Strange behavior with Holding Pattern

[Boeing or not going 578]

Very good point.

That incorrect registration plate in the vc burns my eyes. Go pick up an Aerologic repaint by Christian Mohr or John Tavendale in the avsim library! Although I think the PMDG has the correct ini settings and the other repaints do not. But that screenshot you have where it shows CRZ setting should be CLB Aerologic do not have CRZ enabled. And they have HDG not TRK.

 

http://www.airliners.net/photo/AeroLogic/Boeing-777-FZN/2579512/L/

 

I am obsessed with realism I know...

 

- David Lee

[Alpha Floor 237]

That incorrect registration plate in the vc burns my eyes.

 

Hi David, thanks for your comment and observation. I however don't have a "realism OCD" (no offence intended) and am happy to fly like I do.

 

I call my flying style, "plausible realism", it's not 100% true to real life, but it could be. For instance, I was flying GCXO-LEVT with the Aerologic. I think this flight doesn't exist, but it could. Also real life 777 crews are trained to use the AT most of the time, even when the AP is off. I like to fly manually (AT/AP off) and raw data sometimes, maybe not realistic 100%, but you could do it in real life if you wanted to (they practice it in the simulators for sure).

 

Also I don't really care about CLB/CRZ or HDG/TRK. To me these are minor things, and the time spent trying to find out which configuration the real aircraft has is time taken away from flying itself. I once was a "realism OCD case"; but then I "grew over" it and now I'm more happy

[RVxSpeed 3]

ok. just to confirm the aircraft actually performs the hold according to charts or given radials. but, something has triggered the aircraft to not represent the holding pattern as "racetrack" which clearly have been showing on since 1-2 months, instead now it's showing orbital shape. this bug may have got introduced with the latest update or maybe with the navigraph airac cycle.


 

[downscc 1,327]

Correct, Muntasir, the aircraft proceeds in the correct manner regardless of the magenta line on the ND.  There are several of these rendering problems in the 777.

[RVxSpeed 3]

Correct, Muntasir, the aircraft proceeds in the correct manner regardless of the magenta line on the ND.  There are several of these rendering problems in the 777.

hello, but i think it has something to do with latest airac cycle.

[kevinh 409]

hello, but i think it has something to do with latest airac cycle.

No it's the same with older AIRAC cycles.

[richjb2 195]

Jamie, et al..

 

The manner by which FMS flying holding patterns differ from the way that conventional holding patterns are flown using basic VOR/NDB navigation.  Further, each RNAV brand performs holding differently. In most cases, the leg distance, nav-database coded or pilot entered, is used to calculate the inbound leg distance.  The RNAV system will vary the length outbound leg to make good the programmed inbound distance.  The one exception that we found is the Smiths/GE B737 FMS, which flies the both the inbound and outbound leg the same length.  Based on the Honeywell B777 FMS Pilot's Guide description of holding, I suspect that the FMS only apply the distance to the inbound leg and permits the outbound leg length to vary based on wind as necessary to make good the inbound leg length. Interestingly enough, none of the FMS/GPS systems fly time based holding.  If the plot programs the FMS for a "1 minute" hold, the FMS actually computes an equivalent distance and applies that distance as described above.

 

As far the inbound turn or the outbound turn, some RNAV systems use a constant bank angle on one or both of the turns and let the size of the hold pattern vary with the wind. Some will assume a constant 25 to 30 degree bank turn on end or the other and then vary the other turn's bank angle during the turn.  What is known is that the RNAV system will compute and then a lock the holding pattern entry and turn parameters as some distance/time factor prior to holding entry.  Some systems may recomputed the hold pattern turn parameters (bank angle used, etc.) during each circuit when passing over the holding fix.  According to the Honeywell Guide, the B777 recomputed the holding pattern size passing over the fix each time and re-display the holding pattern on the ND.   It is also important to note that the holding pattern size is predicated on the TAS equivalent of the VNAV target speed for the hold plus wind component.  If you are manually flying or using FLC at speed higher than the computed target speed, the holding pattern flown will not conform to the holding pattern size computed by the FMC.   In other words, make sure the automation is flying the hold as intended and allow it to slow the aircraft appropriately.

 

While some RNAV OEM's claim that the holding pattern computed by the FMS/FMC will not exceed holding protected airspace, this is in fact not true since the FMS/FMC has no way of knowing what size holding template was used to assess holding protected airspace.  Further, the holding pattern template changes every 2000', increasing in size as you go up and decreasing in size as you go down.  The holding pattern size is not coded in the nav-database, so there is no way for the RNAV system to know the holding pattern template size.  This is another reason to slow the aircraft to the recommended holding speed, not to exceed the maximum published speed, for the hold.

 

Best regards,

 

Rich Boll

Wichita KS

[downscc 1,327]

 

 

If the plot programs the FMS for a "1 minute" hold, the FMS actually computes an equivalent distance and applies that distance as described above.

 

Interesting background, thanks for sharing.  Regardless, there are several rendering bugs in the 777 FMS that PMDG is most likely aware of.  Very good point about speed importance to staying within cleared airspace.

[pcubine 143]

 

 

there are several rendering bugs in the 777 FMS

Dan

There are more than several. It seems like the majority of flights in the 777F the SID or STAR looks like wet spaghetti thrown on the floor. The plane navigates them fine but they look like hell on the ND.

[scandinavian13 5,192]

 

 

It seems like the majority of flights in the 777F the SID or STAR looks like wet spaghetti thrown on the floor.

 

Interesting assertion given the fact that there isn't any actual evidence of it here on the forum...

[downscc 1,327]

I'm with Kyle on this.. at most I see is a rendered track that is a fly-over instead of a fly-by and an occasional loop caused by a wrong turn being rendered.  Minor glitches that somehow got introduced during an incremental update I believe, but that is because I want to beta test every change for months on end.  There'd be no more wet speghetti in my world hahahah.

[pcubine 143]

Interesting assertion given the fact that there isn't any actual evidence of it here on the forum...

 

PMDG tech support has the screenshots.

[scandinavian13 5,192]

PMDG tech support has the screenshots.

 

From a single person. If it were as rampant as you claim, it would be reported by multiple people.

[pcubine 143]

From a single person. If it were as rampant as you claim, it would be reported by multiple people.

I am speaking for myself, not all T7 owners.

[coceoca 0]

Hello together,
I have the same issue!
I have created a ticket a long time ago. The PMDG support does not respond anymore to me.
See the two linked images (they were from the same STAR):

http://s1200.photobucket.com/user/qfhgghkhg/media/BASGO1_zpsl852bhhp.png.html

http://s1200.photobucket.com/user/qfhgghkhg/media/BASGO2_zpslrixhxkm.png.html

Kind regards
Jens