A068

OTHER: UniCopter ~ Concerns & Tasks

Overview:

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

Concerns:

1/ Re; Significantly Faster Forward Speeds:

"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.

Effective Reverse Velocity Utilization: (if it can ever be achieved) How to derive an improved lift/power ratio from the region of reverse airflow that is greater than the resulting deterioration in the lift/power ratio from the region of conventional airflow; for both cruise and hover. Specifically;

Optimal airfoil profile for both directions of airflow.

Optimized angle of attack at all azimuths and radii.

The following 2 ideas will provide some improvement; but they will certainly not equal the advantages of effective reverse velocity utilization ~ if effective reverse velocity can ever be achieved.

Blade with Independent Root & Tip:

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

High Rate Blade Pitch Change:

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

Move the propeller further aft to make the air flow cleaner. This will give more room for storage behind the pilot and/or for a tandem second seat.

Change the configuration to the 'Wide Stagger'. ~or~ Use a 'reverse taper' similar to that of the Sikorsky X2 blades.

Concerns and Potential Solutions: DESIGN: UniCopter ~ Pusher Prop - General - Pusher Prop Assist

Concerns and Potential Solutions: DESIGN: UniCopter ~ Dimension, Area & Drag - Drag - In Forward Flight

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

To personnel. Blade tips at side of the single seat UniCopter are 5 feet above the ground. On a 4-6 seat craft they would be 7.5 feet above the ground.

Change the configuration to the 'Wide Stagger'.

Potential partial solutions: See Personnel on Ground

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

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

Concerns and Potential Solutions:

Increase the stagger between the rotorhubs by a few inches;

Change the configuration to the 'Wide Stagger'.

May allow more air to the upper quadrant of the propeller.
Will give greater rotor-to-rotor clearance.
Will give a lower disk loading.

DESIGN: UniCopter ~ Rotor - Disk - Blade to Blade Clearance - 4-blade Rotors

5/ More Efficient Airfoil:

Assuming that an Independent Root and Tip blade works,

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

6/ High-Speed Flight:

Concerns and Potential Solutions:

Reverse Velocity Utilization

Do the changes to the blades and rotors, which are done to obtain lift from the reverse velocity region (and remove the negative lift from this region), provide more lift than the likely loss of lift that these changes cause in the forward velocity region? I wonder???? I think it was Prouty who said that the reverse velocity region should not even be considered until mu > 0.5. However, there is the need to feed the upper quadrant of the propeller with air.

Hub Drag:

See; DESIGN: UniCopter ~ Dimension, Area & Drag - Drag - In Forward Flight ~ Hub Concerns

7/ 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:

Keep the fuselage as aerodynamically clean as possible.

Consider retractable landing gear.

Mount the fuselage and the rotor disk as close together as possible to minimize the frontal area and moment arm.

DESIGN: UniCopter ~ Rotor - Disk - Pusher Prop Assist

Design a low profile rotor hub.

See; Lateral Static Stability:

Low Speed Lateral Instability.

See; Torque - Pitch Cross-coupling

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

8/ Rotor Balancing:

How is a complete rotor to be statically and dynamically balanced? Can it be done as one unit before installation and never to be done again??

9/ High Resistance in Pitch Bearings:

See: DESIGN: UniCopter ~ Control - Flight - Cyclic ~ Pitch-Link Loads

Potential solutions:

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.

Hydraulic controls may dampen oscillations and provide sufficient force.

The concept of OTHER: Rotor Concept - Independent Root & Tip - Torque Tube Method should reduce the load on the pilot's cyclic input.

Consider tension-torsion straps for axial loads and reduced hub size.

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

10/ 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

11/ 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

12/ 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:

High Frequency Leading + Trailing Edge Flaps A reduction of vibration at the source.

High Frequency Modifiable Tip Control A reduction of vibration at the source.

DESIGN: UniCopter ~ Rotor - Disk - Pusher Prop Assist will partially offload the rotors during forward flight.

OTHER: Rotor Concept - Independent Root & Tip (IRAT) will give a better distribution of the thrust.

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.

13/ Cooling of the Engine During Hover:

Can retreating blade root provide cooling? http://www.unicopter.com/UniCopter_Cooling.html

Tasks: (Projects) (in chronological sequence)

CNC workstation:

Order and assemble CNC worktable.
Get CNC controller, motors and encoders etc. working properly.
CNC components for Routing.
CNC components for Composite construction; required for blades, hub.

Work on mockup and upgrade of components toward final items.

Continually look for problems with UniCopter.

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.

Review 4-blade rotor and clearances versus obliquity and stagger (Greater stagger does improve disk loading)

Work on Reverse Velocity Rotors.

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

Evaluation and designing of propeller - rotor relationship.

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.

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).

Design Blade root to Hub interface. Preliminary is done.

Composite Rotor Hub c/w Crossed Roller Bearings. Will crossed roller bearings actually be better?

Design Drive Train. Preliminary is done.

Aerodynamic, Review potential trim, stability & control concerns. Minimizing parasitic drag by optimize the aerodynamics around the hub and working on retractable landing gear.

Develop rotor governor in conjunction with flight controls Preliminary is done.

Work on elastomeric bearings for the rotor and blades.

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

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.

Retractable supports.

Minimize rotor induced vibration.

Can the UniCopter's rotors be made transportable? (i.e. folding blades) DESIGN: UniCopter ~ Rotor - Disk - Folding Blades, DESIGN: UniCopter ~ Rotor - Hub - Twinned Blades.

A turbine, rotary engine and electric motor will result in a cleaner aft fuselage.

Build This at Same Time?

1/4 Scale UniCopter UAV with Electric Motor: ~or ~ 1/4 Scale Interleaving UAV with Electric Motor: For flight-testing and for being a craft with it's own functional advantages.

~or ~

Same size Interleaving - Advanced Very-Light Rotorcraft, utilizing commonality of components with UniCopter.

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

Last Revised: August 1, 2008