Originally Posted by
applecrumble
I think your sim partner probably asked the very same question at the same time. Check out the tech forum. Basically that the safety valve which cuts hydraulic supply to the landing gear is closed above 260kts. If you loose the ADR 1 + 3 there is a loss of the airspeed data to tell the aircraft when it is slower than 260 knots therefore the gear has to be lowered by gravity.
applecrumble, thank you very much!
clearing things up one at a time. this initial training is just pouring information into my brain.