flygirl83
Posts: 8
Joined: Thu Aug 30, 2007 10:38 pm

Replacement Parts On A Plane

Wed Feb 20, 2008 6:44 pm

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!
 
A10WARTHOG
Posts: 200
Joined: Mon Jul 12, 2004 7:32 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 7:05 pm

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.
 
flygirl83
Posts: 8
Joined: Thu Aug 30, 2007 10:38 pm

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 7:15 pm

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?
 
aerobalance
Posts: 4308
Joined: Sat Sep 23, 2000 8:35 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 7:47 pm



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..."
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 8:04 pm

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!
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 8:05 pm



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 :-)
 
BAE146QT
Posts: 981
Joined: Sun Sep 24, 2006 4:58 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 8:21 pm

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
 
flygirl83
Posts: 8
Joined: Thu Aug 30, 2007 10:38 pm

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 8:47 pm

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
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 10:06 pm



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!
 
Dalmd88
Posts: 2391
Joined: Fri Jul 28, 2000 3:19 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 10:12 pm

So what is an 'elastomer'? I've been a mechanic now for 17 years and I've never heard any aircraft part called that.
 
EMBQA
Posts: 7795
Joined: Sat Oct 25, 2003 3:52 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 10:50 pm



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"
 
avioniker
Posts: 1099
Joined: Tue Jan 01, 2002 5:38 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 10:53 pm

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
 
roseflyer
Posts: 9606
Joined: Fri Feb 13, 2004 9:34 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 10:56 pm



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 avatar
Starlionblue
Posts: 17058
Joined: Fri Feb 27, 2004 9:54 pm

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 11:38 pm



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." - John Ringo
 
User avatar
seabosdca
Posts: 4921
Joined: Sat Sep 01, 2007 8:33 am

RE: Replacement Parts On A Plane

Wed Feb 20, 2008 11:57 pm



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.
 
BAE146QT
Posts: 981
Joined: Sun Sep 24, 2006 4:58 am

RE: Replacement Parts On A Plane

Thu Feb 21, 2008 7:33 pm



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
 
EasternSon
Posts: 637
Joined: Fri Jun 02, 2006 10:07 pm

RE: Replacement Parts On A Plane

Thu Feb 21, 2008 8:00 pm



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 avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Replacement Parts On A Plane

Fri Feb 22, 2008 8:15 am



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
I may not win often, but I damn well never lose!!! ;)
 
SEPilot
Posts: 4919
Joined: Sat Dec 30, 2006 10:21 pm

RE: Replacement Parts On A Plane

Fri Feb 22, 2008 11:43 am



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
 
Dalmd88
Posts: 2391
Joined: Fri Jul 28, 2000 3:19 am

RE: Replacement Parts On A Plane

Fri Feb 22, 2008 6:46 pm



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.
 
jetstar
Posts: 1366
Joined: Mon May 19, 2003 2:16 am

RE: Replacement Parts On A Plane

Mon Feb 25, 2008 9:43 pm

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.
 
SEPilot
Posts: 4919
Joined: Sat Dec 30, 2006 10:21 pm

RE: Replacement Parts On A Plane

Mon Feb 25, 2008 10:22 pm



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
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Replacement Parts On A Plane

Mon Feb 25, 2008 10:41 pm



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:


View Large View Medium
Click here for bigger photo!

Photo © Sven De Bevere
View Large View Medium
Click here for bigger photo!

Photo © Edwin Vanoverschelde



2H4
Intentionally Left Blank
 
tbanger
Posts: 253
Joined: Tue Jul 27, 2004 6:11 pm

RE: Replacement Parts On A Plane

Tue Feb 26, 2008 8:04 am



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.
 
SEPilot
Posts: 4919
Joined: Sat Dec 30, 2006 10:21 pm

RE: Replacement Parts On A Plane

Tue Feb 26, 2008 11:04 am



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
 
jetstar
Posts: 1366
Joined: Mon May 19, 2003 2:16 am

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 1:37 am



Quoting SEPilot (Reply 21):

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



Quoting SEPilot (Reply 21):
Can you give me an example? I can't think of any.

