B777 - Amber vertical NPS

[STBYRUD]

Hello everyone!
I've noticed that on several ships I've recently flown the vertical navigation performance scale is amber on ground, climb, cruise, up until descent when a VNAV path is generated.
http://abload.de/img/npsshust.jpg

On others, its white all throughout (as it should be of course) until the criteria for a deviation alert are fulfilled ("ANP bars and scale turn amber if pointer migrates into bar area for more than five seconds. + NAV UNABLE RNP on the EICAS). Vertical ANP in flight of course is not displayed on PROG 4 until in descent, so why would the vertical NPS be amber if there isn't a VNAV path (and thus no deviation pointer displayed) anyway?

The status page is clean, the only response from an engineer I asked about it was a shrug, and that "there aren't any fault messages, so it should be normal". The FCOM only mentions the NPS briefly, they should only be amber if deviation is excessive or if ANP > RNP, the AMM SDS and the FIM don't say a whole lot more either...

Well, can anyone enlighten me as to what is going on? Thanks :ok:

[TopSwiss 737]

STBYRUD,

The amber NPS scale you describe also happens on our fleet. It has something to do with a software upgrade.

With the AIMS-2 BP v14/15/15A software, the scales were updated to match the
ANP bars with respect to color, amber or white. The intent of the addition of the
alerting color (amber) for the NPS scales was to provide enhanced NPS alerting.
However, an error was introduced such that the vertical scales turn amber when
the ANP bars and deviation pointer are correctly suppressed.

A bulletin covering this issue is incorporated into our FCOM, including a workaround procedure to get rid of the amber scales.

I suggest that you contact your flight technical department, they might be able to provide you with more details. I'm surprised they didn't introduce a bulletin into your manuals.

[STBYRUD]

Thank you very much, that would make sense - although I was under the impression that the planes in our fleet were at V16 already. No such bulletin in the fcom either, could you maybe send me the corresponding pages from yours? Time to write to the technical pilot I guess... Cheers!

[STBYRUD]

Found it on MyBoeingFleet after quite a bit of digging, just for the record:

BOEING COMMERCIAL AIRPLANES
FLIGHT OPERATIONS TECHNICAL BULLETIN
NUMBER: 777-29
DATE: April 23, 2010

SUBJECT: Issues Related To AIMS BP V14/BP V15 Software Upgrades
ATA NO: 3141-00
APPLIES TO: All 777 Airplanes with AIMS BP V14 Installed
BACKGROUND:
Several irregular conditions have been identified, both in the lab during regression testing of the
AIMS-1, BP V14 software and from in-service reports when operating with the AIMS-2, BP
V14 software. This bulletin describes the conditions which may be evident to flight crews. It
further provides timing for when Boeing will implement corrective action for each condition.
This information was also provided via Boeing Multi-Operator Message MOM-MOM-10-0156-
01B(R1) dated 09 April 2010.

[...]

4.
Navigation Performance Scales (NPS) - incorrect display of amber bars
This condition results in vertical scales that are occasionally amber when no bars or
pointer are displayed. Boeing introduced the display of amber bars for lateral and
vertical deviation in the AIMS BP05A software upgrade. At that time, the scales were
always white no matter what color the bars were (white or amber).
With the AIMS BP V14 software, the scales were updated to match the bars with respect
to color, amber or white. The intent of the addition of the alerting color (amber) for the
NPS scales was to provide enhanced NPS alerting. However, an error was introduced
such that the vertical scales turn amber when the bars and pointer are correctly
suppressed.
This condition will be fixed in the AIMS-1, BP V14 software upgrade scheduled to be
available in August 2010. For AIMS-2 equipped airplanes, a fix will be available in the
next AIMS upgrade with a major displays software upgrade (BP V16). No schedule has
been established for the AIMS-2, BP V16 software upgrade.

This information is provided to keep 777 flight crews advised of known issues with the AIMS-2,
BP V14 software, the actions being taken, and the timeframes before corrective actions may be
implemented.