(b) Temperature computation The resistance measured by the ADR and compensated for aircraft wiring is then converted into a temperature value (TAT) according to the Callender-Van Dusen equation given for a 500 ohm platinum sensing element:
--
| 3| Rt | (TAT ) (TAT ) (TAT ) (TAT) | -- = 1 + a | TAT - d (--- -1) (--- ) - b (--- -1) (---) | Ro | (100 ) (100 ) (100 ) (100) |
--TAT = temperature in deg.C Rt = Resistance at temperature TAT Ro = Resistance at 0 deg.C = 500 ohm a = 0.003832 d = 1.81 b = 0.1 for temperature below 0 deg.C b = 0 for temperature above 0 deg.C
The computation also compensates the TAT value for heating effect. The ADR knows when the sensor is heated by the state of the TAT Heat input discrete from the PHC. The heating compensation law is provided by the TAT sensor supplier and is function of Mach and air density. The PHC 1 controls the heating of the TAT sensor 1 and the PHC 2 controls the heating of the TAT sensor 2. On the ground, the sensors are not heated (Ref. 30-31-00 for more details). The result of the above computation is available on the following output labels:
-
label 211 Total Air Temperature (BNR)
-
label 231 Total Air Temperature (BCD).
R 1EFF : 001-049, 101-105, 151-199, 201-203, 1 34-13-00Page 12 1 1 Config-1 May 01/05 1 1 1CES 1
(c) AOA computation The A/C is wired in the AOA unique selection, so the ADR computes the AOA with the reading of one resolver. The second resolver is used as a back-up. The monitoring function is descibed in 34-18. The ADR determines the corrected angle of attack value which depends on the system number and the slat/flap position. For a CAS less than 60 kts: AOAc = 0 and status matrix is coded NCD. For a CAS more than or equal to 60 kts, the corrected angle of attack is calculated as follows:
AOA ind AOAc = -------+ I K where: AOA ind = Indicated Angle of Attack (Ref. 34-11-00 for the relation between resolver and AOA indication)
K, I = Correction coefficients which depend on system number, slat and flap configuration and magnitude AOA indication.
The configuration is defined by the status of four input
discretes (Ref. 2.A.(2)(c)).
The results of the above computation is available on the labels:
-
label 221 = Indicated Angle of Attack
-
label 241 = Corrected Angle of Attack
R 1EFF : 001-049, 101-105, 151-199, 201-203, 1 34-13-00Page 13 1 1 Config-1 May 01/05 1 1 1CES 1 (4) Parameter computation
(a)
General The operational software of the ADR performs the following computations:
-pressure altitude and pressure altitude rate function (ALT)
-Mach function (M)
-airspeed function (CAS/TAS)
-temperature function (SAT/TAT)
-maximum operating speed function (VMO/MMO).
(b)
Altitude computation The ADR software computes these different parameters:
label 203 Altitude
label 212 Altitude Rate (BNR)
label 204 Baro Corrected Altitude 1 (CAPT)
label 220 Baro Corrected Altitude 2 (F/O)
label 232 Altitude rate (BCD)
1 Altitude and altitude rate computation
_ The altitude is derived from the corrected static pressure. Standard altitude is computed as :
*
For Ps graeter or equal to 226,323 hPa
0,190263 Altitude = 145442,156 * (1- (Ps / Po) )
*
For Ps < 226,323 hPa Altitude = 148897,4 - 47907,18 * Log (Ps) with Ps = Corrected Static Pressure
Po = Standard day sea level pressure (1013,25 hPa) The accepted range is (-2000 ft, +50.000 ft). The altitude rate is calculated by multiplying the rate of change of the corrected static pressure by the derivative of altitude with respect to corrected static pressure:
dH d Ps dH -- = ---- x ----dt dt d Ps
2 Corrected altitude computation
_ The ADR receives the baro correction introduced on the FCU by each crew member. The ADR uses the values in hPa (labels 234 and 236 from the FCU). The corrected altitude is calculated by a shift of the pressure altitude to a value corresponding to the entered baro correction. The result is sent on label 204 for CAPT baro corrected altitude and label 220 for F/O baro corrected altitude.
R 1EFF : 001-049, 101-105, 151-199, 201-203, 1 34-13-00Page 14 1 1 Config-1 May 01/05 1 1 1CES 1
(c) CAS/Mach computation The ADR software computes these different parameters: label 206 Computed Airspeed label 205 Mach label 207 Maximum Allowable Airspeed. The CAS and Mach computation is based on the conversion of the impact pressure: impact pressure = Pt - Ps.
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