# JASC 4990: APU Oil System

- Type: JASC system/component code (FAA)
- ATA chapter: 49 Airborne Auxiliary Power
- Title in the code table: APU OIL SYSTEM
- Service difficulty reports: 2,650
- FAA code table: https://www.faa.gov/sites/faa.gov/files/JASC_Code.pdf#page=44
- Page: https://openairdocs.org/jasc/4990

## What it covers

The system and components used for APU engine lubrication. Typical parts are filter, pump, relief valve, hose, line, etc.

## Service difficulty reports (2,650, newest 50)

- [SDR WX0A2026102132984](https://openairdocs.org/sdr/WX0A2026102132984), Oct 19, 2026: Airbus A320214. OIL COOLER. LEAKING. (AIRCRAFT NOT GROUNDED) FA REPORTED, ON DESCENT SMELLED CHEMICAL SMELL TURNED INTO DIRTY MUSKY GYM SMELL, IN AFT GALLEY. (N194NV)
- [SDR DALA2026101805704](https://openairdocs.org/sdr/DALA2026101805704), Oct 17, 2026: Airbus A321271NX. OIL SYSTEM. LEAKING. AFT FA SUSPECTED DIRTY SOCK ODOR DURING FINAL APPROACH. REPLACED APU ASSY PER A321 W/C 4900-9002. (LP 8966926, 1870241 - (N528DE)
- [SDR AALA202610192245](https://openairdocs.org/sdr/AALA202610192245), Oct 16, 2026: Boeing 737823. PRESSURE SWITCH. INOPERATIVE. AIRCRAFT WAS GROUNDED: --DECISION WAS MADE TO DIVERT TO GEG. EMERGENCY DECLARED; AIRCRAFT LANDED WITHOUT INCIDENT -- APU (N979AN)
- [SDR AALA202610123316](https://openairdocs.org/sdr/AALA202610123316), Oct 11, 2026: Airbus A321231. OIL SYSTEM. LEAKING. AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANTS SAY THERE IS A STRONG FUMES SMELL IN THE MAIN CABIN - MAINTENANCE FOUND OIL ON  (N974UY)
- [SDR YENA2026100900934](https://openairdocs.org/sdr/YENA2026100900934), Oct 8, 2026: Airbus A321231. OIL SYSTEM. LEAKING. FLT#101, FLL - LAX. STRONG OIL FUMES WITH PACK ONE ON. APU OR ENGINE BLEED IN USE. ( APU SYSTEM ). COMPLIED WITH INFO NO (N947JB)
- [SDR AALA202610108681](https://openairdocs.org/sdr/AALA202610108681), Oct 7, 2026: Airbus A321231. CARBON SEAL. LEAKING. AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANTS REPORTED A CRAYON TYPE BURNING SMELL DURING APPROACH AND TAXI AFTER LANDING. SM (N932AM)
- [SDR AALA202610102521](https://openairdocs.org/sdr/AALA202610102521), Oct 7, 2026: Airbus A321231. VALVE. LEAKING. AIRCRAFT WAS GROUNDED: DIRTY SOCK ODOR DURING CLIMB THEN AGAIN DURING DESCENT - MAINTENANCE FOUND THE APU OIL LUBE UNIT  (N134AN)
- [SDR AALA202610062176](https://openairdocs.org/sdr/AALA202610062176), Oct 4, 2026: Boeing 737823. GUIDE VANE. LEAKING. AIRCRAFT WAS GROUNDED: EMERGENCY DECLARED, AIRCRAFT LANDED WITHOUT INCIDENT. DECESION WAS MADE TO DIVERT TO BNA, FUMES I (N903NN)
- [SDR ASAA2026100367267](https://openairdocs.org/sdr/ASAA2026100367267), Oct 3, 2026: Boeing 717200. DUCT. CONTAMINATED. STRONG DIRTY SOCK SMELL ON TAKEOFF DISSIPATED BUT LINGERED ON THROUGHOUT THE FLIGHT AND CABIN. GROUNDED - YES. INSPECTED (N488HA)
- [SDR ASAA2026092767072](https://openairdocs.org/sdr/ASAA2026092767072), Sep 27, 2026: Airbus A330243. O-RING. LOOSE. CHEMICAL, DIRTY SOCK PASSING 10,000' W/ THRUST AT IDLE. STRONG INTENSITY DURATION PERSISTENT FOR 12 MINUTES. DETECTED MO (N383HA)
- [SDR AALA202609287875](https://openairdocs.org/sdr/AALA202609287875), Sep 27, 2026: Airbus A319132. OIL SYSTEM. LEAKING. AIRCRAFT WAS GROUNDED: AFTER TURNING APU ON AND TURNING ON APU BLEED A HYDRAULIC OR CRAYON SCENT CAME OUT OF THE VENTS,  (N831AW)
