Ask An Aircraft Mechanic

[YourLocalAircraftMechanic]

I see lots of “project planes” on Barnstormers. It doesn’t appear to be economical to pay an A&P to, say, re-cover a Tripacer that’s been in pieces in an Arizona T-hangar for the last 10 years. The majors take their airframes to El Salvador for FAA approved heavy maintenance. Is there a similar facility for GA light piston singles?

I can't comment on that as I frankly don't know. What I can say is getting an aircraft re-covered is increasingly becoming a more specialized thing that is getting hard to find from what I've heard. I believe there are a few shops still around that deal with it but outside of warbird stuff you're going to be hard pressed to find anything I imagine but this is speculation on my part as I simply don't deal with it. Perhaps another mechanic can better answer your question.

 

[Cmm]

In essence very little. In a D check it really depends on what is found that determines exactly what needs to be done. Some aircraft for instance are known to have corrosion issues in various places and may require that the area in question be entirely built from new. It just depends on how much a customer has to spend and what needs to be done. Obviously final aircraft assembly from the factory you're going to have a completely brand new aircraft with 0 time across the board outside of any delivery testing or such things. A D check tends to cost in the million or millions of dollars range so it's pretty intensive. I personally have not done a D check yet but I've done plenty of C and A checks.

Just wondering because you have never done a d check how often are they done and also how often are I believe a cost saving 3c check meant to mimic d done?

 

[YourLocalAircraftMechanic]

Just wondering because you have never done a d check how often are they done and also how often are I believe a cost saving 3c check meant to mimic d done?

I believe D checks on average are done about every 6 - 10 years but don't quote me on that. 3c's aren't meant to mimic a D however they can and do hit up area's that are also done during D checks thus resulting in some things you would do during a D check having already been done. To my knowledge you cannot substitute out a D check for several 3c's like you're probably thinking. The maintenance program is approved by the FAA and any deviation has to be approved by them to my knowledge. This means if you got a D check coming up you are doing a D check whether you want to or not unless you plan on getting rid of the aircraft.

 

[Cmm]

I believe D checks on average are done about every 6 - 10 years but don't quote me on that. 3c's aren't meant to mimic a D however they can and do hit up area's that are also done during D checks thus resulting in some things you would do during a D check having already been done. To my knowledge you cannot substitute out a D check for several 3c's like you're probably thinking. The maintenance program is approved by the FAA and any deviation has to be approved by them to my knowledge. This means if you got a D check coming up you are doing a D check whether you want to or not unless you plan on getting rid of the aircraft.

So then based upon the d check schedule would that mean that some of the a380s being retired right now and other aircraft be not only because of lack of demand but avoiding the costs of a d check as for example af and lh A380s are at d check age Along with deltas 777lr’s?

 

[YourLocalAircraftMechanic]

So then based upon the d check schedule would that mean that some of the a380s being retired right now and other aircraft be not only because of lack of demand but avoiding the costs of a d check as for example af and lh A380s are at d check age Along with deltas 777lr’s?

Yes, among other things. The decision to keep an aircraft around depends on a lot of factors but that does not mean the end of the road for that aircraft. Plenty of times what ends up happening is someone picks it up on the secondary market or another airline may buy it as well. It really depends specifically on the exact aircraft because there's too many variables to take into account when talking across the board.

 

[Daleyjeeper]

Howdy all,

I was pretty excited to see this place come up and wanted to jump aboard as the ball started rolling to help out how or where I can.

If you have questions regarding aviation maintenance, becoming an aircraft mechanic, or anything else along those lines please feel free to ask. I also welcome other mechanics to come on in and answer questions if they desire. I'm a big believer that aviation is a team based industry and half of teamwork is communication. So with that said if you have any questions once again feel free to ask and I will try to answer them to the best of my knowledge and abilities.

Also if you need a good job resource and do not know of one I recommend JSfirm. There you can find all kinds of aviation related jobs that are out there right now.

I am currently in my first month of a 14 month A&P program, what kind of maintenance did you do? i am trying to narrow down what type of job i want to get when i finish. either a commercial airline like delta, a repair facility for general aviation or small private jets, or try to get on with a company than cervices military aircraft. What do you suggest to look for in a job and location as moving is an option for me.

