NTSB alert

[Guest ozzie]

http://www.ntsb.gov/doclib/safetyalerts/SA_028.pdf

 

Might help someone to keep their nuts tight.

 

 

[Patrick Normoyle]

Keep hold of your tight nuts but throw out any loose nuts, is that the gist ?

 

 

[M61A1]

A good reason to use MS21042 nuts, they still wear with repeated use, but the will never melt or deteriorate like that. They are also a proper alternate part for most nylocs.

 

 

[Guest ozzie]

Good idea to never use nylocs under the cowl.

 

 

[cscotthendry]

One of the tips was "never run a tap through these nuts". I can't imagine why someone with even a quarter of their brain functioning would do that!

 

 

[metalman]

http://www.ntsb.gov/doclib/safetyalerts/SA_028.pdfMight help someone to keep their nuts tight.

I hadn't heard the cause of the P51 crash,

Matty

 

 

[M61A1]

One of the tips was "never run a tap through these nuts". I can't imagine why someone with even a quarter of their brain functioning would do that!

I have actually heard aircraft tradespeople comment along the lines of "it seems to get really tight at the end there, maybe I should run a tap through it". Mind you, I have seen run on torques so high, especially a new anchor nut with a new titanium screw, fitted dry, that I thought it could almost rip the floating section out of the the plate. And no, it wasn't cross-threaded.

 

 

[M61A1]

Just reading through a few of the others there, why you would use a self locking (alone) nut on a control run, I don't know. Any moving joint or clevis should be split pinned. Especially on a rotary wing cyclic control.

 

 

[Mriya]

Good idea to never use nylocs under the cowl.

In our workshop it is standard practice to avoid mixing nylocs and engines, however we note an increasing trend for LSA manufacturers to use nylocs in the engine area.

 

 

[Guest Maj Millard]

The dark red nylocs are high temp, the standard green airframe only........

 

I have actually heard aircraft tradespeople comment along the lines of "it seems to get really tight at the end there, maybe I should run a tap through it". Mind you, I have seen run on torques so high, especially a new anchor nut with a new titanium screw, fitted dry, that I thought it could almost rip the floating section out of the the plate. And no, it wasn't cross-threaded.

You 'll get this a lot when folks use stainless screws, into standard steel recepticals or nut plates. Standard recepticals, nut plates or nuts are designed for standard steel blots or screws which have a rolled thread, and a different profile to stainless hardware which has a cut thread, so the tip of the threaded section is higher and sharper. This is what causes the binding , or tight fit.............Maj....

 

 

[kgwilson]

It seems the jury is out concerning the re-use of Nyloc nuts. In theory because the nylon insert is not damaged by installation it can be re-used many times. Re-use is generally allowed if the running torque is not degraded when re-installing the nut but who can check or test this easily. I reckon that they are cheap enough so biff them out & put a new one on. If you haven't got a spare then if you can't turn the nut by hand it is probably OK to re-use it, but not on critical airframe or control surfaces.

 

 

[facthunter]

Even a castellated nut split pinned can wear and lose the pin The nut should pull up tight against a fixed length sleeve on a clevis. Some of the design is crook. Nev

 

 

[Old Koreelah]

Educational thread. I have a trio of captive nuts doing critical jobs. Instead of nylon inserts, they seem to rely on having been squeezed slightly flat. I was advised by the seller that they could cope with being removed and reinstalled hundreds of times without losing their grip. Sounds too good to be true. Any comments?

 

 

[Guest Maj Millard]

Nyloc nuts have a good history if used correctly. Generally you turf them after 3-4 uses max. They generally don't have a habit of backing off if this rule is observed. You have to be prepared to throw them if in any doubt.

 

One major area of concern is when they are used on prop bolts, which you see often. The Rotax prop bolts are metric, and the thickness of the nuts tends to be a little thinner, than your standard aircraft Nyloc. I stick to the three time max rule specifically on these, and also back them up after torquing, with a drop of Locktite on the 2-3 exposed threads.........Maj....

