Rubbish, all they had to do was wait 15 mins or so at the holding point ( or somewhere convenient to ATC ) for the temps to drop below 300 deg THEN depart...they should not have left the gate with hot brakes in the first place..
1/Professional Airline Pilots don't leave the gear down after takeoff for cooling, if the brakes were too hot to takeoff then DON'T TAKE OFF. What would happen if they suffered an Engine failure in such a situation?? They would have to retract the gear for performance and this would be an issue.....see note 2 below
2/ the Airbus doesn't have fire detection in the wheel well ( unlike Boeing ) therefore the 300 deg limit is there so you don't retract hot brakes into the wheels well and thus risk a fire......( a fire you wouldn't know about !!
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