Min ZFW

[John Farley]

I have been asked why a minimum zero fuel weight should be specified/required

I could not come up with any answer that I believed.

Anybody know ?

[javelin]

We asked this question of Airbus - they said it was part of the bending load calculation across the wing with reference to where the tanks are.

Max ZFM - all the punters on and max downward load pivotting on the gear

Min ZFM - no one on or even in a stripped out condition, max upward load pivotting on the gear.

Seemed to make some sense at the time.

[John Farley]

Thank you javelin

Very helpful.

JF

[Thirty Eight South]

Zero Fuel Weight:

MEW - manufacturers empty Weight
OEW - Operators empty weight

OEW + Payload is a function - the delta you looking for is the max mass allowable, ipso Max ZFW (fuel that can be up loaded)

MEW is the A/C mass (static) as produced by OEM
OEW is MEW + customer add ons (customization)

OEW changes based on customer requirements - not a military problem as slinging a few missiles on an fast jet is not the problem that confronts an Ops manager for a civil operation

OEW - ZFW = total fuel load max allowable based on A/c allowables

structure moments and bending are more to do with repairs and static nominal zero for stress jacking ( it's more complicated than that but I can't be bothered going into it)

So, in summary - ZFW is the derived sum of available mass after all optional operational considerations are allowed for i.e how much fuel can I upload for this operational sector is one option, but in general mass and loading are derivatives of commercial Ops

[cheesypeas]

On the aeroplane I fly (Embraer 145), the line for minimum zero fuel weight is the bottom of the C of G envelope and is co-incident with the line for lowest aircraft weight.

I reckon that there isn't techincally a minimum zero fuel weight for the aeroplane, merely a minimum FLIGHT weight. I imagine this is something that was defined during testing when determining Va and generating that graph that you see which plots g loading against speed for a given gust if you know the one I mean???

Not sure if this is a load of old pants though, but I did some research into this too a while ago and couldn't get anywhere.

[john_tullamarine]

There are several design cases which infer min weight restrictions .. right up MFS' alley I suggest .. I have no doubt he will wade into the discussion in due course. I shan't exert myself by flicking through Part 25 to list the likely contenders but I located one not too ancient thread (http://www.pprune.org/forums/showthread.php?t=245955&highlight=minimum+ZFW) which has some relevant commentary ...