Safety Alert!

hjajr

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I believe about all the Heads use that bolt in a AN6 something.
I think I would also Contact Aircraft Spruce. maybe they bought a batch of counterfit bolts.
I have recently replaced a few bolts purchaced from them.
 

cburg

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Note that there are several types of towers used on Butterflies. Some, like Chris’s Aurora have a heavier duty tower with two bolts in shear holding the vertical tower plates to the base plate which has four bolts in tension.

Not sure which of these six bolts failed (one of the four vertical bolts or one of the two horizontal bolts).

Note that most Monarchs, including mine, which I sold to Kent Leighton in Round Rock a few weeks ago, have the Benson style tower. This type is completely different than Chris’s and has only four ¼” bolts in tension holding the vertical tower plates.

Glad you dodged the bullet…

Chuck Burgoon
 

cburg

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I’d take the bolt to a nearby metallurgical lab to see if it’s one of the many counterfeit AN bolts that have made it into the fleet. It happened to Boeing. I’ll look for the article.




I believe about all the Heads use that bolt in a AN6 something.
I think I would also Contact Aircraft Spruce. maybe they bought a batch of counterfit bolts.
I have recently replaced a few bolts purchaced from them.
 

Steve_UK

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I'm not a pilot but have been lucky enough to fly in Mi-24 Hind, Mi-2, Mi-17, Lynx HAS3, Gliders, GA
Paul thanks for your answer.

Question - could or should your PRA do more to help spread the message about this issue - does it post any safety bulletins, ideally online that can be checked as soon as it's uploaded rather than waiting weeks for a print publication ?

I took a look at the LAA website - the LAA manages kits, homebuilts, ultralights and odds and ends on permits here in the UK. The LAA also allow after engineering/structure tests new types of kits, homebuilts, ultralights ( a look on their website shows they have 20 or so new types going through this process currently including the RV-12 ).

The LAA also has an airworthiness alert page where safety problems can be easily disseminated to the many thousands of LAA members - among their current listing is a gyro related issue with Dragon Wing rotors, plus an alert re Rotax 912 and 914 engines that can be found in thousands of light aircraft and "turn key" gyros too.


http://www.lightaircraftassociation.co.uk/engineering/Airworthiness/home_page_airworthiness.html


These might be of interest to those of you out there alone in the US experimental sector.


Regards


Steve
 

JEFF TIPTON

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CA040114008 ROBSIN LYC ROTOR HEAD
INOPERATIVE
12/2/2003
R44
O540F1B5
D0621
TAIL ROTOR
(CAN) UPON RECEIPT OF AD 2003-24-51 HELICOPTER WAS INSPECTED FOR THE SUSPECT NAS6605-31 BOLTS. EVEN THOUGH THE R44 S/N WAS NOT LISTED IN THE AD OR ROBINSON HELICOPTER SERVICE BULLETIN 51 THE T/R HUB NAS6605-31 BOLTS WERE FOUND TO HAVE THE VENDOR IDENTIFICATION MARKING 01D0. THE BOLTS WERE REPLACED AND THE A/C RETURNED TO SERVICE.

http://www.robinsonheli.com/service_library/r44_service_bulletins/r44_sb51.pdf

This Emergency Airworthiness Directive (AD) is prompted by a report of the failure of the bolt that secures parts of the main rotor swashplate and attaches the tail rotor blade. An examination revealed that the bolt failed due to hydrogen embrittlement. Hydrogen embrittlement is suspected to have occurred during the cadmium plating process of an entire batch of bolts, which makes the batch suspect. This condition, if not corrected, could result in failure of the bolt that secures parts of the main rotor swashplate and attaches the tail rotor blade, and subsequent loss of control of the helicopter.

http://www.faa.gov/aircraft/safety/alerts/aviation_maintenance/media/2004/2004_05_Alert.pdf

Not saying this has to do with Chris's problem, but; as noted the Robinson Helicopter had a problem with a batch of bolts that were supplied by Vender 01DO and Chris's bolt is not the bolt called out by tne AD. I do note that Vender 01DO did manufacture the bolt that failed on Chris.

