Boeing 737 and Carbon Brakes.

[Boeing 7E7]

If anyone can shed any light on this I'd be grateful...

The airline I work for suggests that that consideration be given to NOT setting the park brake after completion of an RTO. This apparently, is due to the fact that the (steel) brakes may 'fuse' on and you might not be able to release the brakes afterwards to vacate the runway. This was the advice given when the B737 all had steel brakes...

Many of the aircraft have now been 'upgraded' to Carbon brakes and I would like to know if Carbon brakes are prone to fusing on, in the same way that steel brakes are supposed to do. Or do Carbon brakes absorb the energy differently, thereby negating this 'advice'?

I would be very grateful if someone could offer any insight into whether Carbon brakes are different in this regard and most importantly, direct me to where this info can be found so that one can say with some credibility one way or another.

Much obliged.

B7E7

[Oiga]

Hi,

I know I´m not really answering your question but according to Boeing, setting the parking brake is part of the evacuation check list.
So at that point it doesn´t really matter.

-Oiga

[A37575]

From the B737 QRH. "When the aircraft is stopped, perform the procedures as required...consider not setting the parking brake unless passenger evacuation is necessary."

Despite this you need to consider runway slope, and the fact that even at idle thrust the aircraft can move forward under its own steam as it were. There will be a lot of activity in the cockpit after a high speed rejected take off. And especially at night and heads down reading a non-normal checklist it may be difficult to sense the aircraft is slowly moving if the parking brake is not set upon stopping.

Don't know the answer re carbon brakes though.

[cwatters]

I'm no expert but I can google. Bit old (2003) but see page 10...

http://www.smartcockpit.com/data/pdfs/flightops/flyingtechnique/Brake_Energy_Consideration_In_Flight_Operation.pdf

If a parking brake is applied too soon after a high energy stop, there is a chance that rotors and stators of steel brakes can fuse, or “weld” together. This can result in:

• Inability to move the airplane
• Unscheduled maintenance
• Schedule disruption
• Disruption of airport operations…

Carbon brakes are not susceptible to “welding”

[Boeing 7E7]

cwatters,

Thank you, this is very useful.

B7E7

[chris weston]

Interesting.

Graphitic carbon sublimes at about 4000K and 101.3 kPa (ie 1 Atmosphere/ 1 Bar)

No liquid phase = no welding together on cooling I presume.

I doubt the carbon brakes actually get that hot - they are more likely to combust to COx in air than they are to change state but for the pedants amongst us, yes yes if the pressure from the brakes gets high enough liquid phase carbon is possible but as that scale runs in units of kilo atmospheres I doubt that the even best of hydraulics will get us there.

World of Carbon (http://invsee.asu.edu/nmodules/carbonmod/point.html)

CW

[CL65Driver1234]

QRH, PI-11.13

When in fuse plug zone, clear RWY immediately. Unless required, do not set parking brake.

Do not listen to no one, you’re QRH is the Bible :ok: