Safety Alert!

cburg

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I was shown to give it a shove with your hand before engaging, despite a soft start on my KB-2. Seemed like a good idea...if you can reach it.


I'm wondering if to much torque is being apply when the blades are at "0" RPM.
This instant torque is very high. This is why they must start slow.

A Twinstar two place with an electric prerotator was tried without the soft start and 12v was applied directly to the prerotator. The gyro in a blink of the eye rotated 180 deg. and the blades never moved.

This kind of sudden tork would be damaging to the bolt.
 

James

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Could it have been counterfit? There have been some out there in the past.
 

themonarch

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rotorhead bolt failure-Butterfly

rotorhead bolt failure-Butterfly

Dear Chris,

I am concerned that you had to experience such a close call with the rotorhead bolt failure on your Aurora. Thank the stars that you knew how to handle it. You are impressing me to be an excellent pilot in all regards, and I see you as a resource for myself and the other fledgelings in our sport. I thank you.
Because of your mishap I believe that you inquired who else out there was flying or building a Monarch/Aurora. I read your list, and there is one additional that I can think of. His name is Bill Parent, and he had a very intuitive build going on back then (2 yrs ago). At the time Bill was gracious to me and sent me many emails explaining the details of his build, along with many images. I still have all of it in my saveds. Bill stated that he was affiliated with PRA chapter #39, Yankeerotors.net. #39 was/is headed by a Mr. John Christopher. I have talked with John about my wanting to contact Mr. Parent but this proved uneventfull for us. So I don't know about Mr. Parent and the status of his build but maybe John can shed some light on it. Those of us in the Butterfly community and gyros in general all benefit by staying in touch with one another to help keep everyone safe. My thanks to you, Chris, for caring to shed a light on a possible problem. M. Joe Daly.
 

Texasautogyro

Gyro Master Instructor
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Just set things right Vance I fully understand where you are coming from. I just want to say that the low pulley used was not the quality it should have been for a pre rotator and has a wobble in it. This turns a tension belt that runs through a 90 degree gear box that turns a clutch drive for soft start again with a wobble in it. When put it under load with a rotor the whole aircraft shook like a flap. Then settled when speed increased. I saw this a year ago but Chris was told it was normal by the designer.

After taking the rotor and hub bar off we spun it up and it still shook but not as much as before.

This and maybe a faulty bolt I feel we're possible factors. The gyro ran smooth after the blades were done pre spinning.
 

cburg

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Mentioned was fatigue, work hardening, counterfeit bolt, defective bolt, vibration. I recommended that the bolt be sent out a metallurgical lab for an assessment. So not sure where we disagree...I said “if”. Could be none or all of these things in concert. I have a new owner ready to fly his (was mine) gyro in a few days and would like to see a quick determination for his benefit, and for any others with a similar problem. As far as I can tell the design is similar to many others, but the high speed pre-rotator is not. Very limited pool of pre-rotators that spin up to 300 RPMs like mine does.

I don’t know what happened and would not conclude anything without more info and a metallurgical lab report, which I have conducted thousands of in my job.



I have had experience with assigning an incorrect cause to a failure and have seen the real cause overlooked.

Please don’t feel I am picking on you Chuck. Your response to Desmon’s theory is exactly what I am talking about.

You have held the parts in your hand Desmon so please understand I am not opening a debate. I do not have enough information to reach any conclusion.

My first guess would be not enough torque on the teeter bolt to keep the stack of stuff lined up and supported.

This then opens the door to why? Assembly error? Wear? Poor design?

I have seen many people (not Chris) just snug up the bolt, line up the hole for the pin and call it good. I feel this is not best practice for a flight critical part and I am a torque wrench enthusiast.

The quality of the bolt is also in question. In my opinion that can only be answered by a thorough examination of the bolt by a qualified expert. I am not that person. In my experience it is not an expensive process although it has been more than ten years since I have had fasteners tested so I may be out of date on the prices.

Harmonics should not be ruled out but it would not be my first or second choice.

Because it is a flight critical part I feel all avenues should be explored.

This is the first teeter bolt failure that I am aware of.

Thank you, Vance
 
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Vance

Gyroplane CFI
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We don’t disagree Chuck.

We don’t disagree Chuck.

Mentioned was fatigue, work hardening, counterfeit bolt, defective bolt, vibration. I recommended that the bolt be sent out a metallurgical lab for an assessment. So not sure where we disagree...I said “if”. Could be none or all of these things in concert. I have a new owner ready to fly his (was mine) gyro in a few days and would like to see a quick determination for his benefit, and for any others with a similar problem. As far as I can tell the design is similar to many others, but the high speed pre-rotator is not. Very limited pool of pre-rotators that spin up to 300 RPMs like mine does.

