Aircraft modernized for X-Plane 11.35 and later can make use of the left and right extensions of the bleed air system, and opt to use 1, 2 or 3 air conditioning and pressurization packs. In a typical application, each information word received consists of 32 bits of data in a return-to-zero mode of transmission. Input port 2 receives a signal from the built-in test switch 196 in indicator panel 186 for initiating the built-in test sequence. 1 illustrates in general. air data receiver means for receiving and storing signals indicative of flight data, said air data receiving means outputting a receiver full signal after storing flight data signals; and. 28 - Jun 01/20 LOCATIONS CHG CODE DESCRIPTIONS OF CHANGE HIGHLIGHTS Page 1 Jun 01/20 @A340-200/-300 AIRCRAFT CHARACTERISTICS - AIRPORT AND MAINTENANCE PLANNING LIST OF EFFECTIVE CONTENT Revision No. If no critical faults exist, central processing unit enters the ground mode. They use hot air supplied by the engines and/or the APU. a first AND gate having a first input connected to the output of said first threshold circuit and a second input connected to said computing means to receive an enabling signal therefrom; and. For a given aircraft, the actual cabin altitude schedule is based on the lowest cabin altitude rate compatible with the maximum design aircraft climb rate while the aircraft is climbing to maximum altitude. 2018-2019 2). APPENDIX : 15. In the illustrated embodiment input ports 2 and 3 are spares; and input port 4 receives a no fault signal from no fault indicator 193. The pressurization control system keeps the airplane cabin interior at a safe altitude. Channel 11 receives an internal reference ground signal. Referring again to FIG. Central processing unit 54 triggers operation of time frame generator 126 by outputting a restart frame signal thereto through output port 2 of address decoder 120. When the aircraft altitudes falls to a level 500 feet below the peak value registered by Hmaxdd, the descent detect flag is set and central processing unit 54 enters the descent mode of control. Referring FIGS. 13A and 13B are auto-flight pressure rate control flow diagrams; FIG. 2A-2C are detailed block diagrams of the invention; FIG. T.E. 5 is a graph of a schedule of cabin altitude versus aircraft altitude; FIG. Input port 7 of discrete input buffer 101 receives the output signal of analog-to-digital comparator 100. The apparent cabin altitude remains constant regardless of aircraft altitude change due to turbulence, variations in ambient air pressure, etc., until the aircraft has climbed or descended a predetermined height from the altitude at which the cruise control was imposed or until the difference between the cabin pressure and the ambient pressure reaches a predetermined limit. Cabin Versus Aircraft Altitude Chart 02-35-02 FUNCTIONAL SCHEMATICS Air Conditioning System 02-40-01/02 02-00-01/02. When the cruise-clamp is set, the scheduled pressure value is clamped and remains constant until the cruise clamp is released. The pressurization control system is a pneumatic pressure control system that is controlled by an auto schedule digital microprocessor (pressurization controller). Input port 0 of discrete input buffer 102 receives a no fault signal from no fault indicator 193. a digital-to-analog converter connected to an output of said computing means; a sample-and-hold circuit connected to an output of said digital-to-analog converter; and. The foreground deals with functions and data that must be processed with timing constraint limitations, which include reading information from air data receiver 116, updating the cabin pressure measurement input, updating the pressure rate of output and forming certain high-priority tests. The present invention relates to systems for controlling the air pressure within an enclosure, such as an aircraft cabin. 4 is a diagram of a control panel used in conjunction with the system of the FIGS. means responsive to said pressure rate error signal for regulating flow of air through said aircraft cabin to maintain the air pressure within said aircraft cabin and said actual rate of change of air pressure to predetermined values. clamp control means for maintaining a constant pressure situation in said aircraft cabin, said constant pressure situation being initiated when the change of said aircraft altitude signal over a preset time period is less than a first predetermined value, said constant pressure situation being maintained until said aircraft altitude signal changes by a second predetermined value from the value of said aircraft altitude signal at the time said constant pressure situation was initiated. Rate logic circuit 