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Replacement Parts On A Plane  
User currently offlineFlygirl83 From United States of America, joined Aug 2007, 9 posts, RR: 0
Posted (6 years 6 months 1 week 2 days 21 hours ago) and read 3676 times:

I am curious to know, who decides when it is time to replace the small parts on a plane? For example, ignition systems and components, specialized valves, lavratory hardware, elastomers, latching and locking devices...

Are there a lot of companies that manufacture these parts or do you just get them from the original manufacturer when they wear out?

Thanks!

50 replies: All unread, showing first 25:
 
User currently offlineA10WARTHOG From United States of America, joined Jul 2004, 324 posts, RR: 0
Reply 1, posted (6 years 6 months 1 week 2 days 21 hours ago) and read 3663 times:

Majority of the parts are replace as they fail.

Components like igniters, pumps, batteries, generator, engine, etc are time controlled parts, I believe usually governed my the manufacture and approved my the FAA. On a generator it could just be the brushes that need to be replaced. You just R&R the part and send it to a repair shop, manufacture or in house back shop.


User currently offlineFlygirl83 From United States of America, joined Aug 2007, 9 posts, RR: 0
Reply 2, posted (6 years 6 months 1 week 2 days 20 hours ago) and read 3661 times:

Gotcha.

When the part is replaced does it matter if you use a part from the original manufacturer, or is it popular to use generic knockoff parts if they exist?


User currently offlineAerobalance From United States of America, joined Sep 2000, 4681 posts, RR: 47
Reply 3, posted (6 years 6 months 1 week 2 days 20 hours ago) and read 3648 times:



Quoting Flygirl83 (Reply 2):
When the part is replaced does it matter if you use a part from the original manufacturer, or is it popular to use generic knockoff parts if they exist?

For commercial airline applications, the vendor must be an FAA approved repair station or original equipment manufacturer, I forget the FAR that applies...



"Sing a song, play guitar, make it snappy..."
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9605 posts, RR: 52
Reply 4, posted (6 years 6 months 1 week 2 days 20 hours ago) and read 3638 times:

I only know components that I work with, so my knowledge isn't that extensive, but it is decided based a variety of reasons. For many parts, they are designed to last for the lifetime of the airplane. However it is hard for the manufacturer (and I am talking about Boeing, Airbus, Cessna or whomever else) to pin point exactly what that means. There is qualification testing done on parts based on requirements that are decided upon by design engineers. For example a newly designed part might be tested through 20 years worth of service (obviously done in an accelerated manner). There are also acceptance tests done on each individual part before it is installed on an airplane.

There are Design Review Objectives (I think that is the term for DRO's) which call out how long each part should last in each area of the plane. Specific engineering groups come up with these requirements. Suppliers and the manufacturer try to ensure that parts will last a certain amount of time. A 95-95 rule is often used. 95% of the parts delivered will survive 95% of the life of the airplane.

Many parts are just simply replaced when they fail. If they aren't critical for flight, then this is very common.

Now I don't really work on parts that require regular replacement, so I am not sure how those intervals are decided. There's definitley a cost benefit analysis that is done. You want the lightest part possible that will survive an acceptable amount of time. An acceptable amount of time is often the time between D-Checks or C-Checks or other regularly scheduled maintenance.



If you have never designed an airplane part before, let the real designers do the work!
User currently onlineKELPkid From United States of America, joined Nov 2005, 6371 posts, RR: 3
Reply 5, posted (6 years 6 months 1 week 2 days 20 hours ago) and read 3639 times:



Quoting Flygirl83 (Reply 2):
Gotcha.

When the part is replaced does it matter if you use a part from the original manufacturer, or is it popular to use generic knockoff parts if they exist?

In GA land, it's pretty common for multiple manufacturers to have PMA (Parts Manufacturer Approval) or an STC to exist to allow multiple vendors on parts...also, many common parts with automotive roots (for example, alternators and starters) are merely automotive assembly line parts that underwent an extra inspection at the factory for a PMA approval. The alternator on many Lycoming O-320 powered Cessna 172's will be recognized by auto lovers as the classic Ford Motorcraft alternator from the Ford Mustang, however Cessna places their own part number label on it, and, IIRC, it covers the big "Motorcraft" stamp casting on the back. Also, the starter on many Continental O-470 engines as used in bigger Cessnas is the Mopar starter from mid to late 1960's Chrysler Hemi engines... Don't go out and used unapproved autopart store replacements, however!



Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 6, posted (6 years 6 months 1 week 2 days 19 hours ago) and read 3626 times:

If I were a journalist, I would be looking for flying wrecks with cheap knock-off parts that were about to fall out of the sky. That's news, you see. Corporations sacrificing lives for the sake of profit? Journalistic gold. Maybe we can get someone to slate the triple seven! Maybe we can cull BA totally! That would be a scoop - and the journo gets to bring down the system from inside, just like they promised to do when their dad bought them their first Seat Cupra.

And if I were to post on an airliner forum, I expect I would use a screen name that would make me look like a woman in order to get attention. I might even do a small amount of research to get some terms very nearly right.

I'd probably go too far when I mentioned 'elastomers' though.



Todos mis dominós son totalmente pegajosos
User currently offlineFlygirl83 From United States of America, joined Aug 2007, 9 posts, RR: 0
Reply 7, posted (6 years 6 months 1 week 2 days 19 hours ago) and read 3613 times:

Hmm. Interesting conspiracy theory. But wrong  Smile
I am a woman, but definitely not a journalist and definitely not interested in planes falling out of the sky.

i'm just curious to understand who decides what parts to use for replacement, and when they need to be swicthed out. I recently started looking at a company that manufacturers some of these small parts and as I am not a mechanic myself, I figured you guys would be the best people to educate me.So... thanks for the education! And any other insight into your experiences of determining when to replace the parts and where you get them when they are broken would be great  Smile


User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9605 posts, RR: 52
Reply 8, posted (6 years 6 months 1 week 2 days 18 hours ago) and read 3578 times:



Quoting Flygirl83 (Reply 7):
And any other insight into your experiences of determining when to replace the parts and where you get them when they are broken would be great

As far as where to get parts on commercial aircraft, each part usually has a qualified supplier. It depends on the part on whether there are multiple suppliers. On a large jet, most parts have 1-3 suppliers. Trends seem to be going away from three though to 1 or 2 on components that I am familiar with. However some parts like Seats, for example, might have many more qualified suppliers.

Parts are purchased through spares agreements. Airlines get in maintenance agreements when they purchase a plane. If there are multiple suppliers, they will choose which one for each airplane they purchase. The most well known decision for airlines is engine manufacturer. I think on average there are two engine suppliers on any given jet, but some like the 737 have only a single supplier whereas some like a 777 can have three.

The spares business is an important one. Spare parts are almost always more expensive than the originals.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineDALMD88 From United States of America, joined Jul 2000, 2543 posts, RR: 14
Reply 9, posted (6 years 6 months 1 week 2 days 17 hours ago) and read 3577 times:

So what is an 'elastomer'? I've been a mechanic now for 17 years and I've never heard any aircraft part called that.

User currently offlineEMBQA From United States of America, joined Oct 2003, 9364 posts, RR: 11
Reply 10, posted (6 years 6 months 1 week 2 days 17 hours ago) and read 3560 times:



Quoting DALMD88 (Reply 9):
So what is an 'elastomer'?

LoL... It's a hard rubber shock mount normally found on items that will vibrate

Quoting Flygirl83 (Thread starter):
I am curious to know, who decides when it is time to replace the small parts on a plane?

As said above, many items are switched out only after they fail. Some items are 'time controlled'...... only allowed to be on for so many hours. These are normally items that wear... like starters, generators things like that. Some items are calender controlled like safety items.....Fire Extinugishers, O2 bottles...Medical kits.....



"It's not the size of the dog in the fight, but the size of the fight in the dog"
User currently offlineAvioniker From United States of America, joined Dec 2001, 1109 posts, RR: 11
Reply 11, posted (6 years 6 months 1 week 2 days 17 hours ago) and read 3559 times:

Sounds like "flakbait" to me. . .


BAe146QT, I think I'm starting to like you more.

Elastomer means "rubber". What makes elastomers special is the fact that they bounce. What makes elastomers special is that they can be stretched to many times their original length, and can bounce back into their original shape without permanent deformation.
 

Is anyone besides me having trouble adding to their respected users list?

