Whatever happened to autogyros?

[billfish678]

@md2000

So what’s the design flaw with the RAF?
I see from Google Images that a large number don’t seem to have a horizontal stabiliser. DOes it (a) need one and (b) that should be in the prop flow?

Otherwise it looks like… a gyrocopter.

It should have one. It should have a big one. And it should be in the prop flow.

The big killer was/is not only that it doesnt have stabilizer, the thrust from the pusher engine/prop is WAY above the center of gravity and the thrust is fairly strong to boot.

So, what this means is that if you ever enter a low or zero G condition (like say a strong downdraft) even briefly, you flip over fowards in the nearly the blink of an eye. In a gyro that is virtually aways fatal. AFAIK only one foward flip has not been fatal in whole history of gyros. Most gyro fatalities have been forward flips. Which tells you plenty of gyros over the decades have been poorly designed.

A gyro with an inline thrust and a good stabilizier CANT do that.

Oh and the big cabin on the RAF doesnt help any either. The air drag on the cabin is also trying to flip the craft upside down or backwards.

If a good gyro is as stable as low slung 4 wheeled gocart, a stock RAF is more like a unicycle that kills you if you ever frack up (or even if you dont).

Note, I am not a pilot or gyro designer, but I have literally spent thousands of hours reading about and understanding these contraptions. I’ve also read, often more than once, every accident/incident report the FAA has on these things, and plenty more from other sources as well.

[Rocketeer]

@md2000

Wasn’t the “aircraft in a suitcase” in the James Bond film an autogyro?

Yes. “Little Nell”. There’s a pretty good Airfix kit of it.

[Elendil_s_Heir]

You can briefly see a larger one in the 1935 Hitchcock movie The Thirty-Nine Steps. One of the worst SFX ever, unfortunately.

[billfish678]

On the flip side, here is how SAFE gyro’s USED to be:

From “CIERVA AUTOGIROS” by Peter W. Brooks:

“This was the first Autogiro fatality*. Up to this time, more than 120 Autogiros had been built (including more than 30 prototypes), 30 to 40 pilots had been trained on them, and well over 100 pilots had flown Autogiros in the United States alone. About 35,000 hours had been flown over a total distance of about 2½ million miles. This represented a remarkable safety record. For comparison, General Aviation in the United States had an accident rate of about one fatal accident every 5,000 hours in 1939. This had improved to about one every 40,000 hours by 1969-a rate not attained by General Aviation in the United Kingdom until 1974. Autogiros were therefore remarkably safe during this early period, even while engaged in experimental and development flying, their safety record being comparable to General Aviation 40 years later.”

*Fatal crash of a C.L.10 in 1932.

[coremelt]

@billfish678

It should have one. It should have a big one. And it should be in the prop flow.

The big killer was/is not only that it doesnt have stabilizer, the thrust from the pusher engine/prop is WAY above the center of gravity and the thrust is fairly strong to boot.

So, what this means is that if you ever enter a low or zero G condition (like say a strong downdraft) even briefly, you flip over fowards in the nearly the blink of an eye. In a gyro that is virtually aways fatal. AFAIK only one foward flip has not been fatal in whole history of gyros. Most gyro fatalities have been forward flips. Which tells you plenty of gyros over the decades have been poorly designed.
.

Doesn’t the FAA or another body remove flight certification for a model with design flaws like this? Is there no oversight of gyrocopter designs?

[billfish678]

@coremelt

Doesn’t the FAA or another body remove flight certification for a model with design flaws like this? Is there no oversight of gyrocopter designs?

If its in the experimental/homebuilt/ultralight category pretty much anything goes in the USA.

Theorectically, I could come out with a design for something that flew, yet had dozens of design flaws that anybody who knew anything about flight or engineering would have a shit fit about.

I could then kill lots of unsuspecting customers by selling kits and plans. Eventually, I might be sued outa production, but not before I kill plenty of people with my stupidity.

[Johnny_L.A]

The BD-10 (not an autogyro) was deadly. Five were built, three crashed (all fatal).

[Hail_Ants]

I’m not a pilot but my brother is, private, fixed wing. But he also built his own gyro, a Benson.

The term for the so-called ‘flipping forward’ problem is called a power pushover and it is indeed 100% fatal. But as others have mentioned it’s due to a large percentage of gyros not having what’s called center-line thrust. The reason any are built w/o it is its a much simpler (and cheaper) design. To have center-line thrust the rotor mast has to be much taller and the pilot seat & controls must be higher, inline with the prop’s thrust.

A power pushover happens when the rotor blades become ‘unloaded’, that is when the aircraft flies nose-down for too long and the thrust of the engine slowly starts to exceed the drag of the rotor blades. As this happens the rotor becomes more horizontal to the direction of flight, causing less air flow across it, which in turn lets it slow down, which in turn causes the craft to lose lift and descend. However, the loss of drag from the rotor also means that the engine’s off center-line thrust becomes greater & greater because its no longer balanced by the drag from the unloaded rotor.

What happens next is that the aircraft suddenly begins to severely pitch nose-down, so the instinctive reaction (especially for fixed wing pilots) is to jerk the stick back. Unfortunately, what this does to a gyro in this state is it tilts the unloaded rotor blades back so far that they strike the tail. This immediately causes severe structural damage not only to the tail but, more importantly, to the rotor blades themselves, essentially destroying them. And since the rotor blades are a gyros ‘wings’ all lift is immediately lost and the damaged craft basically falls out of the sky.

