IFDG 757 and PIC FMC

[MarkW]

Ok, I have IFDG installed and the panel configured to use the PIC767. The ZFW is 159,000 lbs vs. the 245,000 lbs for the 767. When I try to enter 159 into the FMC I get an error "invalid amount". Is this normal and if so what number to I enter. By entering a higher ZFW does that change the flight performance, FMC performance, or just the Vr numbers.Last night I took it out for a spin and with a ZFW of 195,000 things appeared to be OK. Just making sure..thanks,Mark.

[Guest crashing_pilot]

hi,according to Iz(who made the flightdynamics) you should use 130tonnes zfw for takeoff,and 115t zfw for landing in the fmc,that will roughly give you correct speeds....hih

[Guest Iz]

And those are METRIC figures, so multiply by 2,2 to give you the numbers in lbs.

[MarkW]

This does not seem to make sense. On page 29 of the FMC manual for the 767 PIC the ZFW is stated as 245,000 LBS.In the 757 we have a ZFW of 130,000 kgs or 266,000 lbs. How can the ZFW of a 757 be more than a 767 ??Mark.

[Guest Ian_Bowden]

Its not! you just put those numbers in to get the closest possible correct V speeds for a 757. All the FMC formulae are based on 767 performance so we have to kid it into being a 757 ;-)Ian

[Guest]

Hi,So should we modify the zfw in the aircraft.cfg file, or just leave it as it is downloaded ?CheersCarl

[Guest Van]

Hi,Do not touch any of the weights in the aircraft cfg as by doing so you will have serious performance problems. If you enter the weight of a 767-300 with only 40,000 lbs of thrust, I seriously doubt you will even get off the ground. All you need do is enter the weights into the fmc in order to get fairly accurate vref speeds and thats it.Regards,Van LatendresseYeoDesigns Panel/FDE Designer

[Guest Martin]

>according to Iz(who made the flightdynamics) you should use >130tonnes zfw for takeoff,and 115t zfw for landing in the >fmc,that will roughly give you correct speeds.... It will give you ballpark speeds, but not correct speeds. If you want correct speeds I suggest using a 757 speed chart and entering the speeds manually into the FMC (it's also a good opportunity to manually set the bugs on the ASI! ;-)).With a ZFW of 159,000 lbs you can trick the FMC to display the correct weight by entering a false manual fuel value (the lowest ZFW that the FMC will accept is 179,000 lbs I believe). For example if you have a ZFW of 159,000 lbs and 40,000 lbs on board, you can enter 20,000 lbs of fuel into the FMC, and a ZFW of 179,000 lbs. If you do this it's probably a good idea to not use the last 20,000 lbs of fuel, or the FMC will go nuts. ;-)... Alternatively, as the above really is just a very unpractical workaround, you could change the ZFW in the aircraft.cfg to 179,000 lbs or more, and enter the actual ZFW and fuel amount into the FMC (still using charts for correct speeds of course).For a ZFW of 179,000 lbs, make sure the "station_load.0" line looks like this:station_load.0=51200.000, 0.000, 0.000, 0.000Martin767 fetishistIt's a lot like life and that's what's appealing

[Guest EGCC]

V-Speeds for the 757 with RR Engines are available at:www.757.org.ukJust click on "Limitations Data" then "V-Speeds".