19 receives an input indicative of the maximum allowable pressure differential between the ambient atmospheric pressure and the actual cabin pressure in addition to receiving a signal from autoschedule controller 18. If the aircraft cruise altitude drifts sufficiently to exceed ±500 feet from the altitude at which cruise control was imposed, the cabin altitude simply unclamps and the cabin climbs or descends at a predetermined rate under the control of central processing unit 54. an actuator motor connected to said outflow valve; means for supplying electrical energy to said actuator motor; and. If the valve closed signal is already at a low state, indicating that the valve is at a limit and with no prior valve-open information, central processing unit 54 must determine if outflow valve 52 is at the full-closed or the full-open position. FIG. AIRCRAFT PRESSURIZATION SYSTEMS . P.E.S. 3 is a functional block diagram illustrating outputs of the central processing unit of FIGS. Digital-to-analog converter 28, which receives a voltage V*REF from reference voltage source 65 through an amplifier 94, converts the digital signal to the corresponding voltage. 46 Information Systems 47 Inert Gas System 49 Auxiliary Power Unit. Since lightly loaded aircraft can climb at higher rates than heavily loaded aircraft, it is possible that the crew may select a rate limit incompatible with the actual aircraft climb; therefore central processing unit 54 includes a pressure differential limit feature to prevent the rate of change of pressure differential from exceeding a predetermined value. Summer 58 outputs a signal PDIF, indicative of the offset difference between the linear approximation of landing field altitude PLIN and the cabin pressure PC to an amplifier 66, whose output is connected to input channel 1 of analog multiplexer 56. OR gate 117 also receives an input from a time frame generator 126, which periodically generates a signal for interrupting operation of central processing unit 54. If verify mode push button 194 has not been depressed and the throttle signal goes high, central processing unit 54 enters the takeoff mode. Central processing unit 54 compares the determined pressure value to the destination pressure after calculating the scheduled cabin pressure and taking into account the cruise-clamp status. See our User Agreement and Privacy Policy. The configuration of threshold circuit 152 is such that the output thereof switches from low to high when a positive speed error signal rises to a predetermined voltage, for example 1.25 volts, and switches from high to low when a positive speed error signal decreases to a predetermined voltage, for example 1.05 volts. 1), a cross-channel switch 298 which is connected to relay 168, a signal indicative of manually controlled descent, an auto enable signal indicative of whether the system is in an automatic control mode, a landing gear signal, and a door closed signal, respectively. As the aircraft levels off at 20,000 feet, the cabin continues down on rate limit until the scheduled value is reached for the aircraft altitude of 20,000 feet. Prior art aircraft pressurization systems have the added deficiency of failing to provide built-in monitoring and testing of subsystems and flight data which designers of modern aircraft require to ensure reliable operation and to minimize risks in the event of system failure. The output signal from port 6 of output buffer 113 indicates whether valve 52 of FIG. Power reset circuit 136 is energized by the voltage VREF from reference voltage source 65 and a 5 volt input from power supply 60. maintaining air pressure in said aircraft cabin constant during said constant pressure situation by clamping said air pressure in said aircraft cabin to a constant value. Additional information supplied to the processing unit 54 through discreet input buffers 101, 102 and 103 is described hereinafter. In the homing in mode central processing unit 54 calculates the pressure as a function of the input to channel 1 of multiplexer 56 and the actual pressure at the landing field altitude. 7, the Los Angeles to Chicago flight involves a takeoff at 126 feet, a 17 minute climb to 37,000 feet, an additional 7 minute climb to 42,000 feet after a short hold period, an approximately 3 hour cruise at 43,000, a 15 minute descent to 20,000 feet with a 10 minute hold, and a 15 final descent to 666 feet. Input ports 1-6 receive signals from valve 52 (FIG. 3, central processing unit 54 has an address decoder 120 connected to the MEMORY READY terminal thereof. 