I have asked a local FAA representative a question regarding the Marking on the bolt if this bolt is equivalent to or is an AN bolt. The markings are 01DO and a recessed small x opposite to the 01DO.

Not pointing any fingers; but it might be prudent to check other machines for these marking.
 

cburg

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From what I read, we are NOT talking about the *teeter bolt*. We are talking about one of her six tower bolts (4 tension/2 shear). I'm sure we will get confirmation which of the six bolts failed.

Note that there are several types of towers used on Butterflies. Some, like Chris’s Aurora have a heavier duty tower with two bolts in shear holding the vertical tower plates to the base plate which has four bolts in tension.

Not sure which of these six bolts failed (one of the four vertical bolts or one of the two horizontal bolts).

Note that most Monarchs, including mine, which I sold to Kent Leighton in Round Rock a few weeks ago, have the Benson style tower. This type is completely different than Chris’s and has only four ¼” bolts in tension holding the vertical tower plates.

Glad you dodged the bullet…

Chuck Burgoon
 

GyrOZprey

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Pivot block ... Not teeter block!!!...... Thanks for posting the picture Jeff!
 
Last edited:

cburg

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OK, it is not your tower bolts (or teeter bolt)…it’s the (two vertical) teeter block bolts that are in compression/shear and bolt to the Dragon Wing hub bar. How much undersling (teeter block height) do you have? Bolt length?

Pivot block ... Not teeter block!!!
 

GaryMac

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Wow........ you are very lucky, Chris. I'm so glad this happened on the ground and not in the air.

Stay safe.

Gary
 

Vance

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Pictures

Pictures

Based on the pictures; if I was to give it a name I would call it the teeter bolt.

It is the dash 6 AN bolt that goes between the towers and manages the stack up of parts that allow the teeter to teeter.

The Predator has one very much like it as do most of the gyroplanes I have had experience with.

I feel it is a flight critical part.

Thank you, Vance
 

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Texasautogyro

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If everyone had read page one of my description you would have noted its the bolt that the head pivots on forward and aft.

It was also most surely caused in part by the spin up vibration from a harmonic in the pre rotation system.

This had been observed by me but was told to Chis by the manufacturer it was no big deal.
 

cburg

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Different bolt than the 8 various bolts previously mentioned.

Kent…you have this same bolt on your Monarch. Please check it.



Based on the pictures; if I was to give it a name I would call it the teeter bolt.

It is the dash 6 AN bolt that goes between the towers and manages the stack up of parts that allow the teeter to teeter.

The Predator has one very much like it as do most of the gyroplanes I have had experience with.

I feel it is a flight critical part.

Thank you, Vance
 

barnstorm2

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Glad you are OK!!!!!


Paul thanks for your answer.

Question - could or should your PRA do more to help spread the message about this issue - does it post any safety bulletins, ideally online that can be checked as soon as it's uploaded rather than waiting weeks for a print publication ?

Traditionally, we have posted such issues on the web page.

It would be great to expand this, and add it to the E-Alert system.

If someone wants to step forward to help write up bulletins to be sent out, we could expand the program.
 

cburg

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Note that Chris’s pre-rotator is different than mine/Kent’s and several other Butterflies. Not to say that this could not happen, it’s just to note the different type of pre-rotator, and perhaps different vibration…if this turns out to be the culprit. Mine is a centrifugal clutched belt drive PTO off the pull-start end of the 582. It’s important to ease in the throttle VERY slowly (by feel), particularly at very low rotor RPMs to avoid excessive vibration.



Different bolt than the 8 various bolts previously mentioned.

Kent…you have this same bolt on your Monarch. Please check it.
 

Vance

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The process.

The process.

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
 

hjajr

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I have there electric prerotor set up.
Was this the electric or the high RPM Pre rotor?
 

Brent Drake

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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.
 
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