0424

Item 0424

OTHER: Helicopter - Inside - Single Rotor - Rotor X Wing - Flight-Control

Overview:

The following rough material is specific to a theoretical Advanced Method of Implmenting Traversing Twist. It does not incorporate the use of Independent Root & Tip control. It may be totally impossible to build at this time.

For a method that is possible at this time see Simplistic Method of Implementing Traversing Twist

Drawing:

Change the number of this drawing

Qualifier:

The following does not consider angle of attack or collective settings. These might be incorporated into the web page at some later date.

Blade Root Activity at All mu Values:

The root experiences both forward and reverse velocity.

The root of the blade (r = 0) oscillates at the same rate as the rotation of the rotor. In other words; the theoretical leading edge is pointing forward (in respect to the craft) when the blade is at 90º azimuth, it is pointing up when it is at 180º azimuth, it is pointing aft when it is at 270º azimuth and it is pointing up when it is at 0º azimuth.

Blade Tip Activity at all mu Values:

The blade oscillates about its feathering axes, at a rate of once per revolution.
The oscillation characteristics at the tip of the blade is independent from the oscillation characteristics at the root of the blade. In other words, the blades are capable of a large amount of active twist.
The tip of the blade oscillates about its feathering axis with characteristics that fluctuates through the oscillation.
The twist of the blade varies and is dependent upon the difference between the root pitch and the tip pitch.. This means that there will be different amounts of twist at different azimuths.

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Blade Tip Activity at mu < 1:

The tip experiences only forward velocity.
The pitch of the tip varies between 0º and < 90º.

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Blade Tip Activity at mu = 1:

The tip experiences only forward velocity, except for azimuth 270º where there is momentary zero velocity.
The pitch of the tip varies between 0º and 90º.

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Blade Tip Activity at mu > 1:

The tip experiences both forward and reverse velocity.
The pitch of the tip varies between 0º and up to 180º.
The blade oscillates about its feathering axes, at a rate of once per revolution.
For example; In the above drawing, at mu = 2, the pitch of the blade tip will be 90º (blade pointing up) at 210º azimuth, 180º at 270º azimuth and 90º at 330º azimuth.

Symbol:		Name	Definition	Unit(s)


	r	r	Radius at blade element	ft

	R	R	Rotor radius	ft
	V	V	Remote velocity, Free stream velocity	ft/sec, knots

	θ	theta	Blade pitch in reference to azimuth about pitch axis; 0 being in the plane of the tip path in a CCW direction or rotor rotation.	radian, degree
	θ_A	thetaA	Blade pitch as per above except at angle of airflow that is at an angle to the chord.	radian, degree
	θ₀	theta0	Collective pitch angle	radian, degree
	θ_T	thetaT	Blade tip pitch angle	radian, degree
	Θ_R	thetaR	Blade root pitch angle	radian, degree
	θ₁	theta1	Blade twist	radian, degree
	θ_1A	theta1A	Active Blade Twist	radian, degree	mine

	φ	phi	Phase angle	degrees
	ψ	psi	Azimuth position of blade (cylindrical coordinate) (0º aft)	radian, degree

	Ω	Omega	Rotational speed of rotor	radian/second
	ΩR	OmegaR	Tip speed of rotor	ft/sec

The following only considers the single rotor configuration; at this time.

Blade Pitch:

HOVER

CRUSE

315º

225º

135º

45º

315º

225º

135º

45º

Coll. Up

Coll. Dn

Pitch Up

Pitch Dn

Roll L

Roll R

By propeller

Yaw

By rudder

Notes re Above Sketch:

Blade Pitch; [θ] The blade pitch is 0º when it is in the plane of the tip path and the leading edge is oriented for CCW rotation. Increasing the pitch take the blade's pitch in the positive direction. When the blade is rotated so that it is in the plane of the tip path but the leading edge is oriented for CW rotation the pitch is 180º.

During hover the rotor is turning at its maximum speed. During cruise the rotor is not turning.

The Collective and the Roll activities switch between hover and cruise.

Sikorsky had a prototype with a tail rotor that pivoted.

In cruise at a theoretical mu near infinity the root pitch and the tip pitch will be identical ???

Activities During Transition from Hover to Cruise:

Assuming that the craft is a Very Light Rotor 600 Kg, with similarities to the UniCopter.

The following are all guestimates as to the transition from hover to cruise..

Forward Velocity:	Rotor Speed:	Tip Speed:	Advance Ratio:	Comments:
0 kts	550 rpm	447 fps	0.00	Hover
40 kts	550 rpm**	447 fps**	0.15**	Slow flight.
80 kts *	550 rpm**	447 fps**	0.30**	Transition to cruise.
80 kts *	166 rpm	135 fps	1.00	Blade is totally in reverse airflow at 270º ψ
80 kts *	?? rpm	?? fps	??	Rotation of blades; Root 180º ψ, Tip 190º ψ ?
80 kts	0 rpm	0 fps	infinity	Blades no longer rotate.
200 kts	0 rpm	0 fps	infinity	Cruise

* The question of interest is; What is the minimum safe forward velocity that allows the retreating side to support half the craft's gross weight during the transitions between hover (rotor) and cruise (wing)?

** Does the rotor's rotation start slowing in this forward speed range? What are the pros and cons?

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Initially displayed: February 27, 2007 ~ Last Revision: March 7, 2007

The above application of reverse velocity utilization In the main rotor(s) of a helicopter 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.