Hi folks 

 

by and then and with various aircraft (LD67, PMDG M11, now PMDG 77W) I fly tribute flights ANZ901 NZAA-(NZPG)-NZCH-NZAA in memoriam of the victims of flight TE901 on Nov28, 1979. Yesterday I flew ...

 

  BROOK LIMES H384 NP H252 NS Q787 NV 51S66 67S65 BYRRD 77S67 NOBEY A338 CH

 

and felt save to manage the filght portion in the icy and inhuman area of the globe near Mount Erebus. 

 

Two deficiencies hampered my flight: 

 

1.

To my surprise the terrain radar did *not* work properly. The system, which would have saved TE901 about 35 years ago, presented only magenta as shown in my screenshot: 

 

 

Please note: I did not activate TERR OVRD, only FLAP and GEAR OVRD due to my low altitude of 1000' and less. 

 

A. How to overcome this? 

B. Is it the real behaviour of TERR in the area of GRID navigation etc.? 

 

2.

Due to bad weather in the area (500' overcast, 500m visibility, heavy snow showers) and the missing TERR low overflights of McMurdo station were not advisable and I decided to abort the most interesting part of the flight. 

However, in comparison to the PMDG M11 the 77W did not expect after my 'early' descend again climb, cruise, descend phases: The FMC did not accept me entering again a (2nd time) cruise altitude 400: 

 

 

Instead I got INVALID ENTRY; also variations 'FL400', '40000' also on the CRZ page etc. (RTE2 with the whole and unbroken flight plan)  --- all to no avail. 

Of course I could climb in V/S mode to the desired cruise altitude (and LNAV worked fine), but even then --- on the legs page --- I could either enter the speed '.84' or the FL400 for the next waypoints. 

 

C. Why is the M11 much more flexible here? Easily I could enter again an second cruise phase. 

D. Right, this flight profile is highly unusual, but does the seen behaviour reflect the real Boeing logic? 

E. Did I make a mistake? How could I have entered the cruise level anew? 

 

 

Thanx in advance. 

Edited October 21, 201411 yr by 19AB67

PMDG does not create terrain, it reads what is in the FSX scenery. This may be the source of your first problem.

 

I would have treated the climb after diversion as a trip to an alternate. Not sure of the steps to enter alternate diversion after the diversion... interesting; however, pretty certain if you had RTE2 preset for alternate then things would have gone much smoother for you.

 

Finally, in keeping with the first rule of aviation, "Fly the airplane first," you could have flown with MCP controlling altitude/speed and heading until you sorted out your diversion to alternate in the FMS.  V/S mode is not the only option, in fact FLCH is a much better mode since it is providing speed controlled pitch.

1.

 

To my surprise the terrain radar did *not* work properly. The system, which would have saved TE901 about 35 years ago, presented only magenta as shown in my screenshot:

 

Please note: I did not activate TERR OVRD, only FLAP and GEAR OVRD due to my low altitude of 1000' and less.

 

 

 

A. How to overcome this?

 

B. Is it the real behaviour of TERR in the area of GRID navigation etc.?

EGPWS is not a terrain radar. It uses a terrain database and relies on GPS position and altitude. So whether you were in a GRID area or not makes no difference.

 

Magenta colour indicates no terrain information available. Either the database PMDG use does not extend this far south or your GPS position was not available.

 

Re the Cruise altitude, you appear to be entering it on the CLB page. Did you try using the CRZ page? I was sure I had been able to reset cruise mode in that way in the 777, but I wouldn't swear to it.

 

PMDG does not create terrain, it reads what is in the FSX scenery. This may be the source of your first problem.

 

Incorrect. PMDG use a terrain database, as per the real system. Their EGPWS does not "read" FSX scenery. whether the database extends this far south is another matter. Honeywell docs show their database extends from 90 deg N to 90 deg S.

 

 

Incorrect. PMDG use a terrain database, as per the real system. Their EGPWS does not "read" FSX scenery. whether the database extends this far south is another matter. Honeywell docs show their database extends from 90 deg N to 90 deg S.

 

I stand corrected. Thanks.  I never noticed the PMDG\DEM folder before, I notice the filenames go up to 90N but only 'down' to 10S, not sure what to make of that. A scan of both 737 and 777 intro manuals doesn't shed any light. I know I've used terrain display going into Rio De Janeiro which is at 23S further south than 10S.

I stand corrected. Thanks.  I never noticed the PMDG\DEM folder before, I notice the filenames go up to 90N but only 'down' to 10S, not sure what to make of that. A scan of both 737 and 777 intro manuals doesn't shed any light. I know I've used terrain display going into Rio De Janeiro which is at 23S further south than 10S.

I didn't know what folder it was in, good spot. I only knew that Ryan mentioned it here pre-release. Some FSX developers use FSX terrain for EGPWS, others use a proper terrain database. There was a discussion here about terrain warnings being dependent on installed scenery and Ryan explained why it wouldn't be.

 

From those file names it looks like they cover 50 deg of latitude each. In which case the database only goes to 60 deg S. McMurdo Sound is 77 deg S. That would explain the magenta terrain display. My 777 is currently sitting on the ice strip at NZIR and the terrain display is indeed as the OP describes.

