft and everything is depending on it.

Until I understood that the FMC is only one "Frontend" to tell the Flight Director what to do - absolutely equally to all other Modi like ALT HOLD oder HDG HLD a.s.o. - so it is not unusual to change the modi everytime and give the control again back to fmc if it is helpful.

So the flight director tells the A/P where to go - not the FMC. And the pilot can obey the flight director without using the A/P by following the F/D's bars.

Normally - if you are in the vicinity of your arrival airport and you are online - you will seldom have any use for the FMC but prefer NAV / HDG HLD and LVL CHG to follow the controllers vectors.

One Addition: To be exactly : Not the FMC itself is a Modus to lead the flight director but LNAV and VNAV and the speed constaints it has computed. If nonsence - corrections are welcome

[EHM-1001 Robert]

Thank you guys the comments I really appriciate those. I am a big fan of frreeware airplanes, where the panel and instrument modelling are realistic without FMC. Those planes are very easy to control, unfortunately, the A/P panel works a little different than in the real life, or with perfectly modelled planes with FMC. So I need to learn a lot, and as an engineer I wanted to understand first what is in the background, so the explanation of the FMC, MCP, and FD cooperation is very helpful.

It is very different on the freeware planes, as you have only MCP, or A/P but does not have FMC. Maybe the most important that the A/P is not only the so-called glareshield panel, but it is a computer in the heart of the aircraft. And you decide if you want to control it via the FMC, or "manually" from the glareshield panel.

Thank you again !

[EHM-1001 Robert]

Yesterday I was playing with the system, and it is not so difficult as I thought before. Although I still could confuse myself and the FMC after a programmed holding, but I will be more careful before changing the original flight plan next time