Curious, what is the load limit of an 8.8 bolt? If that is where the separation occurred.
Gyros have some safety advantages over FW planes. We all know the safety DISadvantages, and they are significant.
But one safety advantage is that the rotor and its attachments to the aircraft can easily be made so ridiculously strong that (unlike FW planes) it's essentially impossible to "pull the wings off" in flight. This has been true from Bensen on down to the present.
By actual tests (published in the print PRA magazine over the years), the 3/8" AN pivot and teeter bolts used in a Bensen-pattern rotor head have a shear strength in the neighborhood of 10,000 pounds. The 1/2" spindle bolt has a tensile strength in the 30,000-40,000 lb. range.
Moving downhill to the cheek plates, each 1/4" AN bolt has a shear strength in the 4,000 pound neighborhood. There are typically four of them sharing the shear load.
Again going back to Bensen, the mast is 2 x 2 x .125 square 6061-T6. The 1/4" cheek plate bolt holes reduce the cross-sectional area to 0.8125 sq. in. If you take the tensile strength of 6061-T6 conservatively as 35 KPSI, then the mast has a tensile strength of 28,000 lb. That's 14 TONS, folks.
Of course, the mast endures some bending, it's subject to cyclic loading leading to fatigue, it's extruded (a pretty crude way to make tubing), etc. But it's still vastly stronger than it needs to be to endure flight loads. No comment on ground-blade strikes.
At the same time, we have a rotor that is incapable of pulling big G's. This is unlike a fixed wing, which will make any amount of lift you ask it to if you jam it through the air fast enough and impose a large angle of attack on it (say, 10 degrees). Again by actual test, gyro rotors seem to be able to produce 4-4.5 G's of lift for short durations if you really horse them about. That load level is of the same order of magnitude as the strength of the rotor's attachment structure for most gyros (although the 3/4-ton enclosed Subaru jobs probably should use 1/2" teeter and pivot bolts, and/or avoid doing loops).
When rotor heads and masts have failed in flight, it has been because of fabrication or assembly errors. The spindle of a Bensen spindle head needed to have smooth radii at the transitions of diameter, or it will break at the sharp corners. Defective 2x2 extrusions can come apart. Deep scratches in mast tubing can render it unsafe. Rotor head pivot designs that put bending loads, in addition to shear, on the 3/8" gimbal bolts can cause failure at ordinary load levels. Forgotten hardware, upside-down bearings, and the like can be deadly.
I'd look for that kind of thing, not pulling G's, in connection with a loss-of-rotor-head accident.
BTW, possibly relevant to Vance's chat with his engineering friend, there are some holes in our knowledge of autorotating rotors, especially teetering ones. Back when NACA was testing gyro rotors in the 1930's, AFAIK they did not look at decay rates at zero disk AOA, the possibility of recovering RRPM after a reduction, or any aspect of rotor behavior at negative disk angles of attack. And they did not investigate teetering gyro rotors at all, because teetering rotors hadn't been invented yet. Once teetering rotors WERE invented, autogyros had been deemed by the rotorcraft community to be obsolete, so no research on teetering gyros happened then, either.
We ARE the research.
"I have flown zero hours in single seat gyroplanes and I have no desire to fly them either so far."Not sure what the point of listing all that personal experience was honestly in this context. I appreciate your personal flying experience but I am not getting your point of listing it all out here specifically.
I know 13 fixed wing pilots right here in Tampa Bay who have died in my 16 years of flying. What does that mean? Absolutely nothing as far as I can tell. One just went down in the water today here in Tampa and was thankfully saved. This has nothing to do with a logical point(s). Rotorcraft having limp wings when the rotor RPM is slow where fixed wings have fixed rigid wings and thus they are different and require different training.
I have flown zero hours in single seat gyroplanes and I have no desire to fly them either so far. The older single seat ones I would not touch with a 20 foot pole. Yes I have heard they are so maneuverable. If I wanted to do aerobatics I'd fly an airplane and I do. But again what does that have to do with any points you or me were making.
I am simply saying that rotorcraft have to be handled like rotorcraft. Trikes like trikes and airplanes like airplanes. Trying to fly one like the other and we shall not see very good results. That point is as simple and plain as it can be. My thousands of hours in trikes did not do jack for me hands on in gyroplanes and they won't for anyone else either.
"I have flown zero hours in single seat gyroplanes and I have no desire to fly them either so far."
I have never once in all my time meeting other gyro enthusiasts who were bitten by the "gyro bug" met anyone who didn't want to try as many different kinds of gyros as they could.
As a manufacturer it would seem to me to be a simple matter of market research to try and learn what all my competitions good and bad points might be as long as the aircraft was safe.
I dunno, this just seems "off" to me. Maybe I'm reading too much into it.
I was referring to more modern versions like the Dominators, Sportcopters and Honeybees or a Butterfly or possibly a Genesis or a Gyrothecnic, there are plenty of singles out there that are safe and some have marvelous designs.
I haven't flown an AR-1 and doubt I will get the opportunity, but have flown lots of other dreadnought class ships and it almost always seems to me that when they are built to be nimble and Lithe they are more fun to fly. But if you have not experienced the flight in a small nimble light Gyro, you perhaps don't know what your missing, does this translate over to the design of your rig? I have no idea.
I will compare it to motorcycles though, would you rather be on a CBR 900rr for an afternoon of fun or a Goldwing?
On another note between all the posts relating to training and experience, I submit that I am an unusual case in that I learned to fly in Gyros and transitioned to fixed wings years later. When I am in the pattern in a fixed wing, I am always just slightly apprehensive about stalls, but never am I apprehensive about maneuvers in my gyro. I suspect that a lot of fixed wingers converting over to Gyros are apprehensive about the maneuvers in Gyros and not about the Stalls in their fixed wings planes.
If the first time you are introduced to a 1911 it has a flat mainspring housing, then you will always prefer flat, if its an arched one, you will always gravitate towards the arched ones....
Dave, I guess it depends on the job you want to do in the air. I Flew my Single seat open Lightning from Mexico to Nevada and it was an awesome adventure. It would have been a ho hum flight in a Beechcraft or Mooney.Ben,
I am fixed wing pilot that converted over to gyro then back to fixed wing. I still feel safer flying the gyro over fixed wing in windy conditions, but fixed wing bush plane is more versatile and practical. Most likely will convert back to gyro again.
Nope. AirCam is not a chick magnet but it’s a nice thoughtEven though this thread has wandered, it's a great discussion. It's all about the mission! I switched from FW to gyro, and back to my FW Aircam amphibian. My mission required a twin engine aircraft for plans to fly extensively low level and over water, short field landing and takeoff and have the fun of an open cockpit, and payload to pack stuff. In many ways the type of flying I do is similar to a gyro, and stalls, even on one engine, are incredibly docile. In addition as a friend commented the other day, with my paint scheme it could also possibly be a chick magnet.
On windy days, and turbulent air, I still miss the gyro, that's why one airplane is never enough.