Active Route No Altitude Info After Change to Route 2 - VNAV won't engage

[Mike777 163]

Hi, everyone,

 

Today I had a rather perplexing event.  I was in cruise, Route 1 active, everything OK.  Then I modified a STAR and runway with transition.  In the course of doing so, I realized that I had somehow selected Direct to a waypoint in the STAR, thus wiping out the intervening enroute waypoints.

 

To solve this problem, I loaded the entire route in Route 2 from disk,  moved the next waypoint aheadof my position up to be the active waypoint  (rather than the first waypoint going back to the beginning of the flight), and activated Route 2. 

 

The aircraft followed the route OK in LNAV, but would not engage in VNAV.  No altitudes were showing on the FMC legs page for subsequent legs except for restrictions included in the STAR (although my current Perf entry and I believe VNAV cruise entry had the correct altitude, FL350, after two auto step-climbs).  The progress page did not show any predicted arrival time or expected remaining fuel.  Active Sky Next, latest beta, was active, and I loaded current wind information, but it made no difference. (I did have a problem later with ASN, but I don't see how it's related to this one).  I also entered the current FL either in the active waypoint or the following one, but the altitudes did not propagate down the list of waypoints.

 

To solve this problem, I went back to Route 1, re-entered the remaining enroute waypoints, activated the route, and lo and behold, altitude information and predicted times returned, Progress display returned to normal.

 

Did I do something wrong or is this a bug?

 

Thanks,

Mike

 

[Budbud 227]

When using the route 2, have you tried to re-enter the cruise altitude on the VNAV cruise page?

Or also re-enter the altitude and CI on the PERF page?

 

I don't often switch to RTE2 but I don't recall having any issue with it. I'm going to try to reproduce your situation to see if I get the same behaviour.

[Mike777 163]

 

 

When using the route 2, have you tried to re-enter the cruise altitude on the VNAV cruise page?

Or also re-enter the altitude and CI on the PERF page?

 

Hi, Romain,

 

I believe the altitude was already in VNAV Cruise, although I'm not sure.  I know it was showing on the PERF page.  Not sure what "CI" is.  I don't think I re-entered the altitudes on either page as they were already there.

 

Thanks for your quick response!

 

Mike

[Budbud 227]

I reproduced the situation and got exactly the same behaviour... Now I'm gonna dig also for the answer into the forum, manuals in case you would have missed an information somewhere.

 

FYI, CI is Cost Index I tried changing it on the PERF page and it didn't fix the issue. And you cannot change the altitude in the PERF page once in flight, only on the VNAV page.

 

EDIT: I have found 2 other topics talking about the RTE 2:

http://www.avsim.com/topic/422698-route-2/

http://www.avsim.com/topic/455719-route-2-automatic-clearing/

 

I didn't swith to HDG (remained in LNAV) before activating the RTE2.

I will retry to see if it gets better.

 

EDIT2: Wow I succeeded in messing up everything! 

I went to the point where I had no more VNAV path available on both RTE1 and RTE2 and not able to flush neither RTE1 nor RTE2 while inactive on flight...

 

When changing the destination airport on inactive RTE2, the new destination airport was accepted but the route remained and was not flushed!

I did tried this also on inactive RTE1 (after activating RTE2) and got the same. impossible to flush it.

 

I get to start the test again from ground and from scratch!

Edited August 19, 2015 by Budbud

[Mike777 163]

 

 

I reproduced the situation and got exactly the same behaviour... Now I'm gonna dig also for the answer into the forum, manuals in case you would have missed an information somewhere.

FYI, CI is Cost Index I tried changing it on the PERF page and it didn't fix the issue. And you cannot change the altitude in the PERF page once in flight, only on the VNAV page.

 

Thanks, Romain, for your efforts!  I think we may have a bug here.  The two threads you mentioned are very interesting too!  I rarely use Route 2, so i haven't experienced problems w/ flushing the inactive route.  I would have thought it wouldn't be that hard.  Maybe if you change the origin airport instead of the destination.

 

Also learned something useful -- apparently according to 777simmer we are supposed to copy Route 1 into Route 2 as part of pre-flight, among other things.

 

 

Mike

[Budbud 227]

 

 

Maybe if you change the origin airport instead of the destination.

 

I tried that too but it was not accepted.

I found the two posts very informative as well.

 

With regards to the RTE2, I think it may not work properly in the PMDG's 777 or at least not with full features as the real one.

Unless I have missed some statement from PMDG regarding limited feature on the RTE2 or already acknowledged bug, it may deserve a ticket to the support.

[pcubine 143]

 

 

To solve this problem, I loaded the entire route in Route 2 from disk

Mike

What do you mean by this statement. The word disk is throwing me. What disk do you mean? Or was there even a disk involved?

