Service difficulty report · Apu · Boeing 737990ER

Difficulty date
September 24, 2024
Submitted
September 30, 2024
Operation
Air carrier
Aircraft
N428AS
Make and model
Boeing 737990ER
Aircraft serial
36353
Aircraft time
31,482 hours, 9,787 cycles
Part
Apu
Part number
38007021
Part serial
P7433
Condition
Leaking
Location
Zone 100
Part time
23,102 hours, 30,007 cycles
Stage of operation
DE
How discovered
O
Nature of condition
K, B
Precautionary procedure
O

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

What was found

DESCENDING THROUGH 11,000', ALL 3 IN THE COCKPIT SMELLED SAME METALLIC SMELL AS PREVIOUSLY REPORTED. APU WAS NOT RUNNING MORE OR LESS AT IDLE POWER FROM TOD TO BELOW WHEN SMELL WAS NOTIFIED. F/AS DID NOT REPORT NOTICING ANY UNUSUAL ODOR. GROUNDED - YES. DURING LATEST MAINTENANCE VISIT THE DRAIN FROM THE LOAD COMPRESSOR WAS SWABBED. THE RESULTS FROM THE SWABS INDICATE THAT THE LOAD COMPRESSOR SEAL IS SUSPECT OF LEAKING. POWER PLANT ENGINEERING RECOMMENDS APU REPLACEMENT. (RESOLVED ON W/O: 2019829 TASKCARD: N/R-00001 ) VERIFIED APU AND APU SGU WITH SEAMC WILL R ADAM 62619 09/29/2024. REMOVED APU REF TC78349010 AND INSTALLED APU REF TC 78349011 UP TO STEP A(4) R ADAMS 62619 09/30/2024.COMPLETED APU INSTALLATION REF TC78349011. CLEARS MEL49-1B. PLACARDS REMOVED NOTIFIED SEAMC JEREMY. OPERATED BOTH PACKS USING APU AS A SOURCE, NO METALLIC SMELL NOTED.