Pressurization

Why pressurization? Humans have trouble breathing at higher altitudes… Sea Level – 100% 10,000 ft – 90% 15,000 ft – 75% 20,000 ft – 40% 25,000 ft – 0%

Why pressurization? This results in a diminishing time of useful consciousness (TUC)… 20,000 ft – 30 minutes 25,000 ft – 3 – 5 min 30,000 ft – 1 – 4 min 35,000 ft – 30 – 60 sec 40,000 ft – 15 – 20 sec 45,000 ft – 9 – 15 sec!

How much pressurization? Based on differential pressure Ratio of outside pressure (at altitude) to inside pressure Beech Baron – 3.6 PSID Altitude 15,000’ – cabin 6,000’ Boeing B-737 – 7.8 PSID Altitude 37,000’ – cabin 8,000’ Chart on next page

Requirements for pressurized flight Cabin strong enough to withstand pressure differential Source of pressurized air Drawn from turbocharger or supercharger Turbine engine uses bleed air from compressor Method to control pressurization Cabin pressure controller Outflow valve(s)

Source of pressurized air Air Pump Roots – type Vane type Hydraulic lesson

Pressurization Control Panel Rate Selector Knob Control pressure changes Cabin Altitude Selector Knob Sets desired cabin altitude Barometric Pressure Correction Knob

Pressurization Control Panel

Pressurized Flight Profile

Pressurization System

Larger Aircraft Similar Higher pressurization differentials Same Basic Components Source, Control Mechanism Outflow Valves

Pneumatics