HiOk, the PIC FMC is able to predict some speeds for the 757 given that the ZFWs of 130t and 115t are used for takeoff and landing. However, that data isn't always right, and I think the best way would be to use the 757 performance booklets, that give you speeds for different weights.My question is:If the aircraft.cfg states EMPTY_WEIGHT=127800 and STATION LOAD=31200,is the aircraft now weighing a total of 159200 kgs (ie. the sum of them) ??To get the proper GW for the speed booklet, I am supposed to add the FUEL LOAD, for example 10t (metric) TO the 159200 kgs = 169.2 t (metric), right ?To make it more simple, is the ZFW of the aircraft EMPTY WEIGHT + STATION LOAD in KGS (those arent lbs, are they?) ?. If so, then I would assume that the GW is gotten from simply adding the fuel to that lot.Confirmation needed :) Wouldn't want to fly on wrong speeds... for the pax safety... hehrgdsTero

Hi,I'm pretty sure that the weights in the aircraft cfg are in pounds. If it were in kg's the plane would never leave the ground due to a serious lack of thrust as the numbers would dictate the weight of a 767-300 with only 40,000 lbs of thrust per engine and thats about 20,000 lbs of thrust per engine less then a 767's. If you enter a 757's zfw into the PIC fmc you will get vref speeds that are way off the mark. The PIC fmc was created with the weight of a 767-300 in mind so this is the trade off unfortunately.Regards,Van LatendresseYeoDesigns Panel/FDE Designer

edit: the weights ARE LBS.Van,Yes, the tradeoff with the FMC is well known, and that's exactly the reason why I'd like to know the EXACT ZFW in LBS, to be able to use the Speed Booklets properly.To repeat:empty weight=127800station load= 31200--------------------+ SUM = 159000 LBS <--- is this the aircraft's ZFW that can be used WITH fuel load to get GW for the speed booklets ?Iz, your help is needed ! What speed tables are you using with the 757 FDE and what ZFW are you using as the basis ?rgdsTero

Well, since it would be ludicrous to make different versions for people who use the US or the metric system in FS, all weights in the FDE and aircraft.cfg file are in US POUNDS!! Also, these weights have NOTHING to do with the weight you enter into the 767 PIC FMC to get some speeds.The example weights I stated for the FMC are only to fool the thing into thinking it's a 767 and coughing up some ballpark v-speeds. It's no exact science and you may just want to print out a 757 v-speed reference card, which I've seen around somewhere. In real life, we always have to check the v-speeds on the card anyway. But if you're just plain lazy, you can get ballpark figures this way.So if you want to get speeds from a v-speed ref card, take the weights in pounds (1 kg = 2.2 lb roughly) and check your speeds that way.Iz

Iz,Yes, all that you said is already clear, but what I am looking for is this:Is the 159,000 LBS the ZFW that can be USED with the speed card. That figure already includes the Station_Load of 31,200 LBS that is in the aircraft.cfg. In the aircraft.cfg there are TWO weights:1. empty weight = 127,800 LBS (which is a normal OEW for a 752)2. station load = 31,200 LBSAm I supposed to ADD those two together to get a PROPER ZFW value to use with the speed tables ? OR am I supposed to only use the 127,800 for ZFW with this bird. Which is it ? 159000 or 127800 ?rgdsTero

Tero,The speed you use in your speed card is your Takeoff Gross Weight.Takeoff Gross Weight (GW) = Basic Operating Weight (BOW) + Payload + Takeoff fuel.BOW equals the FS2002 empty weight entry.Payload equals the FS2002 station load entry.BOW = Weight of the aircraft and interior, unusable fuel (a small percentage of fuel in tanks is physically not usable), operating fluids (oils, hydraulic fluids, drinking water etc except usable fuel), catering (including newspapers, blankets etc.), cabin crew and cockpit crew.Payload = All load that you get paid for to tranport, ie. cargo / people / luggage.Zero Fuel Weight (ZFW) = BOW + PayloadIn this case your ZFW = 159000 lb (or 72,122 kgs). Add the fuel on board to it (check your overhead panel or FMC, it automatically provides the appropriate US or metric units) and add this to your ZFW. Subtract 660 lb (or 300 kgs) of fuel from that number because you will be using that for engine start, APU usage and taxiing to the runway (that's what I mean by using TAKEOFF fuel in your TAKEOFF gross weight calculation). Now you have your Takeoff GW which you can use to check your speeds.Iz

Iz,This is exactly what I needed, and just the way I suspected!!I guess others might have had some confusion as well as to what weight to consider as their ZFW, but I think that is now cleared up.Thanks again for your continuing help!!regardsTero

Need help~~ I tried to enter 159 in ZFW, but the FMC says INVALID ENTRY, what can i do with it? (my FS2002 setting is always US system) Thanks!!

