Safety of nyloc nuts.

[asra]

The ASRA ops manual section 5.09 para 9b. says, "All tightened bolts must have at leat 2 threads showing".As the rules stand the ops manual is the law for our gyros.There was some discussion recently where it was reported that the current acceptable aviation practice was, "The bolt could be flush with the nut as long as the bolt thread comes through to the outer end of the nylon".I have never seen any reference to this and was wondering if I have missed something along the way. I am not asking which is the best practice only what the "Official" ruling is.Any current LAMEs out there who can shed some light on this[?]Aussie Paul.[]www.firebirdgyros.com

[Adrian S]

Paul,The standard acceptable practice is 1.5 to 2 threads but the ASRA Ops Man ers on the side of safety and says 2 threads, so as you have said thats the rule for gyros. The FAA publication AC 43.13-1 &-2 sets the rules and it is available as a download from the FAA website - titled Acceptable Methods, techniques and practice - Aircraft Inspection and repair . Previous ramblings from myself in the Gyro news have advised that this is one of the ASRA TA's main reference documents. Hope that dispels any rumors that may lead to unsafe practices.Adrian.

[asra]

quote:Originally posted by Adrian SPaul,The standard acceptable practice is 1.5 to 2 threads but the ASRA Ops Man ers on the side of safety and says 2 threads, so as you have said thats the rule for gyros. The FAA publication AC 43.13-1 &-2 sets the rules and it is available as a download from the FAA website - titled Acceptable Methods, techniques and practice - Aircraft Inspection and repair . Previous ramblings from myself in the Gyro news have advised that this is one of the ASRA TA's main reference documents. Hope that dispels any rumors that may lead to unsafe practices.Adrian.Much appreciated Adrian. I had a feeling that someone was having me on!!![]This pic was sent to me after my post on the subject.I assume that this would not get signed off, so how would we suggest that this situation be fixed[?] I don't have a pic from the head end of the bolts, but I believe that the same washer is used under the head of the bolt.Aussie Paul.[]Image Insert: 57.39 KBwww.firebirdgyros.com

[NiqueNaque]

Paul,I'm assuming this is a step in the keel connection.Shouldn't the cheek plates extend out to have a minimum of four bolts in each section of RHS? The connection shown only has three in each, and given that the stabiliser is expected to provide down forces the connection is weak because it only has one bolt in the top member where it is in tension, I suggest the cheek plates be made to provide two bolts top and bottom in each section of RHS.I trust those pulley wheels have a bushed spindle so there is no way they can bind in rotation and that the cheek plates are pressed tight to the airframe.. ie, the nylon pulley wheels are not providing the lateral force and cannot be loaded up in that way if the RHS moves in the cheek plates.Regards,Nick.

[asra]

Nick, you missed the whole picture, the short bolts!!!!!!!Aussie Paul. []www.firebirdgyros.com

[Tim]

G'day Paul.Taken from the "Standard Aircraft Handbook" "in the case of self-locking "stop" nuts, if from one to three threads of the bolt extend through the nut, it is considered satisfactory"We obviously have it poorly worded in 5.07 of the Operations Manual and I am probably responsible for that. In fact, it should not even be in the Operations Manual but rather the Technical Manual, which is still under construction.The standard should have read "must have approx. 2 threads showing, with between 1 and 3 considered satisfactory". "At least two" is too loose because every bit as much damage can be done with too much thread showing as with too little. To try to make the tolerance too exact makes it too hard for builders because it would mean that they would have to purchase half washers as well as the normal ones.I will check with Adrian and see if we can get this adjusted in the next update.Most of the bolts in your photo are under spec. and it would be acceptable to remove the washer under the head.Tim McClure