I don’t know what happened and would not conclude anything without more info and a metallurgical lab report, which I have conducted thousands of in my job.

It appeared to me you immediately looked to your prerotator when that hypotheses was suggested.

I have found it is easy to narrow the focus and overlook something with insufficient information.

I felt your response was a good example of that.

Your mind may have still been completely open.

The point I was trying to make was I have found it important to keep an open mind to every possibility even after a viable hypothesis has been found.

That is why I started out by saying please don’t feel I am picking on you.

I wish you all the best my friend.

Thank you, Vance
 

cburg

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Trust me…my mind is wide open.

I did not immediately go to the pre-rotator. First I was trying to figure out which bolt failed so I could have Kent check it. At first it sounded like the tower bolts. Several responses later the PR came into the discussion (by Desmon), after talking about 8 other bolts first.

As stated…”IF” it has something to do with the pre-rotator….as Desmon (who is looking at the parts and saw it happen) strongly indicates then that takes the analyses in a different direction than a generic rotor head problem. I don’t have a favorite conclusion…frankly I don’t like any of them, in terms of the implications.


It appeared to me you immediately looked to your prerotator when that hypotheses was suggested.

I have found it is easy to narrow the focus and overlook something with insufficient information.

I felt your response was a good example of that.

Your mind may have still been completely open.

The point I was trying to make was I have found it important to keep an open mind to every possibility even after a viable hypothesis has been found.

That is why I started out by saying please don’t feel I am picking on you.

I wish you all the best my friend.

Thank you, Vance
 

birdy

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Bloodyell Chris, glad you caught that one on the ground.

BTW, over ere we call it the pitch pivot bolt.

I dout very much that this bolt is 'underrated'.
Iv bent twisted and sheared more n my share of rotors, had spindle bolts bend, teeter bolts jammed but never had a control pivot bolt so much as bend. And lookn at the pic, I recon our standard Oz pivot bolts are not as big as the one you had shear.
As unlikely as it is, id be lookn at the quality of the bolt itself.

And bout the prespinner stress [ not as bad as an electric startup torque] and harmonic vibes, I dout it.
 

GyrOZprey

Aussie in Kansas.
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Digging deep ...

Digging deep ...

trying not to be overwhelmed & just :Cry: !!!!

Getting good support from Larry - he's sending new torque tube,washers, bearings & pivot block brass bushings - no charge!

I'm getting new bolts @ Aircraft Spruce & going to insist on NONE with stamp 01DO ..... taking the broken one into the local metallugical lab for testing! ( Thanks Chuck) -

Going to dismantle & rebuild the rotor head!! DAMMIT ... I need a special socket for the bearing bolt castle nut & bigger torque wrench than the little one we have! (Why we did all that @ Larry's shop -last year!!)

Birdy - your posts always make me :) !!!

Good name --- describes perfectly PITCH PIVOT BOLT!!! ( PPB)

Yes ... my good mates here ( Vance & Jeff & others) have ?'ed the bolt quality .. especially as the ID stamp was the subject to a FAA AD for Helicopters some time ago ..... could have been a counterfeit - sub-standard!

In summary ..... after yesterdays inputs & research....

1. Larry, Jake, Jeff,Vance concur ..... main problem was LOOSE bolt - not initially torqued enough or checked /maintained! ( MY BAD!!! ... though Larry checked it on installation ... I didn't know how to maintain it!!! - or how the pivot assembly needed to function) - we gotta write our own POH!!! :help:

Looking Back - I DID look very very hard at the area on that last preflight as I had a gut feeling that something was off - but just couldn't see that the slop was abnormal!

2. ???? bolt quality

3. MLS PR IS very aggressive .... lossa torque & jerk at start + vibration up to ~90R-rpm ... with as many PR cycles as I've done with all my mains-balance work - certain stress factors there for the low hours ( 38)... probably not experienced in other machines used by experienced pilots! ( Who ACTUALLY GET TO FLY!!!! :rant: :Cry::censored::(!!!) - yes at least I'm not :rip:!!!!

DAMN this learning curve! You think I'd get just a little "reward" before the next "thing" comes up!!!! ARRRRRGGGGHHHHHHH :censored:

DEEP BREATH .......
OK - one step - one day at a time! One can eat an elephant - just one bite at a time!!!( & LOTS of time!) :lol:


Bloodyell Chris, glad you caught that one on the ground.

BTW, over ere we call it the pitch pivot bolt.