Tom,The trick here _is_ that you don't enter the TRUE ZFWs in the FMC.The figures 130t and 115t are just numbers to "fool" the PIC FMC (with 767 data) to give you some speeds that are in the ballpark with this 757.The TRUE ZFW number, ie. 159,000 lbs is used with the separate speed booklets (search for Matt Zagoren in AVSIM file lib.) to obtain the speeds from. It can NOT and it should NOT be entered into the FMC (and 159 is also out of range for ZFWs in LBS anyway... but nevermind that).Hope this helpedTero

Thanks Tero,So i just leave ZFW blank, and follow the performance tables for take off speed and landing speed. Does that WT in the tables all in pounds? I guess this results the estimated arrival fuel Qty could not be calculated out by the FMC? RegardsTommy

Tommy,You CAN use the 130t (metric) for TakeOff and 115t (metric) for landing (in the ZFW), BUT... the speeds from the FMC are then in the ballpark. Of course you have to input something to the FMC to get it work, but the BEST values for speeds you can see in the B757 performance tables available by mr. Zagoren. The weights in the Zagoren's charts are in LBS. So you'll just take the ZFW and add your planned fuel to it and voil

In a nutshell....adjust your FMC ZFW until the v-speeds match the chart fr your actual aircraft Gross weight.Example - 1) 757 is loaded with 23,000lbs of fuel. The config file shows a ZFW of 159,000lbs + 23,000lbs = ACTUAL Gross weight of 182,000lbs less your start/taxi fuel.2) The 757 Flap 5 T/O charts show a V2 of of 141kts. In order to get the PIC FMC to show a V2 of 141kts, you need enter a 'dummy' ZFW in the FMC of 248,000lbs. The 'dummy' ZFW WILL CHANGE with higher or lower ACTUAL gross weights to get the right figures according to the charts. ZFW of 248,000 is ONLY usefull for this example. IF my Gross weight is now 186,000lbs, I needed to enter a 'dummy' ZFW in the FMC of 256,000lbs to get the FMC V2 speed (143kts) to match the chart. The 'dummy' ZFW is variable, not a fixed conversion/baseline.3) The same goes for landing - simpy adjust your 'dummy' ZFW until your vref's match what the chart says for your actual Gross Landing weight. Example - ACTUAL landing weight of 170,000lbs required a ZFW FMC entry of 216,000lbs to get the Flap 30 vref's to match the chart. The landing 'dummy' entry will also VARY based on your gross weight.Clear as mud?Bottom line: Get the charts, manipulate the FMC ZFW until your speeds match the v-speeds as per your ACTUAL gross weight...which in Iz's 757 is 159,000lb ZFW + fuel.Rob.

How about someone taking this on?Create a couple "simple" tablesTake Off TableTake Off Fuel and corresponding "dummy" ZFW entry. Whatever number of values necessary to provide a quick and dirty look-up of approximate ZFW entry.Landing TableA smaller table with Landing Weight "dummy" ZFW entries. That table would only need about 3 or 4 lines. say landing with 4000, 8000, and 12000 pounds of fuel or whatever set of numbers sound realistic.A header at the top could explain the "dummy" thing and indicate these tables are based on ACTUAL ZFW of 159,000 pounds.

Hi!I just noticed that Matt Zagoren's tables don't have the landing speeds in them ?Anyone know where to obtain a table that has them ?Tero

>I just noticed that Matt Zagoren's tables don't have the >landing speeds in them ? Mine does. Maybe because I downloaded them ages ago (?).By the way, another way to use the FMC with the 757 would be to enter your actual ZFW (it's good for reference, but it can be tricky if your ZFW is very low of course), ignore the FMC calculated speeds, and enter the speeds obtained from the tables instead (pretend it's one of those FMCs that doesn't calculate the speeds! ;-)).Martin767 fetishistIt's a lot like life and that's what's appealing