[Edited 2008-02-20 14:56:13]


One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9605 posts, RR: 52
Reply 12, posted (6 years 6 months 1 week 2 days 17 hours ago) and read 3555 times:



Quoting EMBQA (Reply 10):


Quoting DALMD88 (Reply 9):
So what is an 'elastomer'?

LoL... It's a hard rubber shock mount normally found on items that will vibrate

Interesting as I had not heard of a specific part called an elastomer on a plane.

Elastomers are a type of polymer, which means carbon based material normally referred to as plastic. Rubber is a common type of elastomer, but there are many more from silly putty to gum to rubber bands.



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17025 posts, RR: 67
Reply 13, posted (6 years 6 months 1 week 2 days 16 hours ago) and read 3518 times:



Quoting Avioniker (Reply 11):
Is anyone besides me having trouble adding to their respected users list?

Check these two conditions first:
- One or more users currently on the list no longer has an account. Delete these first.
- You already have 25 people on the list.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineSeabosdca From United States of America, joined Sep 2007, 5403 posts, RR: 4
Reply 14, posted (6 years 6 months 1 week 2 days 16 hours ago) and read 3510 times:



Quoting Avioniker (Reply 11):
Is anyone besides me having trouble adding to their respected users list?

A recent and annoying bug... you get a white screen when you try to "Add to Resp Members."

The workaround is to edit your own profile manually, adding the usernae of the user you wish to add at the end of the list. I've added my last couple of respected users this way, and it seems to work OK -- I show up in their "Respected By" lists.


User currently offlineBAe146QT From United Kingdom, joined Sep 2006, 996 posts, RR: 0
Reply 15, posted (6 years 6 months 1 week 1 day 20 hours ago) and read 3360 times:



Quoting Flygirl83 (Reply 7):
Hmm. Interesting conspiracy theory. But wrong

I was just yanking your chain, really. But journalists and muck-rakers do frequent these boards. I've seen a few of our members quoted in the papers, and not always in context.

Quoting Avioniker (Reply 11):
BAe146QT, I think I'm starting to like you more.

I'll keep at it - I don't often come across too well in text.  Wink

Quoting Seabosdca (Reply 14):
A recent and annoying bug... you get a white screen when you try to "Add to Resp Members."

I thought he meant, "I can't find anyone else to respect!"



Todos mis dominós son totalmente pegajosos
User currently offlineEasternSon From United States of America, joined Jun 2006, 668 posts, RR: 1
Reply 16, posted (6 years 6 months 1 week 1 day 20 hours ago) and read 3353 times:



Quoting RoseFlyer (Reply 8):
Spare parts are almost always more expensive than the originals

I'm sorry, maybe I'm misunderstanding you, but spare components (those sold in AR, SV or OH condition) are always cheaper than the originals.

Otherwise there would be no reason for the spare parts market.



"The only people for me are the mad ones...." Jack Kerouac
User currently offlineHAWK21M From India, joined Jan 2001, 31679 posts, RR: 56
Reply 17, posted (6 years 6 months 1 week 1 day 7 hours ago) and read 3307 times:



Quoting EasternSon (Reply 16):
I'm sorry, maybe I'm misunderstanding you, but spare components (those sold in AR, SV or OH condition) are always cheaper than the originals.

Otherwise there would be no reason for the spare parts market.

I guess the poster meant that the cost of the part fitted with the original Aircraft works out cheaper than its replacement spare.
regds
MEL



Think of the brighter side!
User currently onlineSEPilot From United States of America, joined Dec 2006, 6894 posts, RR: 46
Reply 18, posted (6 years 6 months 1 week 1 day 4 hours ago) and read 3286 times:



Quoting KELPkid (Reply 5):
The alternator on many Lycoming O-320 powered Cessna 172's will be recognized by auto lovers as the classic Ford Motorcraft alternator from the Ford Mustang, however Cessna places their own part number label on it, and, IIRC, it covers the big "Motorcraft" stamp casting on the back.