I dout very much that this bolt is 'underrated'.
Iv bent twisted and sheared more n my share of rotors, had spindle bolts bend, teeter bolts jammed but never had a control pivot bolt so much as bend. And lookn at the pic, I recon our standard Oz pivot bolts are not as big as the one you had shear.
As unlikely as it is, id be lookn at the quality of the bolt itself.

And bout the prespinner stress [ not as bad as an electric startup torque] and harmonic vibes, I dout it.
 
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JEFF TIPTON

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In all fairness Chris if the bolt is the problem, and we don't know for sure yet, based on the information in the AD the bolt cracks and relieves the tension. The AD had the people to look for a graying around the bolt head and nut which indicated the bolt was moving. Perhaps you subconsciously picked up on it.

We all know you are having a hard time making progress, but on the bright side you know your machine like no other. ;)
 

500e

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Pulleys running out, clutch drive with wobble, under load it shook like a flap, then it smoothed out!
It only smoothed out due to centrifugal\pedal forces, the cause of vibration is still there either in the drive or in the blades hub bar assembly, even if it is not the problem it is not correct it is not "normal" there is a cause
 

Monarchist

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I've heard no one mention anything about this, but I am a little concerned about the point in time which it failed. As I recall, Chris, you said you had just picked the nose up when it happened. I wouldn't think a shear failure would be gradual. I'm a software guy, not a mechanical guy, so literally, I don't know very much about this kind of thing.

But at that moment, just as the nose comes up, what kind of shear force should that bolt be feeling?

-John
 

MarkG

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Could have been a bad bolt...... There have been bogus AN hardware in the aviation industry in the past..... I would make sure to but your AN hardware from a reputable aviation supplier. All should come with documentation for traceability to insure it is not a bogus part. You may also want to pay a little extra on the critical bolts and have them magnafluxed to insure they are sound. Also make sure that they are properly torqued. Over torqueing can cause bolt stretch and thread damage that can cause failure.

Did the bolt fail at the base of the threads or in the body of the bolt???
 

JEFF TIPTON

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Approximately one third length.
 

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GyrOZprey

Aussie in Kansas.
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Went to the hangar today to pick up a comparison bolt for the lab testers.
Took a quick look at the stamps on the spindle bolt & teeter bolt .... the dreaded 01DO .... OHHH BOY!!! Going to have a big word or two with Aircraft Spruce tomorrow!
Yes WILL definitely get some guaranteed(mangafluxed?) high grade bolts - for those 3!

Dropped off the broken one for testing & we'll see what transpires on Friday!

I looked over all the rest on my gyro - about 50% are the 10DO -in-stamped kind - the rest have the protruding stamp - different brand!

Complete rebuild?????

At the least I will change out head, mast, plates & landing gear & engine mount ones - immediately!

Printed off the powerfin instructions for installing,balancing & repairing their props . Took a coin & did the tap-test along the damaged edges to determine the hidden damage.....? I think I'll replace 2 not just the one Desmon thought!

After reading Larry's email again about a new adaptor he's come up with for the 912 shaft - to make the lower pulley run better ..... I can see where a lot of the vibration may come from - the lower pulley is not truly vertical under the gearbox pulley - running at a slight angle - combined with the quality of pulleys themselves - lots of room for the "wobbles"!!!

SO much work! :(
 

themonarch

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hart michigan
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'06 Monarch 582. 150 hrs. tt. Purchased from the builder. Please see my aircraft on Craigslist.org.
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Ppb

Ppb

Chris, the Pitch Pivot Bolt: this description makes perfect sense. Thank you, and thanks Birdy for your similar description. Often times I think it would have been best If I had done the build instead of being the second owner.... I would know that much more about my machine. I know a bit now, because I have been dissasembling, inspecting, relubing, repairing and sometimes beefing areas up (suspension mainly). Aside from not yet going inside the engine or redrive, because this is an area for a pro and not me, I have not yet fully dissasembled the rotor head. It's been on my mind though. You see, I am not flying my gyro, because I am not instructor qualified, and so I haven't worried. That area is going to get the treatment before I fly, and I WILL have qualified assistance. Looking at the PPB and it's function on my machine, I am just so surprised that it failed on yours. Your gear is a bit different than mine, but... Go's to show what can sneak up on a person, arrrgh! Peace and safety for with all. MJD.
 

birdy

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But at that moment, just as the nose comes up, what kind of shear force should that bolt be feeling?
Buggerall for the size of the bolt.

Complete rebuild?????
Hmmmm.
Glad im nowhere near you rite now. ;)
 
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