CRAN,
The points you bring up have merit. This is particularly true if the objective of this project is that of producing 'just another helicopter'. If the objective is to produce a product that stands out from the pack, then this product must have one or more superior features.
The engine is anybody's guess. One idea that we have previously discussed is the installation of two smaller engines for reliability.
The fuselage, IMHO, must be carbon composite construction, with imbedded Kevlar in the shell around the occupants. The strength of carbon composite is far superior to metal construction because the plies can be laid up to suit the structural loads. The price of carbon cloth is continually coming down.
Empty weight is the albatross of the helicopter. Consider the advantages of weight reduction due to the use of composite construction. Consider a 70-kg saving in the fuselage weight of a 700-kg craft. This is a reduction of 10%. Simplistically, it now means that all of the other components can now be 10% weaker and thereby 10% lighter. This reduction of the weight of the 'other components' now means that ........ Basically, it is a recursive diminishing reduction of the craft's empty weight.
Lastly and most importantly, the rotor. You have mentioned the efficiency of the 2-blade rotor and you say;
" sufficiently beniegn low-g behaviour could be achieved by configuring the aircraft in such a way as to reduce the role-rate in low-g flight - put the tail rotor in the right place! i.e. similar to Jet Ranger." Perhaps this may be valid.
Alternatively, here is a new and crazy idea from the Department of Demented Designs;
Take the Robinson's 3-hinge teetering rotor. Add a simple linkage so the coning hinges cone in unison. Link the coning angle to a
hub spring. The smaller the coning angle <--> the stronger the moment of the hub spring, and visa-versa. The objective is better control over a lightly loaded rotor while not increasing the 2-P vibration during forward flight.
Just food for thought.
