Autorotation NR trend

[Sax412]

May be this is a silly question but it arose among many "professional" pilots without any confirmed explanation.

The question is:
during an autorotation at constant speed and considering a helicopter with a rotor turning CCW like the Agustas, if we turn to the right what is the NR trend and what happens turning to the opposite side?

Cheers,
Sax

[GoodGrief]

Will increase in both cases because the load factor increases.

[Sax412]

What I personally think is that the trend in this situation is to increase turning to the right and decreasing when turning to the left... the opposite in case of CW rotor turning

[jellycopter]

Leaving myself open for some heavyweight abuse here.........

The Nr will rise in turns in either direction due to load factor as GG correctly stated.

However, as the disc is tilted, there will be a transient increase or decrease in RRPM (CCW rotor - Nr increases transiently as rolled right) due to Vsquared effects on drag (and autorotative force) between advancing and retreating blades. The higher the airspeed, the greater the effect. Zero airspeed autorotation = no transient Nr change.

JJ

[dragman]

I'll throw one in too.....

Which has the greater effect of increasing Nr - the load factor increasing; or the rate of descent flow increase causing greater angles of attack?

[A.Agincourt]

LOL how numb.............titlt the disc forwards increase fwd speed and you will get a reduction of Nr the value of which will be proportional to the rate of application and the commensurate with the max value of reduced inflow angle. You also get an increased ROD [which is useful] and a reduced ground track distance. A useful technique for controlling increasing Nr without using the collective following a mishandled turn - in either direction.

Best Wishes