Bends, kinks and splices

[Michael Horowitz]

How does an A&P know if he can simply straighten out a longeron or if
he's going to have to cut and splice? Obviously if it has a kink in
it, it's very weak and would have to be spliced. Is there a reference?

In the meanwhile I'll go read AC43.13 and see what they say.
..
..
..
..
..
Well, 43.13 doesn't say when to bend or when to cut, so, the question
stands.

- Mike

[[email protected]]

Michael Horowitz wrote:
> How does an A&P know if he can simply straighten out a longeron or if
> he's going to have to cut and splice?

-----------------------------------------------

I think you've left a few too many loose ends for a concise answer.
However...

The nature and extent of the damage tends to dictate the method of
repair but the airframe usually defines which repair procedures are
most applicable.

Steel tubing without any traumatic injury such as shrapnel wounds or
bullet holes, the degree of deformation and the surface texture tells
you if the member may be straightened or if it should be replace.
Aluminum, due to the stretch resulting from even a minor deformation,
you generally cut it back to clean, un-deformed metal and make up a
splice.

But I'll tell you pard, getting a kink out of a wooden longeron is a
hell of a chore; trying to straighten that stuff just makes it worse,
your rivets don't hold for **** and don't even think of trying to weld
it. Vast mystery I guess.

Or at least, half-vast :-)

-R.S.Hoover

[Ernest Christley]

wrote:

> But I'll tell you pard, getting a kink out of a wooden longeron is a
> hell of a chore; trying to straighten that stuff just makes it worse,
> your rivets don't hold for **** and don't even think of trying to weld
> it. Vast mystery I guess.
>
> Or at least, half-vast :-)
>
> -R.S.Hoover
>

Mr. Hoover, this being RAH, I can't just let such misinformation go buy
unheeded. Why everyone know that you can weld wood longerons just fine
if you get the right rod. You see, the oak rod is to hard. It won't
stretch as it cools, and tends to pull the parent material too thin.
You have to use a soft, white pine rod. It's weaker, but your weld will
be 3 to 4 times as thick as the parent anyway so it won't matter.

The secret is to use a carbeurizing flame. Do it right, and you'll
never have to worry about crashing the airplane.

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

[W P Dixon]

It also reduces the weight very effectively!

But on a serious note what kind of plane are we talking about? I may be able
to help.

Patrick
student SPL
aircraft structural mech

"Morgans" > wrote in message
...
>
> "Ernest Christley" > wrote
>
>> The secret is to use a carbeurizing flame. Do it right, and you'll
>> never have to worry about crashing the airplane.
>
> <great big chuckle>
>
> You could go as far as saying, that by welding that one piece, it will
> guarantee that you never will have to work on the plane again!
> --
> Jim in NC
>

[Morgans]

"Ernest Christley" > wrote

> The secret is to use a carbeurizing flame. Do it right, and you'll
> never have to worry about crashing the airplane.

<great big chuckle>

You could go as far as saying, that by welding that one piece, it will
guarantee that you never will have to work on the plane again!
--
Jim in NC

[[email protected]]

Michael Horowitz wrote:
> How does an A&P know if he can simply straighten out a longeron or if
> he's going to have to cut and splice? Obviously if it has a kink in
> it, it's very weak and would have to be spliced. Is there a reference?


Mike: Find a copy of the Structural Repair Manual for what you are
working on. Within it there will be enough data that you can make not
only the correct repair decisions but ones that are strucuraly sound
without having to do any anaylsis.

I checked the SRM for my Fairchild and corrosion isn't even listed as a
problem with the tubing as it was an ex-military aircraft. I did note
that there are numerous limitations on dent size, depth and surface
area involved and that the repair limitations and processes differ
based on damage location.

Craig C.

