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P3D v5 Descent profile via airfile

S

staju

Messages
6
Country
germany
I am programming my own A320 homecockpit with C++.
At the moment I am at the descent and TOD calculation. In the manuals of Airbus, I couldn't find any fitting formula and I don't want to enter any rule of thumb.
I've read that some developers use the airfile to calculate the descent path. Does anybody know how that is done or maybe a way I could do it?

My workaround could be to do testflights with high weight and low weight, with fast IAS and slow IAS and interpolate between all those numbers. But I would prefer a more precise way.

Thank you

Julius
 
Most descent profiles are based on either an angle (typically 3*) or a vertical speed (like 3000fpm). I don't see how the air file would have anything to do with a descent profile, to be honest.
 
Download AJPC. Google AJPC for FSX. It will calculate descent profiles in a number of ways straight from the airfile. Just make sure your airfile is accurate to descent times (which it can help you with too)
 
>>I don't see how the air file would have anything to do with a descent profile, to be honest <<
Indeed some parameters don't (depending on intended profile) but many others (TAS at different descent levels, engine thrust data, fuel consumption on descent, to name a few) require additional calculations that have to take into account some air file tables and aircraft.cfg settings. So, it depends upon what is desired or needed
 
Hi,

A vertical descent profile is essentially a trigonometric formula, in where you have CRZ ALT (Cruise Altitude), TA (Target Altitude), a standard/published VPA (Vertical Path Angle) and a given GS (Ground Speed). You need to first calculate the TOD (Top Of Descent) position and afterwards, depending on Ground Speed, the Vertical Speed necessary at any moment to reach the TA.
Basic profile uses current GS for the calcs, but advanced FMS can set predicted winds at different altitudes; also DS (Descent Speeds, with Autothottle active), which will affect GS. Flight Plan path between TOD and TA is also important, to account for leg change angles.

Tom
 
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