Some IFDG performance peculiarities (PW model, a pictur

[teropa]

Hi!I wish Iz was around to comment on these, but I guess he's somewhere cruizin' with the real thing :).Anyway, the PW model performs weirdly at some stages of flight.1. The climb performance. Sure, the 2037s are the least powerful variant, and by changing the numbers in the aircraft.cfg one could get a more powerful 757. However, this does not wipe away the fact that the 2037 performance is not met with the airfile/aircraft.cfg combination, due to something that I can't explain.It is NOT normal even for the 2037 model to climb ~ 1000fpm at FL250 with a ZFW of 159,000 LBS and Fuel 9,000 lbs, like today on my flight from ENTC to EFOU. The climb performance in the 2037 model seems way off, and the flight model itself has some more peculiarities that the RR models don't share.See the attached picture. It is a pic of a VNAV descent. Obviously the N1 of around 70% is not idle descent. I know the RR model does the idle descent just fine, but what is it with these PW models. Is the FDE somehow corrupt or what's going on here. That's not how it's supposed to be.Then something about the FMC calculated speeds with the bogus ZFWs of 115t and 130t metric. I've discovered that the speeeds taken from the 757-200 performance tables are constantly lower than the FMC predicted (4-5 kt), so it's a good idea to use tables, rather than the FMC afterall. However, I don't know if Iz has used IRL tables when creating the FDE, so the real table speeds might be "off" as well. So far I've had no problems with the speeds taken out of the tables, and also the approach speeds in them give always the plane a nice 2.5-3 degree nose-up attitude on approach, so I guess the FDE is correct in this regard.I'd like Iz to comment on the climb performance issue, and also the idle vnav descent. There has got to be a reason other than the static thrust settings in the cfg for these discrepancies between the different models.regardsTero

[Guest GeorgeDorkofikis]

That 1000Fpm at 250 reminds me very much of the old IFDG air file...The onle that struggled to climb even to FL320 with just 7T of fuel!Try this. Copy the RR Airfile and aircraft.cfg to your PW aircraft.(Backup first of course)Then open the PW aircraft.cfg and change the thrust rating in the relative line.Hope this worksGeorge DorkofikisAthens, Greece