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Well-known member
Jun 14, 2002
Sorry guyz, but what's FMC?? heard is Flight Management Computer... what's that? what does it do?

thankz alot

Flight Management Computer...

Basically, it does everything for you...

You can enter routes and store them in it for future use, it is usually interfaced with the autothrottles and the autopilot to constantly make corrections during flight. What it does it it takes all the data from the POH, all the data from approach charts and enroute charts and airways, mea's etc, and stores them in its memory. Then it also stores airport data such as runway length, coordinates, slope, maximum weight capability, all that stuff that causes headaches for 121 dispatchers. Then, it boils down your flight planning into 3 simple steps: 1.) You enter your departure point, 2.) You enter your arrival point, 3.) You enter what altitude you want.

Then it does the rest, automatically determining the proper headings, altitudes, power settings, the whole smash. It will also constantly tell you how much fuel is needed, how much will be remaining, and your enoute time. And if you interface it with the autopilot, all you have to do is sit back and watch a computer do all the work for you.

Kind of takes the fun out of flying, but thats just my opinion. I'll take a whiz wheel anyday
Never heard of it being called an FMC. I usually hear about the FMS, flight management system, which is pretty much what the last poster described. It's a pain when it goes out and you have to do everything the old fashioned way, after you get used to it.
pardon me,but erm... the 'box' ?? what box you refering too?
btw, any of you here have a picture of the FMC??

thanks acestick for the wonderful explaination. i understand :)

The so called box is the tiny little computer usually mounted of the center pedestal. Usually a 4 by 4 screen with a number and letter keypad.

Go to www.airliners.net and look at varios airliners flight deck pictures. You should be able to see what it looks like. They are not all the same but usually have the same general layout in regards to size.
hey, how bout the F-16 or F-22(for they are 'fly-by-wire' , computerized, so was wondering)?? Is FMC used in military aviation?


the book

This is what's in my ERAU Electronic Nav textbook, take it for what it's worth (I sure paid too much:p )...Here it goes:

The FMS provides integrated operation and control of several managment systems to provide automatic lateral navigation (LNAV) and vertical navigation (VNAV) for optimum flight profiles and performance management.

It is compromised of the following components:
- Autopilot/Flight Director System (ADFS)
- Air Data Computer (ADC)
- Electronic Flight Instrument System (EFIS)
- Engine Indicators and Crew Alerting System (EICAS)
- Flight Management Computer (FMC)
- Inertial Reference System (IRS - IRU/INS)
- Radio Navaids
- Aircraft system sensors
- Mode Control Panel (MCP)

The FMC is the heart of the FMS. It contains 2 databases, one for navigation and the other for performance. The nav database includes:
-Airports, Airways, Instrument approaches, Company routes, ruways , published DP's and STAR's, waypoints, and navaids.

The performance database contains the data related to the aircraft aerodynamics considering the weight of the airplane and it's engines. Maintenance personnel can update it when changes are necessary.

Inputs to the FMC are made through the Control Display Unit (CDU). (I believe some call it the MCDU). ACARS can also be accessed through the CDU.

WHEW! Guess I didn't waste ALL my money down here at Riddle!:D (just most) Sorry for any typos, it's early in the morning for me...3pm but oh well, it's Sunday. I skipped around the chapters to give you the basics...I'm not an expert, nor have any experience in FMS aircraft, so please don't blast me if anything's wrong. Ya'll experienced pilots know better than I do!! Basically the way I see it, the FMC takes all the information from the from various systems, nav and performance, includes information from the other systems such as the ADC, EICAS, etc. and computes pretty much everything you could possibly need to know for that flight. This ENTIRE system, the way i read it, is considered the FMS.

Correct me if im wrong! FLY SAFE!!!
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OK, cutting through all the rubbish - this is what you need to know as far as what goes in and what comes out of the FMC

Inputs to the FMC come from;

1) A very accurate clock
2) Fuel sensors for both total fuel and fuel flow
3)Air Data Computers - these provide airspeed, Mach Number, temp ans altitude data.

4) Radio navaids for navigation source info. These aidds can be autotuned by the FMC or manually tuned using the FMC, or by overriding the automatic mode of the VHF/NAV tuning head.

5) Air-ground sensing - records takeoff and landing times, switches various systems from ground to airborne mode, such as pressurisation, aircon,electrical channel isolation and FMC nav mode.

6) Flap position - this enables configuration info to be included when optimum profiles are computed during departure or approach.

7) IRS's - for position, attitude and heading source info.

8) EFIS control panels - this enables the pilots to select the various navigation and performance modes for display on the EFIS screens.

9) Autopilt Flight Director System (AFDS) - the FMS is hard wired to the AFDS. The specific type of FMS link desired is also selected on the AFDS mode control panel. This could be altitude control, nav track,heading, localiser, or glideslope etc. When the autopilot is selected, the link between the FMC and the Flight Control Computers (FCC's) is utilised to achieve the desired performance.

Thats as much as I can remember on that - if somebody wants to add, feel free, as far as outputs from the FMC, here they are;

1) Autopilot Flight Director System
2) The Flight Control Computers
3)The Autothrottle
4) EFIS system - various displays for nav, flight attitude and radio nav bearings can be selected on the EFIS display tubes; and
5) Various annunciators and indicators.

Thats the basic what goes in and what comes out, they really aren't that complicated.
Why are you interested in the FMS or FMC? Are you going to be using one soon?

I just kind of wonder when I see these posts and would like to see them in context to better understand your perspective.

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