Critical Failure of Components.

[Early Bird Dave]

Every manufactured gyro has some weak spot. Try and research/talk with other owners about what they have found out that needed replacement or redesign to make safer.
Example was the aluminum cyclic which many pilots do not feel is safe.
Fly safe.

 

[Jazzenjohn]

You can certainly solve the broken stick by replacing it with steel, but I don't believe a stick made from aluminum is the real fault here, nor do I believe it is too thin. The stick has two problems, where it goes into the thick aluminum round pivot piece there is no graduation in strength. The bottom piece should be taller and then tapered in thickness so it spreads the load to the thinner stick, or the stick should have an inner piece to spread the load. By having a very thick piece with an abrupt strength difference the stress is concentrated exactly at the point where the thin stick meets the thick pivot, and exactly where the hole was drilled. The hole shouldn't be anywhere near there at all. Run the wires up from the bottom , or wrap it around the stick, or lastly drill the hole through the thick piece or several inches up from the connection. Automatically making things thicker or out of stronger materials works, but costs in weight and moves the failure point to another spot.

 

[Redbaron]

well said john!

You can certainly solve the broken stick by replacing it with steel, but I don't believe a stick made from aluminum is the real fault here, nor do I believe it is too thin. The stick has two problems, where it goes into the thick aluminum round pivot piece there is no graduation in strength. The bottom piece should be taller and then tapered in thickness so it spreads the load to the thinner stick, or the stick should have an inner piece to spread the load. By having a very thick piece with an abrupt strength difference the stress is concentrated exactly at the point where the thin stick meets the thick pivot, and exactly where the hole was drilled. The hole shouldn't be anywhere near there at all. Run the wires up from the bottom , or wrap it around the stick, or lastly drill the hole through the thick piece or several inches up from the connection. Automatically making things thicker or out of stronger materials works, but costs in weight and moves the failure point to another spot.

 

[anthom]

Very good suggestions regarding this topic. But now I'm a bit confused.

Gyrodude in post #20 also had the stick break off during a take off run. That was an aluminum stick as well. Now that is too much of a coincidence.

Both failures were obviously due to material failure. Also, should not the load be transmitted from the thin stick to the thicker base? IOW, the loads are generated by the hand movements on the cyclic. In my case, there was also a hole drilled at the base, which would have certainly weakened the material further. I believe that material like steel with a higher yield strength than aluminum for an identical thickness should not fail, like the aluminum did in Gyrodude's and my cases. The increased weight is a trade off for increased safety I feel.

Thank you,

Antony Thomas

 

[Jazzenjohn]

I don't believe they were material failures, I believe they were design failures. However, there is your confidence to consider. If you want steel to fly you should absolutely use steel. It won't be a huge weight penalty, and it would be more than offset by your increased confidence. That doesn't solve the issue of the different strengths at the joint, and the drilled hole is still in the worst possible spot, but you can do it differently with the new stick.

 

[gyroplanes]

Antony, Your stick failure is explainable. I'd venture to say it was a progressive failure or there was a blade strike in there somewhere. I thorough preflight inspection should have revealed the beginning fracture if it was a progressive failure.
Gary, I'd like to hear more about your stick failure. Antony's failure was not a "pump handle" design stick.

The stock sticks on the Air Commands are very adequate for the task of controlling a rotor.

 

[Doug Riley]

Once you've found a poorly-executed critical part like that stick, you should lose faith in the person who built the gyro. True, he may just have had a momentary lapse when he built the stick. It's more likely, though, that he lacked a feel for the real-world loads on gyro components and how to build parts that can handle them for a reasonable service life.

If the builder lacked that feel, then there are going to be other widowmakin' mistakes hidden in the machine. I think complete disassembly is the only rational approach.

I bought a lovely little Kolb Firestar UL plane years ago. There were no flaws that could easily be spotted in the assembled aircraft. In service, though, various outrageous mistakes began to rear their heads. The landing gear legs are round bars that slide inside tubes and are cross-bolted. This builder's cross-bolts missed the legs altogether, though, so the plane's wheels got all pigeon-toed after awhile.

The tailwheel leg was a fiberglass rod that the builder had drilled through right at the fulcrum, contrary to the plans. It eventually broke off through the hole, like Tony's joystick.

The aileron bellcranks were to be riveted onto the aileron spars with fifteen rivets. Once side had ONE of the fifteen installed (I guess he planned to go back and finish up later). I wondered why the roll control got sloppy after awhile.

The point is that once you spot this pattern, you've got to bite the bullet and dissemble down to the last bolt, if you want to live. It takes less time than you think with a typical open-frame gyro.

OTOH, dead is forever.

