About fuel consumption...

[Andrea1 6]

Hi,I've read some days ago into this forum a thread, just little critic, about B744 cruise fuel consumption, someone substained it were (almost) completely wrong (too high) and another one suggested to change fuel flow scalar iinto .cfg file from i.e. 1.06 to 0,5! (absurd for me).I wondered about this also because I know that pmdg addons are very accurate abiut fuel settings: i.e. the pmdg 738-9 fuel consumptions agrees almost perfectly with Continental B738-9 FCOM fuel tables (togheter with N1 and, considering all the others tables max altitude capability, single engine ceilings, attitudes etc.) .I'm not a real world pilot but I think to know the B744 quite well having been a B744 ps1.3 Precision Simulator owner since 1998 ( Iwas one of the first to buy that, very expensive, simulator in Italy) and now by being a regular user of pmdg 744 reading a lot of B744 related articles, manuals ecc.I've to do some considerations before talking about my test:1) Also in real life if I consider two identical engines very rarely I'll find, for the some trusth setting, outside air temp and pressure true airspeed etc exactly the same parameters: EPR, N1 and N2 EGT FF depens on efficiency of intake, compressors, accessory gearbox, generator, hydraulic pumps, bleed air extraction demand, combustor turbines and it's almost impossible that all this efficiencies are exactly the same (also il engine building is for the most part automtized);2) "Level D" full motions simulators parameters establish that the simulator differencies in all systems, indications flight parameters, response time ecc. must be in a narrow 5% plus-minus band vs. real plane parameters.: i.e. if in a real plane at a determinate airspeed, attitude, altitude ecc to mantain level flight I need an attitude of 10,0

[phil747fan 14]

Andrea,no worries about what s wrong or not ... when you have datas you can compare ...BTW before PS1.3 there is some older versions like 1.2 and 1.2A ... Robert at that time published a manual without perfs datas (they were released a little after ...) ...about datas from PMDG there are good with a little calculation errors plus the fact it s a mix between PW from UAL and GE engines but it works very well if you know how to plan a long flight ...thanks againPhil

[Andrea1 6]

Hi Phil,You're right before PS1.3 it was ps1.2 etc, I omitted that 'cause my message had already very long, and maybe boring...I've realized anyway that the only pmdg 744 engine parameter not correct for all the engines modelled is EGT certainly it's not a mistake but a deliberate choice: EGT in pmdg sim is "calibrated" according with RB211-524 engine but it's respectively too low for the CF6-80 (that has got a typical EGT higher) and too high for the PW -4060 engine:i.e. during start max EGT is limited to 870

[phil747fan 14]

Andrea,pretty sure you ll find something not that bad for other engines but as you already know there is around 3 and 5% between GE, RR and PW on fuel burn side ...dont think it is that important to dig in ...what i can say is if i m doing my job very well the PMDG can do very long run easily but the job as flight preparation is very important ... around 10% of higher fuel burn from a clean hull and considering the weather engine of FS9 maybe FSX is better ...have a good day.Phil

[phil747fan 14]

if you want to do some tests here's some datas i found : (not my datas but of course taken from real FFPMs ...)ISA datas and LRC cruise F is for Freighter fuel flow is for one engine ...390TFL300 4.2

[Andrea1 6]

Hi Phil,I really think that this pmdg 744 is one of the best fs addons I've ever seen (and I've been pratcaisinf flight sim from about 20 years) really a pleasure to fly and handfly and really realistic (also if I (until now) haven't realized my best (aeronautic) dream: flying and testing a real B744 full motion "level D" simulator (or at least a B738 or A320) but I know that there is an interesting company in the UK....) In spite of the limits of FS it performs very good l(like PS1.3 but with visual cues) only few important things could be improved i.e. some additional failures involving flights controls: gear, tire blown, trim failures,r a c simulation of depressurization now also by opening a door the plane doesn't depressurize at all and of hydraulic systems failures: now also switching off all the engines driven and the demand pumps you can anyway move the controls lowering the flaps etc (no chanche to trigger the "primary flaps" failure) but others failures are simulated very good like engine failures at takeoff (i.e. before/after V1 cuts)Thanks for your data!Best RegardsAndrea

if you want to do some tests here's some datas i found : (not my datas but of course taken from real FFPMs ...)ISA datas and LRC cruise F is for Freighter fuel flow is for one engine ...390TFL300 4.2