Hello everybody.

I recently acquired the PMDG 737NGX and I'm confused with the FMC.

I'm trying to do a flight from EHAM to EGLL.

This is the route I'm following: GORLO UL980 XAMAN L980 LOGAN. I'm departing from RW 36L using the GORL1Z SID and chose to land at ILS 27R using the LAM3A STAR.

My cruise altitude is FL240, and when I enter this value into the FMC, it automatically changes to FL250, no matter what cruise altitude I choose, and after this, it gives me the "Unable Crz Alt" error.

I don't know if I misunderstood something with the Gross Weight or with the Cost Index, but I simply don't know what payload I have to choose and the respective cost index, since this is a short flight.

So if someone could help me with this issue I would be greatful.

Thanks

 

Not sure why you want FL240 for such a short short flight?!

 

What is the gross weight you will fly with?

 

UNABLE CRZ ALT usually shows  when the upper and lower speed buffets will meet in the middle, meaning the FMC won't compute any performance for the altitude.

 

Have you set the isa temp correctly?

As to the cruise altitude changing to FL250: you've probably got an altitude crossing restriction at LOGAN set to FL250. According to the STAR, this is only applicable to aircraft with a filed cruise altitude of FL300 or higher, so you could and should delete that.

I'm flying at FL240 because I'm following a real flightplan (this one: http://www.edi-gla.co.uk/fpl/view.php?fpl=132280)

I set the fuel to 1/3 and the gross weight is 50.6. Now everything seems to work alright.

Apparently I can't use the FSX Fuel and payload menu and must use instead this menu in the FMC.

About the isa temp I'm not familiar with that

UNABLE CRZ ALT usually shows  when the upper and lower speed buffets will meet in the middle, meaning the FMC won't compute any performance for the altitude.

 

Not this time. Now it shows that T/C is located after T/D. For optimum altitude for a short flight check PERF INIT trip alt field, FMC will take into consideration additional factors there, like distance, airport elevation.

Also don't forget to check airway limits. L980 maximum altitude is FL245.

 

As it said in charts if the cruise altitude is lower than 290, cross LOGAN at FL240, so change this altitude restriction.

 

 

 

Apparently I can't use the FSX Fuel and payload menu and must use instead this menu in the FMC.

 

That's how it should work in FSX.

Alright thanks for the help

 

 

Apparently I can't use the FSX Fuel and payload menu and must use instead this menu in the FMC.

About the isa temp I'm not familiar with that

 

Diogo

 

You might want to read the Introduction and try Tutorials 1 and 2.

 

Michael Cubine

Diogo

 

You might want to read the Introduction and try Tutorials 1 and 2.

 

Michael Cubine

Well I've read almost the entire introduction tutorial and might try both tutorials 1 and 2

go to LEGS page, step down page to the waypoint LOGAN. look at the crossing restriction that came with the STAR.

 

You can't descend from FL240 down to FL250, it's like trying to count down from 10 to 0 to get to 11.

 

*space shuttle launch* "Ten, Nine, Eight, Seven, Six, Five, Four, Three, Two, One, Eleven."

 

 

and might try both tutorials 1 and 2

 

You should do them, as Michael mentioned.  It explains some of the problems you're having and will give you better knowledge of the aircraft.

 

You bought a realistic simulation, and based on your posting here, you're expecting it to behave realistically. In order to do that, you're going to have to give it realistic values and treatment.

 

...which means you're going to have to do some realistic reading of the manuals/tutorials.