(10)
If the difference between T1 and T2 is less than 22 deg. C (40 deg. F), then do this step:
(a)
Replace the primary heat exchanger (AMM 21-51-02/401).
S 975-262
(11)
AIRPLANES WITH THE COMPRESSOR OUTLET TEMPERATURE DISPLAY; Make a record of the COMP OUT display on the ECS maintenance page as T3.
S 975-508
(12)
AIRPLANES WITHOUT THE COMPRESSOR OUTLET TEMPERATURE DISPLAY; Measure the surface temperature of the inlet duct for the secondary heat exchanger.
(a)
Make a record of the secondary heat exchanger inlet temperature as T3.
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757 MAINTENANCE MANUAL
S 975-251
(13)
AIRPLANES WITH THE SECONDARY HEAT EXCHANGER OUTLET TEMPERATURE DISPLAY; Make a record of the SEC HX OUT display on the ECS maintenance page as T4.
S 975-509
(14)
AIRPLANES WITHOUT THE SECONDARY HEAT EXCHANGER OUTLET TEMPERATURE DISPLAY; Measure the surface temperature of the outlet duct for the secondary heat exchanger.
(a)
Make a record of the secondary heat exchanger inlet temperature as T4.
S 975-252
(15)
If the difference between T3 and T4 is less than 125 deg. C
(225 deg. F), then the secondary heat exchanger is OK.
S 975-253
(16)
If the difference between T3 and T4 is more than 125 deg. C
(225 deg. F), then do the applicable step:
NOTE:____The primary and secondary heat exchangers are in series. If the difference between T3 and T4 is more than 125 deg C (225 deg F) then the system performance is degraded.
(a)
Clean the secondary exchanger (AMM 21-51-02/701).
(b)
Replace the secondary heat exchanger (AMM 21-51-02/401).
