1090

Item 1090

DESIGN: UniCopter ~ Rotor - Disk - Large Chord & Low Tip Speed or [High Solidity & Low Tip Speed] ?

Objective:

To evaluate the pros and cons of a large chord and low rotor speed versus a smaller chord and variable rotor speed.

Note:

The Stepniewski ABC Low Tip Speed Design Philosophy has slow constant-speed rotors.

The two Sikorsky ABCs have variable-speed rotors.

The information on this page primarily considers the constant-speed rotor.

If and when Active Blade Twist is implemented in helicopter rotors it will allow the retreating blades to provide lift during high speed cruise and this will mean that the chord can be a little smaller.

Tip Speed:

Stepniewski appears to be considering a constant tip speed of 513 fps.

Sikorsky S-69 (XH-59A) ABC: Design rotor speed = 650 ft/sec. in helicopter mode; 450 ft/sec. in (compound) cruise mode.

Sikorsky X2 ABC: Design rotor speed = ??? ft/sec. in helicopter mode; 338? ft/sec. in cruise mode.

Reference:- The tip speed of the S92 is 761 ft/sec.

From Prouty it appears that 400 ft/sec is the minimum tip speed to have stored kinetic energy for autorotation.

My thoughts ~ The above is probably a valid statement for flare but a rotor governor should allow for a slower rotational speed during flight. This is because the rotor governor will assure that the collective is dropped in time. In addition, the high strength of the rotor will withstand slow RRPM. The previous sentence assumes there is sufficient elevation to gain RRPM for the flare.

Tip speeds under 500 ft/sec are quiet. The Hughes "Quiet One was down to 430 fps.

It would appear that 400 to 500 ft/sec is the ideal range.

It appears that the Mach number at the advancing tip during high-speed flight must be below 0.85

The book 'Principals of Helicopter Aerodynamics', section 2.2.11 covers the subjects of Rotor Solidity and Blade Loading Coefficient. However, this section does not discuss the subject of varying the tip speed (ΩR)². Section 6.3.3 is on Rotor Solidity and it does say "Rotors that are designed for high speeds and/or high maneuverability requirements require a higher solidity for a given diameter and tip speed." For consideration of tip speed [RRPM] see this section below.

Recently Proposed Craft:

This page is very relevant. ~ Implications of the Low Tip Speed Design Philosophy ~ by Stepniewski, Wieslaw Z

This concept appears flawed; ~ OTHER: Helicopter - Outside - Single (large) - Sikorsky's Reverse Velocity Rotorcraft Concept

This patent appears obvious; ~ US patent 6,007,298 ~ Optimum speed rotor ~ Have hard copy There is a second nearly identical one related to tilt rotor.

Existing/Previous Craft w/ High Forward Speed:

The following two aircraft are (were) attempts to increase the forward speed of a craft with VTOL capability.

Osprey V-22:

The Osprey's major problem is that of the Vortex Ring State. In helicopter mode, the small diameter rotors are operating at a blade pitch that is very close to their maximum. This leaves very little allowance for the unexpected.

Sikorsky XH-59A ABC:

The rotor tip speeds were 650 ft/sec in helicopter mode and only 450 ft/sec. in compound mode. This helicopter also incorporated the Advancing Blade Concept (advancing blades provide more thrust than retreating blades), and a forward thrust device. The combination of these three features allowed the craft to be flown at a high forward speed, until the advancing tips experienced high compression and the craft experienced high vibration.

Sikorsky X2 ABC:

The tip-speed is 700 ft/sec in hover and 560 ft/sec during high-speed cruise.

BA609 tilt rotor:

There appears to be no reason why an intermeshing helicopter cannot out perform the Osprey in all areas except maximum forward speed, and outperform Sikorsky's ABC in all areas.

This intermeshing helicopter will be similar the ABC in many respects. It will differ from the ABC in that the blades will have a larger chord.. It appears that the vibration caused by lateral dissimitry of lift during forward flight can be minimized by; three blades per rotor and a 3P higher harmonic control, or alternatively, by four blades per rotor. At high forward speeds, the trailing tip vortices from the lower advancing blades should pass below and outside the upper retreating blades.

Wieslaw Z. Stepniewski said; ~ "Very preliminary studies seem to indicate that placing the ABC rotors in the synchropter position should result in a somewhat aerodynamically cleaner than the coaxial ABC, and definitely a much cleaner design than the considered single-rotor types.[Shaft-driven and Cold Jet]"

Horizontal Flight:

The craft can achieve a higher forward speed than current helicopters because of the slower rotating rotors. The slower rotors delayed onset of compression and also have less profile drag.