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 and standard main wheel assembly bearing number is 08125, these are Timken numbers, not Cessna numbers.

When I was working as a mechanic, there was no such thing as a certificate of compliance so it was legal then to buy the bearing from an automotive parts store, that’s where the repair shop where I worked bought them.

On the Grunmman Gulfstream 1 turbo prop airplane, the nose wheels use the same 13889 Ttimken wheel bearings as my Cessna 150 main wheels. There was a corporate G1 based in the hangar where I worked and their policy was to change the wheel bearing on all the wheels every second tire buildup. I knew the chief of maintenance so he gave me all these perfectly good Timken 13889 bearings, which I used on my airplane, never had to buy a main wheel bearing.
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 1:50 am



Quoting SEPilot (Reply 21):
Can you give me an example? I can't think of any.

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
Intentionally Left Blank
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 1:53 am



Quoting RoseFlyer (Reply 4):
There are Design Review Objectives (I think that is the term for DRO's)

Design Requirements & Objectives.

Quoting Flygirl83 (Reply 7):
i'm just curious to understand who decides what parts to use for replacement, and when they need to be swicthed out.

There are three major kinds of parts on modern commercial aircraft: on-condition, life limited, and damage tolerant.

On-condition parts are replaced only when they fail (or, if they have more sophisticated diagnostics, when they indicate they're about to fail). They don't have any set life. The vast majority of systems parts and non-primary structure fall in this category.

Life limited parts have finite lives, either due to aging or fatigue. Aging affects a lot of safety equipment (rafts, flashlights, etc.). Fatigue life limits typically show up on very highly loaded parts: landing gear, engine turbines, etc.

Damage tolerant parts are pretty much only primary structure. These don't have an infinite life and must be inspected on a regular interval to detect any cracks or damage before it grows large enough to be a threat.

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.

Spare components are *far* more expensive to the end user that what the manufacturer paid for them.

Tom.
 
tbanger
Posts: 253
Joined: Tue Jul 27, 2004 6:11 pm

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 7:59 am



Quoting Tdscanuck (Reply 27):
Spare components are *far* more expensive to the end user that what the manufacturer paid for them

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 purchase a 12 month supply of a given part from the OEM with a delivery schedule of X amount per month say. What this does is allows the OEM to manufacture enough to cover the 12 month PO....knowing that they will be sold. Making say 1200 of a given part is always going to be cheaper to produce than say 100 per month.

Once the aircraft goes to the operator, he has to purchase this replacement part himself. If he is able to buy direct from the OEM he will pay more because his useage is most likely going to be significantly less....and hence cannot get the same buying power as the manufacturer...and it is a perfect scenario for the OEM because he gets to mark up the price knowing full well the aircraft won't fly without that part....until Mr FAA-PMA comes along and Mr airline is suddenly open to more realistic pricing....sometimes this brings the OEM price down and sometimes it doesn't. Depending on the part an Engineering Order (EO) is also often a cheaper alternative.

EO's typically allow you to fabricate or repair parts to a specific set of drawings and use a specified material but allows you the advantage of using a local "non airworthy approved" vendor like your local fitting and turning or plastic moulding shop

Quoting Jetstar (Reply 25):
The Cessna 150 Parts manual lists the wheel bearing part number for the optional
6.00 x 6 wheel main assembly as 13889



Quoting Jetstar (Reply 25):
On the Grunmman Gulfstream 1 turbo prop airplane, the nose wheels use the same 13889 Ttimken wheel bearings as my Cessna 150 main wheels

Just for interest sake (or non-interest sake whichever you want to look at it) the SAAB340 nose wheel uses the Timken 13889 wheel bearing as well.
 
jetstar
Posts: 1366
Joined: Mon May 19, 2003 2:16 am

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 2:28 pm



Quoting 2H4 (Reply 26):
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?

I never did see any automotive alternator/generator drive belts that by part number could be used on an airplane. Belt driven alternator/generators are usually airframe manufacturer supplied components, not part of the engine so the airframe manufacturer would have their own part number on the belt.

