GYROPLANES AND HORIZONTAL STABILIZERS Autogires HORIZONTAL ET STABILISANTS HORIZONTAL STABILIZER
REDUCES NEED FOR PILOT SKILL DURING TRAINING Identifying Benefits
The purpose of a horizontal stabilizer on a "pusher style"
gyroplane stabilisateur surn un autogire
Where did the inventor of the gyrocopter place the horizontal
stabilizer for gyroplanes?
What is the one big danger of horizontal stabilizers on gyroplanes?
NOTE: stabilator and horizontal stabilizer
are two different mechanisms. Note this for reference as you read.
A Stabilator uses airflow over it's surface to modify rotor head position
and influence rotor blade tilt. A stabilizer uses airflow over it's
surface to control the airframe or body of the aircraft. A Stabilator
does not influence the body of the aircraft.
Autogyros sans stabilisateurs horizontaux
autogyros without horizontal stabilizers.) From the air he gave
a big wave, a big smile, kicked his legs out, flew backwards and
even took a picture of the crowd below.
Wing Comdr. Wallis lives at nearby Reymerston Hall and is best
known for inventing Little Nellie, the autogyro which flew in
the Bond movie 'You Only Live Twice'. He still holds around 20
world records and despite his age, is considering trying to win
some back which he has lost to other pilots. After landing Zeus
III, Wing Comdr. Wallis said there had been no question of aborting
his plans to fly into the Wallis Days due to winds gusting at
around 15 knots - and recalled times when he had been up in seriously
"No way!" was his reaction when asked about postponement.
"Weather doesn't bother me. In 1966 there was a storm in Brazil
and the authorities would not let any planes in or out. They said
no plane would survive it and palm trees were being broken out
of the ground.
"But I flew a prototype gyroplane which is the elder sister of
-> Official Wallis Website
Note: gyroplane airframes can be adversely affected by a horizontal
stabilizer set downward to counter a nose heavy machine.
First some history on the gyroplane design. Looking
at old photos of the gyroplane, called the autogiro (autogyro) we can
see that they looked exactly like an aeroplane with a rotor blade on
top much like a helicopter rotor. Later the main wings were removed
from the design as they were unnecessary for flight. (Reference book
available: P.W. Brooks, Cierva Autogiros: The Development of Rotary-Wing
The purpose of a horizontal stabilizer on a "pusher powered"
gyroplane is to make it easier for inexperienced gyroplane pilots to
fly the gyroplane in windy conditions. Many experienced gyroplane pilots
have flown for years making trim adjustments automatically. New pilots
having to think and react, find learning to fly without a horizontal
stabilizer very difficult. On a "pusher" gyro the horizontal
stabilizer is fixed, meaning it has no pilot input controls. An aeroplane
does have control surfaces on the horizontal tail stabilizers. A fixed
horizontal stabilizer only works for positive effect during fast forward
motion of the gyroplane. It has some effect on landing when positioned
directly center on center with a rearward facing propeller. However,
normally, gyroplane landings are accomplished in a parachute style setting
down of the airframe and flare. Many gyroplane pilots execute aeroplane
style landings which are dangerous on unknown grass surfaces. Such landings
can, and do result in dangerous nose up or down situations. see:
A study of flying without a horizontal stabilizer is a must for this
discussion. Lets look at the "Feral* Gyrocopter" flown by
a man in Oz. "Birdy" uses an open frame gyrocopter to "muster" cattle
on a large ranch in Australia. His machine uses only a vertical tail
and NO fixed horizontal stabilzer. He has been flying many years. A study
of his flying technique: see
Note the tail area of the gyrocopter. What's happening
here? He's flying the overhead rotorblades using the rudder, stick and
Watch his foot in the turns in
It's interesting to note that the American inventor of the affordable
gyroplane, Igor Bensen, did put a small stabilizer on his designs that
was below the propeller, not behind.
It was also of a specific design and size. (stone deflector? maybe, but
still a fixed horizontal stabilizer unaffected by the prop wash) Mr.
Bensen is considered to be the inventor of the 'pusher-prop' style of
gyroplane design, he trademarked as a 'gyrocopter'.*1 Later designs
by other manufacturers of gyroplanes have been experimenting with bigger
and bigger fixed horizontal stabilizers placed behind the propeller
in positions ranging from the top of the vertical tail fin to the bottom
of the vertical tail fin. Some designs put the horizontal stabilizer
in place of the vertical tail fin and add two vertical tail fins on
either side of the horizontal stabilizer. All of these more recent designs
are counter to the Bensen design. The noticeable difference would be
that the Bensen design would force air over the top of the horizontal
stabilizer where as the other designs use prop wash above and below
the stabilizer 'wing'.
Is there a 'best postion' to mount a horizontal stabilizer when positioning
it behind the propeller? Yes, and not where you think. Placed between
the tip of the propeller blades and the center of the propeller thrustline
would give the best airflow over most of the horizontal stabilizer.*3
So, what is the one big danger of large horizontal stabilizers on gyroplanes?
That would be in a situation of low forward air speed, close to the
ground (landing) and receiving an unexpected gust of wind to the side
of the gyroplane. Why would that be a problem? It wouldn't be a problem
if the gyroplane airframe is allowed to vane and face the gust of wind.
However the automatic response would be to try and correct the direction
of the gyroplane, which in turn would cause the airframe to roll over
on it's side. This is due to three things happening. First is a large
horizontal surface receiving pressure from below. Second is that the
prop wash coming off the propeller is not like a cooling fan at home,
it's coming off in a cork screw fashion and unless the prop is pushing
a lot of air, useless. In sideways gusty conditions it would add to
the upward horizontal stabilizer force into a roll over situation. Done
quickly enough it would be too fast to counter. Did you ever try to
carry a sheet of plywood across the yard to the house on a windy day?
It's not difficult to see the effect of a sudden gust of wind below
a large fixed horizontal surface.
This happened to a pilot recently in Perth, Australia. On take off a
gust of wind to side of the gyro caused it to loose control and flip
on it's side. The man was injured and the gyro was a "write-off". December
The final danger is twisting the rotor blade 'plane'. You know what
happens to a spinning vertical bicycle wheel (gyro effect) when you
suddenly try to tilt it in a large movement, it flips dramatically 90
degrees horizontal and 45 degrees to the direction of spin (try it).
The smaller the tail area, the bigger wind gusts it can handle, the
larger the tail area the less stable it will be in gusty wind conditions
at slow forward air speed. - "Food for thought".
In fact, on "pusher" gyrocopters, reducing engine speed reduces
horizontal stabilizer control. Or put another way, the less the prop
speed the more the horizontal stabilizer is subject to influence from
The number one fact to remember with gyroplanes is that you're really
flying the rotor disc above your head. Be knowledgable about it, and
it will behave properly for you.
Well, you've certainly shown some variables about fixed horizontal stabilizers
on gyrocopters, so what have you to show on "movable Stabilators on gyrocopters"?
Ok: -see ->
* - Feral is a name associated
with a domestic animal living in the wild on it's own.
*1 - Early Bensen designs were unpowered
and towed by a ground vehicle, with a long cable, to fly
*2 - EDP, uk, August 2006
*3 - Don Shoebridge Hypothesis