Next skip Engines Power is king in the area of sport gyroplanes and most experienced pilots find it difficult to believe that you can get decent performance out of the 40 hp. Rotax used on the prototype. I weight pounds and I certainly would not fly an aircraft with marginal climb performance! Since the aircraft is designed to fly well on comparatively low power, there are other advantages as well.
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They tend to have definite limits with respect to wind, for example, but if flown within these limitations they handle very easily and provide a lot of pleasure to those who fly them. The goal of the Gyrobee project was to achieve something similar in the area of sport gyroplanes. This effort was highly successful, but if you are intent on duplicating the aircraft, despite all my earlier warnings, you must have a solid understanding of why the aircraft is configured the way it is.
Many pilots take a very casual attitude toward the FAA requirements established in Part They may have all sorts of justifications for flying an aircraft that is too heavy or too fast, but the only consequences they see is the remote possibility that they might run into an FAA official. Part issues with respect to the Gyrobee have nothing directly to do with legality! Since the goal was to have the Gyrobee be strictly legal, it was designed so that it would not exceed the 63 mph 55 knot maximum level flying speed mandated in the regulations.
Because it could not be flown any faster in level flight, other decisions could be made with respect to making the aircraft more stable and easier to fly. These design features are not appropriate for an aircraft that can fly at mph!
If I had been designing an aircraft that would fly faster than 63 mph in level flight, I would have done it completely differently. The Gyrobee feels extremely stable and handles nicely, but if it were set up to fly faster, the pitch stability would degrade very rapidly to the point where the aircraft would become dangerous to fly in all but the most expert hands!
In a steep descent, the aircraft might even reach mph, but it still handles well because it is descending. In contrast, if you set the aircraft up so it will reach 75 mph in level flight, the result is increasingly marginal pitch stability and the feeling that the aircraft could bite you with the slightest mis-handling of the stick! There is no magic in the "set-up" area. If the aircraft is built and equipped like the prototype, it cannot fly too fast and you would be extremely pleased with its stability in flight.
If an aircraft with Part legal performance is too "tame" for you, do not modify the Gyrobee! In the sections which follow, I will outline those areas that are most sensitive to modification.
Engines Power is king in the area of sport gyroplanes and most experienced pilots find it difficult to believe that you can get decent performance out of the 40 hp. Rotax used on the prototype. I weight pounds and I certainly would not fly an aircraft with marginal climb performance! Since the aircraft is designed to fly well on comparatively low power, there are other advantages as well. The Gyrobee is a "floater" compared to almost all other gyros out there, which means you get optimum glide performance should the engine fail.
This not only improves your chance of finding a suitable spot to land, it means that you can fly your approach at a significantly lower airspeed and that you can execute a no-roll landing much more easily, even without a stiff breeze to help. Unless you are very heavy or routinely fly from high elevation fields, hp should do just fine. If you have an altitude or weight problem, the design will accommodate a Rotax , but that is absolutely the biggest engine you should use!
Rotor Blades Most gyro pilots assume that blades are basically inter-changeable and the only thing they impact is performance.
While this may be true for most Experimental machines, blade selection is absolutely critical for the Gyrobee. You may assume that the design requires the most efficient blades available, but this is not the case. Highly efficient blades are characterized by relatively low drag. The Gyrobee requires a certain amount of blade drag to limit the maximum level flying speed! These are superb blades for most gyros, but not the Gyrobee! Given that the maximum level flying speed was to be no more than 63 mph give or take a few mph , the rotor was placed on a tall mast with the pilot positioned low on the airframe.
This maximizes pendulum stability and contributes to the mellow handling of the aircraft. At or below 63 mph, the aircraft drag profile is always rotor-dominated and the aircraft is quite stable. With high efficiency blades, rotor drag is lower at any airspeed and the aircraft will fly much faster.
For the aircraft to fly as intended, you must use blades with a higher drag profile. Originally the prototype was flown on Rotordyne blades. These are bonded aluminum blades, which would suggest a low drag profile, but they have a relatively inefficient airfoil section, so they do the job very nicely. They are relatively heavy, so you will only have a few pounds of weight margin with respect to the pound empty weight limit.
Set at 0. Unfortunately, as far as I can tell, Rotordyne blades are no longer being made, but you may be able to find a good used set. Similarly, Brock blades have an efficient airfoil section but lots of rivets.
As a consequence, they fly the aircraft very well but produce enough drag to slow the aircraft down and contribute a very high measure of stability. If you are buying new blades for this project, the Brock blades represent a good tradeoff between performance and drag. They are very light blades hand-start easily, which is a plus if you have no prerotator, or the prerotator is not working for some reason. Rotor Hawk blades also work very well. Use a 24 foot rotor disc and set the pitch to 1.
