I've found that many of the (military) jet models I have in my hanger seem to fall short of their 'At Altitude' maximum speed (mach) and often fail to even reach their ceiling, while at the same time, often exceed their speed ratings at sea level. I've looked at airfile parameters and tables and don't see anything that might offer the casual designer or user a means to fix this characteristic properly (seems you can have it one way or the other, but not both).

 

Is it just me or is this a general problem in FSX or with FDE designs? Is there a way to address this without resorting to custom C++ code in the bowels of some DLL?

From my understand it's coded in the aircraft model (such as Beech_Baron_58.mdl) and that cannot be edited or changed.

 

Best regards,

MSFS takes a few shortcuts with flight dynamics modeling, especially for jets. So without excessive trial & error modeling or fakery, getting 100% accuracy in all flight regimes is not possible.

 

Here's a document on the subject offering a method to improve altitude handling.

http://www.fsdeveloper.com/forum/resources/fs-thrust-vs-altitude-calculations.43/

Military aircraft have a factor that affects them that civilian aircraft don't, namely the drag and weight added by stores hanging off the pylons which will radically alter the performance, including speed. Whats more the quoted numbers are often extremely optimistic. An A-10 pilot will muse at the wikipedia max cruise speed you quote him. With a full load he might break 250 knots if he has a favourable drag index. This complex drag equation makes achieving accuracy in modeling even more complex than is typical in a civilian flight model.

 

As for the sea level performance being more optimistic, well I can't account for that.

 

None of this is to say that the real culprit isn't just MSFS shortcuts and developers simply not going the full measure to reach a PMDG level of accuracy.

MSFS takes a few shortcuts with flight dynamics modeling, especially for jets. So without excessive trial & error modeling or fakery, getting 100% accuracy in all flight regimes is not possible.

 

Here's a document on the subject offering a method to improve altitude handling.

http://www.fsdeveloper.com/forum/resources/fs-thrust-vs-altitude-calculations.43/

Now that looks interesting! I scanned the article and it seems to offer some promising avenues for correcting/improving the anomalies I'm seeing. Cool stuff!

All jet engines suffer reduced performance at altitude, but this is exaggerated in FS by lift induced drag at altitude which means certain aircraft cannot achieve cruise altitude or speed. You can alter this by editing the .air file - in the Primary Aerodynamics, Drag section: *Cdo Drag Coefficient - Zero Lift=

Change whatever number is there already to 10 and that should fix it, if the engine specs and reference speeds in the aircraft.cfg file are correct.

Now that looks interesting! I scanned the article and it seems to offer some promising avenues for correcting/improving the anomalies I'm seeing. Cool stuff!

 

More:

http://www.fsdeveloper.com/forum/threads/too-much-drag-anemic-engines.428881/

 

In short: Get as much reference data as you can, set up drag to match the real deal, set up thrust to match the real deal, set up fuel flow to match the real deal.