Vertical Flight:

The larger chord blades allow the craft to hover at a slower rotating speed. The blade pitch will be greater in hover than it will be in forward flight, but this pitch will still be far less that that of the Osprey in hover. An airfoil with a high maximum coefficient of lift will be advantages, not because of retreating blade stall, but because of low RRPM high pitch hover.

Transition:

This is a non-event. Advancing the cyclic stick adds pitch (thrust) to the propeller, and causes the rotors to give the craft a slight nose down attitude.

Relationship of RRPM and Horsepower during Hover:

The following is a comparison of the UniCopter with NACA 0012 airfoils and a thrust equal to it's GW. The actual values were probably based on the initial lighter UniCopter.

RRPM	Collective Pitch:	Horsepower:
533	5.6º	96
450	7.1º	82
400	8.4º	76

May 21, 2004 ~ I think that the above values are based on the same chord. If both the chord and the pitch are increased as the RRPM is reduced, it appears that the horsepower increases. In other words, increasing the chord increases the HP during hover.

Considerations re Constant Speed Low RPM Rotors during Cruise:

Forward Velocity:	75% of Tip Speed: ⁽¹⁾	Advancing Blade:	Retreating Blade:	Sum: ⁽²⁾
	540 fps * 0.75 = 405 fps = 240 kts	Lift, as related to the square of the velocity	Lift, as related to the square of the velocity	Lift, as related to the square of the velocity
0 kts	240 kts	240² = 57,600	240² = 57,600	115,200
50 kts	240 kts	290² = 84,100	190² = 36,100	120,200
100 kts	240 kts	340² = 115,600	140² = 19,600	135,200
150 kts	240 kts	390² = 152,100	90² = 8,100	160,200
200 kts	240 kts	440² = 193,600	40² = 1,600	195,200
250 kts	240 kts	490² = 240,100	-10² = -100 ⁽³⁾	240,000
300 kts	240 kts	540² = 291,600	-60² = -3,600	288,000

(1) Speed of blades is taken at 75% of rotor disk radius.

The rpm of the rotors and of the propeller are a constant.

The variable pitch on the propeller is increased as the forward motion of the longitudinal cyclic is increased.

(2) The implication is that as a transition is made from hover to fast forward flight, the collective is being reduced as the forward cyclic is being increased. This means that the lift from the rotors is being maintained as the forward thrust is being increased.

(3) Opposed lateral cyclic should be considered as a means of eliminating the negative lift on the inner segments of the retreating blade. Note that this will also decrease the lift on the outer segments of the retreating blade.

Additional Feature:

Low noise due to the elimination of the tail rotor and the low speed of the main rotors.

Aspect Ratio:

My thoughts:

The aspect ratio for the blade of a conventional helicopter is significantly greater than the aspect ratio for the wing of an airplane. One reason may be that of reducing the disk loading, and this would be similar to that of a glider.
I suspect that a second reason is: The blade of the helicopter generates half of its lift from the outer 25% of its span, due to the faster air velocity at the tip end. This being the case, the hypothetical aspect ratio of the outer 25% of the blade is not exceptional large.
A rotor with a low tip speed will have a lesser dissimitry of lift between the tip of the blade and its root when it is on the advancing side of the rotor. Therefore, the center of lift will move inboard from the 75% of span. This in turn will increase the hypothetical aspect ration. Taken to the extreme, the blade on a stopped rotor would be directly compared with the wing of an airplane.
This appears to be a logical reason as to why the slow speed rotor will have a smaller aspect ratio than a conventional helicopter. Of course, the chord of this slow speed rotor must be increased as well.

Disk Loading:

Wing loading in fixed-wing aircraft varies from 6 lb/ft² for a sailplane to 120 lb/ft² for a jet transport/bomber.

Disk loading in helicopters varies from 1.5 lb/ft² for the Ultrasport 254 to 15 lb/ft² for some transport helicopters.

If the tip speed of a helicopter is reduced and the disk area is maintained, then the solidity ration must be increased. Taking this tip speed reduction to the extreme and stopping the rotor should logically imply that the Wing Loading of a fixed-wing aircraft should now be equated with the Blade Loading of the helicopter.

