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Old 07-22-2010, 09:34 PM
magus49 magus49 is offline
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Default New Gyrocopter

I just finished building a gyrocopter that I designed last year.
In designing the gyro I chose a radically different approach from most other builder. My design criteria were simple: design a gyro that had positive G-load static stability, positive airspeed stability, and positive power stability. The stability had to be adjustable for varying load and wind conditions as well as being fairly easy to build. It will be made from 6061 T-6 aluminum using AN standard aircraft hardware. It will have hydraulic wheel brakes, a steerable nose wheel, a pre-rotator that will bring the rotor to near flight RPM, a rotor brake with rotor lock, and have a horizontal stabilizer with a “notch” adjustable elevator. The gyrocopter will be designed for Light Sport pilotage. I have also chosen a complete aircraft instrumentation package for my design, including altimeter, airspeed indicator, slip and turn indicator, CHT & EGT gauges, engine rpm, rotor rpm, fuel gauges, GPS, hour meter, and aircraft radio.

Some gyro pilots may disagree with some of my choices concerning stability and high centerline thrust but I feel my reasoning is sound. Also my decision to use a horizontal stabilizer with an elevator may raise a few eyebrows but again I have my reasons for the choice.

Being a design engineer with my own company I am fortunate to have complete machine shop and plastic forming equipment available to manufacture the components and aerodynamic fairings for my prototype.

Thrustline:

Although many feel that a centerline thrust is the most stable configuration and the only safe method to use. I disagree with this point of view. A forward thrust-line, which is slightly high of the CG centerline, will achieve positive G-load static stability, airspeed static stability, and positive power stability, provided that the gyroplane has a horizontal stabilizer of sufficient size, which imparts a slight downward pressure on the tail end of the airframe.

A downward force of the horizontal stabilizer’s elevator will keep the CG forward of the rotor thrust vector (RTV) providing positive G-load static stability and keeps the CG forward of RTV for airspeed static stability. The HS must be in the prop-wash of the propeller to provide sufficient downward pressure on the airframe. This downward pressure will react to the prop wash and forward airspeed keeping the CG forward of the RTV thereby providing both G-load stability and airspeed stability.

Some may feel that the high prop thrust-line will make the gyroplane susceptible to a power- push-over. This can only be true if the prop thrust-line is excessively high or the resulting nose-down force is not properly balanced by the tail-down force of the elevator on the horizontal stabilizer. The prop thrust-line should be high enough to provide a nose-down force but not excessively high. The horizontal stabilizer on the Magus49 Gyrocopter is an adjustable elevator would provide a “tunable” tail-down force to compensate for the high prop thrust-line and any variations in wind conditions that may be encountered.
The characteristics of dynamic stability are a function of the Moments of Inertia of the airframe and rotor whereas static stability is a function of the prop thrust-line. The rotor and airframe inertias determine the natural rate of pitch oscillation in the system. Gyroplanes, if they have statically stable conditions, have natural tendencies, upon disturbance, to oscillate around those statically stable conditions. If that natural rate of pitch oscillation is so quick that a pilot cannot react with the proper control and timing, a PIO can be the likely result.

Without a HS, the pilot must be the “active” stabilizer and dampen the pitch oscillations. Especially if the reaction rates of the airframe and rotor resonate, or build on each other, the pitch oscillation rate, once excited by a disturbance, can be much faster than the pilot can correct them. If the pilot fails to react quickly or reacts with the wrong control input he could exaggerate the situation culminating in a PPO. The design of the gyroplane must provide for natural dampening of such quick oscillation rates

Dynamic stability is also a function of the HS. The HS provides passive damping of pitch oscillations. Damping is required because all statically stable aircraft have a natural oscillation rate. The HS tends to automatically dampen and reduce the oscillations to zero without pilot interaction. Dynamic stability is not a function of the prop thrust-line or the location of the RTV. A HS is the only proven, and the simplest, method of providing the passive damping required to automatically reduce the natural oscillations to zero.
The HS can provide both the static stability and dynamic damping for dynamic stability

Airframe:

The airframe was constructed using 2” by 2” 6061 T-6 aluminum square tubing with a wall thickness of 0.125 and bolted together using AN standard aircraft hardware. All connecting plates were cut from 0.125 inch thick 316 stainless steel plate.

Wheels:

I chose a 6” steerable nose wheel manufactured by Matco and decided on a steering lever rather then steering peddles. A cable runs from the nose wheel to a control quadrant containing the engine throttle, elevator control lever, and nose wheel steering lever. This is mounted on the left side of the pilot’s seat. The quadrant is housed in and aerodynamic fairing vacuum formed from ABS plastic.

The two main wheels are 6” polished aluminum wheels with hydraulic brakes. The brake handle is a motorcycle type hand lever mounted on the cyclic control stick. The main wheel struts were machined from 6061 T-6 aluminum plates with cantilever cutout to reduce weight and increase strength. They were then curved using a roller brake to give the required ground clearance. The main struts are shock mounted.

The tail wheel is a 6” fixed wheel mounted at the end of the tail boom
Horizontal Stabilizer/Elevator:

The elevator on the Magus49 Gyrocopter is “notch” adjustable from zero degrees to 45 degrees in one-degree increments. This provides a tail-down force to counteract the nose-down force of the high centerline thrust. It also provides lateral stability from wind shear. The control lever for the elevator is housed on the left side of the pilot’s seat and is adjusted by pushing down on the spring loaded locking button on top of the lever and moving the lever forward of rearward.

The horizontal and vertical stabilizers were fabricated using 0.02 thick 6061 T-6 aluminum sheet bonded to a balsa wood core with a two-part epoxy. The rudder and elevator were constructed using the same method.


