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Zero Fuel Weight

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Hi all, :-zhelpJust wondering if someone could explain ZFW a little. I am operating the POSKY 767-300 with PIC panel. Is ZFW the aircraft weight before fuel is loaded? Obvious I know but you know in aviation somethings are not so obvious!How do I work out ZFW on my aircraft and also reserve fuel. In the FMC, say for a flight from EGKK to LEPA and return I load 36678kgs of fuel. What should I put in the reserves? is it a % of the 36678kgs or extra on top of the fuel loaded?Again how do I calculate take off and landing weights? Is there a tutorial (basic for me) on how to do all this. I hate just putting in figures and not doing it properly and also hoping for the best in the climb.Thank you all in anticipation.Si Jones

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Guest GeorgeDorkofikis

Hi,Here's some sort definitions for the various weights used in aviation.BW = Basic Weight. The weight of the aircraft, empty, with no crew, no catering, and no fuel, but including hydralics & water.OW = Operating Weight. The weight of the aircraft including crew and catering but without any load (pax, bags, cargo) and no fuel.ZFW = Zero Fuel Weight. The weight of the loaded aircraft without fuel. This weight is the result of OW + Payload.TOW = Take-Off Weight. The weight the aircraft is expected to have at lift-off. TOW = ZFW + Fuel loaded - Taxi & Take-off fuel (usually 1-2Tonnes used for taxi & take-off fuel).LW = Landing Weight. The expected weight of the aircraft on touchdown. For pre-flight calculations : LW = TOW - Trip fuelFuel loading and aircraft loading & balance in general, are quite complicated as they have a very important role in the aircraft performance.To calculate the required fuel you need to know lots of information, like weather (Origin, enroute and destination), expected delays, safety limits etc.Let's see if I can make this brief (yeah, right! :-) ). Assuming that weather conditions for s standard day (15C, QNH1013, no/light winds to affect us).The ZFW for PIC is always 111 Tonnes (245,000Lbs). If you want to change it you have to edit the aircraft.cfg file, but I'm not going into this detail.Now, you have to calculate your trip fuel. This depends on the distance you will cover, how high you will fly, what is your payload etc. For the sake of this example let's say that your 767 burns 3Tonnes of fuel per hour. Let's also assume that your flight EGKK-LEPA is planned for a normal FL350 and is calculated to approx 2hrs15mins. That makes out approx 7.2Tones of trip fuel.On top of that we have to take into account any holding or delays we may have. Let's say that we plan for the minimum of 30mins for holding. So we add up another 1.5Tones of fuel. We also need fuel to fly to our diversion airport and also plan for holding there too. Let's say that our diversion airport is LEBL (Barcelona). It would take us 40mins to get there and approach. Plus 30mins for extra holding just to be sure, we add up another 3.3Tonnes of fuel.Let's not also forget the APU, Taxi and fuel we will burn for the take-off roll and initial climb (those engine burn a LOT on take-off).So, we add up another 2Tonnes for that.Let's sum the figured until now:Trip 7,200Kgs + Holding 1,500Kgs + Alt/Hold 3,300Kgs + Taxi 2,000KgsThat make it to total 14000Kgs of required fuel.Now, since the weather enroute is not always as forecasted and we may experience different winds, and in general weather conditions, we add some extra reserve fuel for the trip fuel. A 5% is a normal value.So we add another 700Kgs to the above value. There you have it.You need to load the a/c with at least 14700Kgs of fuel to make that trip. To confirm this, you can go to the Prog Page in the FMC after you load the a/c with the proper fuel amount and check the EFOB value at destination. If this value makes up the Holding+Alt/Hold+taxi+Reserves or above, you are ok! If not, load extra fuel or recalculate.Oh, one last thing. We normally don't load the a/c with fuel for the return trip unless it's absolutely needed like a strike at destination, no fuel etc... And watch your weight. If you load too much fuel for a given ZFW you may end up too heavy and exceed the MTOW (Maximum Take-Off Weight).I tried to keep it short. I think it didn't work... :-) but I hope that helped you.Cheers,George DorkofikisAthens, Hellas

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Guest

The ZFW for the POSKY 767-300 is set for the maximum that the aircraft will take (305,000 lbs). If you're happy with flying with a ZFW of 245,000 lbs, simply adjust this number. Its in the aircraft.cfg file under a heading called weight and balance.It will give you a better rate of climb above FL300 although still quite derated.

