DESIGN: UniCopter ~ Fuselage - Body

Outside Aircraft:

Many of the newer recreational planes have the feet at a higher elevation visa-vie the seat than exists in older planes. In planes, this is done for fuselage aesthetics and aerodynamics since the overall vertical dimension of the body is smaller. In the UniCopter this will have a very positive feature since it will reduce the nose down pitching moment caused by parasitic drag. The negative aspect is that the airplane pilot is looking forward whereas the helicopter pilot spends a good part of his time looking down. Perhaps the seat could be designed like the Katana, which has a separate section in front of the seat bottom, to support the calves of the legs. Don't play with the slope of the seat back.

Perhaps I could sit with my knees partially in my chest but give the legs good support.

Mini 500:

6'-1" person and self sitting in Mini-500. Cushion collapses 2.5".

The Mini 500 width is 33.5" at the shoulder and the waist, in fact it is roughly 33.5" all around the door frame. Rick says that this is more than is needed. Ref. The maximum Unicopter width is 29" and Rick says that he designed his B-copter for 30" width.

The door frame is 43" or 47" high and Rick says that it could be less.

 Pitch Change between Hover and Fast Forward Flight:

In forward flight, large increases in drag with speed require more forward rotor thrust, and with high offset rotors, this causes large nose down attitudes. ~ N.L. on alt.recreational.rotorcraft


I'm not sure exactly what the tilt will be without flying it, but I do know that a BO105, with a relatively rigid rotor system, is rather uncomfortably tilted at high cruise airspeed, while a 206, with a teetering rotor system, is not. In a 206, the fuselage tilt attitude is almost independent of the rotor tilt. Most BO105 pilots I know don't fly at max cruise, but somewhat below that, because the passengers are very uncomfortable with the helicopter's attitude, as are the pilots. It gets tiring looking up all the time just to look straight ahead. It will depend on the aircraft, especially the length of it, I would think, but with a completely rigid rotor, the tilt will be even more pronounced. ~ S.G on alt.recreational.rotorcraft


The 206 mast is tilted forward five degrees which helps the fuselage ride in a more level attitude in cruise than it would otherwise. Still, many a LongRanger pilot who doesn't weigh much will attest to using the "straight-arm" method of holding the cyclic in high cruise (85%Q), as the stick position is pretty far forward at such times. This tells me that the tip path plane is at an even lower angle of attack compared to the cabin.

S.G. mentioned that the Bo-105 Bolkow has a pronounced nose-low attitude in cruise, and I'm here to tell you that it is between eight and ten degrees, depending on how much power you're pulling. Very uncomfortable. If you don't think so, sit in a kitchen chair some day, then ask someone else to tip you forward ten degrees and hold it. Don't forget to hold you head <i>up</i> ten degrees as you look at an imaginary horizon. Then just sit there for an hour. Believe me, after about fifteen minutes you'll come to realize that rigid rotors are NOT the way to go.
The Bo-105 is a great 100kt. helicopter. But it really, really sucks at 120. ~ B.B. on alt.recreational.rotorcraft

Some possible solutions;

  1. Good: Provide a means of forward thrust. Partial compound helicopter. One hell of a large cooling fan with variable pitch prop so that it is not providing much thrust in hover.????. This will shift some of the power from the rotors to the propeller and thereby reduces the rotor-rotor induced vibration. See: DESIGN: UniCopter ~ Rotor - Disk - Pusher Prop Assist.
  2. Have the seat rotate about its lateral axis. As well, there may be a benefit from a for-aft track for shorter lighter pilots
  3. Have the seat back only rotate about its lateral axis. This might be the easiest and it may not change the leg distance to the pedals.
  4. Good: Consider pivoting the front edge of the seat bottom on a pair of arms that have the pedals as their pivot point. The seat bottom 's back edge is pivoted to the seat-back's lower edge and the seat-back's top edge is pivoted to the fuselage. For fast forward flight, the seat-botom's leading edge is moved up and forward (maintaining the knee to feet distance. This causes the slope of the seat's back and bottom to change, in respect to the horizontal. See: DESIGN:UniCopter ~ Fuselage - Body - Adjustable Seat
  5. Turbo shaft-jet engine, if they ever make a small one. See: DESIGN: UniCopter ~ Rotor - Disk - Pusher Prop Assist.
  6. Good: Raise the pilots feet by a couple of inches. It will only affect the pilot during hover and it does not entail changing the slope of his body only the elevation of his feet. This will reduce the fuselage's drag slightly, and it is at the greatest distance from the center of the moment arm. As well, keep the fuselage near his feet as narrow as is practical.
  7. Good: Make the fuselage as aerodynamically clean as possible.
  8. Give the rotors an adjustable rotation of about 10 degrees.

Items 2. & 3. probably mean that the seat back cannot be part of the fuselages strength or firewall.




Get the body as high and close to the rotor disks as possible. The highest part of the fuselage will be over the center of the pilot's head, not over the bulkhead. This will allow more air to flow into the upper quadrant of the propeller and it should force a little more air into the cooling openings during cruise.

