>Note - I have seen photos of model helicopters being flown inverted by
>suitably expert pilots.
>The cyclic has to be capable of suitable range to allow blade pitch to
apply
>vertical "lift" in the opposite direction to normal.

        And this is very common! But they say that's impossible in a real
heli, why?!?

Just my guess -

1,    A model can easily be modified to have increased control range needed
to do this.
Doing the same thing in a full sized machine would require major design
changes which would need to go through the horrendously expensive and
complex certification processes for man rated flying. Unless there was a
good economic reason to do this it won't get done.

2.    Scaling up a "model" often leads to designs which are unworkable due
to the square/cube law effects (area increases as square of dimensions,
volume and mass as the cube. This is why ants can carry many times their
weight in food, elephants would break their legs if they were able to jump
even a very little, white men can't jump (whoops sorry, wrong thread), and
matchbox scale model cars can be pushed off 200 foot scale height tabletops
to bounce unharmed on the floor. Mayhaps the scaling up of a model
helicopter able to take requisite stresses in both directions would lead to
a design which was prohibitively expensive or massive when scaled up.

Reason 1 sounds most likely to me.

BTW - you can barrel roll a full scale jetliner - a barrel roll is a 1 g
positive g manoeuvre throughout (done properly) but people frown at doing
this.





            Russell McMahon

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