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Ok - this is a bit confusing to me.FS2002 lists the "empty_weight," "station_load," "max_gross_weight," in the aircraft.cfg. Additionally, the fuel weight can be determined. In some cases, for add-ons especially, the ZFW is also listed in the notes or references, or what not.My question is as follows:How do I determine ZFW if it isn't given in the reference or notes? Specifically, using something like "Weight & Balance Computer 3" or "ACLoader" there are a bunch of different weights such as MGLW, MTOW, AEW, MFW.Given this, is AEW and ZFW the same thing? I ask this question in reference to the difference between ZFW and MZFW - what is it?

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>Given this, is AEW and ZFW the same thing? Never heard of AEW. What does it stand for ?>difference between ZFW and MZFW >- what is it?Simple. ZFW is what *your* aircraft weights with no fuel (the body + cargo + pass.). MZFW is a number given to you by the manufacturer that tells you what is the maximum ZFW for this aircraft. If your ZFW is greater than MZFW then you have too much cargo aboard. Michael J.


Michael J.

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Well then ..ZFW = AEW + all cargo (including humans and animals, he,he)ANDZFW = Total weight - fuelMichael J.


Michael J.

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Si,Good question...Maximum zero fuel weight has a kind of cool idea behind it...The textbook definition is...

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Guest

Thanks to everyone who had input into this string. I really appreciate some of the in depth answers that have helped me to understand ZFW etc.THANK YOUSi

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So does this mean that I should use the higher figure for ZFW as I use Lee's POSKY merge V3 ?. I've used the 245 with the POSKY with no problem, should I either change the figure in the aircract.cfg to read 245,000lbs or start using 305 for ZFW in the FMC ?Confused...Tero


PPL(A)

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Guest Mark McG

Tero,No need to be confused.305,000lbs = Maximum Zero Fuel Weight.245,000lbs = PIC Zero Fuel Weight245 will work just fine in the FMC. Higher or lower werights can be entered into the FMC, but the aircraft cfg will need to be altered to reflect what ever new value you choose.I find that 245,000lbs is a pretty realistic value for the ZFW of a 767-300. On average the ZFW of a 767 from the UK to US East Coast ranges from about 237000 lbs to 255000 lbs. Also with the figure of 245000lbs you can fully load up with fuel if needed.For Example EGPF (GLA) to KSFB (SFB) approx 8.5 - 9 hour flight.Average TOW = 165000Kgs or 363000lbs.Average Fuel Load = between 50000Kgs and 550000 Kgs or 110000lbs - 121000lbs.These figures are based on the averages of a number of GLA-SFB flights this summer. You will see that 363000lbs - 121000lbs gives 242000lbs and 363000lbs-110000lbs gives 253000lbs. Therefore the PIC ZFW of 245000lbs is pretty realistic.Hope this helpsMark

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Mark,Thanks a heaps for the quick reply!I didn't realize that the 305 klbs meant the MZFW :=)cheers,Tero


PPL(A)

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Matthias point is really well taken. Theis thread has some EXCELLENT points about weights. Everyone who contributed did a great service.The link that Matthias just pointed out is very much needed to plan the fuel loads for the PIC 767. This excellent planner is based on PIC flight dynamics and will give you all the input you need for any length of flight. I use it for EVERY flight.Highly RecommendedBob JohnsonPIC Beta Tester


 

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