1219

Item 1219

DESIGN: UniCopter ~ Rotor - Disk - Longitudinal Dissymmetry of Lift (& Drag?) - 4-blade Rotors

Overview:

Evaluation of the oscillating pitching moments with two 4-blade rotors caused by any dissymmetry of lift.

There is insufficient clearance between the blades for sufficient pitch to be put in them, particularly at the location where the chord is greatest. See the rotor in the lower left-hand corner of the actual drawing 0854.dc. This may not be a problem if the lower blades are advancing and the blades have Active Blade Twist. This will allow for high root pitch when the blade is advancing and zero or negative root pitch when it is retreating over top of the advancing blades.

Drawing of Longitudinal Moment Arms of a Single Rotor:

Helicopter is flying up the page

Criteria:

Direction of rotation is outside forward.

Calculated values are; Moment Arm x Nbr. of Blades x Square of Tangential Velocity.

No consideration given for secondary factors affecting lift distribution such as angle-of-attack etc. Note that in forward flight the greatest blade pitch will be at (or very close to) azimuth 0º

FORM: Lateral Dissymmetry ~ UniCopter

Rotational speed is 480 rpm

75% of radius is 7'-0"

Rotational velocity at 75% R is 352 ft/sec

Air speeds are 0, 50 mph (73 ft/sec), 100 mph (147 ft/sec), and 150 mph (220 ft/sec).

The above values may change during development but the equality of symmetry should hold.

Calculations:

Hover:

	Front of Craft:		Rear of Craft:
Retreating blades:	53 x 1 x 352²	6,567	53 x 1 x 352²	6,567
Advancing blades:	53 x 1 x 352²	6,567	53 x 1 x 352²	6,567
Totals:		13,134		13,134

Equal

Airspeed = 50 mph:

	Front of Craft:	Rear of Craft:
Retreating blades:
Advancing blades:
Totals:

Equal

Airspeed = 100 mph:

	Front of Craft:		Rear of Craft:
Retreating blades:	53 x 1 x 248²	3,260	53 x 1 x 248²	3,260
Advancing blades:	53 x 1 x 456²	11,021	53 x 1 x 456²	11,021
Totals:		14,281		14,281

Equal

Airspeed = 150 mph:

	Front of Craft:	Rear of Craft:
Retreating blades:
Advancing blades:
Totals:

Equal

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Last Revised: January 22, 2004