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3.7.7 Engine Pressure Ratio
The ADTS 505 may be used to check EPR sensors and indicators. Use Ps (static) for INLET pressure
and Pt (Pitot) for OUTLET pressure.
To carry out an EPR check, the display must be showing units of pressure measurement e.g., mbar,
inHg, psi.
Note: Altitude correction applies to EPR values make sure this correction does not adversely affect
accuracy. The difference in height between the ADTS 505 and the EPR sensor may be different
to the altitude correction previously set for the aircraft instruments.
To change units:
•
Press F2 [Units].
•
Select required pressure units, the pressure units are selected in set-up.
•
Use CLEAR/QUIT to return to pressure display.
To enter an EPR of 1.8 with inlet pressure of 500 mbar (15 inHg), proceed as follows:
•
If the display shows "Leak Measure", press LEAK MEASURE/CONTROL to go to control.
•
Press [Rate Inlet], F2 and set 200mbar/min.
•
Press [Rate EPR], F4 and set 0.8 EPR/min.
•
Press [Inlet], F1 set an aim value of 500 mbar (15 inHg).
•
Select [EPR] F3, set an aim value of 1.8.
•
Wait for the controller to achieve the EPR aim value. Press [Outlet], F5 to confirm 900
mbar.
Note: EPR testing can also be performed by specifying the actual INLET and OUTLET values. In the
above example, with inlet at 500 mbar, a ratio of 1.8, the outlet value should be 500 mbar x 1.8
= 900 mbar (Pt) [15 inHg x 1.8 = 27 inHg (Pt)].
Some EPR procedures (earlier ECU) may require measurement in aeronautical units:
•
Set to aeronautical units, press LEAK MEASURE/CONTROL and set the inlet pressure
(ALT control aim) to the required value.
•
Change units to pressure, press EPR, set the required ratio.
•
Allow the system to achieve the control aim. Exit EPR and return to leak measure
mode. Change units to aeronautical and record the resulting value in knots.
On completion of EPR testing, select GROUND and wait for the `Safe at Ground' message to be
displayed, see 3.7.8., refit the pitot and static blanking caps.
K0260 Issue No. 8
Operation
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