PNEUMATIC

AIR DISTRIBUTION SYSTEM. The air distribution system is used to supply conditioned air throughout the aircraft using distribution plenums and gaspers.  The cabin air distribution system is used for routing air to the cabin.  The cockpit air distribution system is used for routing air to the cockpit. The distribution system consists of the following components: 1. Variable Opening type Air Outlets 2. Overhead Registers with Gaspers 3. Cockpit Air Check Valve 4. Two Cabin Air Check Valves 5. Two ECS Plenum Assembly Check Valves 6. Two Gasper Air Check Valves 7. Emergency Air Check Valves 8. Cabin Air Ducts 9. ECS Plenum Assembly 10. Splitter Mechanism 11. Ozone Converter 12. Diverter Doors (SB 45-21-5). The Splitter Mechanism, installed at FS 413 within the left and right cabin air splitter elbows, direct the flow of air to either the upper or lower register to provide the proper stratification of the cabin air temperature.  Optional service bulletin 45-21-6 effective for Learjet 45-002 thru 45-2000 provides heated air to the cabin floor. This modification is used to replace the ECS splitter mechanism. This is a temporary installation which blocks off the upper cabin registers, directing all heat to the lower cabin registers. Compliance is optional - At the option of the aircraft owner.

Cabin Air Check Valves. The Cabin Air Check Valves are located in the cabin air duct immediately forward of the aft pressure bulkhead.  The check valves prevent air from flowing aft to the tailcone should the aircraft lose pressurization.  3202736-1 is a spring loaded closed flapper operation characteristics are for -1,000 to 51,000 ft from temperature ranges of -65 to 200° F.  Length open 2.36 in, Closed 1.94 in, Width 5.09 in dia weight 1.1 lb. The Cockpit Air Check Valve is located in the cockpit air duct immediately forward of where the duct enters into the cabin under the aft floorboards.  The check valve prevents air from flowing aft to the tail cone should the aircraft lose pressurization.  3202742-1 is a spring loaded closed flapper operation characteristics are for -1,000 to 51,000 ft from temperature ranges of -65 to 200° F.  Length open 1.70 in, Closed 1.00 in, Width 4.23 in dia weight 0.28 lb.

Gasper Air Check Valves. The Gasper Air Check Valves are located in the gasper air ducts immediately forward of the aft pressure bulkhead.  The check valves prevent air from flowing aft to the tail cone should the aircraft lose pressurization.  3202078-2 is a spring loaded closed flapper operation characteristics are for -1,000 to 51,000 ft from temperature ranges of -65 to 200° F.  Length open 2.36 in, Closed 1.94 in, Width 5.09 in dia weight 1.1 lb. Two Plenum Assembly Check Valves are located on the aft side of the ECS plenum assembly in the tailcone close to the aft pressure bulkhead.  The valves remain closed when the pressure in the distribution ducting is higher than that in the rear tailcone compartment.  When the pressure in the conditioned air duct drops below that in the rear tailcone compartment, the check valves open to permit the flow of ambient air into the cockpit and cabin.  The amount of air pressure is going to be determined by the outside air density and aircraft speed forcing air into the dorsal inlet pressurizing the tailcone compartment.

Plenum Assembly Check Valve. Two Plenum Assembly Check Valves are located on the aft side of the ECS plenum assembly in the tailcone close to the aft pressure bulkhead.  The valves remain closed when the pressure in the distribution ducting is higher than that in the rear tailcone compartment.  When the pressure in the conditioned air duct drops below that in the rear tailcone compartment, the check valves open to permit the flow of ambient air into the cockpit and cabin.  The amount of air pressure is going to be determined by the outside air density and aircraft speed forcing air into the dorsal inlet pressurizing the tailcone compartment. To improve the ECS system noise levels, optional service bulletin 45-21-8 adds mufflers and diffusers to quiet the conditioned air as it enters the distribution system.  Most of the ECS noise is generated when hot air is introduced into the air distribution system. For the cabin, hot air from the cabin temperature control valve is sent through a muffler and diffuser where it is mixed with the conditioned air just above the plenum assembly, then sent into the cabin. Air from the cockpit temperature control valve is mixed with the conditioned air and sent through the cockpit muffler assembly, then on to the cockpit.