12B is shown in two parts as FIGS. & Terms of Use. address decoder means connected to an output of said computing means for selectively applying a trigger signal to said sample-and-hold circuit to cause said sample-to-hold circuit to sample-and-hold the output of said digital-to-analog converter whenever the output thereof is a commanded rate of change of air pressure signal. 4 is a diagram of a control panel used in conjunction with the system of the FIGS. FIG. Input port 4 receives a signal from a verify switch 198; and input port 5 receives a signal from a press test switch 199 on indicator panel 186. Central processing unit 54 will leave the flight mode and go into a landing mode when the weight-on wheels signal goes high provided that the aircraft altitude is less than 15,000 feet. During the auto-flight mode, if either descent detect, manual destination, or cruise-clamp have been established, central processing unit 54 changes the destination pressure to the barometrically corrected landing field altitude pressure. 2A-2C are detailed block diagrams of the invention; FIG. The cabin pressure holds at the scheduled value during the aircraft altitude hold at 37,000 feet and then climbs again on the autoschedule at a rate of approximately 230 feet per minute as the aircraft climbs from 37,000 feet to 42,000 feet. No inflight changes are required unless landing destination is changed. Privacy Policy Many prior art cabin pressurization systems determine the cabin air pressure based upon a setting of the take-off altitude, the cruise altitude and the landing field altitude above sea level; but, under certain atmospheric conditions, such systems permit rapid changes in aircraft cabin pressure, which often causes discomfort to the passengers and crew due to the sensitivity of the human ear to changes in air pressure. Referring to FIG. 71 Engine Cowling. I keep observing a disturbing lack of knowledge and understanding of an aircraft’s pressurization system. After storing the data word, central processing unit 54 outputs a RESET signal through pin 3 of address decoder 120 to the reset input of air data receiver 116 to put air data receiver 116 in condition to receive and store additional signals which may be received from multiplexer 108. 10 is a flow diagram of the ground mode. At takeoff, the cabin climbs on the autoschedule at a rate of approximately 380 feet per minute. Cabin pressure sensor 20, which receives +15 volt and -15 volt inputs from a power supply 60, senses the cabin pressure and outputs a signal PC indicative thereof to channel zero of an analog multiplexer 56, which receives a plurality of analog signals which are selectively converted into digital form and input to central processing unit 54 for processing thereby. An AC/DC converter 172 has an input connected to solid state relay 160 and bleeder resistance 170 to produce a DC signal for input to channel 8 of multiplexer 56. In the illustrated embodiment of the invention, the data bit output from port 3 of output buffer 113 is a spare. 12 Awesome Benefits Of Being A Military Pilot . Thank You Recommended Railway braking system Shrinivas Kale. The ambient air is sucked inside the engine through the fan, it is compressed at high temperature and pressure which makes air molecules to come closer and facilitate easier burning of the air and fuel mixture in the combustion chamber. I have a good friend who owns an early Piper Malibu and says he uses the pressurization for an extra charge of oxygen when he’s feeling tired. After one shot 138 times out, the AND gate 140 supplies a signal to the RESET terminal of central processing unit 54. If that difference exceeds the predetermined valve Hcruise-clamp is assigned the value of the pressure altitude. 2A, 2B, 2C, and 3, an identification code for the transmitted word with the remaining bits constituting flight data. As shown in FIG. This invention, which controls the air pressure in such an enclosure to ensure passenger comfort and safety, includes digital systems for monitoring and testing system components to provide fail-safe operation. 15a and 15b, is a ground mode flow diagram; and. A second input of summer 58 receives an offset voltage VOFFSET1 from a power supply 60; and a third input of summer 58 receives a signal PLIN, which is a linear approximation of landing field altitude, from a potentiometer 62 through a filter 64. I will use the numbers associated with a member of the King Air B200-series. For aircraft, this air is usually bled off from the gas turbine engines at the compressor stage, and for spacecraft, it is carried in high-pressure, often cryogenic tanks. In the manual mode the outflow of valve 52 is controlled by manual inputs to a manual control knob 201 on panel 186. means for limiting the differential between said cabin altitude signal and said aircraft altitude signal, said limiting means overriding said autoschedule means to prevent excessive pressure differential between said aircraft cabin and the ambient air outside said aircraft. 