 

[affinity4aviation]

My dad's Cessna 182 threw a rod years ago. He glided safely, with 2 passengers. Meticulous re safety. Mechanic possibly overlooked signs of metal fatigue, or does this happen sometimes without forewarning?

 

[Plague]

I've read about metal fatigue causing some issues in commerical aviation also.

I think metal fatigue was, and possibly still is, probably the second most common cause of trouble (human error is probably no 1).
MF is better understood now, so less likely to go unnoticed, but it's nature means that it still can. Almost every 'exploding' jet engine you read about every few months is due to it, usually a blade sometimes a disc.

 

[Roichi]

Metal fatigue has many different aspects to it. And every piece of metal is different. Even such highly engineered things as fanblades, which are complex one cristal structures.

 

[Sean]

Fatigue failure is a statistical thing, which is why there's so much redundancy (and added cost) in commercial aviation. Inspection is designed to catch cracks and defects of a certain minimum size, based on an assumed high probability that they won't grow to failure before the next inspection. No part is perfect, and there will be a few defects smaller than the size the inspection is designed to catch. Visual will miss anything below the surface, such as inclusions and microstructural defects and anything that is obstructed by other components. Commercial airliners have much more rigorous (and costly) inspections that not only have higher resolution than the human eye, but can "see" below the surface of a part. Commercial airliners also have much stricter metallurgical standards for all their components, again at higher cost than private, so the defects are smaller, and the cost goes up exponentially as the size of the defects allowed decreases. And still there are terrible surprises.

In your father's case, when the mechanic did the inspection of the part, there may have been nothing to see. The initial crack may have been hidden and it may have encountered an inclusion or internal pore that let it propagate to failure prematurely. Likely your dad's mechanic did a visual inspection (maybe with magnifying lenses and even a fluorescent dye), because he didn't have access to the ultrasonic and other non-destructive testing methods that are available at the heavy maintenance facilities. Best he could do still couldn't catch every possible defect.

If you had the part, you could do a failure analysis (SEM fractographs are way cool) and see the initial crack, the region of slow crack growth, and the region of rapid crack growth. You could deduce whether the crack would have been visible during the slow growth phase. With 2020 hindsight, you could figure out whether he missed something, and whether the part was defective (I've had defective engine parts that failed because they didn't receive the correct heat treatment, that also happens).

Best to be thankful everyone survived the failure of the part and, even if you spend the money for commercial components and inspection, accept that there's always some risk.

 

[Penfold101]

In much the same way, composite structures are notoriously difficult to examine for damage. materials like carbon fibre can be hit by an object but show no signs of damage on the outside, whilst on the interior it's the complete opposite, but you wouldn't know without taking it apart. If you don't know it's been hit, then you'd have no reason to do so, and so damage can go undetected, allowing water ingress and subsequent failure of the part. This is what I believe happened to the F-16 at RIAT in the UK a couple of years ago, when a tailplane panel ripped off in flight. Corrosion, water ingress, unseen damage - anything could have been the cause for the failure with no visible problems on the outside.

This, and metal fatigue, are the reasons why manufacturers and design organisations keep track of all faults found and their fixes for trend analysis - they can see patterns forming on fleets which you'd never come across in flight testing, introduce specific inspections during maintenance or issue service bulletins to check them within a time period. If it's very urgent, and airowrthiness directive can be issued, potentially grounding the aircraft type until it's carried out.

And finally, at the end of the day, any machine can have a completely random failure no-one can predict. Hence we have redundant systems and train pilots to fly without engines.

 

[Chris Hayes]

What is the coolest plane you have worked on?

That's an easy question! 777-200LR.
It's loaded with the latest and greatest avionics and technology!
Well... mostly anyway. The 787 has some more advanced stuff in it, but I have been on some great flight test programs including the modification and installation of the latest technology. This also included a sales tour on the 777-200LR that went around the world. I was also involved with the longest flight (according to the Guiness book records) of a commercial aircraft!!