Today I try reenter with XR5,during the reenter I need Negative AOA for me to desent and slow down(if AOA get above 5 it star to climb)I don't know which one is easy to reenter XR5 or XR2? Why I need negative AOA?
A other question my Areo break MFD jump all over place when I reenter.
Additionally to the wrong AOA (40° is required so the windows don't get too hot), you need to learn that for descending, you need to bank and fly S-turns. The XR-family has a good autopilot for that.
You start at 0° Bank and 40° AOA. When vertical speed is less than -20 m/s, you can start to bank, if your temperatures are still friendly. If your temperature is high, you allow yourself a tiny ascent (less than +30 m/s VV) to get into thinner atmosphere.
The important Rule Of Thumb there: Your decelleration and temperature depends on vertical velocity, not bank, pitch. Even your current speed has less impact there. The faster you descend, the hotter you will get and you will slow down faster as well. The slower you descend, the colder you will get, but will also need longer for slowing down. If you fly at constant altitude, you will slowly cool down.
For XR I recommend an ACC of -16 m/s² on the Surface MFD as target, but that also depends on the distance to the base. You want to be at Mach 1.5 in 20 km altitude in about 40 km distance to the base (assuming you also land by making a HAC turn).
The S-Turns are simple. You increase bank to control your vertical speed and always bank towards the base. You turn until your ground track sweeped a visible bit past the base. Then you reverse your angle of bank, 90° Left becomes 90° right bank, and turn in the other direction, back to the base again and past it.