 

[Steve Weir]

Just some info taken from the Air Command website, this is the Emergency Bulletin NO. 97-1
"This bulletin is recommended as an immediate correction to a potential flight safety problem concerning the joystick on two place Air Command Gyroplanes. The aluminum joysticks should be removed and discarded, and a new joystick fabricated from 4130 steel tubing with a wall thickness of 0.058". The reason for this action is the heavier machines import heavier control system loads, and there is potential to exceed the safe life of aluminum 6061-T6 joysticks. A note should be entered in the aircraft records that this bulletin has been completed when the joystick is changed to 4130. Owners and operators not having access to 4130 steel tubing with a 0.058" wall, may order raw material or a finished replacement part from Air Command. Future production kits will incorporate this change."

I looked at Tony's stick and it appears to be original Air Command as it seems to be anodized the same color as other anodized parts on his gyro. Although I did not mic it, the thickness looks like .035 aluminum.

 

[Doug Riley]

Hmm. I don't recall an Air Command stick that ever looked like the one in Tony's photo.

The original one (referred to in the bulletin) was a one-piece "pump handle" unit bent up from 1" x .058 6061-T6. The pivots, of course, were aft, under the rear of the seat. Where the stick entered the pivot assembly, it was reinforced by a solid insert.

When people (incorrectly) got the notion that pump-handled sticks somehow caused PPO, Bill Parsons came out with an after-market, Ken Brock type of stick assembly. This one looked something like Tony's, but still not exactly.

 

[anthom]

Thank you all again for the inputs. And Steve, that was very good getting that bulletin. The broken stick is 0.058 inch thick, and I will feel a lot better after I replace it with 4130 steel. Regarding the original builder, he had expired in 2009, and I obtained the gyro from his wife six months ago.

The machine flies great, but I have made some changes with an improved suspension including shock absorbers like the Don Parham suspension, to deal with the grass field from which I operate from. Needless to say, I have a lot of dismantling and inspecting to be done.

I also believe that I had subjected the cyclic to large stresses by engaging the rotor brake by pushing the stick forward, and that is why I improved the brake with a simple but effective lever arrangement.

I have been extremely fortunate that both my component failures had occurred on the ground. And I will continue to learn as much as I can.

Tony Thomas

 

[dragonflyerthom]

Bolt, nuts and rods although not a cheap investment in your hobby It'll make it safer for you. Make sure all your holes are debured, clean and snug. If you find slop replace the part. Easy to do.

 

[Brian]

I don't believe that disasembling a gryo and checking everything is as hard as building from a kit. For me it would give me the advantage of knowing exactly what I have. Please be careful I have not meet you but would like to in the future. brian

 

[perbgyro]

My second critical component failure occurred yesterday... I pushed the cyclic forward. Next thing I knew, the cyclic stick sheared off completely at the base.

Since the stick on my machine is used to apply pressure for the rotor brake, I noticed the flex in the AL cyclic stick that made me feel real uncomfortable. I had the guys at AC make me a chromoly steel stick. Worth the weight in my opinion. Judging from the thickness of the AL cyclic control block, it should be fine, but I check for cracks as part of my pre flight. My PTT wire goes out the bottom of the assembly, so no holes in the side of the stick. In the future, I wouldn't have that piece or any part of the cyclic control system annodized.

Another recent area of focus for me was tires. I noticed a buldge and got to thinking about a blow out on takeoff or landing... not good...

 

[hillberg]

Annodize it not much a problem,Just make sure to bake the part before assembley.

 

[Mike484]

Most of the time an anodized part breaks the anodizing is blamed when in fact it was that too thin of aluminum or the wrong aluminum was used.

 

[Earthboundmisft]

I sleep pretty good. My stick is a pretty gold color. Made by a dear friend of mine who worked at the Cape. Titanium fuel line from the shuttle. THICK. Thanks taxpayers.

 

[scottessex]

Mike I had one made from 304 stainless hydraulic tubing, part of my "total compensation package" Can"t touch the Ti though, I'll bet dumpster diving at NASA could be pretty fruitful.

 

[Greg Lockhart]

I appreciate discussions like this one as they cause me to think about possible problem areas with my (still unfinished) SparrowHawk. The control sticks with my SH kit are 1" OD X .125" wall thickness. Is that thick enough to not be a concern? I realize that the stick forces on the heavy two place machines can be greater than on the lighter machines.
Thanks,
Greg

 

[dragonflyerthom]

1" sticks should be fine. Just be careful where you put holes in it.

 

[anthom]

0.125" tube thickness is a lot better than what I had at 0.058". I believe that since the yield strengths of the tubes are calculated on the area in psi, the thicker tubes would be stronger for a similar application than the thinner one.