Cierva C-30 CG

[C. Beaty]

Here’s a drawing from “The Autogiro and how to fly it” by Reginald Brie that clearly shows the CG/propeller thrustline relationship of the Cierva C-30. The CG is several inches above the propeller thrust line.

Dr. Houston at the University of Glasgow, using a complex computer program developed in part by NASA, “proved” Cierva was right.

Poor Cierva had to do his bit with nothing more than pencil, paper and slide rule.

[John Stahl]

why aren't ther more tractors flying today?

[C. Beaty]

Structural complexity.

Flying lawnchairs that follow the Bensen format of 3 aluminum tubes bolted together don’t require engineering talent and go together quickly.

[quadrirotor]

The gyroplanes De La Cierva were so complex, and not so efficient, that any Sykorsky helicopter was simpler and above all, more versatile!!!

[Ga6riel]

anyone that thinks helicopters and efficient fit within the same sentence has been smoking the wrong products.

It is entirely possible to develop a tractor type that just rearranges the same materials, hell there is already someone apparently flying a Benson type backwards anyway. The thing is this, someone has to do it first.

Hi Chuck, gentlemen

Re. your start item, Chuck. I'm afraid NASA had nothing to do with the sim. model - that's all my own work. I've taken a lot of flak in the UK from the gyro community who see the simulation model as no proof of reality, yet the source of much of their current ills. Wouldn't want NASA tarred with my brush!

The NASA contribution is actually a NASA/US Army one - although they've had no direct involvement. Dr. Mark Tischler of the Aeroflightdynamics Directorate pioneered the flight test techniques that I used to validate the sim. model. The UK CAA paid to develop all the data. It's fair to say that without Mark's techniques, validation would have been much, much more difficult.

In terms of who's figured out what, I've an article of Chuck's from many years ago (can't recollect the source but I'll find it when I go back into work) where he espouses CLT for stability, but I don't think the Cierva stuff is mentioned, so probably hadn't come to light then. In a contemporary context then any credit's due to Chuck, not me. I just did some math and had a ball in flight test. I reckon the credit's Chuck's - I don't think Cierva could fully comprehend CLT in the context of static & dynamic stability.

[Udi]

I have an observation and a question re C-30.

The engine is tilted nose down to get the thrust line to within a few inches of the CG. However, the prop thrust line is hitting the horizontal stabilizer from below – making it a lifting surface. It appears the nose down pitching moment created by the lifting stab may be designed to cancel out the nose up pitching moment created by the low thrust line.

Question - If the H stabilizer has a positive AOA vs. flight path, wouldn't that make the airframe airspeed unstable?

Udi

[Mike Jackson]

I'm thinkin' that maybe with helical type flow impinging on the HS, the H tail might be seeing a positive or negative AOA prop contribution on one half and possibly the opposite on the other side of the stab - Possibly even causing causing a roll moment just like a vertical tail can cause roll off.

Even though the prop looks like a positive AOA contributor, the overall flow sum may still be negative.

Even though the tail might be at a positive AOA it still contributes to the dynamic stability of the airframe - CMq - change in pitching moment due to pitch rate (gust stability). It is the relative change in AOA, whether positive or negative which will dampen the airframe IMO.

Might be instructive to tuft this tail if we could find a flying example.

[C. Beaty]

I think, Stewart, it is intuitive to apply propulsive force in line with the center of mass. Our Bronze Age ancestors wouldn’t have hitched the ox to the side of the cart.

Cierva mentions in his 1930 patent application for centerline thrust that fixed wing aircraft traditionally had the CG slightly above the propeller thrust line for reasons of stability. It is my inference that he meant static stability.

Sorry about the NACA blunder.

[C. Beaty]

I Imagine, Udi, that horizontal tailplane incidence was determined by a by gosh and by guess procedure.

The left tailplane used an inverted airfoil for propeller torque balance.

The drawing is from the above mentioned book.

[Ga6riel]

just 2 trivial things
the negative incidence appears on the port side, which is different to the CL 20 dwg of the Westland machine that can be found in my pic file. No doubt due to the opposite rotation of the prop.

C-30's seem to travel with considerable nose up attitude, Im thinking, is this to do with the nature of the arrangement, or because the airctaft was formated for a photograph.

[karlbamforth]

[ I've taken a lot of flak in the UK from the gyro community who see the simulation model as no proof of reality, yet the source of much of their current ills.

Stewart,

I may not have spoken up before, but I think the research was long overdue. It has done a lot to improve the understanding of gyro aerodynamics, and believe will (already has) reduce the dangers of operating one. I hope that funding will continue as I think we still have more to learn.
Don't be too put off by the non believers, some ppl on this ball of rock still think its flat.
Is your research published in full on a website anywhere?