Since their introduction in 1986 by Messier-Bugatti on the Airbus A310, the use of carbon brakes has continued to grow in the airline market. They now offer the best technology for high performance aeronautical braking, which requires considerable amounts of energy to be absorbed.
For a car travelling at 200 km/h, the amount of energy to be absorbed and dissipated is in the order of 1 million joules. For an Airbus A340, it may be over 1 billion joules (the extreme case of braking during an aborted takeoff). Two brake pads are sufficient to stop a car. An aircraft needs a stack of discs rubbing against each other. Metal is sufficient for a car brake, but an aircraft requires far tougher material offering much higher performance, justifying the introduction of carbon.
Compared to steel brake discs, mounted on the previous generation of civil and military aircraft, carbon discs have many qualities that represent an equal number of advantages:
They are efficient and offer high performance: The carbon/carbon composite is perfectly adapted to the friction, maintaining a constant level of efficiency whether hot or cold, at both low and high speeds. Its absorption capacity is between two and three times greater than that of steel, making for substantial savings in material and representing gains in weight.
Intrinsically, they are lighter (around four times lighter): Combined with savings in material, it results in further weight gains of several hundreds of kilos on an aircraft, which in the end affects the additional payload (passengers or freight) or additional fuel, and therefore additional aircraft range.
They are durable and economic: They are insensitive to thermal shock and mechanical fatigue. Carbon/carbon beats all records for endurance, increasing the longevity of the brake discs and lengthening the intervals between replacements. The result is lower cost on each landing, an important economical criterion for airlines and therefore for aircraft manufacturers.