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SDR ASAA2021021034074

Open the Markdown

Service difficulty report · Sensor · Boeing 737990ER

FAA SDR system

Difficulty date
February 10, 2021
Submitted
February 12, 2021
Operation
Air carrier
Aircraft
N431AS
Make and model
Boeing 737990ER
Aircraft serial
43255
Aircraft time
27,584 hours, 8,899 cycles
System (JASC)
4960 · APU Controls
Part
Sensor
Part number
MS280341
Condition
Shorted
Location
Apu Inlet Temp
Stage of operation
IN
How discovered
O
Nature of condition
O
Precautionary procedure
K

As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.

What was found

RAMP REPORTS APU MAKING BACKFIRE NOISE. GROUNDED - YES. REF TSR 710486, ACCOMPLISHED BITE CHECK OF APU IAW B737-900 FIM 49-55 TASK 806. SHOWED SEVERAL OCCURENCES OF MAINT MSG 49-61223, "INLET TEMP SENSOR SHORT CIRCUIT". REMOVED AND REPLACED APU INLET TEMP SENSOR REF B737-900 AMM TASKS 49-61-31-000-801/-400-801. STARTED AND RAN APU. BITE CHECK SHOWS NO CURRENT FAULTS. APU RAN NORMAL WITH NO BACKFIRE OR SURGING. ETOPS GROUND VERIFICATION SUCCESSFUL.