When I bought the FBO at my local airport the previous owner (who was an A&P/IA who would shave nickels any way he could, although I believe always with safety in mind) told me that the aviation alternators looked identical to the automotive ones but in fact were not. How did he know? He had tried several times to use automotive ones, but they had always failed quite quickly. Neither he nor I know what precisely the aviation ones do differently, but they are more rugged.
The bottom line is that EVERY part in an airplane is supposed to be FAA approved for aviation use, even cigarette lighter sockets, for example. Of course most mechanics don't worry about non-critical parts (such as cigarette-lighter sockets) but I'm sure most airlines do. Hardware is a big issue; you don't just go down to the local hardware store to get it. When I overhauled my engine a few years ago I replaced every nut and bolt on it, and spent several hundred dollars doing so.

Quoting BAe146QT (Reply 15):
I've seen a few of our members quoted in the papers, and not always in context.

You mean journalists quote out of context??!!!??? I've never heard of such a thing!!!!!!!!!!
 banghead   sarcastic 



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offlineDALMD88 From United States of America, joined Jul 2000, 2543 posts, RR: 14
Reply 19, posted (6 years 6 months 1 week 21 hours ago) and read 3252 times:



Quoting SEPilot (Reply 18):
Hardware is a big issue; you don't just go down to the local hardware store to get it.

So true, In fact most aircraft mechanics I know take that to heart. We tend to use aircraft hardware for just about everything around the house.


User currently offlineJetstar From United States of America, joined May 2003, 1645 posts, RR: 10
Reply 20, posted (6 years 6 months 4 days 18 hours ago) and read 3128 times:
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Some automobile parts are legal in Cessna airplanes.

The wheel bearings on C-150’s are automotive Timken bearings with the same part numbers and can be bought at any auto supply house, Cessna never changed the part numbers.


User currently onlineSEPilot From United States of America, joined Dec 2006, 6894 posts, RR: 46
Reply 21, posted (6 years 6 months 4 days 17 hours ago) and read 3108 times:



Quoting Jetstar (Reply 20):
Some automobile parts are legal in Cessna airplanes.

Can you give me an example? I can't think of any.

Quoting Jetstar (Reply 20):
The wheel bearings on C-150’s are automotive Timken bearings with the same part numbers and can be bought at any auto supply house, Cessna never changed the part numbers.

I believe that it's the same for all Cessna wheel bearings as far as the part numbers. However, I believe that the FAA still wants you to buy them from an "approved source" so they come with the proper paperwork. I certainly did not bother when I was in the business (as it would at least double the cost), and I don't know any mechanic or FBO that does.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 22, posted (6 years 6 months 4 days 17 hours ago) and read 3104 times:
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DATABASE EDITOR



Quoting Avioniker (Reply 11):
What makes elastomers special is that they can be stretched to many times their original length, and can bounce back into their original shape without permanent deformation.

Also, the composition of elastomers can be tuned to bounce/rebound in a slow, controlled manner. In a suspension application, this would reduce the bouncy, "pogo-stick" effect of some suspension designs.

One disadvantage is their inconsistency across a large temperature range. In very low temperatures, rubber/elastomers tend to harden, becoming less effective if used in a shock absorption application.

Advantages include simplicity, light weight, and low maintenance.

The first aircraft application that comes to mind is Mooney's landing gear design:


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Photo © Sven De Bevere
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Photo © Edwin Vanoverschelde



2H4



Intentionally Left Blank
User currently offlineTbanger From Australia, joined Jul 2004, 266 posts, RR: 0
Reply 23, posted (6 years 6 months 4 days 8 hours ago) and read 3052 times:



Quoting Jetstar (Reply 20):
Some automobile parts are legal in Cessna airplanes.

The wheel bearings on C-150’s are automotive Timken bearings with the same part numbers and can be bought at any auto supply house, Cessna never changed the part numbers.



Quoting SEPilot (Reply 21):
believe that it's the same for all Cessna wheel bearings as far as the part numbers. However, I believe that the FAA still wants you to buy them from an "approved source" so they come with the proper paperwork. I certainly did not bother when I was in the business (as it would at least double the cost), and I don't know any mechanic or FBO that does.

Actually speaking Timken supplies a certificate of conformance with those bearing purchased from reputable aviation suppliers. The CoC specifies that a certain quality inspection has been carried out on that bearing. This isn't to say that the automotive ones are less reliable than the ones batched with a CoC BUT they have not had the same QA insepection carried out.