 

 

[Guest Maj Millard]

Even a castellated nut split pinned can wear and lose the pin The nut should pull up tight against a fixed length sleeve on a clevis. Some of the design is crook. Nev

After working with amphibious seaplanes, I don't use anything theses days except stainless steel split-pins. Even in salt free remote areas I have found exposed steel split pins badly rusted and with very doubtfull locking ability...........Maj.....

 

 

[Old Koreelah]

Nyloc nuts... back them up after torquing, with a drop of Locktite on the 2-3 exposed threads.........Maj....

Is the Nyloc material compatible with Loctite?

 

 

[M61A1]

Educational thread. I have a trio of captive nuts doing critical jobs. Instead of nylon inserts, they seem to rely on having been squeezed slightly flat. I was advised by the seller that they could cope with being removed and reinstalled hundreds of times without losing their grip. Sounds too good to be true. Any comments?

Many of the often removed access panels on military aircraft use captive nuts/nutplates, usually the only reason we have to change one, is that some numpty pushed really hard while undoing it and forced the nut section out of the riveted plate. They do last a long time, and with regular use, even if they start lose run on torque, often you can just use a new screw and it will be fine.

 

 

[M61A1]

the

 

Even a castellated nut split pinned can wear and lose the pin The nut should pull up tight against a fixed length sleeve on a clevis. Some of the design is crook. Nev

Throttle linkage at the gas producer fuel control on a B206, is one that doesn't. By the book, finger tight, then split pinned.

 

 

[Guest Maj Millard]

Is the Nyloc material compatible with Loctite?

I'm just putting a drop on the threads projecting above the nyloc.........have been doing this for some years now with no problem, and it is important those prop bolts stay just as you left them !..........Maj.....

 

 

[Guest Maj Millard]

Most standard aircraft hardware is available in corrosion-resistant stainless steel of course, but it's very costly. The stainless screws that cause people dramas when inserting them into standard fasteners for the first time, would be your general Hardware store types.........Maj......

 

 

[Old Koreelah]

Many of the often removed access panels on military aircraft use captive nuts/nutplates, usually the only reason we have to change one, is that some numpty pushed really hard while undoing it and forced the nut section out of the riveted plate. They do last a long time, and with regular use, even if they start lose run on torque, often you can just use a new screw and it will be fine.

As a precaution, I grease the bolt threads. I hope this prolongs thread life.

 

 

[Guest Maj Millard]

As a precaution, I grease the bolt threads. I hope this prolongs thread life.

A bit of silver anti-seize on panel screws that are removed regularly can be very helpfull, however torque on say a prop bolt/nut combo is often required to be taken with threads dry.

Additionally if you do put a drop of Locktite on your prop bolts, only put on a drop. Any excess could be flung off and it's murder on plastic windscreens !.......worse than fuel...........Maj.....

 

 

[kgwilson]

I'd be wary of stainless steel nuts & bolts. SS is quite soft, even the good quality stuff. It is easy to strip thread on SS screws & nuts & overtorquing can shear the bolt a whole lot easier than a carbon steel bolt. I use AN hardware everywhere.

 

 

[M61A1]

As a precaution, I grease the bolt threads. I hope this prolongs thread life.

In the military aircraft manuals, it usually has a big "Caution", telling you not to lubricate the threads on self-locking hardware, then it will contradict itself, saying that you have to use engine (turbine) oil or a specific grease on some. However, in the standard practices section, it will usually have a torque chart for lubricated or dry. I do recall certain access panel screws that have a torque correction factor of 0.5 if installed lubricated.

 

 

[M61A1]

A bit of silver anti-seize on panel screws that are removed regularly can be very helpfull, however torque on say a prop bolt/nut combo is often required to be taken with threads dry.Additionally if you do put a drop of Locktite on your prop bolts, only put on a drop. Any excess could be flung off and it's murder on plastic windscreens !.......worse than fuel...........Maj.....

Any loctite applied (unless it's wick in ), should be applied before fitting the fastener, as it is an anaerobic polymer and the presence of air will stop it curing.