A068

OTHER: UniCopter ~ Concerns & Tasks

Overview:

Working notes listing the Potential Concerns, Tasks and Thoughts, regarding the development of the UniCopter.

Concerns:

Principle Concern:

A faster helicopter is the reason for developing the Advancing Blade Concept (ABC). However, for the ABC to be successful it must incorporate;
    • These limitations are applicable to the Intermeshing-ABC and the Coaxial-ABC.

1/ Significant Higher Speed Flight:

Concerns and Potential Solutions:

"At stage lengths of about 200 n. mi., where the maximum number of revenue flights occur, rotary wing cruise speeds of about 240 knots are required to produce the same block speeds as existing jet transports." ~ from the 1977 report, 'A review of Advanced Rotorcraft Research'.

This should be obtainable from today's technology, particularly if active blade twist and individual blade control were to be implemented.

However to achieve faster speeds, and therefore a longer range, reverse velocity utilization or some other type of configuration such as perhaps the AeroVantage will be required.

Blade with Independent Root & Tip:

Can the tip pitch control be taken out near enough the actual blade tip to make this concept feasible?

2/ Sufficient Airflow to Upper Quadrant of the Propeller During Cruise:

3/ Danger of Rotating Rotor Blades at the Sides of the Craft:

4/ Rotor to Rotor Clearance with 4-blade Rotor:

The UniCopter concept is based on the premise that extremely rigid blades can be produced.

5/ More Efficient Airfoil:

      1. Can it then be made in an unsymmetrical profile such as VR-7 and NACA23xxx?

6/ Trim, Stability & Control:

Concerns and Potential Solutions:

See; Autorotation:

See; Longitudinal Static Stability:

A 1, 2, 3 or 4º precone may contribute to speed stability.

Potential solution:

        1. Keep the fuselage as aerodynamically clean as possible.
        2. Consider retractable landing gear.
        3. Mount the fuselage and the rotor disk as close together as possible to minimize the frontal area and moment arm.
        4. DESIGN: UniCopter ~ Rotor - Disk - Pusher Prop Assist
        5. Design a low profile rotor hub.

See; Lateral Static Stability:

See; Torque - Pitch Cross-coupling

Link to note about high engine thrust line and mention that it is offsetting the rotors torque-pitch coupling.

7/ Rotor Balancing:

8/ High Resistance in Pitch Bearings:

      1. Seriously consider elastomeric bearings and crossed roller bearings. DESIGN: UniCopter ~ Rotor - Hub - Pitch Bearing - Elastomeric The smaller amount of pitch change required to to change the attitude of a craft with rigid rotors will allow for a better mechanical advantage in the control system. Lightweight helicopters will require less force because of their small size. The load is distributed amongst six or eight blades.
      2. Hydraulic controls may dampen oscillations and provide sufficient force.
      3. The concept of OTHER: Rotor Concept - Independent Root & Tip - Torque Tube Method should reduce the load on the pilot's cyclic input.
      4. Consider tension-torsion straps for axial loads and reduced hub size.

For calculation of loading see: DESIGN: Rotor - Hub - Pitch Bearings ~ Friction

9/ Manual Operation of Blade Tip-Control:

Will the pilot be able to manually overpower the resistance to twist about the feathering axis of the 6 or 8 blade spars?

See; DESIGN: UniCopter ~ Control - Flight - Independent Root & Tip

10/ Storage and Ground Transportation:

The inability (of the current design) to fold the six (or 8) exceptionally rigid blades.

Potential partial solutions: See DESIGN: UniCopter ~ Rotor - Hub - Twinned Blades

11/ Rotor to Rotor Induced Vibration. This vibration will be more pronounced if the rotors are slowed in hover so that it equals the cruise RRPM. See High Frequency Leading + Trailing Edge Flaps and High Frequency Modifiable Tip Control.

General Information: Vibration - Rotor Induced

The twin rotor intermeshing Flettner FL-282 and coaxial Sikorsky XH-59A ABC exhibited very high levels of rotor induced vibration, particularly at high forward speeds.