To increase airflow to the upper quadrant of the propeller: There is a longitudinal distance between the high point on the pilot's head and the centerline between the rotors. Therefore have the canopy behind the pilot's head curve down and inward on both sides as quickly as is aerodynamically possible. It may also be advantageous to minimized the size of the rotorhubs, plus move the final reduction down and in behind the fuselage. Perhaps aerodynamically inline with the wide cylinder heads on the engine. This may also remove some of the powertrain bracing out of the airflow coming over the top of the fuselage.

Consider sloping the pilot back by 3 degrees more than in the SynchroLite and raising his feet quit a bit. The more that the helicopter is used for fast-forward flight v.s. hover, the more lay back the pilot can probably be. This is because the downward pitch in forward flight causes the pilot to be more upright. January 24, 2007 ~ With the current inclusion of the propulsor, this is no longer as valid.

Make the trailing edge of the body very aerodynamic. Consider a 'chopped' off portion if it helps.

Crazy idea 2: Consider having a tube at the center bottom of the cockpit that runs from the nose, between the feet and under the seat to the area of the engine.

This tube will;

  1. Draw air from a high-pressure area.
  2. Reduce the parasitic drag somewhat.
  3. Add reinforcing to the cockpit.

Look at the single seat Angle for a simple and similar cockpit. Note the clamshell opening must clear the blades.

If the vertical mounted engine (item0845) extends out into the fuselage skin then consider putting a bulge in the fuselage at these locations on each side and have the bulge flare into the rear support legs.

For an idea for the canopy see: http://www.synchrolite.com/0922.html

For another idea see this sketch of the CH-7 Kompress;

A-frame Structure:

Consider the load paths as an A-frame structure from the side view. The front leg is from the rotor down to the backboard to the from leg of the skid. The back leg is from the rotor down the motor mounts to the rear leg of the skid. See; DESIGN: UniCopter ~ Landing Gear - Fixed - Left & Right Skids

Pedals & Floor Configuration:

The flight controls could be similar to the SynchroLite, in that the pedals rotate a tube. This might be an ideal arraignment if the blade tip control is going to be basically similar to the SynchroLite. It also may be ideal if there is to be a single front support, since the control tunnel will provide structural strength to the front of the cockpit.

Alternatively, having a rod run back from a downward pointing arm from the inner side of each pedal will allow for a flat floor.


"One of the problems associated with having large concentrated masses in aircraft fuselages is crashworthiness. When subjected to crash inertia loads (6g vertically-down say (benign)) a substantial structure will be required in the aircraft to avoid these concentrated masses detaching from their attachments and crushing the cabin. Therefore, if you were to isolate the aerodynamic and inertial forces for the rotor system using a stiff transmission, you would not be able to attach it to a lightweight fuselage, as it would not be crashworthy. " ~ CRAN on PPRuNe


"A large amount of noise is likely to be generated by the rotors' close proximity to the cabin" ~ CRAN on PPRuNe


Keep the pilot's head up and back as much as is possible.

The UniCopter is designed to have a relatively fast forward speed. The craft also pitches forward during cruise. It therefore may be advantageous to tilt the pilot an additional 3 or 4 degrees further back.This may make reduce the parasitic drag and the flying more comfortable for the pilot. January 24, 2007 ~ With the current inclusion of the propulsor, this is no longer as valid.

Seat Bottom:

The space under the seat should be committed to a crumple zone.

Material for Windsheild :

Polycarbonate/ABS Alloy

By Lu on PPRuNe:

Polycarbonate is much stronger than Plexiglas ® in many ways but it has a very serious problem if the installation is not designed properly and that problem is stress corrosion. If the screws/bolts that hold the Polycarbonate plastic structure in place apply a compressive load and the structure is subsequently cleaned with an alkaline product the material will stress corrode and it will eventually crack to relieve the compressive load.

Stowage and Extra fuel:

Consider having the standard fuel tank as high as possible and between the seat back and the engine. Any area below the tank could then be used for stowage, working equipment or a extra bladder fuel tank.

Stowage Area:

Initially required for test equipment.

Instrumentation and Controls:

Consider mounting some of the smaller switches and instruments in the frames that run down each side of the windscreen, if they do not increase the width of the frame, thereby decreasing the polots outside view.

Canopy Door:

The access to the door is under the blades where they are at their highest elevation.

Cabin Heat System:

This is related to the engine system.

Heat Muff:


Windshield Defrost System:



See; DESIGN: UniCopter ~ Fuselage - Body - Bulkhead


The use of a turbine will make the aft end of the fuselage much more aerodynamic See; Innodyn http://www.innodyn.com/aviation/products.html


Is there enoughg room in the fuselage for crossed-over tuned exhausts?

Two Seats:


In the far, far future and with humongous volume Fiber Placement might be considered. The major provider is Automated Dynamics Corporation. There is a file folder [Fiber Placement].

Same Page ~ Different Craft:


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Last Revised, February 21, 2007