ZFW...why
 

As en ex-dispatcher (quite a few years ago), I was trying to explain to a colleague the relationship between ZFW, MLW and MTOW.
He then asked me "why do you need to calculate the ZFW"? at which point I couldn't answer him.

Can someone enlighten me as to WHY the ZFW is used?

Thanks

Tells the Flight Crew how much fuel they can load without going over the MTOW, Performance Limit Weight, MLW etc. Bound to be unreliable most days;)

On long sectors it would be nice to fill her up but this would result in overloading the airframe with a heavy pax/freight load. HTH.

........and you were a despatcher ???????? :rolleyes:

Yes...........and?


Nobody explained to me WHY, I just did as I was told. I have become wiser over the years but I am talking about a career at least 10 years ago.

Just out of interest, in which area is your new career?

in air cargo. Less grief from boxes than from pax :}

wingzakimbo apologies if I came across a wee bit sarcastic but understanding ZFW is one of the very first things a despatcher should understand. I blame your previous employer for letting you down in that sense. Without a full understanding of ZFW, one really can't understand the laws behind MTOW or MLW.

Your comment "Nobody explained to me WHY, I just did as I was told" would have worried me if I had been in your shoes. If someone said to you "add that pallet to position Z, it weighs 10tons even though the position will only take 5tons", would you have done as you were told ?

I have no intention of starting an argument here, but if in that case you had done as you were told, chances are, the aircraft may not have rotated safely. The STAB trim would have been set at say 3 degrees, when it should have been at 4 degrees, especially as position Z is at the back of the aircraft. You see where I'm coming from ?

Anyway, as you say, you have become wiser over the years. Glad to hear it........:ok:

Don't confuse the duties of a dispatcher with those of a load controller. In some companies the dispatcher is purely responsible for supervising the turnaround, co-ordinating resources and checking the necessary paperwork is in order (ie, AAA bag numbers tally with the loadsheet, loadsheet figures tally with what was passed by the crew and load plan matches the load distribution on the loadsheet). Not all dispatchers are trained in any aspect of load control and so wouldn't need to understand the importance of ZFW.

Now if it was a pilot asking, well............!!!

ZFW
 

I hope U atleast checked the DOW before U started to calculate things

Supervisor - "........yes I said position Z"...........
Despatcher - "........ok then"

Maybe I should check first !

The only stupid question is the one you don't ask.:ok:

Lets start frm basics

Empty Aircraft + Pallets + Pantry = OWE
Also sometimes refered to as DOW

Add Payload ( Pax + Cgo + Crew + Baggage ) you get ZFW

Add Departure Fuel ( in tanks )
PlndRamp Out Weight

While A/c taxies out frm ramp , it burns
the taxi fuel and when it reaches end of Rwy and Intersection take off .Plnd Ramp Out Weight -Taxi Fuel
PTOW ( ZFW + T/off Fuel )

Fly Boyz perform RTOW computation based on ATIS and Airport Elevation and other performance They get RTOW ( Regulated TOW )If limiting , RTOW overrides PTOW and the necc things done .Offload cgo , Packs off T/off etc

MTOW /MLDW are aircraft certifed limits
PTOW /RTOW must not excess these limits

TOW/RTOW - Burnoff ( Trip Fuel ) = PLDW.It must not excess MLDW

Enuf said

OpsControl

Thanks for all replies/remarks - but I just feel I need to make a point clear, I don't want anybody to think that it was a danger being dispatched by yours truly.

I was a dispatcher and certified loadcontroller, and (for what it is worth) had done my City and Guilds dispatch/airline ops.

At that time (and we are still talking 10 years ago) I would have been able to SAFELY load and trim an aircraft in my sleep using a manual load- and trim sheet. My comment about "doing what I was told" did not mean that I didn't know what I was doing, and NO .... I would not have done anything to make a flight unsafe, I was perfectly capable of making sound judgements, and in fact pilots asked for me specifically on their turn around as they knew I would provide a safe and secure service. When doing my various courses I knew exactly WHAT the ZFW was, and the relations with all other operational weights, but I never asked WHY.

My question was spurred by a current colleagues questions of "why use ZFW, and not only TOW and LW" - I could have gone home and looked in my manuals/books/notes but needed and answer there and then.

....so in summary, all I needed was a someone to refresh my memory about WHY we use ZFW (not what it is) - )more of an existentialistic question ....this has now been done so I can answer my nosy colleague.

(but I dare say that I had dispatch colleagues who had worked for years, but still would ask questions like "what does 'in trim' mean?" ... but that is another story

Hi everyone, thought this might help:

Bending moments, which apply at the wing root, are maximum when the quantity of fuel in the wings is minimum. During flight, the quantity of fuel located in the wings, decreases. as a consequence, it is necessary to limit the weight when there is no fuel in the tanks. this limit value is called MZFW therefore the actual ZFW < = MZFW

cheers

lunatismic - A point very well made

MZFW is a STRUCTURAL LIMITATION which if exceeded will mean a broken or structurally unsound aircraft.

I find it very alarming the number of dispatchers/load controllers who are unaware of this and are happily packing aircraft full of traffic load before fueling, oblivious to the damage they could be causing to the airframe.

Conveniently ZFW will tell a pilot how much fuel he can take for a given traffic load.

This is a very worrying indication of the standard of dispatch training in the UK and definatley justifies the introduction of JAA dispatch lisencing legislation.

Captain 101 I total agree with your coment regarding lack of training in Dispatch in Europe.As an Expat living in Canada I have both my FAA Ticket and Transport Canada.The Transport Canada isnt worth the paper its printed on.But the FAA Liscense is a good Course and its valid for Life.I hope JAA does something along the same lines.I also feel if dispatchers/Load Controlers were liscened their pay should increase to level that it deserves.US and Canada is considerble better paid for the same job than blighty.Just my $0.2

Lot of bollox spoken here
It's simple - if you exceed the MZFW without fuel in the wings then the lift created will exceed the structural design loads and the wings will separate from the airframe at the wing root. See C130 on fire fighting over California C 2002
Regards
Feba

Its important to distinguish between the role of the 'Ramp & Flight dispatcher'. Typically the use of the term 'dispatcher' in UK refers to 'ramp' dispatch, those who work the ramp and will usually supervise the turnaround, loading, load control, boarding etc. Opposed, to the role of the Flight Dispatcher/Flight Operations Officer ( a la FAR 121 Dispatch) responsible for flight planning/operational control and for which the JAA have recently introduced the requirement to train those engaged in this role to ICAO Doc. 7192 D3 syllabus.

Now having said that, its is of course equally important that both have a clear understanding of the subject matter discussed here. Sadly, our training of both in the UK is left wanting. Captain101 has hit the nail on the head, airlines and handling agencies really do need to embrace the new training standard, and why not apply those relevent parts of 7192 D3 training to to the 'ramp dispatchers' role.

My post and picture concerning the B727 on it's ass is a serious statement. I've seen that sort of mess for real.

no sig is right, it's high time airlines, agencies etc get to grips with training and standards.

In regards to loading an a/c with pax and freight before fuelling, I see no problem with it as long as the MZFW is not exceeded (i.e. the a/c should be safe from structural damage). The only things you need to watch out for from there are that you dont exceed other structural or performance limits once fuel has been loaded, hence planned loads and the EZFW (estimated ZFW). If the flight crew reuire additional fuel due wx or alternate requirements then they can set the MZFW so we can get their fuel on.