Why do gyros use tilt head rather than swashplate

(Stephen Austin) wrote in message ...
Let me jump in here a little. I got to ride with John Potter at
Paducah, KY last winter in an Air & Space.

I think the key word there is winter. Low density altitude is key.

Once the proper rotor rpm was reached, John reached to the panel and
pressed a button.

Hmm, well, the button on the panel is to engage the prerotator clutch. If
you'll remember, once that button is pushed the throttle is increased so the
engine is about 1500 RPM. At that point you begin pumping the hydraulic lever
to engage the clutch. You slowly pump the handle to maintain continous
pressure while at the same time working the throttle to maintain 800 RPM. It
is very much like engaging the clutch on an Enstrom. Once rotor RPM and engine
RPM marry the handle is quickly pumped until the engage button on the panel
pops out. This indicates the system is fully engaged. From then the RPM is
increased to 370 RPM.

The blades instantly repitched and we shot straight
up like a rocket. I'm sure that the transmission disengages
simultaneously.

The blades are depitched by pushing a button on the top of the throttle. Hehe,
it all happens so quickly that it is easy to lose track of what happens when.
That's why the depitch button is on the throttle. It would take too long to
push a button on the panel and then have to bring your hand back to the
throttle.

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.

Winter had a lot to do with that. Jump takeoff is unlikely above a 2000' DA.
No doubt pilot skill, gross weight, wind, etc. play a major part. But I do
know that when I've flown the 18A it was in the summer. Max jump height was
about fifteen feet and after the jump we sunk to about five feet before we got
ahead of the power curve and established a climb. I do remember also that if,
after the jump, the aircraft settles to the ground, power must be reduced and
the sequence started all over again.

BTW, for a jump, the rotor is spun to 370 RPM. Operating RPM green arc is from
200-320 RPM. It's all a bit tricky but quickly becomes second nature.
Regardless the 18A is a great flying ship.


Stephen Austin
Austin Ag Aviation
Charleston, Missouri

Hi Steve,

Thanks for the technical straightening out. It does happen quickly
and you're right, I missed a lot of it. It is a kick to ride in. It
was the middle of winter....I think the temp was in the low 20s. I'm
sure the jump wouldn't be as impressive on a hot day at some altitude.

John is still restoring them at about 2-3 per year and you can buy one
ready to go in like-new condition......I'm going to guess here
again.....around a 100 thou if I recall the number John gave me. I'm
thinking it was either a little more or a little less. Short-term
memory must be going.

Ken J. - Sandy Eggo