Ozone Converter.  There are two OZCs in the system, one on each low pressure bleed air supply line. In the case of the catalyst in ozone converters the targeted reaction is the conversion of ozone (O3) to oxygen (O2). Since theory says that the catalyst is not consumed while performing its function, one would think that an ozone converter should last indefinitely. In the real world, the ozone catalyst needs cleaning. Most contaminants, primarily atmospheric pollutants and aviation fluids, mechanically coat or clog the catalytic surface. A few actually chemically combine with the catalyst to form new compounds that no longer act as a catalyst. This, along with erosion of the catalyst, acts to reduce the effective surface area of the catalyst to the point that ozone decomposition efficiency becomes unacceptably low. The minimum acceptable efficiency for an ozone converter depends on the aircraft it is installed on.  The 1800FH time change/cleaning limit was set as a safe interval until we can baseline the required efficiency at this interval and possibly push it out. ice Bulletin 45-21-8 To improve the ECS system noise levels, optional service bulletin 45-21-8 adds mufflers and diffusers to quiet the conditioned air as it enters the distribution system.  Most of the ECS noise is generated when hot air is introduced into the air distribution system. For the cabin, hot air from the cabin temperature control valve is sent through a muffler and diffuser where it is mixed with the conditioned air just above the plenum assembly, then sent into the cabin. Air from the cockpit temperature control valve is mixed with the conditioned air and sent through the cockpit muffler assembly, then on to the cockpit.

PRESSURIZATION CONTROL SYSTEM. The pressurization control system consists of: 1. Two (2) outflow valves 2. Cabin pressure controller 3. Manual pressure switch 4. Pressure control switch 5. Emergency de-pressurization switch 6. Cabin air filter 7. Check valve 8. Jet ejector pump. The poppet assembly is positioned through torque motor control to allow vacuum pressure to adjust the poppet to a commanded value determined from the CPC or manual adjustment. The position of the poppet will determin the amount of cabin pressure that will be vented to the outside.

Valve Position Switch Altitude Limit Control Valve Pressure Relief Valve. The primary outflow valve position switch signals the cabin pressure controller when the primary outflow valve is fully open. The both outflow valves will be forced open to prevent negative differential pressure. The valve will open when atmospheric pressure is 0.5 psid (3.4 kPa) greater than cabin pressure. The altitude limit control valve is used as a backup for minimum cabin pressure altitude limiting to 8,000 (±200) ft. The pressure relief valve is used as a backup for cabin differential pressure limiting to 9.4 (±0.10) psid (64.8 [±0.7] kPa). The pressure relief valve is used as a backup for cabin differential pressure limiting to 9.4 (±0.10) psid (64.8 [±0.7] kPa). The altitude limit control valve is used as a backup for minimum cabin pressure altitude limiting to 8,000 (±200) ft. The primary outflow valve position switch signals the cabin pressure controller when the primary outflow valve is fully open. The both outflow valves will be forced open to prevent negative differential pressure. The valve will open when atmospheric pressure is 0.5 psid (3.4 kPa) greater than cabin pressure.

Indication Condition. 1300 Cabin altitude range within acceptable limits. 8750 Caution condition when the cabin altitude exceeds 8750 ft, indication boxed in amber. 10,000 Warning condition when the cabin altitude has exceeded 10,000 ft, indication boxed Red. ---- Invalid cabin altitude data. To prevent possible injury resulting from closing or opening the cabin door with the aircraft partially pressurized, the outflow valves are fully open when the CPC is in ground mode. The CPC remains in ground mode until the left throttle is advanced to begin pre pressurization (takeoff mode).

