T2 cat a switch
The cat a switch was introduced to the uk with the introduction of the 135 t2 variant and was also part of the upgrade for existing t1 models to t2 standard. The raising of the Nr during cat a operations reduces droop following engine failures which means cat a t/o weights are increased. The airspeed at which the cat a mode is deselected was driven by noise constraints ie turn off as soon as possible due to increased noise in cat a mode.