Where I worked as a mechanic we had an airplane in for an annual and the owner took the old belt down to the auto parts store and had had them match it up with an auto belt, he wanted us to install it and we would not because it was not legal. We would not sign it off because if anything happened it would be us who had to answer to the FAA, not the airplane owner. I think he eventually put it on himself.
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 3:35 pm



Quoting RoseFlyer (Reply 12):
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.

Elastomers on aircraft are thing like "O" Rings, Seals (Door, Window, etc). These parts normally have an unlimited life once they are installed. However, they have a "shelf life" when sitting in the store room waiting to be installed.

Quoting Tdscanuck (Reply 27):
There are three major kinds of parts on modern commercial aircraft: on-condition, life limited, and damage tolerant.

On-condition parts are replaced only when they fail (or, if they have more sophisticated diagnostics, when they indicate they're about to fail). They don't have any set life. The vast majority of systems parts and non-primary structure fall in this category.

Life limited parts have finite lives, either due to aging or fatigue. Aging affects a lot of safety equipment (rafts, flashlights, etc.). Fatigue life limits typically show up on very highly loaded parts: landing gear, engine turbines, etc.

Damage tolerant parts are pretty much only primary structure. These don't have an infinite life and must be inspected on a regular interval to detect any cracks or damage before it grows large enough to be a threat

Tdscanuck, you are Basicly correct but your definition of On-Condition is slight off. The actual definition from the FAA is:

Items and appliances listed as "On-Condition" must be restricted to components on which a determination of continue air-worthiness may be made by inspection, measurements or test. These "On-Condition" checks are to be performed within the time limitations prescribed for the inspection or check. Performance tolerances and wear or determination limits shall be contained in the Air Carriers Maintenance Manual. If an item or appliance cannot be maintained in a condition of continued airworthiness by the use of "On-Condition procedures, it may be placed on a specific time limitations (for example, reliability or condition monitoring).

The actual term what you describe as "On-Condition" is is described by the FAA as "Condition Monitoring" which is defined below:

The maintenance process for items that have neither hard time limits nor On-Condition maintenance as their primary maintenance process. Condition Monitoring is accomplished by appropriate means available to the operator for finding and solving problem areas. These means range from notices of unusual problems to special analysis of unit performance. No specific monitoring system is implied for any given unit.
 
SEPilot
Posts: 4919
Joined: Sat Dec 30, 2006 10:21 pm

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 4:18 pm

Quoting 2H4 (Reply 26):

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?

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 08:21:55]
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
jetstar
Posts: 1366
Joined: Mon May 19, 2003 2:16 am

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 7:47 pm

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 brought his airplane in for an annual inspection. He had installed a second battery, an automobile battery behind the pilot seat attached to the floor and had it wired parallel with the airplane battery. The battery was not mounted in a vented and closed battery box, so it was venting into the cabin.

I was the IA who was assigned to do the annual and when I saw this I told him I could not pass the airplane because of this battery installation. He left and a few days later he brought the airplane back and the battery and all the wiring was gone, so I did the annual and signed it off. I am sure the next day the battery was back in but what he did after the annual inspection was his business.
 
2H4
Posts: 7960
Joined: Tue Oct 19, 2004 11:11 pm

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 8:14 pm

Very interesting, Jetstar.

This begs for a sub-topic within this thread:

In terms of safety and legality, what's the most questionable modification you've ever seen installed in an aircraft?

2H4
Intentionally Left Blank
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 8:54 pm



Quoting 2H4 (Reply 33):
In terms of safety and legality, what's the most questionable modification you've ever seen installed in an aircraft?

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 down and bought the replacement  Wink I always wondered how the IA was able to sign off on the annual with that...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
jetstar
Posts: 1366
Joined: Mon May 19, 2003 2:16 am

RE: Replacement Parts On A Plane

Wed Feb 27, 2008 10:22 pm

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 when they did the annual inspections.

Years ago there was an IA in New England where some owners of airplanes that we would work on during the rest of the year would take their airplane to for the annual because they were much cheaper than our shop. We referred to him as Nick the Quill because he basically did very little work on the airplane before he signed it off. Sometimes just after the annual, the owner would have a problem that should have been caught on the annual inspection and we would work have to work on the airplane to fix it. I always told the owner you get what you paid for.

One incident I remember where the airplane owner came into the shop after one of these cheap annuals and said the airplane just wasn’t delivering enough power, after doing some troubleshooting we found the spark plugs had never been torqued down tight and were starting to loosen.

Another name we used for these cheap annuals was P-51 annuals, as in the Parker P-51 pen, because instead of a flashlight and an inspection mirror, all the IA used was his pen.

On a slightly different topic, we had some airplane owners who would buy their own parts like spark plugs, tires, brakes, oil, etc instead of buying it from us and expect us to install these parts for free during the annual. The general manager of my shop told these customers that if we sold them the parts, we installed them for free, otherwise they have to pay the labor charge to install their parts. Try bringing your own parts to a car dealer or garage and see how far you get.

And these were the same people who constantly complained about our labor rates, the general manager often told them that the local car dealers charged a higher shop rate to work on their cars than we did to work on their airplanes. Sometimes these people would get to the manager and a few times he told the owners in no uncertain terms what they could do with their airplanes.
 
Dalmd88
Posts: 2391
Joined: Fri Jul 28, 2000 3:19 am

RE: Replacement Parts On A Plane

Thu Feb 28, 2008 5:20 am

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 stores person with the number. They tell me where to find it in the stock room or that we don't locally stock it. If it is out of stock or not allocated for our station I either put it on MCO or ground the plane.
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: Replacement Parts On A Plane

Thu Feb 28, 2008 11:58 am



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?

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 exists a list of approved sources in the font matter of the AMM (used to be under chapter 20).

Quoting Jetstar (Reply 35):
Try bringing your own parts to a car dealer or garage and see how far you get.

I do this all the time, because with my slightly exotic car, I have better spare part sources than the local garage (I source the parts from all over Europe via the internet, while they will be restricted to go to the approve Land rover dealer, who charges inflated prices). On the other hand I find it only fair to pay them for the labour.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
jetstar
Posts: 1366
Joined: Mon May 19, 2003 2:16 am

RE: Replacement Parts On A Plane

Fri Feb 29, 2008 2:25 am



Quoting DALMD88 (Reply 36):
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 stores person with the number. They tell me where to find it in the stock room or that we don't locally stock it. If it is out of stock or not allocated for our station I either put it on MCO or ground the plane.

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 went to the airlines and most of them loved it there. But what turned me off about the airlines was when I found out the at TWA, AA and UA it took an average of 15 to 18 years seniority just to get on day shift, it just wasn’t for me so I decided to give general aviation a try and it was good to me, I would never have been able to do what I did while working for the airlines.

I liked working in general aviation because of the diversity of the work and the airplanes I worked on. In the repair station where I worked we did not have any sheet metal, hydraulic or electrical shops or any other specialists, we did it all.

And the best part of it was I worked Monday to Friday, 8:am to 4:30 pm, anything else was overtime if I wanted it, it was never forced on me. I had the keys to the shop and had everything I needed in maintaining my Cessna150 and was able to buy any Cessna or other parts I needed through the shop at the shop discount from our suppliers. Of the 8 mechanics in our shop, 4 of us were pilots and and 2 others besides myself owned airplanes. While the pay was less than the airlines and we had no travel benefits, for me the quality of life was much better than with the airlines.

I also worked on about every Cessna, Beech and Piper airplane at the time and almost all the corporate jets up to Gulfstream’s. Quite often corporate biz jet operators needed additional maintenance personnel to assist their maintenance people and we would be farmed out to these companies, sometimes for a week or more. If a company liked you they would ask for you again and this led directly to my Chief of Maintenance/Pilot jobs on the Lockheed JetStar.

At my JetStar gigs, they were 1airplane operations, I was Chief of Maintenance of one person, myself, so I wore many hats, I was the mechanic, inspector, records keeper, parts and stockroom manager. Biz jets carry a large variety of snacks, candy, crackers, cookies, peanuts etc. in addition to the beer, wine, soda, and booze and it was part of my job to keep the pantry cabinet in the shop stocked. I answered to the chief pilot who reported to the president of the company, if I need the airplane for a day or two for maintenance, my boss would check with the presidents office and if nothing was scheduled the airplane was taken out of service for maintenance.

