1544

Item 1544

DESIGN: UniCopter ~ Vibration - Rotor Induced - Control - High Frequency Modifiable Tip Control

Objective:

A means of minimizing the blade vibration at the blade (at the source).

A means of rapidly and momentarily increasing, or decreasing, the lift and/or drag on the rotor blade.

Possibly a two position (fixed amplitude) motion.

A variable high rate pulse modulation.

Increased lift is achieved by having an extendable projection reduce the amount of tip loss ~ or ~ by morphing the tips angle of attack.

To utilize Lift Overshoot. (see; Vertiflite, Winter 2001 ~ 'Dynamic Lift', p. 30, by Prouty.) and Adaptive Airfoil Dynamic Stall Control

Aerodynamically Variable Tip

The center of the torque-tube on the OTHER: Rotor Concept - Independent Root & Tip - Torque Tube Method has a passage from root to tip. This passage could be used to;

Run electrical wires. [electrical]
Insert a rod [mechanical]
Explosive pulses, sonic shock wave [aerodynamical]

Which causes the tip to change its lift (and drag) at a very high rate, perhaps by a 2-position action.

Notes:

The 'click' must directly change the aerodynamics of the tip, not change a 'flap etc.' which in turn changes the aerodynamics of the tip.

Have not looked deeply into existing patents.

Assuming that the extension curls up or down, its effect will be different when the blade is pointing forward or aft. In other words the azimuth and the forward velosity of the craft will both effect the the amount of lift and drag. Develop this further.

Idea A:

The tip weight is part of the actual blade. A mini very light-weight bladelet pivots a few degrees about the feathering axis. The 'click', which changes the pitch of the bladelet in respect to the pitch of the blade-tip must react off the tip end of the blade. By putting the mass(inertia) in the tip end of the blade it is the bladelet that will re-orientate, with little effect on the tip end of the blade.

Idea B:

The bladelet extends out and up, or out and down, just like a mini winglet.

Idea C:

This consists of a non-movable modification to the blade tip. It therefore does not truly belong under the heading of this page.

The objective of this idea is not one of offsetting the vibration at the blade, before it gets to the hub. It's intent is to minimize tip vortices generated by the blades so that proceeding blades do not have to pass through or near any tip vortices.

The advancing edge of the blade's tip is curled up slightly.
The trailing edge of the blade's tip is curled down slightly.
The intent is that this will attempt to rotate a portion of the air in the opposite direction from that which a tip vortex wants to rotate.

This method may not experience the loads and stress mentioned by Prouty below because the twist is not anhedral or dihedral. Then again, during cruise, when the blade is near 180º azimuth it might want to impart a positive pitch to the blade and when the blade is near 360º azimuth it might want to impart a negative pitch to the blade. This might assist with speed stability or be compensated for by the flight-controls.

The angle of attack at the locations of highest and lowest pitch can probably exceed ⁺/_- 15º by a large amount. This is because the double curvature shape will result in 3D airflow. Composite construction provides the opportunity to have double curvatures.

Very high forward velocity combined with a slowed rotor rpm will result in the airflow crossing the blade, when it is near 0º and 180º azimuth, at a angle that is approaching 45º to the chordline.

Related Information:

See article in Vertiflite, Winter 2003, page 16, ~ Prouty. He mentions that the S92, RAH-66 Comanche, EH-101 and the newer Lynx have tip anhedral and it can account for 2% to 4% increase in the Figure of Merit. However, he also mentions that there is indication that it produces higher control loads and blade stress in forward flight.

From PPRuNe, Gael Warning ~ I recall reading a paper written some years ago by the RAF at Bedford regarding the BERP and trailing edge swept down technique. The results if memory serves were pretty conclusive regarding control loading, and do seem to be borne out by in service operations, at least on EH101. Basically during the trial, various abrasives were attached to the outer 25% on the blade leading edge, everything from course sand to sea salt etc. The results showed that the finer the abrasive, the more pronounced the effect. The effect was that with abrasive build up, e.g. flying over the sea, the effect on the blade tip increased load on the pitch control mechanism to the extent that in some cases, the pitch control rods were at maximum stress loading at only 40% of aircraft max forward speed. This resulted in the aircraft chewing pitch change rod bearings like you can't believe.

Also see; DESIGN: UniCopter ~ Vibration - Rotor Induced - Control - Embeded High Frequency Leading + Trailing Edge Flaps

Related Patents:

Search; ["tip vortex" AND helicopter]. 64 hits. I only did cursory look, so far.

7,100,875 ~ Apparatus and method for the control of trailing wake flows

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Initially displayed: January 26, 2007 ~ Last Revised: February 4, 2007

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.