Hi guys,In FSX and XML I'm using AP_ATT_HOLD_OFF and AP_ATT_HOLD_ON, and if on with the AP on, I can use AP_PITCH_REF_INC_DN and AP_PITCH_REF_INC_UP to set the pitch angle. BTW, (>K:AP_PANEL_ALTITUDE_ON)turns this feature off.Anyone know how to set this up so that the AP will still capture the selected altitude?I'm also using SYNC_FLIGHT_DIRECTOR_PITCH which successfully synchronises the FD to the existing pitch.How is AP_PITCH_REF_SELECT used? It says in the SDK, 'Selects pitch reference for use with +/-' ???

Normally in Boeings the altitude is entered in the window and ALT_HLD is not engaged. PITCH_UP/DN or VS could be used for climbing/descending to the altitude in the window. Once the current altitude is close to the ALT window then engage ALT_HOLD with the Window value --> ALTITUDE LOCK VAR. A scaler may be needed depending on the rate of climb nearing the altitude to prevent overshoot. The alt window is not the same as the ALTITUDE LOCK VAR. That way if during a VNAV climb for instance ATC issues a hold. Press hold at the requested altitude. That altitude --> ALTITUDE LOCK VAR and ALT_HLD on. Then when VS, PITCH, VNAV is reengaged the aircraft will climb to the Alt Window setting. The coding for this should be in the VS, PITCH, VNAV operation coding.To put it simply - The ALT window is a user variable with the stock FS AP ALT functions running in the backround. The same could be said for the VS window if needed. Roman

Thanks Roman.I'm still interested in how to use AP_PITCH_REF_SELECT

As mentioned in your first post -- AP Master ON, A:AUTOPILOT ALTITUDE LOCK, bool = OFF A:AUTOPILOT ATTITUDE HOLD, bool = ON, use this until the aircraft reaches close to the Altitude Window (User Variable) then auto-engage ALT HOLD which shuts off ATT HOLD.Roman