If there is no FMC, how do the pilots fly? I mean do they have to do anything manually or setset each VOR after passing it? I have no idea how that type of aircraft can fly. Or am I misinformed?
Understand that the vast majority of airplanes of all types flying worldwide do not have FMC's. You fly a Cessna 172, you're not going to have an FMC. Most airliners in service probably still do not have FMC's if you're talking worldwide (modern airliners do have FMC's, but a lot of airlines around the world don't fly the most modern planes). This includes most 747-100's, 747-200's and 747-300's, unless they've had their cockpits upgraded.
Yes, with no FMC you set your radios manually. This is not that big of a deal, honestly; it's just turning a dial or punching in a couple numbers every once in a while (usually every 30 minutes to an hour or so, though it depends on what part of the world you're in). I believe some older airliners had FMS's (not FMC's) that would auto-tune radios when on auto-pilot set to inertial nav, but these were not full-blown FMC's.
Every pilot is still trained on how to use VOR navigation and how to set his radios himself. It's a trivial thing to learn and manual navigation can still be used in an airplane with FMC if something happens to the FMC.
The main function of an FMC is actually not to set radios; if that was all it did, it would be a pretty pointless device. The FMC is a sophisticated computer system; it does a whole lot of things, and its main function is to reduce pilot workload and increase airplane efficiency. Most of the things the FMC does (calculating V speeds, takeoff power settings, top of descent, climb, cruise and descent speeds, fuel usage, etc.) used to be accomplished by the flight engineer - this is why FMC-equipped cockpits only require two pilots vs. the three that was common in the old days.
But everything that an FMC does can be done manually. The FMC, like all computers, is really just doing a lot of math on a continuous basis and then feeding that data to the auto-pilot and/or the flight director, along with making sure all the important systems on the plane are operating normally. You can do all that math yourself, and you can scan all those instruments yourself, it's just going to take you longer to do it and it's going to pull you away from other tasks and reduce your situational awareness.
Changing radio frequencies and navigating manually by VOR is probably the least labor-intensive task for a pilot that the FMC has taken over.
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