FMC questions 737 ngx

[wheels1911 1]

After i put in my route my FMC always says "NO DEST PATH AFTER" "then it says the waypoint"   but my route makes since its perfect.

[wheels1911 1]

I also was not able to engage VNAV on this flight i just did for some reason it mostly works flawlessly

[Dick 47]

 Can you confirm it said  "NO DEST PATH AFTER" .. or did it say "NO DES PATH AFTER" ?

"DES" in the latter would stand for descend and would indicate that the FMC does not have the correct information to compute a descend path, which is in line with your observation that you could not engage VNAV.

FCOM2 page 1134 (11.60.16) provides the cause and the corrective action

b rdgs / Dick

=

 

[wheels1911 1]

yes im sorry it says "DES" Soo how would i fix this issue??

[Dick 47]

23 hours ago, dick said:

FCOM2 page 1134 (11.60.16) provides the cause and the corrective action

Is there something that is not clear on the mentioned FCOM page ?

Without having seen your flightplan It is impossible to know how to solve it. But you will need to change a speed or altitude restriction in your flightplan on the RTE Legs page in the FMC  in such a way that the FMC can construct a descent path.

 

 

 

 

 

 

 

 

[Nick Dobda 24]

Cliff's notes:

The FMC can't calculate a descent path, and it is letting you know.

Resolution:

You will have to do something on the way down to get to where you want to be.

Extreme Example:

Point A in the FMC has a restriction of above 9000

Point B in the FMC has a restriction of below 5000

Point A is 1 mile from Point B
The FMC cannot calculate a way to get the plane from 9000 to 5000 in 1 mile. It lets you know with the NO DES PATH AFTER error

You can still execute the plan.  You can still fly the route, but when you get to point B you will probably be at about 8500 unless you do something (like deploy the flaps, increase your airspeed, open  up the speedbrakes, change your heading / route.
 

[downscc 1,327]

16 hours ago, wheels1911 said:

yes im sorry it says "DES" Soo how would i fix this issue??

 

6 hours ago, Nick Dobda said:

You can still execute the plan.  You can still fly the route

This exactly.  The message is not an error and should not prevent the use of VNAV, it is advisory only.  It is a pretty common message, and by the time you reach point A you have probably already slowed to the point where the path has long since been calculated...., or you need to use drag as Nick explains.

If VNAV is not engaging, it is for a different reason.