Missed Approach

[Guest Murf]

Hi folks,I wound up doing a missed approach at CYOW tonight. Everything went well, except after climbing to the MAP I noticed that the MAP was the only thing left on the ND. I went to the legs page and the MAP was the only waypoint listed. So I entered the initial fix for the runway again and placed it at the top of the legs page. I went to the DEP/ARR page and selected the runway but it would not place the runway on the legs page, nor did it show up on the ND. I tried selecting different rwys but none would show up. I wnt ahead and flew the vectors and intercepted the localizer no problem. Landing went well this time around. Once on the ground, everything reappeared on the ND, with the blue line showing my planned route.Sorry couldn't grab any screenshots this time.Is this normal or did I do something wrong?

[Guest Murf]

Good Morning!BUMP!

[Guest tmetzinger]

>Good Morning!>>BUMP!>>Give me an hour, Murph, I'm going to test the following out.According to Bulfer (Diverting, page 183), once you've flown to the destination airport via a climb-cruise-descent profile, the FMC thinks it's DONE as far as route management goes.One way around this is to punch in your alternate airport into the destination field on the route page. That should reset the FMC.But in your case, you want to divert back to your same/original destination airport.What I'm going to try is to first put in another airport into the DEST field, to reset the FMC, then put the original destination in. Then I should be able to select the STAR or approach again.Also, I'm going to check whether the functionality for alternate airports is included in SU2, I don't think it is.More in an hour.

[Guest tmetzinger]

>One way around this is to punch in your alternate airport into>the destination field on the route page. That should reset>the FMC.>>But in your case, you want to divert back to your>same/original destination airport.>>What I'm going to try is to first put in another airport into>the DEST field, to reset the FMC, then put the original>destination in. Then I should be able to select the STAR or>approach again.>>>Also, I'm going to check whether the functionality for>alternate airports is included in SU2, I don't think it is.Okay. The workaround I suggested DOES allow you to get your arrivals and approaches back into the FMC. However, it only works for LNAV, and you'll have to manage your altitude and airspeed separately.I tested this with the ILS into KTNT using a self-build approach file for ILS 09. Try it at your airport and see how it goes.Anthony may have more info and a better workaround.Oh, and the Alternate destination pages and nearest airports aren't implemented yet... hopefully we'll see them in the 800/900 package (BIG HINT).

[Guest Murf]

Hi Tim,Thanks for the reply and the work around. I'll give that a try this evening.If I understand your message correctly this is the way it would be handled in the real thing as well?

[Guest tmetzinger]

>Hi Tim,>>Thanks for the reply and the work around. I'll give that a>try this evening.>>If I understand your message correctly this is the way it>would be handled in the real thing as well?>Perhaps... there's some logic for alternate airports and such that's not implemented in PMDG yet. I don't know if this would be the normal way to go missed with the FMC.I promise that when I go to FlightSafety (hopefully in 2004) I'll find out!

[brucek 38]

Hi Timothy,Since the MAP is truely the last of the approach segements, and any further clearances (to an alternate, or to re-try an approach) have to be obtained by ATC (and therefore cannot be assumed), shouldn't it be normal to terminate the FMC legs at that point? Is this the question- why there is not automated re-try at the approach after the MAP?Thanks,Bruce (instrument student) :)

[Guest tmetzinger]

>Hi Timothy,>>Since the MAP is truely the last of the approach segements,>and any further clearances (to an alternate, or to re-try an>approach) have to be obtained by ATC (and therefore cannot be>assumed), shouldn't it be normal to terminate the FMC legs at>that point? Is this the question- why there is not automated>re-try at the approach after the MAP?>>Thanks,>>Bruce (instrument student) :)>>That's more or less it... I think the issue has to do with the fact that the FMC breaks routes into CLIMB, CRUISE, and DESCENT/APPROACH, and has specific criteria for switching between those modes.The missed approach is sort of an "exception" to the logic, but the FMC is still thinking the route is complete when you're heading to the holding fix.Normally, when you're going back for another try, you're not using the FMC, it's a easy transition or vectors for the approach from the holding fix. However, when you divert to another airport, you then DO punch in the new airport in the RTE pages, and that resets the logic to allow CLIMB and CRUISE segments again. That's covered in the Bulfer FMC manual.I don't know if you have to "fake" out the real FMC by using my workaround if you want full functionality back to the same airport.

[brucek 38]

Thanks. Interesting information!Bruce.

