737-800 performance

[Kyle David]

Hello good evening and happy holidays to my fellow crewmembers. I'm here because I have a question regarding the 737-800 PMDG FS9. Is there any new modification for the CFG file for the drag numbers. I've noticed that on most of my flights it is hard to descend at a higher FPM without increasing the airspeed when the spoilers are deployed thus making it more difficult to reach altitude constraits. I was wondering if anyone had any info on that issue.
Thank you
Kyle

[Wayne Pierce]

Kyle,
Messing with the .CFG files for flight specs may have other consequences and not what you want to happen. I am sure PMDG has built in the way the aircraft would/does perform, I have them and they seem to be correctly modeled.

You cannot make your aircraft lighter than air or fight gravity. Those are given and non changeable. When I descend and need to lawn dart to make up the distance and no matter what your flying the airspeed will still go up even with full spoilers out and a lower speeds the gear and other anchors. If this is the case your descent is not correct.

Now, this is not intended to be a smart alec remark, but, whether it is a PMDG, FS9, FSXor any other aircraft you need to plan your descents ahead. Yes I know that it doesn't always work that way, but....

Good point here for your question. We at the checkride office want to see you fly at altitude and then plan your descent to reach the required altitude when your supposed to. Your descent start is looked at by us on a checkride and scored accordingly.

If you have a correct descent rate, your airspeed will be held in its proper place by virtue of the mechanics of the aircraft.

Now,I have noticed this and I am sure it is mechanical, when your descending, the auto throttle on the engines drop,in most cases, to an idle and gravity takes over. You put on the spoilers to slow down. Now the aircraft thinks you will go too slow and then applies power to the engines which cause you to speed up. When that happens you are now in overspeed and it is hard to get control of that power curve.

So this goes back to basics. Set up a descent airspeed for your aircraft. Slow down before you start your descent and it should go easier. (crossed fingers here).


FAA pilot handbook 7/13/04 Page 3-15/16

DESCENTS AND DESCENDING TURNS
When an airplane enters a descent, it changes its flightpath
from level to an inclined plane. It is important that
the pilot know the power settings and pitch attitudes
that will produce the following conditions of descent.

PARTIAL POWER DESCENT—The normal
method of losing altitude is to descend with partial
power. This is often termed “cruise” or “enroute”
descent. The airspeed and power setting recommended
by the airplane manufacturer for prolonged descent
should be used. The target descent rate should be 400 –
500 f.p.m. The airspeed may vary from cruise airspeed
to that used on the downwind leg of the landing pattern.
But the wide range of possible airspeeds should
not be interpreted to permit erratic pitch changes. The
desired airspeed, pitch attitude, and power combination
should be preselected and kept constant.


Now hopefully your asking this as ATC has told you to be at an altitude and you could not make it without dropping like a rock? I know this happens. It has happened to all of us.

Ok, if a real world pilot and/or engineer says I am totally wrong lets hear it.

[Kyle David]

Hello Mr. Pierce thank you for that information I will use it for my next flight.
Regards,
Kyle

[Kyle David]

Hello. You do have a point I do enter the winds in the forecast page however it doesn't seem to make much a difference. Overall I do enjoy the pmdg 737-800 it's very stable and reliable.