View Full Version : 747-400 FMC CDU "ROUTE FULL" Message

9th Sep 2012, 03:58
Gents, I was just wondering how you (and the FMC) would respond if the ROUTE FULL message appeared in the MCDU scratchpad?

If a route is uploaded (or selected from the Co Route list) and it exceeds the 120 waypoint limit, the ROUTE FULL message appears. Our airline used to have a few such routes from Asia to Europe a few years ago, but I don't know how they were handled. During ground tests, I seem to recall that most of the Route was accepted, with the final waypoints missing.

Q1. Will the full Route structure appear on the ROUTE pages? (even though not all the LEGS waypoints will be presented)

Q2. Will it be possible to enter the same Company Route in Route 2 and delete Airways and/or delete waypoints at the start of the Route on the ROUTE or LEGS pages and have the missing waypoints at the end of the Route automatically appear on the LEGS pages? (Then allowing you to switch to Route 2 at a convenient time)
Q2a. If the missing waypoints at the end of the Route do not appear, will the route end have to be programmed manually, waypoint by waypoint/airway by airway (using the paper flight plan)?

Q3. If a SID is added to a Co Route, causing the 120 waypoint limit to be exceeded, will the SID be accepted and the end waypoints dumped? If a STAR is added, causing the 120 waypoint limit to be exceeded, will the STAR be rejected or will waypoints at the beginning of the route be dumped?

Thanks for any insight


9th Sep 2012, 11:21
I've only had it happen a couple times, but as far as I remember...

A1: No. Only to the last waypoint loaded.

A2: No. Nothing will "automatically appear." You can delete the first part of the route in Route 2 and fill in the end manually, if you like.

A3: The SID or STAR will not be accepted. You have to manually delete sufficient waypoints to add any more in any manner.

I simply deleted waypoints at the end of the route, input the SID, and then input the remainder of the route some time after TOC.

9th Sep 2012, 11:27
What is a MCDU?

9th Sep 2012, 22:38
Intruder.. Excellent... Much appreciated :ok:

JammedStab... MCDU = Multi-function Control Display Unit. Used for FMC, ACARS, Satcom, CMC, Nav Radio tuning, etc.


By George
10th Sep 2012, 03:21
I have seen this many times especially Europe to Asia. If you 'make space' by deleting the waypoints at the end of the flight it can change the final fuel calculations if it's not a straight line, so to speak. I always looked for waypoints way down-route on the same track and deleted them. You have to high-light on the plan in some way to avoid not loading them back in. I used a red pen. Normally once the SID is completed and established in initial CRZ there is plenty of room to re-enter the deleted waypoints and fix it all up.

I also, always made sure that my partner in crime was aware of what was deleted and he also marked his copy of the plan. If the deleted waypoints are on the same track in a straight line you are at least protected and the FMC predictions are accurate.
It all sounds very suspect but by constantly cross checking and recording any deletions on the flight plan I never had any problems. The box needs more memory and it's a weakness of the system.