Pre-rotator:

The Magus49 Gyrocopter uses an electric pre-rotator with a solid-state speed control to bring the rotor to a speed of 280 RPM in three stages. An astable multivibrator controls the duty cycle of a silicon controlled rectifier circuit to provide power to the pre-rotator in three different power level stages. This prevents the electric motor from over heating during spin-up. The gear ratio between the motor and rotor is designed to provide a final RPM of 280 to allow for short takeoff rolls.

Instrumentation Housing:

The instrumentation housing was vacuum formed from ABS plastic and is mounted forward of the pilot’s seat on a slanted spar connected to the gyro’s keel. The instrument housing contains an altimeter, airspeed indicator, slip and turn indicator, CHT & EGT gauges, engine rpm, rotor rpm, fuel gauges, 7” GPS, and aircraft radio.

Engine/Propeller:

I chose a Rotax 503 engine with dual ignition system and a “B” gearbox. The propeller is a three bladed ground adjustable IVO prop.

Fuel:

The fuel capacity is 7 gallons in three aluminum tanks. The main tank holds five gallons of fuel and is mounted under the engine aft of the mast. The other two tanks are one gallon each and cylindrical shaped mounted on each side of the pilot’s seat just above the keel. These tanks are tied together with a common fuel gauge. The main tank has its own fuel gauge.

Rotor Blades/Brake:

I chose 15’ aluminum Dragon Wing rotor blades and a Wunderlich rotor brake with spring loaded parking lock.

Paint:

The painting was done with etching primer and baked-on automotive enamel paint. It was painted with a dark Burgundy color with gloss Black trim. A wizard was airbrushed on the main fuel tank.

I will start the flight tests next week if things work out.
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Old 07-22-2010, 09:50 PM
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Good luck magus49. I look forward to pics and flight reports.

Aussie Paul.
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Old 07-22-2010, 09:56 PM
magus49 magus49 is offline
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Thanks, I am looking forward to getting it in the air.
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Old 07-22-2010, 10:20 PM
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Quote:
Originally Posted by magus49 View Post
Some gyro pilots may disagree with some of my choices concerning stability and high centerline thrust...
Magus, welcome to the forum, and welcome to your interesting project!

Terms are sometimes important to allow readers to follow your thoughts. The convention is to call a thrust centerline which is above CG "high thrust line," or "HTL." The term "centerline thrust" is generally accepted to mean a thrust centerline which is within about 2" of CG.

"High centerline" will be a little confusing, but your context here makes it pretty clear you mean HTL. You are not alone in believing the a slight offset high, compensated by a horizontal stabilizer's downforce, is the easiest way to get airspeed static stability. (Minority, yes...but not alone!)

Quote:
Originally Posted by magus49 View Post
The elevator on the Magus49 Gyrocopter is “notch” adjustable from zero degrees to 45 degrees in one-degree increments. This provides a tail-down force to counteract the nose-down force of the high centerline thrust. It also provides lateral stability from wind shear...
Do you have reason to believe you'll need that much elevator deflection range? Will you develop a table or chart during testing, then do a weight-and-balance calculation during pre-flight to determine the setting?

When you get a chance, elaborate on how an adjustable horizontal stabilizer aids lateral stability in wind shear. That's a new concept for me.

And yes, by all means...pictures, please!

All the best in your testing. There are several interesting ideas here.
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Last edited by PW_Plack; 07-23-2010 at 12:30 AM.
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Old 07-22-2010, 10:57 PM
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you describe your project very well, I am anxious to see the pictures.
How much is "slightly high" thrust line. ? I don't think you will need 45 degrees in you elevator. In fact you probably won't need much at all if it is slightly high.
Please post some detail pictures soon and good luck with the testing.
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Old 07-22-2010, 11:02 PM
magus49 magus49 is offline
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Paul, I don’t thank I will need a lot of travel of the elevator to compensate for the HTL but the added control may come in handy for wind shear. The addition of the elevator gives an additional control surface for stability and laterial control. I have compiled a vector graph of the airframe for weight and balance of the Gyro and plan to build an elevator setting table during flight testing. Thanks for the comments.
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Old 07-23-2010, 05:12 AM
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gyromike gyromike is offline
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Quote:
Originally Posted by magus49 View Post
Rotor Blades/Brake:

I chose 15’ aluminum Dragon Wing rotor blades and a Wunderlich rotor brake with spring loaded parking lock.
This has to be a typo. 25 footers maybe?

Also you mentioned the elevator providing additional lateral control, and authority during wind shear.
Could you explain please?
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Old 07-23-2010, 05:47 AM
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Why would you adjust horizontal stab incidence for different wind conditions? And why would you want anywhere near 45 degrees of travel?
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Old 07-23-2010, 07:14 AM
Mayfield Mayfield is offline
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Hi Charles,

How do you steer the aircraft during the early stages of the takeoff roll?

Jim
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Old 07-23-2010, 11:36 AM
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I don't see any photos yet...
Standing by for photos...
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Old 07-23-2010, 11:38 AM
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Quote:
Originally Posted by ironcowboy View Post
I don't see any photos yet...
Standing by for photos...
Yaw Mon, we love pictures...
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Old 07-23-2010, 05:46 PM
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Magus you may start an insightful riot here soon if you don't post picture soon.
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Old 07-23-2010, 08:06 PM
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It also provides lateral stability from wind shear...
??????????????
Id be interested in learning how an adjustable/controlable HS can assist control in any way laterally. [ i assume you mean in roll]
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Old 07-23-2010, 09:08 PM
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I'm always eager to learn something new!
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Old 08-02-2010, 06:09 PM
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Gess we aint guna learn this one Pete.
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