In other words, when considering a [Large Chord & Low Tip Speed Helicopter] there might have to be a graph where the Y-axis is between disk loading and blade loading of a conventional helicopter and the X-axis is the reduction of the RRPM below some nominal conventional helicopter rotational speed. In even more other words, a diagonal line which has one end at the intersection of disk-loading and conventional RRPM, and the other end at the intersection of blade-loading and zero RRPM.

____________________________

Blade Loading:

The following is a comparison of The UniCopter to a comparable helicopter and airplane

Aircraft:	Disk Loading:	Blade (Wing) Loading:	Velocity Calculated at:	Avg. Velocity of 4 Quadrants of Blade or Wing at Cruise (mph)	Col. 5 / Col. 3
Sikorsky ABC⁽¹⁾	8.84 lb/ft²	57.87 lb/ft²	r/R = 0.75	√((677²+ 339²+ 2²+ 339²)/4 = 415² = 172,044	2,973
Stepniewski ABC
Robinson R22	2.76 lb/ft²	90.8 lb/ft²	r/R = 0.75	√((636²+ 474²+ 313²+ 474²)/4 = 488² = 238,144	2,623
UniCopter	3.48 lb/ft²	17.9 lb/ft²	r/R = 0.70 ⁽²⁾	√((588²+ 334²+ 80²+ 334²))/4 = 379² = 143,641	8,024
Midget Mustang	~	14.7 lb/ft²	~	215² = 46,000	3,129

Notes:

I don't know exactly what I am tryng to find out here; perhaps to reconcile the lift of a helicopter, airplane and perhaps a compound helicopter. Develop further with [RWA, Book II, Chapter IV]

In forward flight, a portion of the helicopter's disks will be in a vertical velocity.

The UniCopter may have to be reevaluated in light of the fact that the advancing blades are carrying a large percentage of the load. This will also apply to the Sikorsky ABC.

The future possibility of reverse velocity utilization will have a effect on any considerations and calculations

Based on cruise speed of 200 knots and tip speed of 450 fps.
This is less than the R22 because of the UniCopter's large taper and active blade twist.

Outside Information:

A report 'Development of the Autogiro ~ A Technical Perspective' [ http://www.enae.umd.edu/AGRC/Aero/Leishman_giro_paper.pdf ] by J. Gordon Leishman mentions on page 16 the following report which studied the load sharing between the rotor and the wing of an autogiro. ~ Have hard copy

Article by Prouty in Vertiflite, Winter 2004, page 24.

'Wing pressure distribution and rotor-blade motion of an autogiro as determined in flight' ~ Wheatley, John B ~ NACA Report 475 1935 ~ Have hard copy It might give some info on this pages subject. Then again it may not.

What might be more interesting would be the load sharing on a compound helicopter.

Effect of Rotor Tip Speed and Solidity on Figure of Merit. ~ [Source ~ AH p.62]

Variable Speed Rotor and Propulsor:

An optimal arraignment may be to have propeller and the rotors mechanically connected so that the rotors slow down as the propeller speed up.

See: DESIGN: UniCopter ~ Pusher Prop - General - Variable Speed Rotors and Prop

Segment from PPRuNe thread 'Why are Helicopters with the Flettner-System so slow?'.

My Posting;

Nick & Mart.

Nick, there is no argument with what you say. However, your statement "that the profile power is too high when a big blade is hovered" got the neurons firing.

The theme of this thread relates to forward speed and a craft with twin main-rotors. The three of us, and others on the forum, have an interest in what might be called the next generation rotorcraft. Therefore ...

During cruise, all future rotorcraft will likely slow their rotors. This reduced rotational speed strongly suggests that their chords will be increased over that of current rotorcraft. During hover, a larger chord will increase the profile drag (as you say), however, a slowing of the rotor speed during hover will reduce the profile drag. This raises the question as to which will win the tug-of-war over the profile drag.

