Sometimes older aircrafts needs em.

Please correct to:
static_thrust = 17000
parasite_drag_scalar   = 0.68
induced_drag_scalar    = 0.68


dirceu wrote on Apr 23^rd, 2012 at 4:09pm:

Currently riding the values from Mark and, without having seen anything before 1.0, this is way better for me. She still climbs good, but I don't blow my flaps or the gear out right after takeoff. But, true, she needs quite some thrust to start taxi.

Ok, when looking at the PDCS, it says some EPR 2.18 and a speed of 261 kts for an ECON climb. I still overshoot the speed by a large margin, when I set that EPR while already climbing with 4000+ ft/min. So I guess some higher drag may be advised. That's at some 49t GW in the -200.

I will try Dirceu's values later.

CoolP wrote on Apr 24^th, 2012 at 11:18am:


Induced drag probably should not be reduced as much as parasite drag in this case.

Parasite drag is generally caused by the aircraft surface moving through the air. It could be reduced to achieve proper idle-power descent.

This lower parasite drag will naturally also reduce the amount of thrust needed for accurate cruise EPR sttings, therefore a lower static_thrust value is needed too.

IF these two modified values give us the desired descent configuration (idle thrust @ -2700 fpm) and normal cruise EPR,
but not enough power for proper climb EPR, then we reduce induced drag.

Induced drag is caused by increased angle of attack. If this value is reduced then the 737 should climb with less effort, and by default the CS732 has no shortage of climbing power. So we don't want to begin our tweaking with significantly reduced induced drag.

And lastly, approach speed/pitch attitude will also need to remain realistic. So there will need to be slight compromise in all areas for a well rounded FDE. I think keeping within .05 EPR in all phases of flight is acceptable and achievable.

So, to summerize:

Reduce parasite drag for proper descent rate with idle thrust (rate varies with altitude of course).
Reduce static thrust to compensate for the reduced parasite drag.
Reduce induced drag only as necessary to compensate for the reduced static_thrust, for accurate EPR settings whenever there's a nose-up pitch (climb, approach, etc)

Process illustrated here:
http://www.youtube.com/watch?v=3EdeuVL-nv8

Looks good. I still struggle a bit with the video link as my balloon always blew up.  More seriously, the tested values of yours look very promising. Keep up the good work.

I'm still wondering if this has something to do with the weight.. I've said it a few times, any 737 needs to just get rolling then you taxi at idle thrust.. I think the drag tweaks that I recommended are just band aid fixes for an inaccurate model.. Just throwing that out there.

I wouldn't focus on the rather high 'start taxi' values. FSX models too much friction there (e.g. helping a lot on breaking) and the only way to circumvent this one would be an engine model outside of FSX' scope, to allow a higher thrust while the gauges read close to no increase. Sort of cheating the pilot due to that too high friction level.

Since the 737 is bound to the default FSX engine model, you can't really establish that one. So we may look at it as a tradeoff of some kind. You folks are right to focus on the regimes the plane mostly operates in, that's everything on the flying.

So if Bud's values give us some nice numbers on the climb, cruise (most important) and descent, that's a big win.