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rjsampson
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Can steel brake pads be used in systems designed for carbon?

Wed Aug 10, 2022 9:19 pm

I posed this question in the CivAv forum on the Russian Invasion thread but didn't get an answer.

In the respective news thread, I posted an article on Russia instructing pilots to "brake less". What could possibly go wrong? :roll:

It's been reported that countries like Iran will be manufacturing knockoff parts for Russia's [largely stolen] A/Cs. Someone also mentioned that manufacturing carbon brakes can take over a year, plus the requisite know-how. I suggested that steel brake pads could be far more easily manufactured, to which people agreed.

Back to my original question: Could such pads be used in modern braking systems never designed for steel? I imagine that would throw off electronic systems governing the brakes' function, at the very least. Thoughts?
 
dispatchguy
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Re: Can steel brake pads be used in systems designed for carbon?

Wed Aug 10, 2022 10:47 pm

If the Airplane Flight Manuals have the performance data. sure, but if they dont (and most dont) no.

If they don't, your operation will be asking for a supplemental type certificate, which for this will be painfully expensive as the OEM would have to certify the takeoff and landing data again with the steel brakes, and OEMs aren't going to do that except for a very pretty penny.
 
Dalmd88
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Re: Can steel brake pads be used in systems designed for carbon?

Wed Aug 10, 2022 11:40 pm

I doubt it. The wheel itself is likely not compatible. We converted our 737 NG fleet to carbon. The old steel brake wheels could not be used if carbon brakes were fitted. The key ways that the brake rotors sit in were of a different pattern.

For a few months we had to stock both spare wheels and brakes. The plane need to be all one type of brake or the other. The type of brake was stenciled on the tire so we could easily tell them apart.

We were happy to see the steel brakes gone. They were a lot heavier than the carbon ones.
 
Chaostheory
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Re: Can steel brake pads be used in systems designed for carbon?

Thu Aug 11, 2022 3:53 pm

I imagine a lot of the short haul aircraft in Russia are specc'd with steel brakes. I would also imagine all Airbus and Boeing widebody aircraft are now fitted with carbon as standard.

One of the few advantages of steel is that it tends to perform better around de-icing fluid.

I'm not a materials or manufacturing man so I don't know how easy or difficult it would be to reverse engineer and clone OEM parts. The Iranians of course have been doing this for years.
 
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rjsampson
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Re: Can steel brake pads be used in systems designed for carbon?

Thu Aug 11, 2022 9:10 pm

Just read a few articles from OEMs on their aircraft carbon brake manufacturing process. This is not look like something that's easily achievable by any "rogue" supplier without experience -- at least not for a couple of years. Two questions then:

1) How often / how many cycles do fresh brake pads/rotors last before they need to be replaced?

2) Once Russia's aircraft get to the point where their brake components are sufficiently worn to be effective, and their spare stocks of carbon brake components are exhausted, how on Earth could they fly those aircraft ever again?
 
Chaostheory
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Re: Can steel brake pads be used in systems designed for carbon?

Thu Aug 11, 2022 10:34 pm

rjsampson wrote:

1) How often / how many cycles do fresh brake pads/rotors last before they need to be replaced?


A little over 2000 cycles for our 777s I believe.

No idea about the rest.
 
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zeke
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Re: Can steel brake pads be used in systems designed for carbon?

Fri Aug 12, 2022 12:53 am

Chaostheory wrote:
A little over 2000 cycles for our 777s I believe.

No idea about the rest.


That is about right, depending on how the aircraft is being used. Steel brakes about 1/3-1/2 the life of carbon brakes.
 
StereoTechque
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Re: Can steel brake pads be used in systems designed for carbon?

Fri Aug 12, 2022 3:35 am

Slightly off-topic but do Carbon multi disc brakes have negative expansion coefficient?
Like do the wear indicating pins come slightly out when brakes are cooled off?
 
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jetmech
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Re: Can steel brake pads be used in systems designed for carbon?

Sat Aug 13, 2022 7:38 am

Dalmd88 wrote:
We converted our 737 NG fleet to carbon.

What other changes needed to be made aside from the wheels and brakes themselves? Did you need to modify the ABS system for instance?

Regards, JetMech
 
atlamt
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Re: Can steel brake pads be used in systems designed for carbon?

Sat Aug 13, 2022 10:28 am

jetmech wrote:
Dalmd88 wrote:
We converted our 737 NG fleet to carbon.

What other changes needed to be made aside from the wheels and brakes themselves? Did you need to modify the ABS system for instance?

Regards, JetMech


It is more than just the brakes and wheels. I cant remember if it was a LRU change or a software update for the anti-skid / autobrake. There are a few things that get modded or replaced. The final part is done to the gear itself at the next shop visit but it is airworthy before that visit with all the other steps taken.

Fun fact. You can still put a steel brake on after the mod to carbon brakes but it's not airworthy and has to be replaced before further flight. I haven't seen it myself but heard of at least one occurrence.
 
Dalmd88
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Re: Can steel brake pads be used in systems designed for carbon?

Sat Aug 13, 2022 2:07 pm

jetmech wrote:
Dalmd88 wrote:
We converted our 737 NG fleet to carbon.

What other changes needed to be made aside from the wheels and brakes themselves? Did you need to modify the ABS system for instance?

Regards, JetMech

I'm sure there was a LRU change to the box that controls the anti skid. I was working line mtc at the time and only saw the end product. During the fleet transition we had to be mindful of what the plane we were working had, to get the correct brake or wheel assy during routine brake or wheel changes. Same would be for the controller box, but those don't get changed much.
 
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jetmech
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Re: Can steel brake pads be used in systems designed for carbon?

Sun Aug 14, 2022 12:10 pm

atlamt wrote:
It is more than just the brakes and wheels. I cant remember if it was a LRU change or a software update for the anti-skid / autobrake.

Dalmd88 wrote:
I'm sure there was a LRU change to the box that controls the anti skid.


It make sense as the two types of brakes would most probably have different friction characteristics.

I recall walking into the hangar once and seeing eight new sets of brakes awaiting installation on a 767.

Apparently the existing brakes were too grabby at taxiing speeds. IIRC, it was a fleetwide change. Either of you two aware of this?

Regards
 
celestar345
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Re: Can steel brake pads be used in systems designed for carbon?

Mon Aug 15, 2022 3:23 am

I remember about 20 years ago CFM made adverts about using geunine parts, the one that sticks to my mind is the picutre of using a cloth hanger in place for a car antenna.

Well if you ignore all regulations then yes you can manufacture your own brake parts and install onto aircraft. and in RA- registered aircraft if the authority accepts then it can be done. How safe would that become is another matter though...
 
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Horstroad
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Re: Can steel brake pads be used in systems designed for carbon?

Wed Aug 17, 2022 3:56 pm

zeke wrote:
Chaostheory wrote:
A little over 2000 cycles for our 777s I believe.

No idea about the rest.


That is about right, depending on how the aircraft is being used.

For our 777F it's a little over 1400. Of course they're heavier than a pax aircraft, so there is more wear.
Our MD11F brakes were good for a little less than 2000 cycles.

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