User currently onlineSEPilot From United States of America, joined Dec 2006, 6894 posts, RR: 46
Reply 24, posted (6 years 6 months 4 days 5 hours ago) and read 3032 times:



Quoting Tbanger (Reply 23):
The CoC specifies that a certain quality inspection has been carried out on that bearing. This isn't to say that the automotive ones are less reliable than the ones batched with a CoC BUT they have not had the same QA insepection carried out.

Precisely. You pay big bucks for that little piece of paper.



The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
25 Jetstar : The Cessna 150 Parts manual lists the wheel bearing part number for the optional 6.00 x 6 wheel main assembly as 13889, and the 5.00 x 5 nose wheel a
26 2H4 : In addition to Jetstar's excellent bearing story, how about the alternator belt? Might that be a part that's shared between cars and airplanes? 2H4
27 Tdscanuck : Design Requirements & Objectives. There are three major kinds of parts on modern commercial aircraft: on-condition, life limited, and damage tolerant
28 Tbanger : And this is primarily due to buying power. Boeing for instance know exactly how many aircraft they will assemble in the next 12 months. They can purc
29 Jetstar : I never did see any automotive alternator/generator drive belts that by part number could be used on an airplane. Belt driven alternator/generators a
30 474218 : Elastomers on aircraft are thing like "O" Rings, Seals (Door, Window, etc). These parts normally have an unlimited life once they are installed. Howe
31 SEPilot : Again, to be legal, the belt must have FAA approved paperwork. Don't tell anybody, but I bought mine at the local auto parts store.[Edited 2008-02-27
32 Jetstar : In my years working at a FBO, I have seen numerous airplanes have questionable parts installed. One I remember was the owner of an older C-182 who bro
33 2H4 : Very interesting, Jetstar. This begs for a sub-topic within this thread: In terms of safety and legality, what's the most questionable modification yo
34 Post contains images KELPkid : How 'bout a duct tape repair for a damaged elevator tip on a 172? And my instructor flew the bird like that for a couple of years before he broke dow
35 Jetstar : I have seen some questionable annuals done by IA’s or repair stations, sometimes I wonder if the inspector was on the same airport as the airplane w
36 DALMD88 : These stories just reinforce why I have never worked in GA. When I find something that I need to replace I look it up in the IPC then I go to the stor
37 MD11Engineer : Basically you are only allowed to use parts listed in the IPC, from a list of manufacturers given by the aircraft manufacturer. Even foer consumables
38 Jetstar : I am just the opposite, I am glad I went into general aviation, I have nothing against airline maintenance jobs, almost my entire class in A&P school
39 Flygirl83 : Under what circumstances would you be able to do this and use a non-certified part? From previous posts, I had the impression that parts had to be FA
40 474218 : Under these circumstances! Say the OEM does not have a part in stock and can not supply the part in a timely manner. An operator, with the OEM's appr
41 Tdscanuck : It's not a non-certified part. I forget what the acronym stands for but it's called a SMA. The OEM provides the drawings and blueprints to the airlin
42 Post contains links Tbanger : You've slightly misunderstood what I said. I said the use of a NON APPROVED VENDOR. Not a NON CERTIFIED PART. At our airline we mostly use Aeronautic
43 MD11Engineer : My old employer Shannon Aerospace Ltd. had a similar permit: We had a whole room full of blueprints for all aircraft we maintained and were allowed t
44 HAWK21M : How economical would that be,considering the costs of manufacturing & theuse of just a few parts in comparism. regds MEL
45 Tdscanuck : If you have the capability to manufacture it, very. The markup on spares in absolutely enormous. Cost of fabrication is only a small piece of the tot
46 MD11Engineer : Also, imagine the money saved if the OEM can't provide a spare part in time to finish the check (remember the story about the fuselage frame our shee
47 474218 : However, if the part is available from the OEM (or an other source) it would be illegal to use the locally fabricated part.
48 SEPilot : I do not believe that this is accurate. The FAR's specifically allow the owner of an aircraft to make parts for it providing that the parts conform t
49 474218 : It has nothing to do with the FAR's. I am sure the other OEM's do the same thing we do and that is make the operators sign an agreement that limits t
50 SEPilot : That is different. When you said "illegal" I thought you were referring to the FAR's. I do not know anything about such agreements that you refer to.
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