SA Airbus Brakes...
Gentlemen,
Please reference the OEM Digest 2004 "Summary of Braking Recommendations in the SOP." Also, please reference a Flight Safety notice dated 29 OCT 2003 with reference to FCOM Vol 3 03. "Airbus Performance and Operations Conference Reports 1998/2001."
Extract from the OEM (reference to the 300c limit), "Prevents hydraulic fluid ignition in the main landing gear bay in the event of a fluid leak."
In my opinion, this figure is related to the ignition point of Skydrol which is around 450c (plus or minus, depending on the manufacturer). It has to do with brake fans, the location of the brake temperature sensors, the reading (low) of the temps by about 125 degrees or so, etc.
This is how (again, in my opinion) Airbus designed the 320 series without any wheel well fire warning. By following this limitation, no wheel well fire warning system is necessary.
A totally separate issue is the 150c temp figure and RTO certification. For this discussion, I direct you to the "Airbus Performance and Operations Conference Reports 1998/2001."
Let me start by emphasizing that "Airbus recommends to keep the brakes temperature as cool as practicable for take off."
I'm going to quote:
"The A320 has been certified according to FAR 25 amendment 42 (extracts): RTO at max brake energy has to be demonstrated with new brakes (initial temperatures at around 150 degrees)."
"The A321 has been certified according to FAR 25 post amendment 42 / JAR 25 NP 244 (extracts): RTO at max brake energy has to be demonstrated with 90% worn brakes (initial temperature around 150 degrees) and a bench test must demonstrate that max energy can be absorbed by 100% worn brakes."
I quote the paper further:
"Consequence: FAR / JAR intentionally disregards any higher initial brake temperature influence. Therefore, on an ASDA limited RWY, even with new brakes (A320) or worn brakes (A321), without reverse, nobody knows if it is possible to stop before the end of the RWY in case of RTO if the initial brake temperature is between 150 and 300 degrees (and actually, it is not for any airliner in the world)."
To further explain (and to quote):
"A320 (amendment 42) Maximum brake energy should* be sustained in the case of an RTO, with 100% worn brakes up to 150 degrees only on dry RWY with reversers."
"*should because all of this has not been demonstrated but is the result of a mathematical model."
I hope this clarifies the issue. In fact the 150 degrees issue and the 300 degrees issue are totally separate. One is for an RTO, the other is for a wheel well fire.
Tom