It was a salaried job, so if I wasn’t scheduled to fly, when the airplane was out as long as the paperwork was up to date and the shop was clean, I was free to do what I wanted. Some of our trips were day turns, the airplane would depart at 7:am and return at 5:pm, so sometimes in the winter I would depart the airplane in the morning, drive to a local ski area, ski for the day and get back in time to meet the airplane when it returned.

And then there was the other hat I wore, First Officer, but that’s another story in itself.
 
flygirl83
Posts: 8
Joined: Thu Aug 30, 2007 10:38 pm

RE: Replacement Parts On A Plane

Tue Mar 11, 2008 3:05 pm



Quoting Tbanger (Reply 28):
EO's typically allow you to fabricate or repair parts to a specific set of drawings and use a specified material but allows you the advantage of using a local "non airworthy approved" vendor like your local fitting and turning or plastic moulding shop

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 FAA approved.
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Replacement Parts On A Plane

Tue Mar 11, 2008 8:57 pm



Quoting Flygirl83 (Reply 39):
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 FAA approved.

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 approval can fabricate the part, following the OEM supplied blueprint, for use on the operators aircraft. However, to offer these operator fabricated parts for sale to another operator would take OEM and FAA (PMI) approval.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Replacement Parts On A Plane

Wed Mar 12, 2008 12:56 am



Quoting Flygirl83 (Reply 39):
Quoting Tbanger (Reply 28):
EO's typically allow you to fabricate or repair parts to a specific set of drawings and use a specified material but allows you the advantage of using a local "non airworthy approved" vendor like your local fitting and turning or plastic moulding shop

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 FAA approved.

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 airline/MRO and they have it fabricated locally. It's certified by process: the design is certified already by the OEM and the part itself is certified via the airline's operating specification procedures...at least in the USA. Provided you have an agreed process between the regulator and the airline/MRO, the airline/MRO can certify things themselves (technically, it's a delegated authority and they're certifying on behalf of the regulator).

Tom.
 
tbanger
Posts: 253
Joined: Tue Jul 27, 2004 6:11 pm

RE: Replacement Parts On A Plane

Wed Mar 12, 2008 8:25 am



Quoting Tbanger (Reply 28):
EO's typically allow you to fabricate or repair parts to a specific set of drawings and use a specified material but allows you the advantage of using a local "non airworthy approved" vendor like your local fitting and turning or plastic moulding shop



Quoting Flygirl83 (Reply 39):
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 FAA approved.

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 Aeronautical Engineers Australia, A company that specialises in certifying EO's for Australian Registered aircraft. Refer to this link or AEA

What AEA do for us is provide the service of writing the Engineering Order under the provision of a Civil Aviation Regulation 35 and we then certify for the part under our system of maintenance.

Let's not get too anxious about what we are doing here. Take a cowl stay for example. These things are what is used to hold the engine cowling in the open position while the engine is being worked on. They are worth about $1500USD from the OEM. There are PMA ones on the market which cost about half that price maybe a bit less. All in all though the design means they only last a year or 2. We have designed an EO that allows us to go to our local machine shop and fabricate the piece that always breaks for about $50.

Another example is aircraft carpet. We purchase the carpet on a roll. 3.66 metres wide by 20 or so metres long. If we have an aircraft in mx we can simply cut the carpet to size, overlock the edges and install it into the aircraft as a part of aircraft maintenance. However if we want to cut the roll up into aisle and under seat carpets and overlock them and then sit them on the shelf as a servicable spare they must have a certificate of conformance or in house component worksheet done on them. The way to achieve the certification is to have an EO drawn up which provides the dimensions, the part number of the carpet and a copy of the FAR 25....burn cert and the certifying mechanic then has a legal document that he can certify to.

Another EO we have is to allow us to put decals on our aircraft instead of paint.

Another example of an EO we have is this: Our aircraft steps tend to break a lot. They consist of a hollow alloy frame, a honeycomb centre and some anti-slip tape on top. The IPC allows us to replace the anti-slip tape. The IPC also allows us to replace the honeycomb centre. The IPC even allows us to replace the alloy frame. However often the frame cracks near the rivnut hole. To save about $2500 on a new frame we had an EO drawn up (about $240AUD for the EO) which allowed us to have an approved aviation welder weld the crack.

