Brother Dixson as usual makes a very difficult explanation sound childishly simple!
The only helicopter I know for sure I had RBS happen was in a CH-47A due to a slightly over gross external load......and it occurred in the 46-48 knot range. Being Tandem Rotor....it was a very unusual result.
We had managed to trundle off with just over 16,000 pounds of 105 MM Howitzer Ammo due to a great amount of indiscretion. We realized our mistake when the FE counted the Projectiles.....and we tweaked to the fact we had grabbed a CH-54 Sky Crane Sling Load by mistake.