They are lighter than the Rotordyne blades, spin-up easily when hand-starting, and seem to retain energy very well. The low-drag Dragon Wings blades are not recommended. This is strictly a function of the way the Gyrobee is designed, for these blades are probably the lightest and most efficient blades you can buy. They also hand-start with some difficulty, which is not optimum if you fly without a prerotator.
These would be the blades of choice, based on performance, for an ultralight tractor design, such as the Lite Wing Roto Pup, or a machine with high-pilot seating and a lower engine thrust-line, much like the Dominator Experimental machines.
The Sky Wheels composite blades have an excellent reputation, but they are heavy enough that you would have a problem meeting the pound empty-weight limit required by Part We have not had the opportunity to test fly the aircraft with other blades and, for reasons that should be obvious by now, I cannot recommend any blades that have not been test flown on the Gyrobee. Rotor Diameter The major problem early in the flight-testing of the prototype was how to get a good climb rate when using blades of moderate performance and an engine of only 40 hp.
Fixed-wing ultralights solve the problem by having a relatively high wing area for their weight, resulting in low wing loading. The solution with the Gyrobee was similar increase the diameter of the rotor disc to improve the disc loading.
The typical single-seat gyro flies at a disc loading of 1. In the case of the original Rotordyne blades, we used with a 5 foot hub bar, producing a 25 foot rotor disc and a disc loading of about 1. This produced excellent performance yet the aircraft could easily be flown in winds up to 30 mph, assuming a reasonable level of pilot experience.
The ten-foot Brock blades were lighter and were flown with a 4 foot hub bar, producing essentially identical disc loading on a 24 foot rotor disc.
The tall mast provides ample rotor clearance in either case. Although the aircraft will fly at a disc loading of 1. Wide Main Gear The main gear of the Gyrobee is quite wide, over seven feet, compared to most gyros. This wide stance makes it a bit harder to design a trailer for transporting the machine, but you should resist the temptation to narrow the stance by shortening the axle struts.
This would have no impact on flight characteristics, but would degrade the ground roll-over angle. Most damage in typical gyro accidents occurs when a pilot touches down in a "crabbed" angle, often when executing an off-field landing with the engine out. All-toocommonly, the gyro will tip over, destroying the blades and severely damaging other parts of the airframe. The wide gear stance makes the Gyrobee highly immune to such roll-over accidents.
It has been landed at the most bizarre angles and never shown the slightest tendency toward tipping over. I would suggest that you keep the main gear as documented on the drawings!
Fuel Tank The fuel tank mounting looks a bit unusual to many and might appear to be insecure or cause major trim changes as fuel is burned off. In fact, the fuel tank stays solidly in place in the air or when the aircraft is jolted around on a rough field.
There is no detectable trim change with fuel burn either. The major convenience of the approach taken in the prototype is that the entire tank can be removed and taken to the nearest gas pump if no fuel can is available! Is it possible to use a seat tank on the Gyrobee? The answer is yes, but some thought and work would have to go into the installation.
The fiberglass bucket seat far more comfortable than any seat tank , along with the aluminum back plates, functions as a shear web that reinforces the seat braces. This would have to be integrated with adequate attachment hardware for the lower seat U tube as well as hard points for the attachment of the upper seat back to the structure. It can be done but you will have some homework to do it right. If you plan to try, work with an experienced gyro builder if you have any doubts about the problems to be solved!
If you do mount a seat tank, the fuel tank mounting shown in the drawings can be eliminated. The reason is quite simple. This means the highest standards of craftsmanship using the proper tools for the job. Just because there are no mandated inspection requirements for Part aircraft, this does not mean that we are not dealing with life and death issues. Materials Only aircraft grade steel and aluminum alloys and hardware should be used to build an aircraft.
Materials and hardware available from other sources such as hardware stores are not suitable. This is a gentle way of saying that something will eventually fail and kill you! Legitimate aircraft suppliers such as Aircraft Spruce and Specialty Company, Wickes Aircraft Supply, Leading Edge Airfoils LEAF , California Power Systems, and other suppliers advertising in magazines such as Kitplanes and Rotorcraft stock the proper materials and should be your only source for materials and hardware unless you are really know what you are doing.
Cutting Tubing and Angle Stock Although you can cut everything needed with a hacksaw, the job would not be fun and it would also take forever! A powered bandsaw is the ideal took for most of the work. Be sure to allow for the width of the cut when making all pieces - the finished size should match the prints! All cuts should be carefully-dressed with a fine file and steel wool since sharp edges can concentrate stress and lead to the formation of cracks. Drilling Drilling tubing, sheet, and angle stock is the most critical operation you will do on an aircraft construction project.
Holes must be placed with absolute precision or the parts will not fit when assembled.