MD500 RoD in Autorotation

[CRAN]

Responses

Guys,

Thanks for all the responses, they have been really useful and have completely answered my question.

Power of the PPRuNers!!!

Hughes500 - Do you know what gross weight you were operating at during your OH6 sortee?

Thanks Again Guys

CRAN

[Hot and Hi]

Involved aerodynamic discussions aside (to which I wouldn't have anything to add) normal high-school physics suggest that weight doesn't matter. An autorotation is similar to a free-fall under gravity (well, in a 500, very close to free-fall). Remember the balls of steel rolling down a ramp? Heavy ball, light ball, all fall at the same speed. We learnt that in a vacuum (to eliminate the effects of friction or drag) all bodies subjected to the same force move at the same speed, regardless of mass. Practically, even in air, two bodies of same shape and size (but different mass) will fall at the same speed.

When we looked at the math behind it, we found that the mass of the body is both above (potential energy stored) and below (inertia) that fraction, hence cancels itself out.

[Hughes500]

Cran

Ac weight from memory about 1360, 300lbs of fuel, pilot 180, fat bastard examiner (me) 220 lbs and about 50 lbs of luggage

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Hot and Hi - objects are affected by air resistance and a rotor disc acts like a parachute of approximately the same size in autorotation (Gessow and Myers) - any object falling in air will reach a terminal velocity and mass will be a factor.

If the heavier aircraft doesn't fall faster, how does the Nr increase?

[Thomas coupling]

Hot and Hi - I don't think so???