Plane: correct description of Q_TAILSIT_MOTMX param

ArduPlane/quadplane.cpp

@@ -425,8 +425,8 @@ const AP_Param::GroupInfo QuadPlane::var_info2[] = {
     AP_GROUPINFO("TRANS_FAIL", 8, QuadPlane, transition_failure, 0),
 
     // @Param: TAILSIT_MOTMX
-    // @DisplayName: Tailsiter mask
-    // @Description: Bitmask of motors to remain active in forward flight for a 'copter' tailsitter. Non-zero indicates airframe is a tailsitter which pitches forward 90 degrees in forward flight modes.
+    // @DisplayName: Tailsitter motor mask
+    // @Description: Bitmask of motors to remain active in forward flight for a 'Copter' tailsitter. Non-zero indicates airframe is a Copter tailsitter and uses copter style motor layouts determined by Q_FRAME_CLASS and Q_FRAME_TYPE. This should be zero for non-Copter tailsitters.
     // @User: Standard
     // @Bitmask: 0:Motor 1,1:Motor 2,2:Motor 3,3:Motor 4, 4:Motor 5,5:Motor 6,6:Motor 7,7:Motor 8
     AP_GROUPINFO("TAILSIT_MOTMX", 9, QuadPlane, tailsitter.motor_mask, 0),