[Michael Horowitz]

WP- steel and fabric taildragger. - Mike

"W P Dixon" > wrote:

>It also reduces the weight very effectively!
>
>But on a serious note what kind of plane are we talking about? I may be able
>to help.
>
>Patrick
>student SPL
>aircraft structural mech
>
>"Morgans" > wrote in message
...
>>
>> "Ernest Christley" > wrote
>>
>>> The secret is to use a carbeurizing flame. Do it right, and you'll
>>> never have to worry about crashing the airplane.
>>
>> <great big chuckle>
>>
>> You could go as far as saying, that by welding that one piece, it will
>> guarantee that you never will have to work on the plane again!
>> --
>> Jim in NC
>>

[Michael Horowitz]

VB - sorry about the vagueness, but we will need to remove fabric
before I can see anything except the bend in the tailcone; the
horizontal stabilizer sustained a considerable blow when it hit
something on the ground - Mike

wrote:

>
>Michael Horowitz wrote:
>> How does an A&P know if he can simply straighten out a longeron or if
>> he's going to have to cut and splice?
>
>-----------------------------------------------
>
>I think you've left a few too many loose ends for a concise answer.
>However...
>
>The nature and extent of the damage tends to dictate the method of
>repair but the airframe usually defines which repair procedures are
>most applicable.
>
>Steel tubing without any traumatic injury such as shrapnel wounds or
>bullet holes, the degree of deformation and the surface texture tells
>you if the member may be straightened or if it should be replace.
>Aluminum, due to the stretch resulting from even a minor deformation,
>you generally cut it back to clean, un-deformed metal and make up a
>splice.
>
>But I'll tell you pard, getting a kink out of a wooden longeron is a
>hell of a chore; trying to straighten that stuff just makes it worse,
>your rivets don't hold for **** and don't even think of trying to weld
>it. Vast mystery I guess.
>
>Or at least, half-vast :-)
>
>-R.S.Hoover

[Stealth Pilot]

On Tue, 16 Aug 2005 15:55:30 -0400, Michael Horowitz
> wrote:

>How does an A&P know if he can simply straighten out a longeron or if
>he's going to have to cut and splice? Obviously if it has a kink in
>it, it's very weak and would have to be spliced. Is there a reference?
>
>In the meanwhile I'll go read AC43.13 and see what they say.
>.
>.
>.
>.
>.
>Well, 43.13 doesn't say when to bend or when to cut, so, the question
>stands.
>
> - Mike

the limitations regarding size of dings is usually in the repair
manual for the aircraft. presumably it is related to just how close
the strengths are to the predicted max g loads/stresses.

if you can persuade the longeron back into shape with a rubber mallet
without distressing the metal anywhere then it's your call.
(it helps not to look at it when you hit it or to speak to it in the
preceeding 5 minutes :-) ) put a block of wood on the tube and hit
the block.

looking at a truss tube that is broken . divide it mentally into
thirds. you may not splice, join or weld in the centremost third.
....because this will lead to fatigue failures.
if you have a repair needed in the centre third then you need to
remove the piece back into the outer thirds.
you can then splice in and weld a new section.

ac43-13 does have a few different repair methods. the rivet ones are
only intended as temporary field repairs.

dont forget that you can often repair in the outer thirds by welding a
piece of sheet over the problem area.

tig welding for preference, oxy-acetylene if that is all that is
available. when you've finished stick some tube seal back into the
tubes.

the hot area of the weld will try to shrink as it cools from red heat.
lightly clamp the repair in position and it will cool straight.

Stealth Pilot

[W P Dixon]

Michael,
As was mentioned , the know all see all is the Structural Repair Manual.
And with saying that I will add , if it is an old plane it still may not
help you much. If it is a plane that still gets made you probably will find
everything you need in the SRM. ( As the previous post I was glad to learn
the no corrosion stuff in that SRM) SRM's sure usually cover corrosion,
damage repairs, and what is acceptable. For things not acceptable you are
usually given a proper repair. And alot of times even told when engineering
analysis was necessary. Since this is a homebuilt forum, I will say that
SRM's are for certified aircraft published by the aircraft maker.
Using AC43.13-1B, I would say anything you felt would take an engineer
to approve of a fix , replace the tube. If you don't see a repair in there
it's usually because the fix will have to come from higher up..DME.
Homebuilts get alot of freedom in their fixes, but holding your airplane to
some FAA standards can be a good thing as well. Most homebuilders nor A&P's
are engineers,....and you may have a case here where you need one. Your
other option would be replace the tube in question.
Of course since myself nor any of us on here have seen the damage in
question my answer is on the side of safety and caution. When it comes to
airplanes it always seems to work out best that way ;)

Patrick
student SPL
aircraft structural mech

"Michael Horowitz" > wrote in message
...
> WP- steel and fabric taildragger. - Mike
>