Forum: F-16 Procedures

If there are no specifications for a torque value on a bolt with pre-installed threads, or a bolt/nut combination written on a TO, there is an equation that will determine the value. I cannot remember the equation; it has something to do with length of shank thread, # of threads, and diameter of the bolt/nut. Can someone look this up in the general maintenance practices TO and post the equation?

What determines in/lbs and when does ft/lbs come into play generally speaking?

Also, with regard to safety wiring, how much tension is there supposed to be between two pieces of hardware upon safetying something thats locked up?

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the to is the 1-1-8. It is available electronicly.

Thank you CrewDawg, the reason why I'm asking is I plan on helping someone do some minor maintenance on an aircraft and I wanted to review some procedures I lost track of. I will try to locate the TO, thanks again.

The determination for in vs ft lbs is basically determined by the size of the fastener and what its job is. Obviously little fasteners can't take big torque - but just because it's big doesn't mean it gets a big torque. Some of the largest torques are found in C-130 prop nuts. But the engine mount bolts (coke bottles) on an F-16 don't take as much as you'd think.

As far as safety wire tension - that's a really good question that can't be answered as it's very subjective. For drilled head hex bolts it needs to be tight enough that the loops going around the bolts don't flip up but not so tight that it stresses the wire on sharp corners. It really doesn't have to be real tight as even if it flips up the bolts will only turn so far and can't back all the way out. But it's one of the few art forms left to maintainers so we take pride in them looking nice. Interesting side note - there is no safety wire used anywhere on the F/A-22.

Not even on the engines? Unreal! I understand your notes on safety-wiring, was just wondering if there was a standard? When I was crewing and when I wrote gen maint prac on the MD-11, there was supposed to be some play, about the width of three diameters of the twisted wire to either side from the center of the length of wire. Is this about what everyone has been doing?

Not even on the engines. There are some spots that use a braided cable safety but your traditional twisted wire is a thing of the past. Has to do with CW suits more than anything else. Three diameters sounds like about right to me. But I wouldn't necessarily reject one that was a little tighter either.

The 1-1A-8 states in Chapter 16 that for the tightness of the safety wire......"The wire shall be tight". Thats all it says anymore. It also says that "it will not be overstressed". Talk about something thats subjective!!!

Tight is tight and too tight is twisted off.....

Most of the time tight is when you can't flip the safety wire, looped on the bolt or nut head, up the side of the nut or bolt and over the top. I always check it by trying to pull it loose, Iie. pull it over the head of the fastener. Techniques very from wrench to wrench but that is the way I was shown many moons ago.

There used to be better guidance than this. I have spent 27 years in aircraft maintenance and to me safety wire is an art form and it seems it has slowly gotten worse over the years.

CDCs used to have an entire section on it, at least my Career Field did. I would assume they still do.

mark wrote:

There used to be better guidance than this. I have spent 27 years in aircraft maintenance and to me safety wire is an art form and it seems it has slowly gotten worse over the years.

So true, so true... And now we've even gotten the so called "SAFE-T WIRE". A pre twisted wire where you thighten the wire and crimp on a lock bead with a tool. May be great for thight spots but I prefer the good old safety wire.

Last edited by allenperos on May 26, 2005 - 11:04 PM; edited 1 time in total

Does anyone know the equation for determining torque if none is specified?

This was perhaps the main point of the forum, anyone know, safety-wiring has been very well covered thus far, lets go to torquing.

allenperos wrote:

Does anyone know the equation for determining torque if none is specified?

This was perhaps the main point of the forum, anyone know, safety-wiring has been very well covered thus far, lets go to torquing.

I don't remember a general formula but I do know most aircraft manufacturers put generic tables in their manuals. It's usually listed as "general torque values". I would never use a general value for any loadbearing component. General torques are usually for panels and trim type stuff. Here is a non-aircraft link http://mdmetric.com/tech/tech4/3.htm that will give you a rough idea.

After looking all day, I've found the answer to my own question with a little help from a friend. When you see how easy this is and how I could not remember it, I really deserve a little humiliation from the forum.

TORQUE = MASS * ACCELERATION * MOMENT ARM, MOMENT ARM = INCHES*LBS

OR MOMENT ARM = FT*LBS

Apparently, this is for a standard torque value.

Safety wiring does not have a specified value of tension.

Forum: F-16 Procedures

Safety Wiring/Torquing Hardware Procedures