Item 1215

OTHER: Flight Dynamics - Control - Comparative Cyclic Generated Moments

Objective:

To compare the pitch (or roll) moments generated by different rotor types.

Common Criteria:

Input pitch (control plane) (βC) = 10º

Thrust (T) = 1,000 lbs.

Disk radius = 10

Centrifugal Force (per side) = 8,000 lbs.

Drawing:

REQUIRED CHANGE in 'D' above;

T should be 500 and the '7' remains plus a second T of 500 should be added directly above the CG

, or T remains at 1000 and '7' changed to '3.5'.

 

Sketch:

Rotor Type:

 

A

Teetering Rotor

 

B

Articulated Rotor

 

C

Teetering (or CVJ) Rotor with Hub Spring

 

D

Absolutely Rigid Rotor

Moments:

A

B

C

D

1,000 x 1.74 = 1,740

1,000 x 0.97 = 970

 

7 x cos(36º) x 1,000 x 0.5 = 2,831

 

8,000 x sin (Beta) x 2 = 2,778

 

~or~ 3.5 x cos(36º) x 1,000 = 2,831

Total: = 1,740

Total: = 3,748 (1)

Total will be between value for A and D, depending on the strength of the spring.

Total: = 2,831 (2)

 

  1. Offset is exceptionally large.
  2. This is based on a rotor with 4 blades. The blade that is pointing in the direction of tilt has transferred all of its thrust to the blade pointing away from the tilt. The location of thrust on this blade is at 70% of R, which is the mean thrust location of a tapered and twisted blade. This blade will be providing 50% of the total thrust and the remaining two blades will be providing 25% each of the thrust. In other words, the center of thrust will have a nondimensional arm length of 3.5

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UniCopter ~ Trim, Stability & Control - Musings on Trim

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Last Revised: October 12, 2006