[asra]

quote:Originally posted by TimG'day Paul.Taken from the "Standard Aircraft Handbook" "in the case of self-locking "stop" nuts, if from one to three threads of the bolt extend through the nut, it is considered satisfactory"We obviously have it poorly worded in 5.07 of the Operations Manual and I am probably responsible for that. In fact, it should not even be in the Operations Manual but rather the Technical Manual, which is still under construction.The standard should have read "must have approx. 2 threads showing, with between 1 and 3 considered satisfactory". "At least two" is too loose because every bit as much damage can be done with too much thread showing as with too little. To try to make the tolerance too exact makes it too hard for builders because it would mean that they would have to purchase half washers as well as the normal ones.I will check with Adrian and see if we can get this adjusted in the next update.Most of the bolts in your photo are under spec. and it would be acceptable to remove the washer under the head.Tim McClureGreat Tim, thanks. That was the answer I was looking for.Yes, the maximum threads should be included or at least a comment about thread bound nuts. I have had several instances over the years where the correct torque was not appied due to the nut using all of the availible thread and still not tight enough.We can all get used to the long threat commercial bolts, and forget about the correct length thread of an aircraft bolt.Aussie Paul.[]www.firebirdgyros.com

[asra]

Guys,I was always taught to allow one and a half threads protruding, The Std Aircraft "hardware" bolt (grade five) has two built in length coverings..........the bolt lengths go up in 1/8 inch increments and there are two washer thicknesses, for example the 1/4 inch washer AN960-416 is 1.60mm thick and the AN960-416L (low profile) is 0.80mm, the whole aim is to make sure that the thread does not impinge into/onto in our case, cluster/head plates for example, that is the shank of the bolt takes the loading and not the thread which would be under shear. Pete Barsden

[asra]

Need to jump in here to make a correction!According to the real manual "ACCEPTABLE METHODS, TECHNIQUES, AND PRACTICES" as in the "AIRCRAFT INSPECTION AND REPAIR" as issued by "The Department of Transportation Federal Aviation and Administration".This book was issued to us by CASA at a Technical Advisors Course, which of course we had to purchase. In it the section on NUTS, relating to Fiber or Nyloc Nuts, Section 1. paragraph 230 page 152 (2) States; and quote, (After the nut has been tightened, make sure the rounded or chamfered end bolts, or studs, or screws extend at least the full round or chamfer through the nut. Flat end bolts, studs, or screws should extend at least 1/32 inch through the nut).This represents less than 1 thread as the the threads on the smaller diameter bolts such as 1/4" or 5/16" are 25 threads per inch.The reason for this is obvious, on some bolts the nuts can become thread bound ie. reach the end of the thread on the bolt if the nut is screwed in up to two threads, subsequently not allowing the nut to have sufficient grip or torque.Jeff H-S

[asra]

Guys,I would just like to add what may be termed "useless snippets of trivial information".The Std AN bolt reguardless of thickness size is approx one and a half threads longer than the stipulated bolt length size, grab any AN bolt and measure it, and you will see this, if you grab a AN bolt and screw the nut fully "home" you will see approx 4.00mm of thread protruding past the nut, now......if you take for example an AN4 bolt (1/4 inch) thick and pass it through your mast material and head/cluster plates and have the shank end level with the material and you fit a thin and then a thick washer over the bolt in that order (thin washer up against the material) when you Torque the bolt up you will have approx one and a half threads protruding past the nut as stated above the main aim is to have the shank in the material and not the thread, this is why the Aviation industry washers come in thick and thin profile.Pete Barsden

[NiqueNaque]

Paul,[" Nick, you missed the whole picture, the short bolts!!!!!!!"]Ah, no, I didn't.I knew that you knew about the short bolts, so I didn't bother to comment any further on the bolts.I will reiterate, I think the bolted connection shown is a bad one, is that plain enough for you?Regards,Nick.

[bones]

Hey fly,your opinions far out way your experience, just to point it out for you, there is now way that it can pull up (as your worries seem to be)as for it to do that it has to shear off the bolts holding the bottom of the mast!!!Now if that clear enough for you!!!!!!!!!![}]r0t0rcraft.com.au

[asra]

Mark,At least he's having a say, and that's the important bit. As to whether he is right or wrong, well we'll leave that too the experts.This forum can only thrive on imput, its then up to us as to whether we agree or dis agree any opinion.TedStrongly opposed to the retriction of free speech

[asra]

For info of Forum members, Mark and Nick's last posts here have been deleted under item 11 of the Forum Editorial Policy for personal attacks on each other which will not be tolerated.Moderator

[asra]

Well done Moderator, Quite correct, any personal "slanging" can be done by Email.Pete Barsden