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"Safety wire" -- any kind in particular?

Palamedes

Well Known Member
I'm finishing up the elevators and the very last stop is bending and securing the hinge pin on the trim tabs.

It specifically says to "secure [the hinge pin] with safety wire".

Dumb question here but, is there any particular type of wire that is considered "safety wire" or will any 22 gauge (guessing at size) wire work?
 
I'm finishing up the elevators and the very last stop is bending and securing the hinge pin on the trim tabs.

It specifically says to "secure [the hinge pin] with safety wire".

Dumb question here but, is there any particular type of wire that is considered "safety wire" or will any 22 gauge (guessing at size) wire work?

The most common wire is .032 made of stainless steel. larger wire (.041) is used for situations where torque is very high, like prop bolts. Smaller wire (.020) is used for lighter jobs and brass wire is used for "break the glass" type applications like fire extinguishers.

The wire should also fill 50% or more of the hole in whatever bolt/pin it is used on (if 25 year old brain matter serves me).
 
can anyone explain????

why do I not see cylinder bolts safetied?
seems they might be pretty important.
they are drilled for safety wire it would appear.
NEVER seen it done!

WTH? what the hey? :)
 
why do I not see cylinder bolts safetied?
seems they might be pretty important.
they are drilled for safety wire it would appear.
NEVER seen it done!

WTH? what the hey? :)

Primarily, but not exclusively, aero fasteners are loaded in shear. Heavy equipment , engines, etc have fasteners that use clamping loads (contact stresses) and friction and/or tension to carry loads. This is why they have a lot higher torque and material strength specifications. All these fasteners are torqued fully oiled to ensure full tension. This is particularly true for applications with higher plus to minus cyclic loads. This type of joint does not need locking devices, lock washers, safety wires. They actually make the joint less reliable/durable. Like connecting rods. Make sense?
 
... larger wire (.041) is used for situations where torque is very high, like prop bolts.

There seems to be a persistent belief that .041 safety wire is required for prop bolts. This is not the case, at least for Hartzell propellers. The quote below is straight from the Hartzell Compact Hub Owners Manual:


(8) If required by the aircraft maintenance manual, safety all mounting studs with 0.032 inch (0.81 mm) minimum diameter stainless steel wire or equivalent aircraft safety cable and associated hardware (two studs for each safety). Refer to Figure 3-6.​

Skylor
RV-8
 
Silly Question...

... but do you have a decent pair of safety wire pliers? It's a lot easier with the correct tool (although when I was in A&P school I had an old instructor who like to twist the wire by hand...).
 
There seems to be a persistent belief that .041 safety wire is required for prop bolts. This is not the case, at least for Hartzell propellers. The quote below is straight from the Hartzell Compact Hub Owners Manual:


(8) If required by the aircraft maintenance manual, safety all mounting studs with 0.032 inch (0.81 mm) minimum diameter stainless steel wire or equivalent aircraft safety cable and associated hardware (two studs for each safety). Refer to Figure 3-6.​

Skylor
RV-8

Interesting. Every application I've seen called for .041 by the aircraft MFG manual. I wonder which takes precedence if the prop MFG disagrees? (Speaking of Certificated AC)
 
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What ought to be safety wired?

Suppose you are inspecting an airplane to determine if you want to buy it, or you just bought it.

Now you'd like to know where there ought to be safety wires so that you can determine if they exist.

Is there some way to determine what needs to be safety wired?

thanks!
 
Not 100%. Typically, if it has a stop nut it doesn't require safety wire. Platenuts supply the self-locking ability that elastic stop nuts do but I have seen some applications where safety wire is used in conjunction. Castellated nuts use either cotter pins (typical) or safety wire (like prop nuts). But when there is no nut, you have to rely on specs. Typically, if it calls for a drilled-head bolt, it needs safety wire; otherwise it is not required. For example, the case bolts on my Superior engine did not require safety wire but the set screws securing the tappet guides did. Caveat: don't rely on what you find installed as your guide. I've seen people 'temporarily' replace a drilled bolt with an un-drilled one 'just to get home' which was then forgotten.
 
Interesting. Every application I've seen called for .041 by the aircraft MFG manual. I wonder which takes precedence if the prop MFG disagrees? (Speaking of Certificated AC)

I see no disagreement there... the prop manufacturer specifies minimum .032, aircraft manufacturer specifies .041.
 
Interesting. Every application I've seen called for .041 by the aircraft MFG manual. I wonder which takes precedence if the prop MFG disagrees? (Speaking of Certificated AC)


I too was told that .041 safety wire must be used for prop studs/bolts. I then read the Hartzell manual and it says minimum of .032. .032 is much easier to bend and twist so I elected to use it and I'm not the least bit worried about my prop falling off :eek:
 
Safety wire

Didn't matter to me... My FAA inspector wanted .041, so the 32 came off! Thought the larger wire was harder to work with. OK once you go thru the learning curve....
 
Interesting. Every application I've seen called for .041 by the aircraft MFG manual. I wonder which takes precedence if the prop MFG disagrees? (Speaking of Certificated AC)

The aircraft manufacturers maintenance data always takes precedence over any component maintenance manuals if there is a difference or if the aircraft manufacturer publishes maintenance procedures for vendor sourced components. It is actually up to the aircraft manufacturer to determine part/component compatibility/eligibility for installation and operation on each aircraft model. The airframe OEM can and will determine installation and check out procedures, operational limitations and scheduled maintenance requirements and frequencies. Often times the airframe OEM will use the component manufacturers data for all of the above, but not always.
 
Didn't matter to me... My FAA inspector wanted .041, so the 32 came off! Thought the larger wire was harder to work with. OK once you go thru the learning curve....

So once again, an FAA inspector making up his own rules and regulations, this time *in direct contradiction to the prop manufacturer's instructions*.

I guess they can just make up anything they want on whatever whim they have on any given day, eh?
 
So once again, an FAA inspector making up his own rules and regulations, this time *in direct contradiction to the prop manufacturer's instructions*.

I guess they can just make up anything they want on whatever whim they have on any given day, eh?
If you want the prize, resistance is futile. Or as Kenny Rogers would say "you gotta know when to hold'em, know when to fold'em..."

I basically agree with you, if there is a published, accepted standard that should suffice. However sometimes that old greybeard has a perfectly good reason for their "preference". Often experience trumps judgement.

George
 
Actually safety wire is optional on experimentals Hartzell propellers because there is no MM that calls for it.
 
If you want the prize, resistance is futile. Or as Kenny Rogers would say "you gotta know when to hold'em, know when to fold'em..."

I basically agree with you, if there is a published, accepted standard that should suffice. However sometimes that old greybeard has a perfectly good reason for their "preference". Often experience trumps judgement.

George

You know that post was 5 years ago, right? :)
 
In some applications, Nord-Lock washers instead of safety wire work great. My Matco brake calipers came with them.

You do have to be careful to install them in the correct orientation...the "cams" face each other, and the serrations contact the bolt head and caliper body.
 
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