The following results are calculated from Prouty's 'Combined Momentum and Blade Element Theory with Empirical Corrections', in the chapter 'Aerodynamics of Hovering Flight'. It consists of incremental changes to the blade's chord and then finding the RRPMs that gives matching thrusts. The constants are: Pitch = 8º. Taper = 0º. Twist = 0º. Blades = 4. Profile = NACA 0012

Thrust:	4972#	4987#	4994#	4994#	4985#
Chord:	0.5'	1.0'	1.5'	2.0'	2.5'
Horsepower:	473	409	411	416	394
RRPM:	370	295	261	242	229
Tip Mach:	0.69	0.55	0.49	0.45	0.43
Aspect Ratio:	40:1	20:1	13.3:1	10:1	8:1
Coefficient of Thrust:	0.0027	0.0042	0.0056	0.0065	0.0073
Sigma:	0.032	0.064	0.096	0.127	0.159
C_T/Sigma	0.084	0.069	0.059	0.051	0.046

Interestingly, after excluding the first column, the horsepower does not vary much. This appears to imply that wide chord blades on high-speed rotorcraft will not be detrimental to their hover.

From Nick;

Interesting! Can you run the 1' chord blade down in speed, increase collective to keep Thrust constant and see what happens as you make that blade go to .12 Ct/sigma?

My reply;

The following results are calculated from Prouty's 'Combined Momentum and Blade Element Theory with Empirical Corrections', in the chapter 'Aerodynamics of Hovering Flight'. It consists of incremental changes to the blade's pitch and then finding the C_T/Sigma for matching thrusts.

The constants are: Chord = 1 ft. Aspect ratio = 20:1. Sigma = 0.064. Taper = 0º. Twist = 0º. Blades = 4. Profile = NACA 0012

Thrust:	4987#	5014#	4981#	5000#	4986#	4996#	4994#
Blade Pitch:	8º	9º	10º	11º	12º	13º	14º
Horsepower:	409	384	367	367	360	358	359
RRPM:	295	275	257	244	232	222	213
Tip Mach:	0.55	0.52	0.48	0.46	0.44	0.42	0.40
Coefficient of Thrust:	0.0042	0.0050	0.0058	0.0066	0.0071	0.0077	0.0084
C_T/Sigma	0.069	0.0794	0.090	0.101	0.111	0.121	0.132

From Nick;

Dave,
As predicted, the HP drops as Ct/sigma rises to .12 If you keep running the Ct/sigma up, the power will start back up again.
Note that the 1 foot chord at Ct/sigma of .12 uses about 9% less power than any of the other cases use.

My reply;

All very interesting.

Nick, your statement [i]" As predicted, the HP drops as Ct/sigma rises to .12 If you keep running the Ct/sigma up, the power will start back up again.'[/i] is certainly not being questioned. However, you picked a specific chord size and this changed the chord from a variable to a constant.

For the fun and the knowledge, another comparison is made. The turquoise is the [Chord: = 2.5'] column in first chart above. The yellow column is the same as the turquoise except that the Blade Pitch has been changed to 13º. This 13º is the pitch in the second chart where the [C_T/Sigma] = 0.121.

The constants remain the same.

Blade Pitch:	8º	13º
Thrust:	4985#	4972#
Chord:	2.5'	2.5'
Horsepower:	394	260
RRPM:	229	150
Tip Mach:	0.43	0.28
Aspect Ratio:	8:1	8:1
Coefficient of Thrust:	0.0073	0.0135
Sigma:	0.159	0.159
C_T/Sigma	0.046	0.0847

This third chart shows that changing the chord from 1' to 2.5' drops the horsepower further, from the 358 hp in the second chart, to 260 hp.

This suggests that a low solidity ratio is good for existing helicopters, for a number of reasons. One is the utilization of centrifugal force.

However very, very early attempts at hovering, were best served by a very high solidity ratio, to work with their slower rotational speed. Of course, to keep the weight down they used cloth for the airfoils and guy wires for the strength.

It appears that future helicopters will move back toward the earlier ones in that they will have large chords and slower speeds. Of course, the cloth and guy wires will be replaced by composite construction.

Any thoughts?

Calculations re Constant Speed Slowed Rotors

The following looks at the blade's velocity; over the span of the blade, at eight azimuths, in hover and in fast cruise (250 kts).

It takes the equation L_nd = C_l* ((ρ * A_b * V_tan ^ ²) / 2) and then assumes that all the values on the right side of the equation are constants except for the Tangential Velocity [V_tan]. It then assumes that the distribution of Nondimensional Lift [L_nd] can be express by the distribution of the Tangential Velocity [V_tan], about the disk.

Drag is not considered; since it is assumed that there will be a close correlation between Lift and Drag.

This evaluation is based on the premise that the rotor(s) only provide lift. All forward propulsion is provided by the propulsor(s).

Only one rotor is considered, however it is obvious that two rotors will be require on the actual craft.

