Why a 3rd FMS?

[PHX767]

Why do some long range corporate planes have a 3rd FMS? In the overwater airliners I have flown, they have 3 IRU's and 2 FMS. I am looking at the specs for a variety of biz jets and see that a lot of them have 2 IRU's and 3 FMS. Can't seem to figure this out on my own. Obviously this is a reduncancy (sp?) issue, but not a requirement. Looked over the NAT manual and see the requirement for 2 long range nav systems, is this just a way to dispatch with part of the nav system mel'd?

What is the value/return on investment on the 3rd FMS vs. other equipment. The SATCOM seems to be a great idea, but what about that against a 2nd HF, etc?

Thanks in advance for the info. Got some good info from the discussion on MNPS and NAT in the past few days, thanks.

 

[G100driver]

With 3 FMS's you should not ever get stuck crossing a large body of water. We had one FMS fail on us getting ready to go to HI. You cannot MEL an FMS priror to entering RNP-10 airspace. The flight was canceled needless to say. (At least we could not (135). I am sure someone will correct me if I am wrong )

For some folks, it is worth the cost I guess.

 

[empenage]

We have 3 FMS, 3 IRU, 3 HF, 2 GPS, 1 SATCOM and a partrige in a pear tree.

Load'er up baby.

 

[semperfido]

...add one starbucks coffee grinder

 

[fokkerjet]

Why 3? Because it looks really cool to get a triple FMS failure when you did something stupid like request NOTAMS along your route:uzi: You can't pay for that much excitement, especially if it happens at 30W!

 

[sydeseet]

Burp, why not?????

(Name the movie)

 

[Gulfstream 200]

Why do some long range corporate planes have a 3rd FMS? In the overwater airliners I have flown, they have 3 IRU's and 2 FMS. I am looking at the specs for a variety of biz jets and see that a lot of them have 2 IRU's and 3 FMS. Can't seem to figure this out on my own. Obviously this is a reduncancy (sp?) issue, but not a requirement. Looked over the NAT manual and see the requirement for 2 long range nav systems, is this just a way to dispatch with part of the nav system mel'd?

What is the value/return on investment on the 3rd FMS vs. other equipment. The SATCOM seems to be a great idea, but what about that against a 2nd HF, etc?

Thanks in advance for the info. Got some good info from the discussion on MNPS and NAT in the past few days, thanks.

You can cross the lonely dark North Atlantic (or Pacific) with the bare bones equipment and save a few bucks, or you can have everything possible at your disposal....

the choice is yours.

I know which one I would want my crews having if they operated under these conditions....

Think resale - outfit your long range aircraft the same way everyone else's is --- to the max.

3 FMSs
3 IRUS

(and a forward crew lav)

 

[G100driver]

Why 3? Because it looks really cool to get a triple FMS failure when you did something stupid like request NOTAMS along your route:uzi: You can't pay for that much excitement, especially if it happens at 30W!

Why miseur (heavy frog accent), it is because we designed it that way.

 

[fokkerjet]

:laugh: :laugh: :laugh:

 

[rice]

You can cross the lonely dark North Atlantic (or Pacific) with the bare bones equipment and save a few bucks, or you can have everything possible at your disposal....

the choice is yours.

I know which one I would want my crews having if they operated under these conditions....

Think resale - outfit your long range aircraft the same way everyone else's is --- to the max.

3 FMSs
3 IRUS

(and a forward crew lav)

Absolutely, positively will not fly without that!!!!!!!!! Nothing more important when 5 hrs into the trip and you get up just to find out that Mr. and Mrs. Rich are racked out in the back and blocking access to the lav .