-7 Blades
B.max,
as always, enjoyable following your input. Concur with your S-S couple disruption by the use of fasteners through a bonded surface.
The -7 blade matter speaks potentially of a different issue of causation than the past events, given the CAANZ interest in the inner region proximate to the TE expansion of chord of the -7, and RHC's bulletin on inspections. As you are aware, when we independently strain gauged the root of the blades, the trailing edge showed relatively high variations in peak to peak strains which is expected given the structure of the blades, relative to the leading edge. The highest strains were recorded in the touchdown, as expected, and in the entry into autorotation, which was a surprise, but obvious after the fact with the reorientation of the flow through the disc. Cyclic strain amplitudes pretty much were consistent with research done by NASA in our area of interest, and that points to the subject here; an abrupt step in the chord will result in localised strain from the high amplitude unsteady angle of attack outcome, which we were able to mitigate without the usual massive drag rise. I would think that the design could do with a bit more finesse in this area, to avoid stress concentrations, and mitigation of the SR from unsteady aerodynamics.
Hope that bond hydration is a past tense matter, however the design of the lap joint on these blades is tough on the bond, and so it will be an area of concern as long as a metal blade is fabricated with a bond line in an area subject to torsion/bending conditions.
I happen to love the RHC aircraft. We record and measure it in depth, and I still like the aircraft to fly. It is elegantly spartan, but the other side of that is that it is sensitive to damage, and care is needed in its operation. The marginal time constant of the -22 is always mind concentrating, but the pure joy of flying such a responsive device makes up for that concern in part. The -44 really is an amazing design. I am not a fan of the RHC's product component removal from service without effective compensation, and that corporate stance may need to change when a fun, capable, and relatively cost effective alternative machine turns up from anywhere, EASA, PRC, or RUS, then RHC may have some issues with marketing.
Composite rotor blades do not come without issues, have a look at any out there and view the erosion of the resin in the area behind the embedded erosion protection. (EC, Carson CMRB etc... even the GE90 fan blade), or look at the NH90s pressure face erosion in service... interesting matters for CAME.
cheers.