12. Proper operation of the system requires sequential turning on of time frame generator 126, fault flip-flop 128, and flip-flop 130 to actuate relay logic drive circuit 134. Resources: Boeing. 3, amplifier 88 connects data output bus 85 from central processing unit 54 to output buffer 113 and to an output buffer 184, each having 8 data bits numbered 0-7 for controlling various components of the system. Learning Objective: Recognize the purpose and function of aircraft pressurization systems to include maintenance and troubleshooting operations. entering the altitude of the landing field before takeoff; comparing the altitude of said aircraft with altitude of said landing field; and. 2A-2C; FIG. I’ve never heard of anyone injecting perfumes or chemicals into the cabin air stream. As with all AC material, it is not mandatory and does not constitute a regulation. Potentiometer 62 produces the signal PLIN by dividing a voltage VREF input from a voltage reference source 65. In the auto modes the invention positions valve 52 in response to sensed cabin pressure according to cabin pressure control program logic. Upon receipt of a logic high input from threshold circuit 152 and the drive enable signal from central processing unit 54, AND gate 156 outputs a motor open drive drive command signal to input port 5 of discrete input buffer 103 and to a solid state relay 160, which electro-optically isolated from spurious inputs. Let me try to set the record straight … or at least straighten it out a little bit. Use the Fan Laws along a system curve. AND HOW AIR IS KEPT HEALTHY. IN THIS I EXPLAINED BASIC SYSTEM USED FOR PRESSURIZATION , AND HOW THIS SYSTEM IS SAFE, PRECISE. AIR CONDITIONING AND PRESSURIZATION GENERAL The air conditioning system serves four independently controlled zones; the cock- pit and three passenger zones. Control of aircraft cabin air pressure is important for both the comfort of passengers and crew and safe aircraft operation. Rate logic circuit 19 provides outputs to OR gate 16 and to a rate limit circuit 26 which also receives an input from OR gate 16. The signal PLIN from filter 64 is also connected to input channel 2 of analog multiplexer 26. logic circuitry controlled by said computing means for switching said relay between an energized position and a deenergized position for selectively applying electrical power to said actuator motor. 4, panel 186 includes an altitude selector 202 which provides selection of landing field altitude between -1000 and +15,000 feet. Accordingly, there is a need in the art for an aircraft cabin pressurization system which requires minimal attention from the crew, maintains constant pressure under adverse atmospheric conditions and sudden, small changes in aircraft altitude, and which includes means for monitoring and testing critical components within the system to ensure safe, reliable operation. 1 through a circuit comprising solid state relay 160 connected in parallel with a bleeder resistance 170. When the aircraft approaches the landing field central processing unit 54 implements a special homing in routine to enable an improved accuracy in controlling the cabin air pressure to the actual landing field pressure. The system design is best understood with this diagram: The center components provided for compatibility are clearly marked. bypassing said calculating step if said comparing step indicates landing field altitude is higher than the altitude of said aircraft, and commanding air pressure in said aircraft cabin to decrease at a constant rate until air pressure in said aircraft cabin is approximately the same as air pressure at said landing field. If the difference is less or equal to the predetermined feet, the cruise-clamp condition becomes effective. FIG. According to the state of inputs from mode selector 216 of indicator panel 186, central processing unit 54 will execute the automatic flight control mode or the manual control mode. Referring to FIG. Barometrically corrected altitude enables central processing unit 54 to establish cabin air pressure in preparation for landing. A potentiometer 68 receives a voltage VREF from ten volt reference source 65 and outputs a voltage to a filter 70 which is connected to channel 3 of multiplexer 56. first means for providing a cabin altitude signal indicative of the air pressure in said aircraft cabin; second means for providing a cabin altitude rate change signal indicative of the actual