H_RSC_MODE parameter change failed

ArduCopter Copter 4.0
1

Using fw 4.0.1 for helicopter.
No way to change this parameter.
It is fixed to 2: External Governor. Tested in Mission Planner and QGC

2

When downgraded to fw 3.6.11, this parameter is writable again

3

This parameters is now writable for me using MP 1.3.70 build 1.3.7353.42041 beta and FW AC4.0.2