OK Floppy! sorry for the fundamental junk, but I had no Idea of the person and the machine that was involved. Now I do.
g) As you probably know, all geometric BS must be checked and recorded to establish the start point.
h) If I were doing my own Mosquito, I'd start by confirming that some possum-eating Pennsyltuckian hasn't lifted upward or let their 14 year old grandchild hang from the blades and ruined them.
i) As a minimum, I'd remove the blades 1 at a time. Weigh them to the nearest gram. Then strap the root underside snug to a long flat table and see what the tip does. Check and record tip incidence/twist if any from root to tip. Then balance the blade spanwise on a row of utility-knife blades and determine and record the exact distance to the spanwise CG, FROM THE ROOT.
j) When both blades are done, compare the numbers. Worse case-this will tell you to saw the blades into and scrap them.
k) Before you can proceed, both blades must match. Serial no's are probably sequential or a & b etc.
l) Inspect with a bright, 36"+ fluorescent light, top & bottom looking for the ever-so-slight wrinkling/debond. Wrinkling between rivets on underside means the blade has been pulled down and ruined, Wrinkles on top mean a ham-fisted pilot was doing autos and had the collective up in his armpit during touchdown and forgot to put it down while rpm was still high. The blade turns to spaghetti when centrifugal force gets low and angle of attack is high.
NOTE: I would not be suggesting all this if you hadn't presented the case as being problematic. Truth seems to be...you just don't KNOW THE HELICOPTER ...yet
Just be patient with me please. I'm really trying to help you. I can usually get vibes on a 2 blade helicopter below 0.03 IPS. To do that though, the machine and blades have to be real close to perfect. In my experience, 0.30 IPS will break things if you keep flying.
In the FAA's opinion 0.30 is safe. They make no claims about when your helicopter will crack or your pitch links will wear-out.
More Later.
