// Define actual_prograde, which automatically switches from SHIP:SRFPROGRADE to SHIP:PROGRADE
local function set_actual_prograde {
    if NAVMODE = "SURFACE" {
        print "Switched actual_prograde to surface SRFPROGRADE".
        lock actual_prograde to SHIP:SRFPROGRADE.
    } else {
        print "Switched actual_prograde to orbit PROGRADE".
        lock actual_prograde to SHIP:PROGRADE.
    }
    return true.  // preserve trigger 
}
on NAVMODE {return set_actual_prograde().}
set_actual_prograde().


// ANGLES
lock actual_prograde_pitch to VANG(actual_prograde:VECTOR, UP:VECTOR).



// // the following are all vectors, mainly for use in the roll, pitch, and angle of attack calculations
// lock rightrotation to ship:facing*r(0,90,0).
// lock right to rightrotation:vector. //right and left are directly along wings
// lock left to (-1)*right.
// lock up to ship:up:vector. //up and down are skyward and groundward
// lock down to (-1)*up.
// lock fore to ship:facing:vector. //fore and aft point to the nose and tail
// lock aft to (-1)*fore.
// lock righthor to vcrs(up,fore). //right and left horizons
// lock lefthor to (-1)*righthor.
// lock forehor to vcrs(righthor,up). //forward and backward horizons
// lock afthor to (-1)*forehor.
// lock top to vcrs(fore,right). //above the cockpit, through the floor
// lock bottom to (-1)*top.

// // the following are all angles, useful for control programs
// lock absaoa to vang(fore,srfprograde:vector). //absolute angle of attack
// lock aoa to vang(top,srfprograde:vector)-90. //pitch component of angle of attack
// lock sideslip to vang(right,srfprograde:vector)-90. //yaw component of aoa
// lock rollangle to vang(right,righthor)*((90-vang(top,righthor))/abs(90-vang(top,righthor))). //roll angle, 0 at level flight
// lock pitchangle to vang(fore,forehor)*((90-vang(fore,up))/abs(90-vang(fore,up))).               //pitch angle, 0 at level flight
// lock glideslope to vang(srfprograde:vector,forehor)*((90-vang(srfprograde:vector,up))/abs(90-vang(srfprograde:vector,up))).
// lock ascentangle to vang(srfprograde:vector, forehor).     //angle of surface prograde above horizon