[Budbud 227]

I guess he means loading the route using route request datalink function. At least it is what I have understood and used to reproduce the test.

[downscc 1,327]

I assume that the datalink route loads to RTE1.. but it's just an assumption.

 

Lack of VNAV can simply be a result of the FMS unable to resolve the vertical path calculation. This could be related to the root problem rather than the problem itself.

[Budbud 227]

 

 

I assume that the datalink route loads to RTE1.. but it's just an assumption.

 

You have the route request option available from both RTE1 and RTE2 page. I had no route loaded on RTE2 and could load a route with this option on RTE2 the same way we do on RTE1.

 

When I tried to activate the route 2, I was at the initial cruise altitude set on the PERF page and close the beginning of the route.

I agree that something definitely prevents the FMC from resolving the vertical path but I can't see what.

[pcubine 143]

 

 

I agree that something definitely prevents the FMC from resolving the vertical path but I can't see what.

Romain

Tonight I will do EDDF-KIAH and set RTE 1 for a SKNRD4 ILS 9 and when at initial cruise altitude I will set RTE 2 for DOOBI2 ILS 27. During the flight I will make RTE 2 the active route and see what happens. I will keep track of the keys, pages, clicks, etc. that I use.

[Budbud 227]

Great thanks.

[Mike777 163]

Thanks to everyone for responding!

 

 

Mike

What do you mean by this statement. The word disk is throwing me. What disk do you mean? Or was there even a disk involved?

 

 

 

I assume that the datalink route loads to RTE1.. but it's just an assumption.

 

Lack of VNAV can simply be a result of the FMS unable to resolve the vertical path calculation. This could be related to the root problem rather than the problem itself.

 

 

 

You have the route request option available from both RTE1 and RTE2 page. I had no route loaded on RTE2 and could load a route with this option on RTE2 the same way we do on RTE1.

 

When I tried to activate the route 2, I was at the initial cruise altitude set on the PERF page and close the beginning of the route.

I agree that something definitely prevents the FMC from resolving the vertical path but I can't see what.

 

 

You can load a route into Route 2 by using the request function.  I should have been clearer, but that's what I mean by "loading from disk."   I did this in flight, after I messed up route 1 as I described in my first post.

 

Dan, the problem is that the flight plan in Route 1, when I added back the missing waypoints, calculates altitude and other VNAV information just fine, but the identical flight plan in Route 2 does not.

 

Romain

Tonight I will do EDDF-KIAH and set RTE 1 for a SKNRD4 ILS 9 and when at initial cruise altitude I will set RTE 2 for DOOBI2 ILS 27. During the flight I will make RTE 2 the active route and see what happens. I will keep track of the keys, pages, clicks, etc. that I use.

 

 

I experimented a little more last night.  If I use the Route Copy function, copying Route 1 into Route 2, then in Route 2 VNAV info is calculated and works OK.  But if I load the flight plan into Route 2 by using the Request function, it does not work OK, even though Route 2 is active and is controlling LNAV, and the flight plans are identical (after I moved up the next waypoint from my location to be the next waypoint in the Route 2 flight plan - because when I used Request in Route 2, it loaded the entire flight plan, beginning to end).

 

Note that I am using the Request Route function (in Route 2) in midflight, which may have something to do with the issue.  So, Michael, if you use Route Copy to copy your EDDF-KIAH plan from Route 1 to Route 2, it will probably work OK.  Also, I am guessing that there may be a difference if you load Route 2 on the ground using the Request function, rather than in the air.  I know the problem happens when I use the Request function in Route 2 while in the air.

 

I also want to mention that 777Simmer, in one of the threads Romain linked to above, said that SOP is to copy route 1 to route 2 during preflight.  If I had done that, I think Route 2 would have worked fine after I messed up Route 1.  But I still don't understand why the FMC can't resolve the VNAV data in Route 2 that it can resolve in Route 1 with the identical flight plan.

 

Finally, I want to mention that the aircraft did not always follow the waypoints, either in Route 2 or Route 1 after my initial problem.  At the time I assumed it was because I entered the wrong waypoint as next or some other error, and eventually it went back to following the plan,  but now I am wondering if there was some other FMC issue.  I did not get any "not on intercept course" messages.

 

I have at least one autosaved situation from this incident and will go back and check further this evening, if time allows.  The plan was KSFO-LFPG, and I was at cruise altitude not too far from TOD when this incident happened.

 

Thanks again to everyone!

 

Mike

[pcubine 143]

 

 

So, Michael, if you use Route Copy to copy your EDDF-KIAH plan from Route 1 to Route 2, it will probably work OK.

Route Copy is what I use to copy 1 to 2 during the climbout. Where is the Request function located?

[Budbud 227]

Go to the RTE2 first page it is as the same place as on the RTE1 (LSK3).