[Guest Iz]

Actually, you pretty much ALWAYS use the FMC when returning after a missed approach. Doing so greatly enhances situational awareness. Don't forget that in real life, it is all a much more complex system than portrayed here, and doing a missed approach in bad weather is not something you do daily but is a very high workload situation.You have your weather (embedded thunderstorms?), other traffic (some also holding, doing go-arounds), your cabin, ATC and your fuel management to worry about. Don't forget that most flights are planned with strict minimum legal fuel and you need to pay close attention to that, whether you should (or even can) divert, how long you can wait till the weather gets better, how far in sequence ATC is gonna put you for the approach etc.etc.Just a simple task of going to the DEP/ARR and re-selecting the approach, will give you lateral situational awareness, the FMC gives you fuel calculations, you see where other traffic (TCAS) is and if there's weather in your approach path.I did find that the FMC in the PMDG737 gets a bit screwy when you do a missed approach and want to divert (even during cruise) or return. I've had a scratchpad message "ERROR IN LINE T1" once, no idea what that was, it screwed up the departure airport. VNAV calculations completely gave up on me and the LNAV path does zig-zags around the final approach waypoints.Other than that, great progress on the PMDG737, it's a very very complex one to program.Iz

[Guest tmetzinger]

>Actually, you pretty much ALWAYS use the FMC when returning>after a missed approach. Doing so greatly enhances situational>awareness. Don't forget that in real life, it is all a much>more complex system than portrayed here, and doing a missed>approach in bad weather is not something you do daily but is a>very high workload situation.>>You have your weather (embedded thunderstorms?), other traffic>(some also holding, doing go-arounds), your cabin, ATC and>your fuel management to worry about. Don't forget that most>flights are planned with strict minimum legal fuel and you>need to pay close attention to that, whether you should (or>even can) divert, how long you can wait till the weather gets>better, how far in sequence ATC is gonna put you for the>approach etc.etc.>>Just a simple task of going to the DEP/ARR and re-selecting>the approach, will give you lateral situational awareness, the>FMC gives you fuel calculations, you see where other traffic>(TCAS) is and if there's weather in your approach path.>>I did find that the FMC in the PMDG737 gets a bit screwy when>you do a missed approach and want to divert (even during>cruise) or return. I've had a scratchpad message "ERROR IN>LINE T1" once, no idea what that was, it screwed up the>departure airport. VNAV calculations completely gave up on me>and the LNAV path does zig-zags around the final approach>waypoints.>>Other than that, great progress on the PMDG737, it's a very>very complex one to program.Excellent points! in the scenario I was using the MAHP was also the FAF for the approach (KTNT), so I was already on the approach and had only to exit the hold and activate APP mode.Iz, how about your full name? I feel funny referring to you soley as "Iz".I hope Anthony can improve the FMC behavior on the missed for the 800/900 release. In my opinion, unless it's an easy fix, it's not a high priority, and others (the problem with the PBD waypoint discussed elsewhere) are.

[Guest Iz]

Now, Timothy, you don't have to feel funny, my friends call me this too!I'm just usually too lazy to write out my full name or make a sig.Iskander HannivoortATPL - B737/B757/B767/E120

[brucek 38]

Thanks Iz.".....great progress on the PMDG737, it's a very very complex one to program..."Is the NG FMC much more complex than, say, a B757/767 or B744? I know they are a generation apart now. How does the NG FMC compare to that of the 777?Thanks,Bruce.

[Guest Iz]

Apart from some aircraft type differences, the 757/767 and 744 FMCs are the same, just like the whole autoflight system.The 777 and 737NG FMCs are also quite alike, they are newer versions of the 757/767/744 FMCs.In terms of complexity, it does not matter that much. Suffice to say, the systems are complex to program from scratch, like PMDG did, trying to figure out all the logic. You'd need weeks and weeks on end with a real FMC simulator to get all actions correct. I noticed the Cost Index isn't really modeled here, still.I personally prefer the 767PIC FMC, it seems more solid than the PMDG one, nonetheless, they are both very good now. I think they both cover about 80% of full FMC functionality.Iz

[brucek 38]

Thanks Iz.Talking about the similarity of the NG and 777 FMC's, I wonder why the entire cockpit arrangement wasn't standardized (as say- the A320 and A330), to allow crew commonality? Maybe it's that a fly-by-wire aircraft is always fundamentally different from a conventional control system aircraft,a nd so the issue pf cross commonality was dead at the design stage between these two aircraft.Thanks,Bruce.