One of the principles that has to be used when writing emergency procedures or insisting on warning or caution lights is that the symptoms must be clear and easily understood so that the correct action can be taken.
Can't have two separate and distinct procedures for the same indications, for example. Also can't have the same indications for two different problems.
Hence the question - what are the symptoms, in the cockpit, that the pilot will see to know whether he has 'settling with power' or 'vortex ring state'?
Given that many helicopter pilots can't describe what they'll see in the cockpit with VRS to begin with, how can we help to educate them about the difference.
Having re-read this wonderfully done discussion, my suggestion would be:
Symptoms:
Power / Engine Indications - at maximum power or engine limits
Airspeed - zero to 20 KIAS
Rate of Descent - 200-500 fpm/ Not slowing down / Not being arrested
Rotor RPM - May be decreasing
This might be called 'settling with power' but most probably should be called 'power required exceeds power available'.
Recovery action - maintain collective position, increase throttle in piston engine helicopter / lower collective to regain rotor RPM apply forward cyclic to gain airspeed. Reconsider attempt to land.
Symptoms
Vibrations - low frequency airframe buffeting
Airspeed - less than 20 KIAS
Airframe - may have uncommanded pitch, roll and yaw
Rate of descent- greater than 500' fpm
Power - initially may be less than any limits of airframe or engine
Raising collective results in increase in rate of descent
May be downwind if wind is known
Recovery action - apply forward cyclic and hold till airspeed increases, simultaneously increase collective (this based on Nick's advice)
I realize this appears to violate the first part of my post- the recovery action appears to be much the same for the two situations, but they are slightly different.
Further suggestions?