with Y tubing for input to the instruments. This is done to  compensate for any variations in static air pressure on the  vents due to the aircraft’s attitude. Regardless of the number  and location of separate static vents, they may be heated as  well as the separate ram air pitot tube to prevent icing. The pitot-static systems of complex, multiengine, and  pressurized aircraft can be elaborate. Additional instruments,  gauges, the autopilot system, and computers may need pitot  and static air information.  Figure 10-27  shows a pitot-static  system for a pressurized multiengine aircraft with dual  analog instrument panels in the cockpit. The additional set  of flight instruments for the copilot alters and complicates  the pitot-static system plumbing. Additionally, the autopilot  system requires static pressure information, as does the cabin  pressurization unit. Separate heated sources for static air  pressure are taken from both sides of the airframe to feed  independent static air pressure manifolds; one each for the  Figure 10-27.  Schematic of a typical pitot-static system on a pressurized multiengine aircraft.  10-15 Autopilot amplifier Static manifold Static manifold 1 3 1 3 2 2 4 5 1 2 3 4 5 Altimeter indicator Airspeed indicator Rate-of-climb indicator Cabin pressure controller Cabin differential pressure gauge Drain valves Static selector valve Cabin pressure control panel Static drain tee Static selector valve Sumps and drains Copilot’s flight instrument panel Pilot’s flight instrument panel Flush-mounted heated static vents Flush-mounted heated static vents Autopilot static drain  valve Pilot’s equalizer manifold Copilot’s equalizer manifold Static vent drain valve in nose gear well Static vent drain valve in nose gear well Flush-mounted unheated static vent Flush-mounted unheated static vent Pilot’s instrument pitot tube Copilot’s instrument pitot tube Static system Pitot pressure system