The following uses the Sikorsky XH-59A ABC specifications, modified for simplification;

The XH-59A had a tip speed [ΩR] of 450 fps in cruise and a tip speed of 650 fps and in hover. The rotor diameter is 36 ft, therefore the RRPM is 239. In this evaluation the tip speed of 450 fps will be used for both cruise and hover.

The targeted maximum forward velocity of the XH-59A was 250 kts = 288 mph = 422 fps. It will be used for cruise in this evaluation.

Unlike the XH-59A, no taper and no twist will be used for this evaluation.

There is no consideration for root cutout.

In Hover:

The square of rotational speed at the root [ΩR] is 0. The square of the rotational speed at the tip is 450² = 202,500. The mean speed will be √((0 + 202,500)/2) = 318 fps and it will be located at 318/450 = 0.71R.

This mean speed and radius will be common to all azimuths about the disk of the rotor.

In Maximum Cruise:

At 45º azimuth the speed will be = 299 fps at the root and 749 fps at the tip. From Access 'Tangential Velocity' Form. The square of the rotational speed at the root is [Ω0] 299² = 89,401. The square of the rotational speed at the tip is 749² = 561,001. The mean speed will be √((89,401 + 561,001)/2) = 570 fps and it will be located at 570 - 299 / ((570 - 299) + (749 - 570)) = 0.60R.

At 90º azimuth the speed will be = 422 fps at the root and 422 + 450 = 872 fps at the tip. The square of the rotational speed at the root is [Ω0] 422² = 178,084. The square of the rotational speed at the tip is 872² = 760,384. The mean speed will be √((178,084 + 760,384)/2) = 685 fps and it will be located at 685 - 422 / ((685 - 422 ) + (872 - 685)) = 0.58R.

At 135º azimuth the conditions will be the same as at 45º, therefore the mean speed will be 570 fps and it will be located at 0.60R.

At 180º azimuth the conditions will be the same as in hover, therefore the mean speed will be 318 fps and it will be located at 0.71R.

At 225º azimuth the location of zero velocity is at 0.66R. At 1.0R the velocity will be 152 fps. At 0.0R the velocity will be -299 fps. The square of the speed at 1.0R is 152²= 23,104. The square of the speed at 0.66R is 0 fps. The square of the speed at 0.0R is 299²= -89,401. The mean positive speed will be √((23,104)/2) = 107 fps and it will be located at 0.9R. Used the Access Form to determine location. The mean negative speed will be √((89,401)/2) = -211 fps and it will be located at 0.19R. Used the Access Form to determine location.

With a conventional blade the average speed will be 107 - 211 = -104 fps unless the blade can be feathered.

With an active twist blade the negative value in the area of reverse velocity will actually give positive lift but it should probably be reduced by approximately 50% because of inefficiency of a reverse velocity airfoil. I.e. (107 + (211/2)) / 2 = 106 fps.

At 270º azimuth the inner 16.87 ft of the blade's 18 ft radius will be in reverse velocity. At this azimuth the speed will be = 0 fps at 0.94R and -422 fps at the root. The square of the rotational speed at 0.94R is [Ω0] 0. The square of the rotational speed at the root is -422² = 178,084. The mean speed will be √((0 + 178,084) / 2) = -298 fps and it will be located at (298 / 422) / 0.94 = 0.75 from the root = 0.25R.

With a conventional blade this -298 fps would constitute negative lift unless the blade can be feathered.

With an active twist blade the negative value in the area of reverse velocity will actually give positive lift but it should probably be reduced by approximately 50% because of inefficiency of a reverse velocity airfoil. I.e. -(-298 * 2) = 149. The positive lift from the 1.13 ft at the tip will provide very little additional lift. √((298 + ) / 2) = 12 fps.

At 315º azimuth the conditions will be the same as at 225º, therefore the mean speed will be xxx fps and it will be located at 0.xxR.

At 360º azimuth the conditions will be the same as in hover, therefore the mean speed will be 318 fps and it will be located at 0.71R.

Conclusion:

In Hover:

The total average mean speed over the rotor is 315 fps

In Maximum Cruise:

With conventional blade: The total average mean speed over the rotor (assuming that the negative lift at 270º azimuth is feathered out) is 570 + 685 + 570 + 318 + 0 + 0 + 0 + 318 / 8 = 308 fps.