Ground Mode. To prevent possible injury resulting from closing or opening the cabin door with the aircraft partially pressurized, the outflow valves are fully open when the CPC is in ground mode. The CPC remains in ground mode until the left throttle is advanced to begin pre pressurization (takeoff mode). During normal takeoff, the cabin pressure control system transfers directly from takeoff mode to the climb mode of control when the CPCS receives the airborne signal from the landing gear (squat) switch, or the airspeed of the aircraft exceeds 150 knots.  The 150 knot airspeed input is used to enter climb mode in the event of a squat switch failure.  Regardless of squat switch position, if the aircraft exceeds 150 knots with the left throttle at or above the MCR position, the controller will enter climb mode.  When the CPC enters climb mode, a schedule of cabin altitude versus aircraft altitude is calculated based on the current cabin pressure and will be different for each takeoff altitude. The cabin altitude is controlled to this schedule while in climb mode.

Takeoff And Landing < 8,000 FT. This condition is prevalent for takeoff and landing altitudes at lower elevations (< 8,000 ft).  During the take-off roll, the cabin altitude is driven down toward 150 ft below the takeoff field altitude (pre pressurization). As the aircraft climbs, the controller continually checks the climb schedule value corresponding to the aircraft's altitude against the takeoff altitude in the cabin.  When the climb schedule altitude value exceeds the current cabin altitude, the system rates the cabin altitude up to keep the cabin on the climb schedule at a maximum rate of 600 slfpm. The cabin altitude will not exceed 8,000 ft. The software contains special logic for operations at landing altitudes above 8,000 ft. This high altitude landing mode is active whenever a landing elevation in excess of 8,000 ft is selected and the aircraft altitude is below 24,500 ft.  For flights where the takeoff and landing altitudes are greater than 8,000 ft, the aircraft will pre-pressurize normally when the throttles are advanced for takeoff (takeoff mode) and the CPC will transition to climb mode upon lift-off.  When the CPC enters climb mode, it will rate the cabin altitude downward at 600 slfpm if the takeoff is between 8,000 ft and 11,000 ft, or 725 slfpm if the takeoff altitude is greater than 11,000 ft. the cabin altitude will descend to 8,000 ft and remain there until the CPC enters either high-altitude landing mode (aircraft descent of 1,000 ft and altitude less than 24,500 ft) or flight abort mode.  In high altitude landing mode, the cabin altitude will ascend to the selected landing field elevation. If an aircraft ascent of 500 ft is detected while in high altitude landing mode, the CPC will descend the cabin altitude back to 8,000 ft. The cabin altitude will return to the selected landing field elevation when a 500 ft aircraft descent is detected.

ECS Controller. The ECS controller is installed in the tail cone compartment.  The controller contains the integrated circuitry and transistors required to operate the HP shutoff valves, ECS pressure regulator/shutoff valves, and the emergency pressurization valves.  When the Emergency Pressurization Switch (DS79) is depressed, setting the switch to ON, a signal is sent to the ECS controller (A73) to close both pressure regulator/shutoff valves (L37, LH; L38, RH) and both HP ECS valves (L39, LH; L40, RH) and to open both emergency pressurization valves (L35, LH; L36, RH).  During normal operation, the emergency pressurization valves (L35, LH; L36, RH) are de-energized in the closed position. The valve will remain closed as long as the valve solenoid remains de-energized. With the solenoid energized, bleed air is allowed to flow into the cabin for emergency pressurization.

