It is now possible to step through a route in PLAN mode before it has been activated

[Epikk 62]

Hi there NGX drivers,Just curious about this item... I'm not sure anymore.Aren't we supposed to be able to step through a route in PLAN mode even if the IRS system is not fully aligned?Since this is not possible in the NGX (SP1) I'm wondering... Any clue about this?

[nawarren 83]

Hi there,I reported this issue when ngx was first released. Have not tried this after sp1, but was led to believe that this had been fixed.AFAIK correct functionality should be that in PLAN mode with the IRS turned off, you can input a route and step through that route viewing each leg on the ND in plan mode. (this is how 744 757 767 and 777 work in real life). Am sure Boeing have done same for 737.I will have to check if this works properly on my setup post SP1.CheersNeil

[Epikk 62]

Thanx for your input Neil.

[henkie 0]

Not working unfortunately.Regards daniel verhaal

[Epikk 62]

Then SP2 it will be...

[JRBarrett 3,049]

AFAIK correct functionality should be that in PLAN mode with the IRS turned off, you can input a route and step through that route viewing each leg on the ND in plan mode. (this is how 744 757 767 and 777 work in real life). Am sure Boeing have done same for 737.

I think there is a bit of a misunderstanding here. The new functionality added by SP1 permits the route to be stepped-through in PLAN mode before it has been activated (by pushing the EXEC button on the FMS CDU.) That way, the pilot can see an overview of his proposed route on the ND before actually committing to it by activating the route, (which takes the FMS out of route-entry mode, and moves it to Perf Init mode.)Activation (of a route) and alignment (of the IRS) are two different things.You can, or course, enter a route in the FMS before the the IRS alignment is complete, but full IRS alignment is still necessary to display a route on the ND. Until full alignment is achived, the FMS has no way of knowing where the aircraft is currently located on the surface of the earth, nor the aircraft's vertical and horizontal orientation - all of which are pre-requisites to display waypoints.

[Epikk 62]

No worries. I know the difference between activation of route and IRS alignment.The thing is, in the real thing, I think you can see the fp and step through the waypoints when in PLAN mode even if the IRS system is not fully aligned.I think you can even see some Fuel/Time predictions in the Progress page (provided you completed the Perf Init page) before IRS is fully aligned.I may be wrong though.

[nawarren 83]

Hello Again,Jim you say: "but full IRS alignment is still necessary to display a route on the ND."Jason you say: "If the IRS's are not aligned how do you guys propose to be able to see a route on the ND ??" This is our point! We do not believe this to be the case. In real life, as I have stated above you can view any route you input on the ND when in plan mode, and you can step through the route. All this can be done on 744 757 767 777 with the IRS not aligned. Remember IRS alignment is to tell A/C where on planet it is. Any route can be displayed in plan mode from nav database.Please can a developer or real world 737 pilot chip in and clarify what is real world ops.CheersNeil

[Epikk 62]

I'm confident PMDG is working on it...I'm just surprised it's not already in though.It's a very helpful tool during preflight. We'll have to wait a bit more.Cheers!

[badderjet 181]

You can, or course, enter a route in the FMS before the the IRS alignment is complete, but full IRS alignment is still necessary to display a route on the ND. Until full alignment is achived, the FMS has no way of knowing where the aircraft is currently located on the surface of the earth, nor the aircraft's vertical and horizontal orientation - all of which are pre-requisites to display waypoints.

Of course it can. Even I can. Take out any street map, and I'll show you whatever route you like, and I don't need to know where I am to do that at all. As has been confirmed by some of the r/w drivers around here, it's in fact very much possible to step through the route without any alignment whatsoever. There is zero need for the system to know where it actually is, as a route simply consists of waypoints that have relative bearings and distances to each other, which are all very well-known to the FMC.Would really like to see this "in a future SP" as well.

[JRBarrett 3,049]

Of course it can. Even I can. Take out any street map, and I'll show you whatever route you like, and I don't need to know where I am to do that at all. As has been confirmed by some of the r/w drivers around here, it's in fact very much possible to step through the route without any alignment whatsoever. There is zero need for the system to know where it actually is, as a route simply consists of waypoints that have relative bearings and distances to each other, which are all very well-known to the FMC.

Perhaps. The only proviso (so far as my own experience is concerned) is that I haven't worked on a Boeing FMS system specifically - but I do have 20+ years experience as an avionics maintenance engineer working in the installation and maintenance of both Honeywell and Collins AFG, IRS and FMS systems on quite a variety of large transport-category aircraft... and I have never seen an IRS-based Honeywell or Collins FMS installation where waypoints or routes can be displayed graphically on the ND before the IRUs are fully aligned - and that is in either PLAN or MAP modes.But, again, perhaps the Boeing FMS is an exception. Would be good if a R/W NG driver or AME could chime in here to either confirm or deny.

[nawarren 83]

Hi Jim,I have worked on both Boeing and airbus A/C for approx 10 years and in my experience it is possible to step through flight plans on both types without aligning IRS's. Incidently i believe this was modelled on PMDG 744 and MD11? Just not 737NGX!CheersNeil

[JRBarrett 3,049]

Hi Jim,I have worked on both Boeing and airbus A/C for approx 10 years and in my experience it is possible to step through flight plans on both types without aligning IRS's. Incidently i believe this was modelled on PMDG 744 and MD11? Just not 737NGX!CheersNeil

In that case, I stand regarding the Boeing FMS! I have both the PMDG 747 and MD11, if I can manage to tear myself away from the NGX for awhile, I'll have to fire them up and see how the plan mode is modeled in the sim. I do know that FMS systems that use a dedicated Attitude Heading Reference Sytem (AHRS) like the Collins Proline 21, can definitely display waypoints and route lines on their ND even with no external position reference, but I had never encountered an IRS-based FMS that had that ability.

[badderjet 181]

Hey Jim, not my info. I only remembered what one of the r/w drivers here mentioned, and I found it sounded logical to me. I haven't had the chance to try it in a sim or on an actual NG though, so I relied on that info. But yeah, maybe someone knowledgable could confirm the actual behavior of this particular issue.