Hello,

 

Just on the tailend of studying the FMC section in FCOM2 which has been readable and interesting. although I did not completely absorb everything on offer. Just a question regarding route changes and terrain in the FMC. If I was to plan a manual approach into an airport and selected a runway extension with the default G/S and their was a terrain conflict, would the FMC permit this modification? In another example if I decided to use one of my five alternate airports and selected "Direct To" and Mt Everest (or some other obstacle) was between my point and the alternate airport would the FMC construct a safe pathway to the alternate airport or fall back on the GPWS. I understand (but am unsure) that the world's geographical vertical heights (for each Lat. and Long.)are known and wonder if they have been integrated into the FMC. I am thinking with this one, probably not.

 

I realise pilots use chart planning and ATC interaction but I just wanted to know more about the capabilities and limitations of the FMC.

 

Regards,

Magpie

I don't think the FMC cares one bit about obstacles. You can tell it to fly into a mountain just fine. Hopefully you pay attention to the GPWS when it tells you there's an obstacle ahead.

 

In other words, don't make up your own stuff. Use an approach if you're IMC. I'll make a runway extension if there's nothing better for a back-up to a visual.

Hello Spin737,

 

Thanks for the reply.

 

"If" the information is known about landform heights, I would have thought the FMC would be smart enough to plan a safe route to an alternate airport. Obviously not, It seems to do some great things elsewhere. If the alternate airport is a "direct to" or "missed approach"  and you are required to climb or make a long diversion your fuel reserves might diminish if this is unplanned and the FMC doesn't care about obstacles. Regarding runway extensions, of course, the safer option is better.

 

 

I would have thought the FMC would be smart enough to plan a safe route to an alternate airport.

 

In this regard, the box is only as smart as you. My company gives a a route to the alternate from the destination, so no FMC guesses are required.

 

 

 

If the alternate airport is a "direct to" or "missed approach" and you are required to climb or make a long diversion your fuel reserves might diminish if this is unplanned and the FMC doesn't care about obstacles.

 

Your fuel planning should have already accounted for the climb and the routing to the alternate. It's unexpected that you'll go to your alternate, but not "unplanned."

Hello Spin737,

 

Thanks again for all your kind replies.

 

I think you have made your point regarding the FMC, it is what it is (for now). Fortunately you have a company that does the planning for you removing some stress and workload.