The non-fatal way to correct for this is to cut the throttle so that the non-center-line thrust is reduced stopping the nose-forward pitching, and let the gyro enter a stable descent so that more air flows past the rotor and allows it to gain RPMs and lift. This lets the craft return to normal flight. Provided, of course, you have sufficient altitude (even if you don’t there’s no other choice but to do this!)

Of course, the real method is to not ever let the rotor become unloaded!

The real reason this is a problem at all is because all modern gyros are pushers. Originally the first autogyros were pullers. They were essentially planes with the wings removed and a rotor mast & blades affixed to the fuselage. A puller gyro cannot ever suffer a power pushover. However, a pusher configuration is inherently much smaller and simpler.

[Nava]

@'[Undecided

Adrian;12181501’]Nava, I’m not aware of any Sikorsky autogyros, Sikorsky mostly manufactures heavy helicopters.

I thought they had some giros, but none of their current models is one. I guess it’s not really worth it to try and look for old ones, so I stand corrected.

[coremelt]

The Groen Brothers website seems to make a good case for using “Gyrodynes” instead of regional jets, for one thing the VTOL capability would eliminate runway waits entirely. Seems like it it would make a lot of sense for short hops.

http://www.groenbros.com/commercial.php

Given the chronic lack of runway space at most airports, what’s stopping this happening?

[Bosda_Di_Chi_of_Tricor]

Whatever happened to autogyros?

They’re hiding.
Look under the sofa cushions.

Dibs on any Monocycles you find there.

[billfish678]

@Hail_Ants

What happens next is that the aircraft suddenly begins to severely pitch nose-down, so the instinctive reaction (especially for fixed wing pilots) is to jerk the stick back. Unfortunately, what this does to a gyro in this state is it tilts the unloaded rotor blades back so far that they strike the tail. This immediately causes severe structural damage not only to the tail but, more importantly, to the rotor blades themselves, essentially destroying them. And since the rotor blades are a gyros ‘wings’ all lift is immediately lost and the damaged craft basically falls out of the sky.

The non-fatal way to correct for this is to cut the throttle so that the non-center-line thrust is reduced stopping the nose-forward pitching, and let the gyro enter a stable descent so that more air flows past the rotor and allows it to gain RPMs and lift. This lets the craft return to normal flight. Provided, of course, you have sufficient altitude (even if you don’t there’s no other choice but to do this!)

.

In something like a high thrustline RAF, once you are in zero G, the thing will do IIRC a 180 (90?) forward flip in about 2 seconds. And obviously a decent number of degrees in MUCH less than that time. I don’t know how many degrees you need to flip foward before it becomes unrecoverable, but I imagine its more like 45degrees and possibly significantly less. Also, if you go the shut the engine off route to save the day, thrust does not got to zero instantly.

Put those together in combination with the non-zero reaction time even a near superhuman would be capable of and its a recipe for disaster. If the flip is fast, or the pilot a bit slow, its gonna be over before the pilot can even begin to cut the thrust or move the stick appropriately. Its the aerodynamical equivalent of being a sprinter waiting for a long and unknown period of time for the starting gun to fire. Thats okay for test pilots WHEN necessary. Its totally unacceptable for general/recreational flight.

There is NO good excuse for something like an RAF.

About 250 of em are registered in the US. Apparently they are also mechanical POS so a good fraction probably arent even flying on a regular basis. About 50 of em have already crashed, and a decent fraction of those have been fatalities. A similar number of something like Cessnas or even “normal” helicopters flown a similiar number of hours would have crash and burn rate a tiny fraction of that.

And I’d check your brothers Benson. IIRC some of those models had inadequate stabilizers and unacceptably high thrust lines.

[billfish678]

@coremelt

The Groen Brothers website seems to make a good case for using “Gyrodynes” instead of regional jets, for one thing the VTOL capability would eliminate runway waits entirely. Seems like it it would make a lot of sense for short hops.

http://www.groenbros.com/commercial.php

Given the chronic lack of runway space at most airports, what’s stopping this happening?

Not sure that lack of runway space is really a problem. Either the runway is long enough or it isnt. Now, how BUSY it is different story.

Now, if you want to talk about making NEW airports to be used, something that has a very short or zero take off roll would help immensely. And for shorter flights to a “real” airport or hops to other small airports would or could make sense.

IMO the Groens face two uphill battles. It won’t be cheap(er) until they build alot of em. But they won’t get alot of orders until they are cheap(er).

Also, they are nearly in direct competion with helicopters. Decades and trillions of dollars have been invested making those things better, faster, cheaper, and more reliable. Even assuming that the Groen craft is inherently cheaper to buy,more reliable, and cheaper to operate in theory than a helicopter, thats alot of time and research money to make up for.

[Johnny_L.A]

@Hail_Ants

Of course, the real method is to not ever let the rotor become unloaded!

This is an issue in helicopters with semi-rigid rotors, too; like Robinsons and many/most Bells. It got so bad that the FAA mandated special training for Robinson pilots. (Only Robinson pilots. They tend to be low-time, and often come from fixed-wings and have developed habits that can lead to a negative-g situation. Turbine pilots tend to have the experience to avoid low-g.)