Welcome back to the our channel for a feature on the measures and precautions taken to ensure safe landing of commercial aircraft. Reverse thrust isn’t really effective below certain speeds and they are usually retracted while still on a slow roll. Jet engines need a cool down period before shutdown so this is another reason to keep reverse thrust to a minimum. The reason for the cold down is so the case doesn’t cool a lot faster than the turbine blades. This is why helicopters have a long cool down periods because they use high power settings on landing. Also using reverse thrust at slower speeds can kick up FOD that can damage the engine. This is the first time I am hearing of this. Wouldn't the exhaust from the engine be hot and also flow at a high speed? If anything, I would think that blast would be kept away from the landing gear. No, the air that leaves the Reverse Thrust doors is cold air that has not gone through combustion, through cascade vanes from the bypass duct. I can tell the lack of knowledge here now.