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Little Wing Autogyro |
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Dominator Gyro |
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Hi, I'm Michael,
I'm a wannabe gyrocopter pilot. I've been dreaming about them for over 20
years, and I've finally started building a Little Wing autogyro.
Check out my builder's
log and see how I'm doing.
I've done some skydiving, have 5 hours of fixed wing
instruction, and I used to own a powered parachute
but the gyrocopter bug has never left my system. At this point, I
have been up several times for demo flights plus 3 hours of gyro
instruction. In this site I've included some info, pictures, and links
that you may find interesting if you're an airhead like me.
Please keep in mind that all writings on this page are from
a layman's point of view, I have no engineering background, and I highly
encourage you to go to my Books and Links page to find
other sources of information, so you can form your own understanding of these
amazing and fun aircraft.
UPDATE 3/14/06
I have completed my original design tractor gyro. You can see how I went from building a Little
Wing to my original design by going through the builder’s log.
I made several changes to the gyro after I quit adding to the
builder’s log.
You can see a movie of my current flying gyro here.
Gyros, gyrocopters, or gyroplanes, are perhaps the most
misunderstood aircraft. When designed properly, and flown by a pilot with
the proper training, they are VERY SAFE; yet over the years they have
developed somewhat of a bad reputation, due to poor design by some kit
manufacturers and builders, and people with little or no training trying to fly
them.
The rotor blades on a gyrocopter are not connected to the engine, they use air
moving upward through the blades to keep them spinning, or
"autorotating". The engine provides forward thrust, causing the
craft to move forward, and air into the rotors. Therefore, if the engine
quits, the blades don't stop, they keep rotating as long as they are
"loaded" with air moving upward through them. It is
possible to stop forward movement, zero airspeed, and the craft will enter a
controlled vertical descent, therefore, IT WILL NOT STALL!
Gyros come
in two basic configurations:
1.
Tractor: the engine is mounted on the front, and pulls the craft
through the air, like the Little Wing gyro in the picture on the left.
This design has been around since the thirties, and is known to be a very
stable design.
2.
Pusher: the engine is mounted in the rear, and pushes the craft
through the air, like the Dominator in the picture on the right.
This design was pioneered in the fifties by Dr. Egor Bensen, and is currently
the most popular configuration.
PIO and
PPO
are responsible for a large percentage of gyrocopter
accidents. This is the Achilles Heal of the gyro, and what has
contributed to it's reputation as a "dangerous" aircraft. With
proper design and training, the chance of either of these occurring can be
greatly minimized.
PIO (Pilot Induced
Oscillation)
Due to a wind gust or over-control by the pilot, the craft pitches up or down;
the pilot makes a correction with the stick, but due to a lag in control
response, he/she over-controls; now the craft is pitching too far in the other
direction, and the pilot repeats the process; and again. This results in
an increasing up-and-down oscillation that usually results in the craft
entering a negative G state on the third oscillation. This unloads the
rotors: if it is a "high thrust line"
machine, and the power is on at this point, the craft "bunts over",
or tumbles forward, into an unrecoverable state. If the power is not on
at the point of entering negative G, the rotor speed decays quickly, with perhaps
a small chance of recovery. But, if the power were not on, it would have
been very difficult to enter this condition in the first place.
PPO (Power Push
Over)
Snowbird
Adventurer
This is a condition that happens in "high thrust line"
machines. If the rotor becomes unloaded for any reason, whether by pilot
error or wind conditions, and thrust is applied, the drag from the rotor disc
decreases, allowing the thrust to rotate the craft forward around the vertical
center of gravity, entering an unrecoverable tumble.
You can see that these two conditions are very similar, the PIO being started
by the pilot, but usually ending in a PPO. It is possible that most of
these accidents are initiated by wind gusts, and the pilot trying to deal with
a poorly designed, unstable craft, resulting in a "bunt over" or PPO.
High Thrust Line Machines
Gyros that have the thrust line higher than the vertical center of
gravity. You can sometimes tell by looking if a machine falls into this
category; the pilot sits low to the ground, and the thrust line (a line drawn
through the center of the prop) is higher than the center of
mass. The result is a machine that is prone to PPO. Sometimes
looks can be deceiving, and a double hang test and/or calculations should be
done to establish the CG/thrust line offset.
Center
Thrust
This is the idea of
having the center of thrust pass through the vertical center of gravity.
This will help prevent PPO from occurring. You can tell by looking
whether a gyro at least comes close to this condition. The 2 gyros in the
pictures at the top of the page are considered center thrust; notice that if
you draw a line straight through the center of the prop, and through the
rest of the craft, it seems to pass through the center of mass. This way,
if the blades become unloaded with the power on, there will be no tendency to
rotate or "bunt".
You can tell by looking at some pusher gyros, that they are not center
thrust. The center of the prop is obviously higher than the center of
mass. This is usually done to accommodate longer, more efficient props.
Gyros with cabins are frequently this way. A wide cabin being below the
thrust line can make the problem worse, as drag from the cabin increases with
airspeed. Some single-seat cabin designs actually have less drag than
open frame types. If the center of drag is below the thrust line, the faster
you go, the more the craft is trying to rotate forward, and the only thing
keeping it from doing so is the drag from the rotors. If the rotors
become unloaded, rotor drag decreases, and it only takes a fraction of a second
to enter an unrecoverable tumble.
Horizontal
Stabilizer
This
is the horizontal tail surface, which adds a great deal of stability. In
fact, most builders and manufactures now consider this a MANDATORY part
of a aerodynamically stable machine. If the machine you are considering does
not include a horizontal stabilizer, INVESTIGATE THOROUGHLY and ASK
QUESTIONS about why it does not. I have not heard or read of any machine
that will not benefit from a horizontal stabilizer of sufficient size.
The tractor designs had these from the beginning, the pushers have started
using them in recent years. This addition greatly reduces the chance of
bunting, even in a high thrust line machine. A horizontal stabilizer
combined with center thrust design can add up to a very stable and safe
machine; BUT YOU SHOULD STILL GET TRAINING!!!
This site created and maintained by Michael Guard
Last updated 3/9/03
are responsible for a large percentage of gyrocopter accidents. This is the Achilles Heal of the gyro, and what has contributed to it's reputation as a "dangerous" aircraft. With proper design and training, the chance of either of these occurring can be greatly minimized.
Snowbird
Adventurer
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