APU Audible Surge (APS 3200)

TASK 49-00-81-810-901-A
APU Audible Surge (APS 3200)

1. Possible Causes

APU air inlet
Magnetic Drain Plug (8077KM)
CHECK VALVE-APU BLEED [7260HM]
APU [4005KM]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 36-12-51-200-001	Remove and Check Auxiliary Power Unit Bleed Check-Valve for Condition
AMM 49-00-00-710-008	Operational Test of the APU
AMM 49-11-11-000-003	Removal of the Power Plant (APU) (APS 3200)
AMM 49-11-11-400-003	Installation of the Power Plant (APU) (APS 3200)
AMM 49-16-00-210-805	General Visual Inspection of the APU Air Inlet Plenum and APU Air Intake (APS 3200)
AMM 49-16-42-000-002	Removal of the Air Intake Duct (APS 3200)
AMM 49-16-42-400-002	Installation of the Air Intake Duct (APS 3200)
AMM 49-16-48-000-003	Removal of the Lower Inlet-Plenum (APS 3200)
AMM 49-16-48-400-002	Installation of the Lower Inlet-Plenum (APS 3200)
AMM 49-20-00-290-001	APU Power Plant Borescope Inspection (APS 3200)
AMM 49-91-42-200-003	Inspection of the Magnetic Drain Plug (APS 3200)

3. Fault Confirmation
Subtask 49-00-81-710-262-A ** ON A/C NOT FOR ALL

A. Not applicable

4. Fault Isolation
Subtask 49-00-81-810-187-A ** ON A/C NOT FOR ALL

A. If there is an APU audible surge:
(1) Check the CFDS for the fault messages that follow:

LC SURGE- BLEED CTL VLV (8051KM)
LC SURGE AND BCV - BLEED CTL VLV (8051KM)
OSCILLATING LC SURGE AND BLEED VLV.FAILED OPEN - BLEED CTL VLV (8051KM)
OSCILLATING LC SURGE BLD FLOW XDCR (8039KM)/BLD CTL VLV (8051KM)

(a) If a fault message shows:

Do the related troubleshooting procedure.

(b) If no fault message shows:
1 Do a visual inspection of the APU air inlet for airflow blockage, FOD/DOD, plenum splitter loose and/or detachments AMM 49-16-00-210-805.

If necessary, repair and/or replace AMM 49-16-42-000-002 AMM 49-16-42-400-002 AMM 49-16-48-000-003 AMM 49-16-48-400-002.

Subtask 49-00-81-810-188-A ** ON A/C NOT FOR ALL

B. If the fault continues:
(1) Do a check of the Magnetic Drain Plug (8077KM) for debris AMM 49-91-42-200-003.

Subtask 49-00-81-810-195-A ** ON A/C NOT FOR ALL

C. If the fault continues:
(1) Do a check of the CHECK VALVE-APU BLEED [7260HM] AMM 36-12-51-200-001.

Subtask 49-00-81-810-196-A ** ON A/C NOT FOR ALL

D. If the fault continues:
(1) Do a borescope inspection of the Power Section Impeller and Diffuser AMM 49-20-00-290-001.

Subtask 49-00-81-810-197-A ** ON A/C NOT FOR ALL

E. If the fault continues:
(1) Do the operational test of the APU AMM 49-00-00-710-008.
(a) If there is an audible APU surge without a fault triggered:

Replace the APU [4005KM] AMM 49-11-11-000-003 AMM 49-11-11-400-003.

(b) If there is an audible APU surge with a fault message triggered:

Do the related troubleshooting procedure.

[Rev.8 from Aug 2018] 2026.04.04 04:34:31 UTC