 

 

Finally, in keeping with the first rule of aviation, "Fly the airplane first," you could have flown with MCP controlling altitude/speed and heading until you sorted out your diversion to alternate in the FMS.  V/S mode is not the only option, in fact FLCH is a much better mode since it is providing speed controlled pitch.

 

Hi Dan, 

 

yup, I climbed first to FL380 as the second picture shows. 

I think I had problems also in earlier flights to re-enter a cruise altitude. The question remains whether 777 FMC logic is not truly not ready to accept after a descend. 

 

 

A. How to overcome this? 
B. Is it the real behaviour of TERR in the area of GRID navigation etc.? 

 

A. Add data.

B. Yes - terrain data is unavailable for that area, so it displays as magenta (as has been mentioned).

 

 

 

C. Why is the M11 much more flexible here? Easily I could enter again an second cruise phase. 
D. Right, this flight profile is highly unusual, but does the seen behaviour reflect the real Boeing logic? 
E. Did I make a mistake? How could I have entered the cruise level anew? 

 

C. It isn't - you're just not doing it right.  As Kevin noted, you are trying to enter data on the CLIMB page.  You need to do it on the CRUISE page.

D. Yes - adjust cruise values on the cruise page and you'll be fine.

E. Yes - see above.

 

 

C. It isn't - you're just not doing it right.  As Kevin noted, you are trying to enter data on the CLIMB page.  You need to do it on the CRUISE page.

 

Hi Kyle, 

 

thanx for your answers. 

However, as written in my original post ...

 

 

 

Instead I got INVALID ENTRY; also variations 'FL400', '40000' also on the CRZ page etc. (RTE2 with the whole and unbroken flight plan)  --- all to no avail. 

 

... I failed to enter the 2nd cruise FL also on the CRZ page. 

Was it because something in the logic switched to kind of approach mode because I was so low, and therefore it couldn't come back to cruise mode? 

 

 

However, as written in my original post ...

 

Sorry - I trusted the physical evidence (the picture, which shows the CLB page) over the recounted (spoken/typed).  The human mind is capable of many amazing things, but it's also capable of simply making things up because it "fits." A lot of the gear-up landing stories have some element of "I swear I put the gear down!"

 

I do know that the FMC has been 'taught' monotonic paths in that it assumes that it will climb at the beginning, cruise in the middle (even if there are small climbs in there, occasionally), and then descend - in that order (this is partially how the FMC automatically changes the VNAV pages). That's just how it handles things in an automatic sense, though. I'm not aware of some type of approach mode kicking in preventing a CRZ ALT assignment again. I'll check in the sim.

 

 

B. Yes - terrain data is unavailable for that area, so it displays as magenta (as has been mentioned).

 

Hi Kyle again, 

 

do you mean, terrain data is not available for the PMDG 777? 

I would expect that the real ship truly scans the terrain, does it not? 

 

Or does it also rely on stored data?

This would have the advantage that no real scan is necessary, and that the obstacles not 'visible' in the line of sight (e.g. due to low altitude) are still presentable ... 

 

:huh:

would expect that the real ship truly scans the terrain, does it not?

 

Not at all, the terrain is not 'scanned' but a database of terrain and obstacles is used. If you are operating outside the bounds of the data then you should have current charts for terrain avoidance. It is not easy to use radar to define terrain elevations from a side ange, and airborne weather radar is most definitely not designed for this task. Sure, there are ground returns but other than defining coastlines and cumulogranite straight ahead it's hard to use... radar bombing has been mostly replaced by better technologies for the task.

 

 

I would expect that the real ship truly scans the terrain, does it not? 

 

As Dan noted - and as has been mentioned already in this thread - it does not.

 

So:

 

 

do you mean, terrain data is not available for the PMDG 777? 

 

...it means that terrain data is not available in the database - PMDG 777 or real world 777 (this is something that could've been answered with the real world manual as well).

PMDG 777 or real world 777 (this is something that could've been answered with the real world manual as well).

 

Thank you Kyle for pointing us back to the paper work (RTFM...), yeah. 

 

However, a first scan of the provide docs led me to what might have let me think that TERR uses true radar (it does not, I got it now, only stored data): 

FCOMv1 and FCOMv2 refer to the Look Ahead Terrain Alerting. Here I assume that a forward looking radar beam feeds a computer to announce imminent impact to terrain or obstacles. 

 

 

FCOMv1 and FCOMv2 refer to the Look Ahead Terrain Alerting. Here I assume that a forward looking radar beam feeds a computer to announce imminent impact to terrain or obstacles.

 

The 3d page I came to using search string "Look Ahead Terrain Alerting" was L.10.9, which clearly referred to GPWS terrain database and references the Honeywell documentation.

 

Honest, weather radar really sucks at mapping terrain other than water/land boundaries. It's optimized for rain drops.

 

 

FCOMv1 and FCOMv2 refer to the Look Ahead Terrain Alerting. Here I assume that a forward looking radar beam feeds a computer to announce imminent impact to terrain or obstacles. 

 

Nope. It's a feature that scans the database versus the current path and alerts you to any conflicts. This is what triggers the EGPWS aural alerts that everyone is familiar with.

 

Further reading: http://www.skybrary.aero/bookshelf/books/1744.pdf