With active twist blade: If the reverse velocity is considered as lift, at 50% of its theoretical positive lift value then the total average mean speed over the rotor is 570 + 685 + 570 + 318 + 106 + 149 + 106 + 318 / 8 = 353 fps.

With conventional blade: at a fixed tip speed of 450 fps, the total average mean speed over the rotor in hover, is 315 / 308. ≈ 102% of the total average mean speed over the rotor in cruise.

With active twist blade: utilizing the reverse velocity (active twist blade) at a fixed tip speed of 450 fps, the total average mean speed over the rotor in hover, is 315 / 353 ≈ 89% of the total average mean speed over the rotor in cruise.

Summation;

The utilization of single speed slowed rotors appear to be slightly more efficient in hover than they are in forward flight. Assuming that this is correct, there appears to be no reason to have rotors turn faster during hover.
Line 1 may not be exactly true for the Sikorsky XH-59A ABC since the blades on this craft had taper and twist.
It will be interesting to hear what the rotor characteristics of the Sikorsky X2 ABC will be.

Addendum;

It appears that the efficiency in hover will probably be less than that of cruise when reverse velocity utilization is implemented on future rotorcraft.

However, the use of blades with an inverse taper may improve the lift in hover visa vie the lift in cruise because in hover the speed differential between the tip and the root will be greater; at least at 90º azimuth it will, at 180º and 360º it won't make any difference and at 270º it will ????????

In addition, the use of blades with positive twist may provide an improvement similar to that of inverse taper. A small positive twist should also improve autorotation. This positive twist would be implemented by the flight-control 'mixer box' that is controlling the active twist blades.

3 and probably 2 will not be valid. In hover a large negative twist will be preferred. In cruise it will be reduced on the advancing side and will be positive on the retreating side.

PPRuNe ~ December 6, 2006

It was mentioned by IFMU, in a different thread, that Sikorsky's new X2 coaxial ABC will have multiple-speed rotors, as did its predecessor, the XH-59A ABC.

However, the possibility of using single-speed, low-rpm rotors with wide chord blades (large solidity ratio) for tomorrow's high speed rotorcraft appears to have significant advantages.

Two bits of information have come to light while digging deeper into this subject.

1/ A cursory review of the technical papers on the XH-59A ABC show that the 'solidity ratio' is much used in the evaluation of many variables. However, I cannot find any place where the solidity ratio, itself, was evaluated as a variable.

2/ Stepniewski considers the rpm of the rotors as a variable in his conceptual Intermeshing ABC, but it appears that this evaluation was only to pick the optimum single-speed RPM.

Can anyone suggest one of more potentially viable reasons for using multiple-speed main rotors?

Autorotation:

The RRPM may be below that which is required to maintain autorotation in a conventional helicopter. However, due to the strength of the rotors and the active blade twist, the rotors can be placed in an authoritative state,
If for some reason the rotors were to reach a very slow RRPM and if the craft is at a sufficiently high elevation, it can be pitched forward and the extremely rigid rotors will allow the desired RRPM to be acquired. This is little different from a fixed wing.

Consideration of the Two-speed Rotor on the Sikorsky XH-59A ABC and its effect on opposing gyroscopic precession moments of the two rotors:

For blade element method, the centripetal force F acting on a body of mass M is given by the equation F = (Mv²)/r, where v is its velocity and r is the radius of its path. [F is in pounds], [M is in slugs (1 slug = 32.175 lbs)], [v² is in ft/sec.], [r is in feet].

Design rotor tip speeds;

650 ft/sec. in helicopter mode (hover)
450 ft/sec. in compound mode (cruise)

The square of the velocities at 450 ft/sec is 48% of what it is at 650 ft/sec Without looking furthere into gyroscopic precession, the preceeding probably means that the 450 ft/sec rotor will probably/possibly produce moments that are half of what they would be at 650 ft/sec. Look further into themoments created by the gyroscopic precession at some point in time.

Related Web Page - At this Site:

OTHER: Aerodynamics - General - Blade Loading Coefficient

OTHER: Aerodynamics - General - Solidity

Initially displayed with section on Calculations and Addendum: November 27, 2006 ~ Last Revised: August 18, 2008

The above utility invention is openly and publicly disclosed on the Internet to negate an entity from patenting it, to the exclusion of all others whom may wish to use it. ~ Reference patent law 35 U.S.C. 102 A person shall be entitled to a patent unless - (a) the invention was known ... by others in this country, ..., before the invention thereof by the applicant for patent.