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IAF747

How does aircraft get fixed at airport incidents

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When the fuselage is damaged by a truck or another aircraft for example I was wondering how these get fixed? Or even more critical wing parts.

Incidents at airports are very common but I don't know how they would be repaired.

 

Daniel

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When the fuselage is damaged by a truck or another aircraft for example I was wondering how these get fixed? Or even more critical wing parts.

Incidents at airports are very common but I don't know how they would be repaired.

 

Daniel

Hi Daniel,

Interesting question.

As far as I know, damaged metallic parts can be patched (or maybe even hammered back into shape ?).

For composite parts, I assume that, depending on the dimension of the damage, they can be either repaired or replaced but I admit I am no expert.

Rgds,

Bruno

 

PS : I guess, not all parts receive equal treatment. Some fairings bear no load and can therefore be easily repaired. Load bearing structures are probably another story.

 

(edited)

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Well that is a very open ended question. The metallic parts of which a large percentage are usually aluminium are typically very strong and stiff. But when they are bent generally can not be "hammered" back into shape as this will cause a weak point and you can get stress cracking. The skins are generally easy to replace. But if they are damaged, can either have the damage cut out with a patch repair to the area or a complete replacement of the part. It is rare for only the skin to be damaged though as there is a lot of structure holding the aircraft together, so there is usually damage to the underlying structure also, if there has been an incident with a truck or other aircraft. 

 

If it is only minor like say a small scratch the scratch can often be blended out up to say 20% of the thickness of the part as usually aircraft parts are designed with at least a 1.5 times designed load limit, built into the part 

 

The applicable aircraft's repair manual will usually have repairs for damage to structure also in which case the damage is cut out with a new piece inserted and a repair doubler to hold it altogether and return the structural integrity of the part or again replacement of the part, depending on the location of the damaged part,size,cost, time taken and structural load of the part etc are all considered. 

 

There are typically 3 class's of structure on an aircraft. Primary, secondary and tertiary. primary and secondary are both load bearing and critical to the structural integrity of the aircraft. Tertiary is fairings and the like that if damaged will not affect the structural integrity of the aircraft

 

If the damage is very bad and outside of the aircraft's repair manual an aircraft engineer will design a one off repair especially for the part, for then the structural and mechanical tradesmen to carry out.

 

Note that some parts are made by hammering them into shape for the many different shapes and curves of the aircraft but these are made from aluminium that is soft and once the desired shape or curve has been made the part is then heat treated to a high temperature which strengthens the aluminium and then be ready to fit to the aircraft. This unfortunately is happening less and less as more and more composite aircraft are coming out. It is a hard skill to master but is really awesome to see some of the shapes on parts that can be made

 

If it is composite it can vary from simply adding some resin or adhesive to the damaged part to cutting out the damage usually in steps as you cut through each ply of the skin and then if the honeycomb core is damaged cutting it out and replacing it with new honeycomb then laying new plies on each layer of the skin as it was step cut, all in the same orientation as each original ply or layer. Usually with a few extra plies over the entire repair tying the repair into the original part returning the strength to the part.

 

For me it is disappointing to see all these new composite aircraft. Composite repairs are usually very time consuming boring and monotonous, and although you have to be a highly trained person to carry out the repairs, i feel there is actually not much skill in the process. Compared to repairing an aluminium part where especially if it is a curved part requires much more skill in turning a flat sheet of metal into an intricate shape. Aluminium is also much nicer to work with than composite and for me tend to get a higher job satisfaction. 

 

But you can not deny the strength and weight characteristics of composite generally are superior than aluminum 

 

Hope that clears up some things for you. :rolleyes:

 

Regards

 

Hayden

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Thanks Hayden for the detailed reply! Above and beyond the call of duty!

Thanks Bruno for giving me your best answer.

Daniel

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An easily removable component like a control surface, access panel, baggage hold door, or nose dome might be replaced with a spare and shipped back to a central maintenance facility to be repaired. That way the aircraft itself isn't out of service for a long period. There might be a short grounding while the spare is air freighted from a central warehouse and/or a staff or contractor mechanic travels in.

 

When patching either metal or composite structures the extent of the damage has to be determined and the width of the repair layers plotted out. Since angled corners would concentrate structural loads the corners must meet a minimum radius and blend into the adjacent straight edges. Locations for rivets and similar fasteners have to plotted out with consideration for those which previously connected the aircraft skin to underlying structures. Often multiple rows are required with staggered positions. Outer rows require additional rivets in the corners). If high loads make steel fasteners in aluminum skin or underlying structure necessary they need to be painted immediately before insertion to retard corrosion.

 

Air bubbles have to expelled from any patches that rely on adhesives, including repairs to composite structures. Patches might require an application of plastic film over the "wet" patch and the application of a powerful vacuum pump to extract sir from under the film (environmental air pressure clamps the patch to the surface). The resin eventually holds the patch layers together and attaches the patch to the original structure. Effective materials might require the resins to be soaked into the reinforcing material at the materials manufacturer and shipped and stored at dozens of degrees below 0°F until shortly before use. Wherever the resin is produced the ingredients, some of which might be toxic until the patch hardens, need to be measured in precise quantities. An application of heat might be required to make the resins cure properly.

 

On at least one military aircraft damage to certain composite structures could produce splinters of the reinforcing material that were very brittle and difficult to effectively extract if they penetrated an employee's hand or finger.

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Another excellent reply!

Thanks Robert, I suppose you guys get training in safety on that?

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