So you see it isn't about having unuapproved parts...but simply finding other ways about doing things that can save your company a hell of a lot of money.

Quoting Tdscanuck (Reply 41):
I forget what the acronym stands for but it's called a SMA

Supply Material Availability???
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: Replacement Parts On A Plane

Wed Mar 12, 2008 2:51 pm



Quoting Tdscanuck (Reply 41):
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 airline/MRO and they have it fabricated locally. It's certified by process: the design is certified already by the OEM and the part itself is certified via the airline's operating specification procedures...at least in the USA. Provided you have an agreed process between the regulator and the airline/MRO, the airline/MRO can certify things themselves (technically, it's a delegated authority and they're certifying on behalf of the regulator).

Tom.

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 to manufacture parts as per OEM specs, but we were only allowed to install them on aircraft we maintained (e.g. as a replacement during a D-check), we were not allowed to manufacture them for sale.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Replacement Parts On A Plane

Wed Mar 12, 2008 3:18 pm



Quoting MD11Engineer (Reply 43):
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 to manufacture parts as per OEM specs, but we were only allowed to install them on aircraft we maintained (e.g. as a replacement during a D-check), we were not allowed to manufacture them for sale.

How economical would that be,considering the costs of manufacturing & theuse of just a few parts in comparism.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: Replacement Parts On A Plane

Thu Mar 13, 2008 2:13 am



Quoting HAWK21M (Reply 44):
Quoting MD11Engineer (Reply 43):
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 to manufacture parts as per OEM specs, but we were only allowed to install them on aircraft we maintained (e.g. as a replacement during a D-check), we were not allowed to manufacture them for sale.

How economical would that be,considering the costs of manufacturing & theuse of just a few parts in comparism.

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 total price. If you can built it yourself, you avoid all the overhead.

Tom.
 
MD11Engineer
Posts: 13916
Joined: Sun Oct 26, 2003 5:25 am

RE: Replacement Parts On A Plane

Thu Mar 13, 2008 7:34 am



Quoting Tdscanuck (Reply 45):
Quoting HAWK21M (Reply 44):
Quoting MD11Engineer (Reply 43):
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 to manufacture parts as per OEM specs, but we were only allowed to install them on aircraft we maintained (e.g. as a replacement during a D-check), we were not allowed to manufacture them for sale.

How economical would that be,considering the costs of manufacturing & theuse of just a few parts in comparism.

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 total price. If you can built it yourself, you avoid all the overhead.

Tom.

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 sheeties manufactured after a crack was discovered three days before the end of the check, with Airbus stating that they would need 3 months to have a spare ready?).
We had a full machine shop, a welding shop certified for steel, aluminium and titanium, a heat ttreatment shop, a composite shop and a paint shop.

Jan
Je Suis Charlie et je suis Ahmet aussi
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Replacement Parts On A Plane

Thu Mar 13, 2008 2:32 pm



Quoting Tdscanuck (Reply 45):
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 total price. If you can built it yourself, you avoid all the overhead.

However, if the part is available from the OEM (or an other source) it would be illegal to use the locally fabricated part.
 
SEPilot
Posts: 4919
Joined: Sat Dec 30, 2006 10:21 pm

RE: Replacement Parts On A Plane

Thu Mar 13, 2008 6:34 pm



Quoting 474218 (Reply 47):

However, if the part is available from the OEM (or an other source) it would be illegal to use the locally fabricated part.

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 to the manufacturer's specifications. There is nothing about whether or not the part is available from the manufacturer. Mike Busch has an article about it available at Avweb.com.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Replacement Parts On A Plane

Thu Mar 13, 2008 7:22 pm



Quoting SEPilot (Reply 48):
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 to the manufacturer's specifications. There is nothing about whether or not the part is available from the manufacturer. Mike Busch has an article about it available at Avweb.com.

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 them from fabricating parts that are available from the OEM or an approved source. This contract prohibits the operator from fabricating parts, without the manufactures approval.

Who is online

Users browsing this forum: No registered users and 11 guests