Emergency Operation of Pilot's Oxygen System

If the pilot's oxygen-low caution light [6, fig. 5-1] comes on after the X-15 oxygen system has been selected, be prepared to actuate the emergency oxygen supply as soon as you are aware of breathing difficulty. The time between illumination of the light and when breathing difficulty is first encountered is dependent on several factors, including breathing rate, pilot size, and cabin pressure altitude.

Note: This is done automatically in the simulator.