AIR COOLING SYSTEM. 1. Three-wheel air bearing air cycle machine (ACM) 2. Pack Control & Indication switches/indications 3. Pack Bi-level Pressure Regulating & Shutoff Valve 4. ECS Controller 5. Heat Exchanger 6. ECS Flow Control Venturi 7. Water separator 8. Water Spray Aspirator.  The Hi-Flow Switch is a pushbutton operated switch with an illuminated lens. The switch is considered to be set on when the switch lens is illuminated ON, and off when the switch lamp is extinguished. The light is grounded through it's own contact and may not indicate system operation. A secondary contact supplies 28 VDc power from the pack circuit breaker to the Bi-Level PRSOV for high flow, this power is tapped off and sent to the #1 DAU A3AP1 pin 48 to post the PACK HIGH FLOW white CAS message.  The Hi-Flow Switch applies power to open further the pack bi-level PRSOV when the lens is illuminated ON.  With Hi-Flow selected, bleed air operating pressure increases from 18 +/-2 psi to 26 +/-2 psi.

Hi-Flow Switch.  The Hi-Flow Switch is a pushbutton operated switch with an illuminated lens. The switch is considered to be set on when the switch lens is illuminated ON, and off when the switch lamp is extinguished. The light is grounded through it's own contact and may not indicate system operation. A secondary contact supplies 28 VDc power from the pack circuit breaker to the Bi-Level PRSOV for high flow, this power is tapped off and sent to the #1 DAU A3AP1 pin 48 to post the PACK HIGH FLOW white CAS message.  The Hi-Flow Switch applies power to open further the pack bi-level PRSOV when the lens is illuminated ON.  With Hi-Flow selected, bleed air operating pressure increases from 18 +/-2 psi to 26 +/-2 psi.  The low limit temperature subsystem is designed to prevent icing of the water separator and the downstream conditioned air supply distribution ducting while maintaining maximum cooling capacity.  A low limit temperature sensor sends pack outlet temperature to the ECS for monitoring. To maintain temperatures above icing conditions, the ECS will control the low limit temp control valve that will mix hot air as required.

Air Cooling System. he Cooling System consists of the following components: 1. Three-wheel air bearing air cycle machine (ACM) 2. Pack Control & Indication switches/indications 3. Pack Bi-level Pressure Regulating & Shutoff Valve 4. ECS Controller 5. Heat Exchanger 6. ECS Flow Control Venturi 7. Water separator 8. Water Spray Aspirator. The Cooling system conditions the air to a pilot controlled envoronment in the cabin and cockpit. The system provides ventilation, temperature control, and dehumidified air supply for the main cabin and cockpit, as well as the avionics systems aboard the aircraft.  The system also provides air to pressurize the occupied portions of the aircraft fuselage.  Control over the cabin and cockpit temperatures is accomplished by mixing hot compressed air and refrigerated compressed air.

BLEED AIR DISTRIBUTION SYSTEM CONSIST OF. 1. ECS controller 2. Two HP switches. 3. Two HP bleed air shutoff valves 4. Two ECS shutoff valves 5. Four ECS check valves (two LP and two HP) 6. APU air control valve.  The controller contains the integrated circuitry and transistors required to operate the HP shutoff valves, ECS pressure regulator/shutoff valves, and the emergency pressurization valves.  Bleed pressure requirements are input to the ECS controller from switch position on the environmental control pane.  The HP pressure switch inputs HP pressure to the ECS controller along with (TLA) throttle lever angle position for HP shutoff valve control.

SERVO AIR DISTRIBUTION SYSTEM CONSIST OF. 1. One Servo Air Pressure Regulating Valve 2. Two Servo Air Check Valves 3. Servo Air Tubing 4. Servo Air Filter (SB 45-21-16 or 45-233 & Subsequent. A tee is installed in the tubing to provide servo air to the hydraulic reservoir pressurization system.  A second tee is installed to provide servo air to the cabin pressurization control system.  Additional tees are installed in the tubing downstream from the servo air pressure regulator to provide servo air to the temperature control valves and the low-limit temperature control valve on the Environmental Control Unit (ECU).  There are two Servo Air Check Valves, LH and RH. The valves are installed in the outboard High Pressure (HP) bleed air manifold assemblies.