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After speaking with a LAME mate of mine, and showing the rotor heads we use, he could not beleive we trust this one AN bolt with normaly a nylock or castle nut to hold our machines connected to our blades.His argument was AN hardware is very poor quality, and is only designed to be used in shear loading.He explained that we are trusting the load carrying propertys of the bolt and nut's thread.When using a bolt and nut in a non shear (loads along the length of the bolt) we should use a special bolt designed for this purpose.I asked him for a price, and it seems a purpose bolt could cost up to $200.00 aust.Would anyone like to comment ????????
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My comments for what they are worth:-I would assume that your mate means the main bearing bolt because the others are in shear. Ask him to do the tensile strength figures on a 5/8" bolt, and then calculate the strength of the brackets that hold the wing lift struts on a Cessna. If he is serious, he should never fly a Cessna again. The AN bolts are manufactured to American military specifications and it is a standard that the Aircraft industry has adopted, for want of any other Standard. ASRA came under much fire for regulating that AN bolts be used in the main frame joints and all connections from the "hands to the rotors". You could imagine what the protesters would say if we told them that all bolts in tension had to be $200 bolts.I have never yet heard of a failure of an AN main bearing bolt. A failure would mean death, so if the number of hours flown to date in Australia was taken into account, then the failure rate would be better than the GA aircraft standard for the number of deaths per 100,000 hrs flown.Your friends suggestion that "AN hardware is very poor quality" means that the military standard is very poor and the general aircraft industry is happy to adopt this poor standard.Tim McClure
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Yes he does mean the main bearing bolt.He explained the problem is AN Hardware is not designed to be used in this application.The thread size, and cut, on these purpose bolts is rounded at the base of each thread, and higher at the top.Each thread is also wider to increase strength.The bolt nut is longer with more threads and is slightly oval shapped at the end giving it its locking properties.This bolt is also stronger, and less prone to rust. I will ask tommorrow for the name and composition of one.Regards Sam.
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crikey,don't tell me those 3.3 bolts I've been flying aroundon are indaequatre?
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Nicely and well explained Tim. Good post.Aussie Paul. [
]www.firebirdgyros.com
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The bolt is called an MS 2000 series bolt, and he is going to get me a comparison chart of it compared to AN.He also explained that AN hardware is the cheapest in aviation and they are not allowed to use any in commertial aircraft.Will post the comparisons when I get them.Regards Sam.[]
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Dear GentlemenAs a LAME for 28 years I have seen a lot of aircraft bolts ranging from H8 AJAX bolts to Boeing spec costing about #1,200.00 each, and the airlines do use those AN bolts to in given situations, and they are all good quality with specific purposes, the beauty of an AN bolt is its ductility which gives it a good fatigue life when correctly tensioned and if over stressed will cause the bolt to draw and strech rather than break, a very critical part of this feature is the rolled threads, please never be tempted to cut the threads of a tension bolt with a thread die as this will create a stress point and the rest is statistics. Enough add nauseum I can feel a soft start rotor forum coming on.Gyro Gearloose
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Originally posted by Gyro GearlooseDear GentlemenAs a LAME for 28 years I have seen a lot of aircraft bolts ranging from H8 AJAX bolts to Boeing spec costing about #1,200.00 each, and the airlines do use those AN bolts to in given situations, and they are all good quality with specific purposes, the beauty of an AN bolt is its ductility which gives it a good fatigue life when correctly tensioned and if over stressed will cause the bolt to draw and strech rather than break, a very critical part of this feature is the rolled threads, please never be tempted to cut the threads of a tension bolt with a thread die as this will create a stress point and the rest is statistics. Enough add nauseum I can feel a soft start rotor forum coming on.Gyro Gearloose [
]Hey mate ....you've got my undivided attention regarding soft starting rotors etc.Share your thoughts with me..us[]RDC
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Stupid question from a stupid person,wot the hell is a LAME???[besides a cow with a broken leg,you idiot]Ignorance is bliss............but only till you realise you were.Ingratitude stinks.......be generous carefully.
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I've got news for you Birdy, I'm known as a DAME [no relation to Dame Edna]. It stands for Designated Aviation Medical Examiner.My understanding is that LAME stands for Licenced Aviation Mechanical Engineer.Wouldn't it be great if there was an acronym dictionary?John EvansThink logically and do things well, think laterally and do things better.
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Thanx Doc.Ignorance is bliss............but only till you realise you were.Ingratitude stinks.......be generous carefully.
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[8D]Feed back on comparisan of MS21250 in tension compared to an AN-9.MS-21250 = 30,900 pounds (in tension) AN-9 = 18,100 pounds (in tension)An equivilent AN bolt to the MS 21250 (special purpose bolt) is an AN-16.(big difference)When compared in shear both are very similar.I am still waiting on figures for the nuts.Regards Sam.
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That is correct Sam. That is why Gyroplanes are rediculously over engineered.I always thought LAME stood for "Licenced Aircraft Maintainence Engineer". Looks like I could be wrong again.Tim McClure
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I love an active forum, Gyro Gearloose here again. You could be forgiven for coming up with any sort of response about LAME's, I have often been scorned at work for addressing my collegues as "Lame Brains". But it sometimes is a rather apt comment about the profesional Aircraft maintenance sector, but by no means indicative of all "licenced aircraft maintenenance engineers"I liked the cow with broken leg analogy. Tim I think your response was great and Sam I like your diligence, if you have the money and the resources and suffer no weight penalty you could only suffer from peace of mind using high spec hardware, I can tell tou That a BACN10JCHR(X) nut would be the highest spec nut you can buy and is self locking. I will look forward to seeing any of you in another forum topic soon.(maybe the soft start rotor topic).Cheers from the opinionated man with a limp.Gyro Gearloose
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Sam , I know its hard to believe but gyros have been accumalating many thousands of hours using AN bolts and nuts without a problem so I wouldnt worry too much mate.You never know how far you can go, till you get there !
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