Vgmin???

[Cornish Jack]

I suspect that this is probably John T's territory, but does anyone have the definition of Vgmin, please?
The context is the Honeywell FMS handbook, which quotes Vgmin as the basis for holding speeds, but doesn't give a definition. Again, from the context, I could guess that it is minimum groundspeed but have never come across that as a performance type parameter before. The rest of the defining para sees groundspeed as a basis for calculating min. holding speed by using instantaneous wind updates to generate CAS as an additive to groundspeed. Anyway, a 'book' definition of Vgmin would be helpful - TIA

[john_tullamarine]

... pass .....

have to admit to gross ignorance ... a new one for me in this Industry, although the abbreviation is not uncommon elsewhere ...

[Cornish Jack]

Thanks anyway, John.
This was raised with me from a friend who has since contacted Honeywell with the query. Their response was that this was an engineering reference which shouldn't have been incorporated in the handbook - (didn't say what it was, though!).
I did what I should have done first, and trawled through the 'stickies'. There is one reference there in abbreviations and acronyms to VG as Ground Velocity so maybe my guess in the thread opening wasn't far out. Would still like the definitive version, if anyone has it.

[4PON4PIN]

CJ you auld Bu***r, thought you would have followed my lead t'other day. Go to Dogpile and type V Speed Definitions. The 5th result should give you header of Vg Diagram with faa website www1.faa.gov/fsdo/orl/files/pp/pres.ppt
This is a presentation explaining how Vg is determined and is, as I understand it, the Design Manoeuvering Speed (Va) for a specific weight and configuration. Other leads give sites which amplify Va but am sure you are up to speed (groan!)with that.
The powerpoint presentation runs automatically so you will need to right click and "reverse" in order to stop and study the diagrams. They are fairly complex but if you can't do The Telegraph crossword then you'll have little hope with these so you can always give me a call on Montag. Have a Bon w/e mon brave:D

[john_tullamarine]

4PON4PIN,

I think that we are talking two entirely different things here. The "Vg" diagram to which you refer (more usually referred to as "nV") relates to design standards ... the post is looking at something which Honeywell developed in their internal procedures.

[mutt]

Checked out a couple of FMC Supplementary Data documents, (B772/ B744/ B74C) they refer to VG as the "Ground Speed". Vmin is also defined as "Minimum Speed".

Putting the two of these together gives you the "Minimum Ground Speed", but i cant find that exact definition.

It should be noted that the VG speed is distinct from the VMCG speed and is used for cruise/holding calculations.



Mutt.

[Cornish Jack]

Thanks everyone - seems like the first guess was correct. I'll pass the details on.
4PON4PIN
Enough of the puns - not Montag, I'm watch and clocking all day - talk to you on Tuesday.
John T - I think that 4Ps may be correct, since the Honeywell response indicates that the reference is to an engineering based calculation. Anyway, they say that it should not have been included in the handbook so the relevance is decidedly less.
Again thanks to all.

[john_tullamarine]

CJ,

In the absence of some definitive Honeywell docs I can only speculate ... but I suspect that the two are still totally unrelated ...