Potential solutions:
        1. UniCopter ~ Vibration - Rotor Induced - Analysis
        2. UniCopter ~ Vibration - Rotor Induced - Control
        1. DESIGN: UniCopter ~ Rotor - Disk - Pusher Prop Assist will partially offload the rotors during forward flight.
        2. OTHER: Rotor Concept - Independent Root & Tip (IRAT) will give a better distribution of the thrust.
        3. DESIGN: UniCopter ~ Control - Flight - Swishring. The 3P cyclic control should eliminate the vibration caused by lateral dissymmetry of lift in fast forward flight. So will rotors with 4 blades.

12/ Cooling of the Engine During Hover:

Tasks: (Projects) (in chronological sequence)

  1. CNC workstation:
    1. Order and assemble CNC worktable.
    2. Get CNC controller, motors and encoders etc. working properly.
    3. CNC components for Routing.
    4. CNC components for Composite construction; required for blades, hub.
  2. Work on mockup and upgrade of components toward final items.
  3. Continually look for problems with UniCopter.
  4. Test and develop; Torque tube and Unidirectional Spar idea. Independent Root and Tip - Torque Tube Method - to test the concept. Plus, Converter and Generator programming.
  5. Review 4-blade rotor and clearances versus obliquity and stagger (Greater stagger does improve disk loading)
  6. Work on Reverse Velocity Rotors.
  7. Design and Construction for Independent Root and Tip - Torque Tube Method and Independent Root & Tip Flight Controls. 3P at root and 1P at tip. Working on it
  8. Evaluation and designing of propeller - rotor relationship.
  9. Move propeller back 6" and motor back 3-4" and rotors back 2-3" for more space at center of gravity and for better aerodynamics.
  10. Consider if there are any disadvantages by counteracting the rotors' torque-pitch coupling by the propeller's thrust line versus the craft's CG and center of drag (includes rotors). Should the current angle of the engine, and thus the moment arm of thrust, be changed, (regarding vertical climb, forward speed and autorotation).
  11. Design Blade root to Hub interface. Preliminary is done.
  12. Composite Rotor Hub c/w Crossed Roller Bearings. Will crossed roller bearings actually be better?
  13. Design Drive Train. Preliminary is done.
  14. Aerodynamic, Review potential trim, stability & control concerns. Minimizing parasitic drag by optimize the aerodynamics around the hub and working on retractable landing gear.
  15. Develop rotor governor in conjunction with flight controls Preliminary is done.
  16. Work on elastomeric bearings for the rotor and blades.
  17. Consider the inclusion of a 3-spoke tension-torsion strap pack or DESIGN: UniCopter ~ Rotor - Hub - Twinned Blades. This will eliminate the axial pitch bearings and should reduce the height of the rotorhub slightly. Might the strap-pack consist of carbon tow. Also, might the 'strap-pack' just be an un-epoxied, or uncured, continuation of the of the pultruded spar tow, to a central 'coupler'. Or if the transmission is lowered so that the drive shaft has minimal clearance ofer the top of the engine,and the final gear ratio is smaller
  18. Reconsider the use of single boom, which passes through the propeller's hub. Particularly if the rotorhubs and final transmissions are reduced in size and/or the stagger is reduced.
  19. Retractable supports.
  20. Minimize rotor induced vibration.
  21. Can the UniCopter's rotors be made transportable? (i.e. folding blades) DESIGN: UniCopter ~ Rotor - Disk - Folding Blades, DESIGN: UniCopter ~ Rotor - Hub - Twinned Blades.
  22. A turbine, rotary engine and electric motor will result in a cleaner aft fuselage.

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~or ~

Same Page - Different Craft: ~ Electrotor-Plus ~ UniCopter-UAV ~ Electrotor-Simplex ~ Electrotor-SloMo ~ SynchroLite ~ Nemesis ~ AeroVantage

 

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Last Revised: December 26, 2008