The only helicopter I know of that doesn’t have washout on the blades is the Rotorway Exec/Talon. They were designed like this to ease the manufacturing process for the kit builder and the same design has been maintained by the factory since they offered fully built blades. With a few hundred hours on type, my observations of no twist are;
1. Excellent NR recovery in auto (2degs negative pitch also helps, as does the semi-symmetrical profile).
2. A very marked flap-back tendency; I believe this is due to the uneven ‘toroidal’ lift distribution causing the onset of translational lift to be abrupt and non-linear. This often manifests itself in porpoising in the cruise on gusty days by inexperienced pilots.
3. Drop-off in aft cyclic authority when hovering with a tailwind as the down wash is heavily focused towards the tip and ‘falls off’ the horizontal stabilizer abruptly as the negative airspeed builds. It’s just not as progressive as a ‘conventional’ blade. (Exacerbated by the limited control power of the teetering head).
4. Interestingly, the uneven lift distribution isn’t readily seen when observing the coning/bending of a hovering helicopter. This is probably due the centrifugal force being relatively greater than the bending forces produced by lift having a ‘straightening’ effect plus the fact that the Rotorway blades are very stiff.
JJ
Last edited by jellycopter; 17th Nov 2017 at 02:13.
Reason: Typo