Gyrocopter Aerodynamics - Page 26

mnowell129 · Feb 28, 2009, 09:07 PM

The Art of the Helicopter, by John Watkinson
Elsevier Butterworth-Heinemann, London, 2004
p. 349

Quote:

The cyclic control requirements of the helicopter and the gyroplane are identical. As was seen in Chapter 4, the tilting hub with flapping hinges gives exactly the same cyclic control as a hingeless head with feathering hinges and a swashplate.

p. 350

Quote:

The upward inflow of the gyroplane suggests a rather different rotor design to that of the helicopter. The blade twist should be reversed compared to that of the helicopter, i.e. the root should have less pitch than the tip, although the amount of twist needed is smaller. In practice, many gyroplanes are built with no twist at all, for economy.

PeterO_UK · Mar 01, 2009, 04:12 AM

Micky,

I'm not quite sure what the second quote means. For example it could mean....

1) Tip has positive pitch and the root has less positive pitch
or
2) Tip has positive pitch and the root has negative pitch
or
3) Tip has zero pitch and the root has negative pitch.

All those examples could have the same twist on the blade, so I guess it comes down to what is the average (collective?) pitch ?

PeterO_UK

mnowell129 · Mar 01, 2009, 08:29 AM

The blade will generally have positive pitch with respect to the local airflow. But this is not the same as pitch with respect to the rotor shaft. A blade with negative pitch with respect to the rotor shaft can and will have positive pitch with respect to the local airflow. The point of the quote is that the blades will benefit from twist with the root being less than the tip, regardless of what the tip setting is compared to some fixed reference like the shaft.

akelelias · May 28, 2009, 02:31 PM

I still don't understand how forward motion keep spinning the blade and create lift.

bikerestorer · Jun 07, 2009, 05:07 AM

delete me

May 28, 2009, 02:31 PM	#379
akelelias Registered User Join Date: May 2006 Location: Fort Worth Posts: 101	I still don't understand how forward motion keep spinning the blade and create lift. Last edited by akelelias; May 28, 2009 at 02:38 PM.

Jun 07, 2009, 05:07 AM	#380
bikerestorer Registered User Join Date: Jun 2009 Posts: 1	delete me Last edited by bikerestorer; Jun 07, 2009 at 04:36 PM. Reason: read stiky

Mar 01, 2009, 04:12 AM	#377
PeterO_UK Registered User Join Date: Aug 2006 Posts: 1,374	Micky, I'm not quite sure what the second quote means. For example it could mean.... 1) Tip has positive pitch and the root has less positive pitch or 2) Tip has positive pitch and the root has negative pitch or 3) Tip has zero pitch and the root has negative pitch. All those examples could have the same twist on the blade, so I guess it comes down to what is the average (collective?) pitch ? PeterO_UK

Mar 01, 2009, 08:29 AM	#378
mnowell129 Registered User Join Date: Nov 2004 Posts: 1,867	The blade will generally have positive pitch with respect to the local airflow. But this is not the same as pitch with respect to the rotor shaft. A blade with negative pitch with respect to the rotor shaft can and will have positive pitch with respect to the local airflow. The point of the quote is that the blades will benefit from twist with the root being less than the tip, regardless of what the tip setting is compared to some fixed reference like the shaft.