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1 NBAA 2003 Civil Aviation Flight University of China Air Data Computer System 大气数据计算机系统 Aiirr Daattaa Coomppuutteerr SSyysstteem((ACDSS)) 2 NBAA 2003 Civil Aviation Flight University of China The ADC takes inputs from the pitot and static pressure sources, converts them to electrical signals, and then transmits them via a data bus to the various flight instruments. In addition, input from the outside air temperature probe is used to calculate the true airspeed. In some later models of ADC, angle of attack (alpha) sensor inputs are also provided. Normally there will be two ADCs to provide redundancy, each pilot being able to switch to the output of the other ADC. Outputs from the ADC go to the altimeters, VSI, and ASI/ Mach meter. In addition, outputs are fed to such systems as the flight director (FD), automatic flight control system (AFCS), flight management computer (FMC), ground proximity warning system (GPWS), the flight data recorder (FDR) and others. Aiirr Daattaa Coomppuutteerr SSyysstteem((ACDSS)) 3 NBAA 2003 Civil Aviation Flight University of China Pitot Static Temp LADC R ADC Pitot Static Temp Capt ADC alternate F/O ADC alternate Capt ALT VSI ASI F/O ALT VSI ASI FD AFCS FMC GPWS FDR and others Aiirr Daattaa Coomppuutteerr SSyysstteem((ACDSS)) 4 NBAA 2003 ADC Pitot Pressures Static Pressures Total Air Temperature Angle of Attack Instruments Systems 5 NBAA 2003 Civil Aviation Flight University of China Figure 1.2 Inputs Static Pressure Computer Outputs Altitude Hold Altitude Indicated Airspeed Mach Number True Airspeed Static Air Temperature Air Density Density Static Air Temperature True Airspeed Mach Number Dynamic Pressure Pitot Pressure Pitot Pressure Transducer TotalAir Temperature Systems Using ADC Outputs Automatic Thrust Control Cabin Pressurisation Flight Management Flight Recorder Flight Director Automatic Flight Control Altitude Reporting GPWS Stall Warning Transducer Altitude Memory Static Pressure Annaalloogguuee aannddDiiggiittaallADCss Loss of air data input activates a warning logic circuit within the ADC, which causes warning flags to appear on the associated indicators and annunciators to illuminate on the computer control panel. Air data computers are usually of the digital type; that is, they transmit data in digital format which is compatible with other computerbased systems. Analogue air data computers, which transmit their output data to servo-operated devices, are less common, although a few are still in existence. 6 NBAA 2003 Civil Aviation Flight University of China Mach/airspeed Indicator The instrument receives its information from its associated air data computer, and presents airspeed against a single needle, and both Mach and airspeed in digital displays. AiirrDaattaa IInnssttrruumeennttss 7 8 7 285 60 80 100 120 140 160 200 180 250 300 350 400 MACH KNOTS PULL TO SET IN VMO OP M Man ua l Mo de Fl ag Max Ai r sp e ed Poi nt e r VMO Fl ag Comman d Ai r s pe ed Bu g Ai r sp e ed Po i nt e r Comman d Ai r s pe ed Kno b Manu a l Se t (Pu l l Out ) Pe r f .Da t a Compu t e r (Pu sh In ) Ai r sp e ed Command Ai r s pe ed Ino p Fl ag Ex t e rn a l Ma rk e r Ma ch Figure 1.4 7 NBAA 2003 Mach/airspeed Indicator 8 NBAA 2003 Civil Aviation Flight University of China The striped needle (barbers pole) shows the maximum permitted airspeed (VMO). The Mach display is normally blanked out at low Mach numbers, typically below M 0.4. The five little bugs mounted on the external face of the instrument are manually positioned, and are used to remind the pilot of various significant speeds, such as V1, V2, flap retract speeds and so on. AiirrDaattaa IInnssttrruumeennttss 7 8 7 285 60 80 100 120 140 160 200 180 250 300 350 400 MACH KNOTS PULL TO SET IN VMO OP M Man ua l Mo de Fl ag Max Ai r sp e ed Poi nt e r VMO Fl ag Comman d Ai r s pe ed Bu g Ai r sp e ed Po i nt e r Comman d Ai r s pe ed Kno b Manu a l Se t (Pu l l Out ) Pe r f .Da t a Compu t e r (Pu sh In ) Ai r sp e ed Command Ai r s pe ed Ino p Fl ag Ex t e rn a l Ma rk e r Ma ch Figure 1.4 9 NBAA 2003 Civil Aviation Flight University of China The command airspeed knob sets the commanded airspeed bug, to which the autothrottle will respond when engaged; this command airspeed is also fed to the air data computer, to govern the FAST/SLOW display on the attitude indicator. If the ADC fails, the digital readouts of Mach number and airspeed will be covered by a flag, and the airspeed pointer will read zero. AiirrDaattaa IInnssttrruumeennttss 7 8 7 285 60 80 100 120 140 160 200 180 250 300 350 400 MACH KNOTS PULL TO SET IN VMO OP M Man ua l Mo de Fl ag Max Ai r sp e ed Poi nt e r VMO Fl ag Comman d Ai r s pe ed Bu g Ai r sp e ed Po i nt e r Comman d Ai r s pe ed Kno b Manu a l Se t (Pu l l Out ) Pe r f .Da t a Compu t e r (Pu sh In ) Ai r sp e ed Command Ai r s pe ed Ino p Fl ag Ex t e rn a l Ma rk e r Ma ch Figure 1.4 10 NBAA 2003 Mach/airspeed Indicator 11 NBAA 2003 Civil Aviation Flight University of China Altimeter The electric servo altimeter is driven by its associated air data computer. The display has both a needle and a digital readout, the needle turning once per thousand feet. The digital display is blanked if ADC information is unreliable, or if power is lost. Figure 1.5 AiirrDaattaa IInnssttrruumeennttss M B I N . H G AL T 1 2 3 6 5 4 7 8 9 0 BARO 1 0 1 3 2 9 9 2 31 7 0 0 100 Feet Pointer Baro Knob Altimeter Settings ALT Indicator 12 NBAA 2003 Altimeter 13 NBAA 2003 Altimeter 14 NBAA 2003 Altimeter 15 NBAA 2003 Altimeter 16 NBAA 2003 Civil Aviation Flight University of China Vertical Speed Indicator The vertical speed indicator (VSI) receives its information from its associated air data computer, and may show an OFF flag if the data is unreliable or if power is lost. Modern VSIs, called IVSIs, are fitted with an inertial mechanism to improve response times. Figure 1.6 AiirrDaattaa IInnssttrruumeennttss VERTICAL SPEED 1000 FPM 1 2 4 6 1 2 4 0 .5 .5 OFF 17 NBAA 2003 Vertical Speed Indicator 18 NBAA 2003 19 NBAA 2003 -75 |
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