Airbus dent dress-out

[mindRAGE]

in a300 srm thers a diagram showing the allowable dent and i satisfied all the requirements.
- depth is allowed (vs. skin thickness and fastener distances)
- no cracks (as per ntm)
final verdict: NO REPAIR ACTION REQUIRED (iaw -same ref.)

but....below

thers an instruction for: ALLOWABLE DENTS ON SKIN PLATES CAN BE DRESSED OUT

Im confused..what course of action should i take?
no repair action or dress-out?

help me out..please

and one more thing..if the depth is not allowed, can i dress it out to make it allowable(no crack)?

thanks

 

[berkshire]

You do not say where the dent is located on the aircraft.
Is it where a mechanic can get behind with a dolly to hand dress it, or is it where electromagnetic dent removal is required.
One thing you have to consider when removing a dent is work hardening of the skin by the planishing action. If you did not have a crack before ,you might end up with one.
The other thing you can do, if the dent is allowable but looks ugly, if the aircraft is painted is just use micro ballon putty and paint over it.
B.E.

 

[Benbarca7]

Where is the damage located?
Are you in areodynamic flowpath

I would say, it is not explicitly saying that you have to dress out.
The definition of an allowable damage is that you dont need a repair, but if a small repair it is explicitly said, like in a requirement column where it is written "blend it 10:1 refere to repair XX, or dress out or anything."

re-read the tables/diagrams, for me, can be means that you dont have to.
In any case, you case ask Airbus or the OEM to know what you exactly need to do.

Then for your second question, dont deviate from the SRM.
If your damage depth is not allowed, you cant dress out to make is allowable.
Think that your dent is stress sized according to a method so unless you know how the dent is justified (FE model, or net section calculation,...), then you cant do anything, because you dont know if your allowable is dependent to the depth.
Then a dent in a skin means that it probably has plastified so even if you dress it out or make any touch to it, you still have your stress concentration.

In my opinion, you should stick to the SRM limits, or ask to the OEM for a minor deviation.

Hope this helps,



Ben
Nacelle Stress Engineer (repair on Civil Aircraft)

 

[mindRAGE]

Thanks guys..
I think i stopped too early.
As berk said about putty/filler..I found a reference for that (accidentally)
51-73-10 repair of minor damage also for dress-out.

I was looking at 53-10-101 so i stopped when it said no action required when i plot my figures to the diagram.

this was an early confusion since chapter 53-10-101 didnt cross-ref 51-73-10 if the dent depth is allowable. I was expecting: "If the conditions are allowable please proceed to 51-73-10" but instead they said "no action required"

Also thanks to Ben. Now its concrete that "not all dent are depth dependent or distance-to-nearest-structure dependent" correct?

Actually this is just an exercise for me, not actual. Given the depth of dent, specific location, distance nearest fastner, aircraft type etc.

I just want to be more effective and efficient in getting references and getting help from people with more experience.

 

[Benbarca7]

Not all dents are depth dependent.

Usually, we consider a dent as a hole. so the depth has no influence.
but some analysis can consider a real dent, modeled with finite element, where a depth/diameter ratio is taken.

It really depends on the method that has been used to justify the dent.

As for the distance to the fastener, when you are close to fasteners, until a certain distance you wont have any stress concentration. So It has to be considered too.

Basically in the SRM you can only do what it written and any minor deviation should be validated by the competent institution (OEM, MROs,...)

Regards,

Ben
Nacelle Stress Engineer (repair on Civil Aircraft)

 

[lisa247]

I used to work in repairs and I found that sometimes the SRM would contradict itself, it's not exactly the easiest of things to follow. It sounds to me as though your dent is within SRM limits and it is telling you that the dents CAN be dressed out, but only if required, i.e. if there is an aerodynamic requirement or some other non-structural requirement.

Lisa

 

[Benbarca7]

And if you still doubt, you can always ask to the SRM owner, and discuss with him if it is contradictory or unclear.
The SRM is updated several times in a year, so if a mistake is found they can correct it.

Ben
Nacelle Stress Engineer (repair on Civil Aircraft)