A320/321 GWFK
 

The older MSNs I flew have a PARAM ALPHA callup in the box which allowed one to view the GW as calculated by the FAC once above 14,000ft, say at cruise level when everything settles down. One inserted "GWFK".

The later MSNs don't appear to have this parameter. Is there any way one can call it up? "GW" only gives the FMC calculated gross weight as I understand it. I've also attempted GWFC. No joy.

Thanks.

As far as i'm aware they are still available on newer aircraft in the same place as the older but need to be inserted with the ususal GWFK code. I've seen it on MSN's 5000+. Have a look at the FCB section for the criteria for when its calculated. It's only calculated below 14600', not above but should be available to view throughout.

ElitePilot, would you care to share what "unusual" code that is? I have looked around but can't seem to locate it.

The other option is of course to look at green dot value and work out the calculation in reverse (GD-80 then divide by 2 for IAE, use 85 for CFM) and needs to be corrected for altitude above 20,000' (see QRH speeds table for details).

Of course the problem is, when in cruise, GD is rarely visible on the speed tape.

Hi Flex, sure its an Alpha/maintenance code indicating gross weight computed by the FACs based on AoA values. Basically the weight the aircraft thinks/calculates it is compared to the weight we tell it it is.

Yes I understand that. I was wondering what code this might be.

Thanks for replies so far.

I used to enter both GWFK and AOA in PARAM ALPHA call up. This gives an indication of FAC weight, as compared to the calculated FMC GW with preflight-entered ZFW and FOB. I check AOA for reasonableness, so that I can have some faith in the FAC computed GW.

I also would like to know what that Alpha code is Mr Elite. I'm buggered if I can find any ref to FAC weight anywhere in the box or FCOM in these latest MSNs.

I'm pretty sure I saw them in the maintenance manual. Not listed for sure in FCOM/FCTM. Will have a look when I get a chance. Which MSN range does it not work on?

Well, I have the AMM too, but could not find any ALPHA entry for FAC Weight with the new FMS standard.

Always ready to learn! :ok:

GW is the correct code and it works. However, FMS computed weight is displayed when on the ground, and when airborne both FAC 1 and 2 data is available with the same code (GW). Also available below 14000. Cheers.

Using this, how close do people find the two weights generally? Especially on an empty aircraft (where there is no error in standard pax weights).

As far as I know the FAC derived GW can not be displayed by using ALPHA callup. the only way is to use the GD formula (GD on PFD).

Sometimes, the GWFK value is really close to the GW value on ND but I have already found big differences like 1,5 or 2 tons (no error in ZFW insertion after crosscheck). In the FCB, it says 0,3° AOA error equals to 3 tons so...which one is good ? It is just pure curiosity as the load sheet is the reference but would be interested to know...

Some people have way too much time on their hands in the cruise:ok:

Yes, I have noticed up to 1.5t differences at time on empty aircraft so definitely no payload errors.

I wonder whether its to do with different equipment manufacturers or even aircraft (i.e. 320/319/321).