Wrathall Mark wrote:

Does the LAEV have provision for adjustable fine and

coarse pitch stops?

Mark Wrathall

*********************************************************

Hi Mark; ..............Good Question!!

If I understand your question correctly the answer is NO.
There is no slide and lock-vernier adjustment.

The present LAEV-2 (Yes there is an LAEV-1, that's
bigger and heavier), is designed to compliment Bill
Freeman's blade pitch parameters of MIN 7deg-MAX 32deg,
this results in a net adjustable range of 25deg, (which
according to Bill is over-kill and could never be that
high since part of the blade will go negative well
before that point). This is externally adjustable and
locked by means of a 32 pitch thread (One turn =.03125in
travel / 1.375deg)

Mark, I hope this is clear, if not let me know and I'll
include graphics.
                                    Butch

Mark Wrathall wrote:

Butch, do you mean the pitch is locked in whatever pitch you set by the
motor leadscrew?. What happens if you have just commanded finer pitch with
your pitch switch, and the switch fails on. This would drive the motor till
it hits a physical stop. It is desirable that this be a ground adjustable
stop, which is set to control static RPM.

It would be dangerous if a stuck switch allowed the prop to fine out through
to negative thrust.

In the small hydraulic CS props for the  single engined aircraft I worked on
in the air force (Pacific aerospace CT 4 Aitrainer -a Hartzell I think), the
same thing happens when oil pressure is lost, spring pressure and or blade
turning moment drive the prop full fine. The resulting RPM is set on the
ground with the fine pitch stop. A simple, locked screw through the front of
the dome restricting piston motion forward is used by Hartzell.

Given 25° of blade rotation, if you avoid the need for adjustable stops by
setting your blades at a climb pitch setting with the motor at it's fine
stop (something in the pitch change mechanism is going to hit something else
and provide this physical stop), you will have a very coarse pitch in the
event of a runaway (switch failure) in the other direction. The consequences
of this failure will depand on how clean the machine it is installed on is.

If you decide not to fit adjustable stops, are the features in pitch change
mechanism which collide at the ends of travel designed to survive this? Will
the motor burn out or the gearbox strip gears?

Keep up the outstanding work.

In a twin, counterbalances are often used to drive the prop to feather in
the event of oil px loss.

Mark Wrathall.

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