500e,
Nodrama has hit the nail on the head. If you can read through the site, it will explain your questions.
As is also mentioned on that site, for too long the rotary wing industry has had a very poor understanding of arguably the most important thing which we all depend - the rotor and how it works, balance wise.
This is typified by the common misconceptions as amply demonstrated by
Gomer Pylot. His ideas about depending upon the blades age, stiffness (blades are designed to flap - if they didn't we would not have a job) and mismatched blades is a classic statement which proves the widespread lack of understanding of rotor blades. When you hear these statements uttered the first thing that should cross your mind is - "this person does not understand the problem and is simply guessing". It is not their fault, it is simply an indication of how ignorant we have become and that we have not passed on corporate knowledge of such things.
It is how the wider industry still tries to explain away the simple phenomina of migrating span moment arm. (See ). When the greater industry begins to understand this basic phenomina and accept that it begins to happen as soon as you put a new set of blades on a rotating head, it must then accept what to do about managing this age old problem. See
http://www.rwas.com.au/blade-management.html
Trying to match rotor blade hours, mass etc were early crude ways in trying to handle this problem - but rather unsuccessfully.
While we have theorised till infinitim over the aerodynamics involved (and still can't agree on the finer points), we have largely ignored the balancing of the rotor system. We appear to have been happy to leave it to the Noel Triggs (Helitune), Chadwicks or Stewart Hughes to come up with "Black Magic" solutions. THey have done wonderful jobs of solving the Dynamic Balance problems.
We now have to understand the interaction of the Static and the Dynamic imblance and how to correct for each....
The rwas web site will hopefully shed some light on the not-so-black-magic "art" of rotor track and balancing. In particular the blade adjustments and how they work and when they should be used. The interaciton of Static and Dynamic balance.
How we should have easy access to the Span Adjustment weights at operator level and be adjusting these weights to get the static balance within close OEM tolerances, then use the Dynamic adjustment packages to correct for purely dynamic problems (aerodymanic variatiopns, engineering tolerances in assembly, worn bearings, alignment variations etc) which they are designed to compensate for.......not chew up these dynamic adjustments by tryng to compensate for a Static problem (migrating or shifting Span Moment Arm).
These Span weight adjustments and balances should only be done with appropraite tooling. Tooling which enables simple, accurate measurment and comparison to OEM design ideal specs. That tooling is available....just needs OEMs to accept and approve its use.......
After the industry grasps how important the control and adjustment of Span moment arm is to the almost guaranteed success of the Dynamic Balance, they will hopefully begin to apply pressure to aircraft manufacturers in order to force them to change the design of their blades away from sealing the Span adjustment weight packages in the tips pf rotors (eg B412, AW139 ect)but instead design them with easy access to enable easy adjustment such as B205, 206 UH60 CH47 etc. (While these are still not what you would call "easy access", it is better than B412 or AW139 which require blades to be sent back to overhaul for tips to be debonded at much cost to the operator and revenue to the OEM/blade overhauler).
Hopefully industry design engineers will get the message and redesign their blades to make them more user friendly and lower operating costs.
One major Helicopter company is about to release a revolutionary design with the Span Adjustment weight packages totally exposed for easy access and designed for easy adjustment at operator level (onya Boeing). If other OEMS have any brains, they will ultimately follow suit.
Hopefully Nick Lappos may take a new broom through Bell and change their design philosophies to incorporate similar design features to make rotor track and balance far more straight forward and less time consuming than traditionally has been the case.
Sorry this has ended up much longer then intended. But hopefully this will provide food for thought, help answer some widespread misconceptions and promote discussion........