basspaul wrote:Why would a low pressure on green require a rollout of the fire crews who were apparently interested in the brake temps? Does a low green mess up the braking performance? Or does the pilot have to brake harder with the low pressure?
A green hydraulic low pressure is the first warning to the pilots. On that warning, they initiated a diversion to YUL. (Note, that was a decision made by the Captain. They could have legally continued to YYZ with two remaining functioning systems).
It was followed by a green hydraulic low fluid level warning, indicating (correctly) a leak.
An approach and landing with green system inop requires special attention. First of all an emergency gear extension must be made. (You can see in the pictures, the gear doors are left open, a result of the emergency extension). Nose wheel steering will be inop as well, requiring a tow to the gate. Also, primary braking is lost, and they landed using alternate braking without antiskid. Spoilers 1 and 5 will be inop on each wing.
However, full reverse is available on both engines and flaps and slats are available as well, albeit slow.
All considered therefore, an emergency would have been declared with ATC. This brings the emergency response vehicles out and per their SOPs they would be assessing brake temperatures and looking for leaks, following the aircraft to the gate.
This is a common simulator exercise and appears to be handled well. (F/Os get a single hydraulic failure, Captains get a dual hydraulic failure in the simulator).