rate of change of air pressure in said aircraft cabin; third means for providing an aircraft altitude signal indicative of the ambient air pressure on the exterior of the aircraft, and hence the altitude of the aircraft; autoschedule means for calculating a commanded rate of change of air pressure in said aircraft cabin in response to aircraft altitude; means for controlling the air pressure in said aircraft cabin in response to said cabin altitude signal and said commanded rate of change; and. 12Ba and 12Bb) are auto-flight mode flow diagrams; FIGS. If there is no failure in the system or if central processing unit 54 receives an input indicating clearance of a previously-existing fault, central processing unit provides a clear fault signal to fault flip-flop 128 through output port 7 of address decoder 119 to permit fault flip-flop 128 to output a signal to flip-flop 130, which also receives an ACTIVATE RELAY signal from central processing units 54 via output part 7 of address decoder 120. System Description. Central processing unit 54 has a DATA driver connected to a DATA bus 85 from which data output signals are supplied to a latch 86 through a data buffer amplifier 88. 8, shown in two parts as FIGS. The automatic mode of operation includes an autoschedule controller 18, which outputs signals to OR gate 16 for controlling the cabin air pressure as a function of the ambient atmospheric pressure, the landing altitude, and the actual cabin air pressure. As long as the descent detect flag has not been activated, an ascent schedule will be chosen and implemented. 12A-12E (FIG. A/C and Pressurization Systems: Critical in High-Altitude Aircraft. ending said constant pressure when the altitude of said aricraft changes by a second predetermined value from the value of said aircraft altitude at the time said constant pressure is initiated. THIS PRESENTATION TAKES OVERVIEW OF AIRCRAFT CABIN PRESSURIZATION SYSTEM. 14. tachometer means for providing a signal indicative of the speed of said actuator motor; a first summing circuit for producing an output which is a function of the difference between the actual and commanded rates of change of air pressure within said aircraft cabin; and. 2-4 Revision 1—January 2003 Northwest Airlink CANADAIR REGIONAL JET FLIGHT CREW OPERATING MANUAL—Volume 1 Pinnacle Airlines COCKPIT SUPPLY (GASPERS) CABIN SUPPLY (FLOOR LEVEL) LAVORATORY COCKPIT SUPPLY COCKPIT SUPPLY (GASPERS) BAGGAGE BAY The ground mode drives and maintains outflow valve 52 at a full-open position to prevent pressurization of the cabin, which could prevent opening of the doors of the aircraft. 3. A cabin pressure control system for aircraft includes a controller for receiving and comparing set point and actual values for an aircraft cabin pressure. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If there is an electrical fault in the system, central processing unit 54 supplies a disengage signal to fault flip-flop 128 and to a second flip-flop 130 through an output buffer 113. A first threshold circuit 152 and a second threshold circuit 154 receive the amplified speed error. sensing air pressure in said aircraft cabin; generating a signal indicative of the actual rate of change of air pressure in said aircraft cabin; measuring ambient pressure on the exterior of the aircraft to provide an indication of the altitude of said aircraft; calculating a commanded rate of change of air pressure in said aircraft cabin in response to aircraft altitude; controlling the air pressure in said aircraft cabin in response to said cabin altitude signal and said commanded rate of change; initiating a constant pressure situation in said aircraft cabin when aircraft altitude varies by less than a first predetermined values over a preset time period; and. In order to complete the process of reading an addressed channel of multiplexer 56, central processing unit 54 outputs a digital read signal from output port 4 of address decoder 104 to the digital read 1 input port of discrete input buffer 101 (FIG. The configuration of threshold circuit 154 is such that the output thereof switches from low to high when a negative speed error signal drops below a predetermined value, such as -1.25 volts, and switches from high to low when a negative speed error signal rises above a predetermined value, such as -1.05 volts. As the depicted schedule descent exceeds 300 sea level feet per minute, the cabin descent is rate limited at that value. The above-described process continues until central processing unit 54 outputs a signal which approximates the output of multiplexer 56 within a prescribed tolerance.

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