Let me jump in here a little. I got to ride with John Potter at
Paducah, KY last winter in an Air & Space. The prop is constantly
engaged. There is no transition from the engine powering the rotor
and then switching to the prop after the jump in this craft. The
Lycoming turns the prop just like any other prop in a pusher
configuration. The rotor is engaged via a multi-belt driven geared
transmission. The rotor spins up to somewhere over 300 rpm (while
depitched)if my memory isn't letting me too far down. The tires alone
keep the gyro from counter-rotating. One wheel was on a piece of ice
during one of the spinups and John had to move it onto a dry patch.

Once the proper rotor rpm was reached, John reached to the panel and
pressed a button. The blades instantly repitched and we shot straight
up like a rocket. I'm sure that the transmission disengages
simultaneously. The ship reaches maybe 30-40 feet and smoothly
transitions into forward flight and a climb mode. There is no loss of
altitude during the transition. Now I suppose someone could screw it
up and not have enough throttle on during the jump start, but the
engine rpm seemed to up there some to get the blades going, and the
jump happens very quickly. As I recall, full throttle is applied as
soon as she jumps. It's a very, very fast sequence. You're at the
top of that jump before you can blink.

We took off on the runway and then from the tarmac perpendicular to
the wind, and there didn't seem to be any problems.....no more than a
plane taking off in a crosswind. I felt no yawing or unsteadiness
from the crosswind jump and never experienced any dropping.

Now I'm going strictly by memory on the mechanics, but I believe I
have the basics correct.

Ken J. - Sandy Eggo



Rod Buck wrote in message ...
In message , Charlie+
writes
On Wed, 30 Jul 2003 21:06:07 +0100, Rod Buck
wrote as underneath my scribble :

Rod, as a matter of interest have you personally done one of these
takeoff jumps? Sounds exciting/scary!

Not done it personally - seen it in the flesh once, and on film lots of
times. Scared me sh*tless to WATCH it - never mind fly it!

Presumably the change over to propdrive is immediate on initiation so
there is some element of forward drive from the start of the leap?

Yup, dead right. My impression is that there is some sort of changeover
mechanism, whereby the motor drives either the rotor hub, to spin-up the
rotor to well above flight RPM, or the normal propeller to provide
inflight thrust as in a normal gyro.

So, when you get up to 150% flight RPM, you pull the lever, the hub is
declutched, and the prop engaged....

Is the direction of the leap unpredictable / local wind etc causing
major imbalances?
Also is there some drop in initial altitude until full gyro level
flight and control can be achieved? if so - how much swoop do you
estimate?
Charlie+

From what I've seen, you obviously line the gyro's nose into wind, (and
as in all aviation, a decent wind helps no end).

Got to be careful to get the cyclic central, so the thing leaps up
vertically (but with some forward thrust from the prop during the leap,
so the leap is actually forward, even if the rotor is horizontal)

Then, at the top of the leap, the rotor must be angled back to the
normal gyro angle to ensure upward airflow through the rotor (and drag
to balance the prop thrust) as you move into wind.

Where there is a wind of, say, 15mph or more, I saw no evidence of drop
or swoop at the top of the leap - it just flew off.

In nil-wind, I would anticipate there must be some drop, maybe 50ft.
Depends on the engine thrust, and how quickly it accelerates the gyro to
normal forward flightspeed. This is why a wind prevents drop, of course.
A 15mph wind means you've got at least 20mph airspeed at the top of the
leap - you must gain at least 5mph forward speed in the leap if the prop
is running.

This is enough to maintain level flight.