- [SDR ASAA2026092567105](https://openairdocs.org/sdr/ASAA2026092567105), Sep 25, 2026: Airbus A330243. O-RING. LOOSE. PUNGENT ODOR IN CABIN AND COCKPIT WHEN USING APU AIR ( APU BLEED AIR SUPPLY SYSTEM, APU AIR NOT AVAILABLE; WILL NEED GRN (N383HA)
- [SDR DALA2026092805370](https://openairdocs.org/sdr/DALA2026092805370), Sep 25, 2026: Airbus A330941. OIL CAP. LEAKING. ATB - DIRTY SOCK SMELL AFTER TAKEOFF. RETURNED TO BOS. CORRECTIVE ACTION: FOUND APU COMPARTMENT CONTAMINATED WITH OIL FR (N435DX)
- [SDR AALA202609249984](https://openairdocs.org/sdr/AALA202609249984), Sep 22, 2026: Airbus A319132. OIL SYSTEM. LEAKING. AIRCRAFT WAS GROUNDED: FLIGHT CREW REPORTED AN ODOR IN THE CABIN A FEW MINUTES AFTER TAKEOFF AND THEN AGAIN ON DESCENT G (N816AW)
- [SDR AALA202609180655](https://openairdocs.org/sdr/AALA202609180655), Sep 17, 2026: Airbus A320232. OIL SYSTEM. LEAKING. AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND TRHGE AIRCRAFT RETURNED TO PHL DUE TO THE FLIGHT CREW REPORTING THA (N657AW)
- [SDR AALA202609181936](https://openairdocs.org/sdr/AALA202609181936), Sep 15, 2026: Airbus A319115. OIL SYSTEM. LEAKING. AIRCRAFT WAS GROUNDED: PUNGENT DIRTY LAUNDRY SMELL MID CABIN AT ROW 24 DURING DESCENT - MAINTENANCE FOUND EVIDENCE OF AN (N4032T)
- [SDR CALA2026090919336](https://openairdocs.org/sdr/CALA2026090919336), Sep 7, 2026: Boeing 777224. LUBRICATION UNIT. FAULTED. LARGE PLUME OF WHITE SMOKE FROM APU EXHAUST ON NORMAL SHUTDOWN. VERIFIED APU OIL AT A SERVICABLE QTY ON EICAS 5.7 WITH A (N78013)
- [SDR DALA2026090605006](https://openairdocs.org/sdr/DALA2026090605006), Sep 5, 2026: Airbus A330323. DRAIN. LEAKING. AFTER NR 1 & 2 ENG START STRONG OIL ODOR WITH HAZE IN CABIN, REPORTED BY MULTIPLE F/A'S COULD ALSO SMELL IN FLIGHT DECK. (N821NW)
- [SDR AALA202609069698](https://openairdocs.org/sdr/AALA202609069698), Sep 4, 2026: Airbus A319112. OIL SYSTEM. LEAKING. AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANT IN AFT GALLEY REPORTED SMELLING A MUSTY ODOR DESCENDING THROUGH 10000 AND AFTER  (N705UW)
- [SDR IPXA2026090472160](https://openairdocs.org/sdr/IPXA2026090472160), Sep 3, 2026: Airbus A300F4622R. DRAIN LINE. LEAKING. DESCENDING OUT OF FL 30500, APU AUTO SHUTDOWN. STATUS PAGE STATES APU INOP. REPLACED APU PER AMM 49-10-00/401. (N150UP)
- [SDR AALA202609063169](https://openairdocs.org/sdr/AALA202609063169), Sep 2, 2026: Airbus A321231. VENT LINE. COKED. AIRCRAFT WAS GROUNDED: DIRTY SOCK MUSTY SMELL IN FLIGHT DECK ONLY UPON STARTING DESCENT ALL THE WAY THROUGH ENGINE SHUTD (N912UY)
- [SDR AALA202609066516](https://openairdocs.org/sdr/AALA202609066516), Sep 2, 2026: Airbus A321231. SEPARATOR. LEAKING. AIRCRAFT WAS GROUNDED: DIRTY SOCK MUSTY SMELL IN FLIGHT DECK ONLY UPON STARTING DESCENT ALL THE WAY THROUGH ENGINE SHUTD (N912UY)
- [SDR AALA202608274465](https://openairdocs.org/sdr/AALA202608274465), Aug 23, 2026: Airbus A321231. OIL TANK. OVERSERVICED. AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANTS REPORTED A STRONGER THAN NORMAL CLEANING OR CHEMICAL SMELL EMANATING FROM THE M (N579UW)
- [SDR AALA202608198150](https://openairdocs.org/sdr/AALA202608198150), Aug 17, 2026: Boeing 737823. OIL COOLER. INOPERATIVE. AIRCRAFT WAS GROUNDED: APU WAS RUNNING AND THE LIGHT EXTINGUISHED. AFTER 15 MINUTES APU SHUTDOWN AND THE R IGHT SOURCE O (N874NN)
- [SDR AALA202608144736](https://openairdocs.org/sdr/AALA202608144736), Aug 12, 2026: Airbus A321231. OIL SYSTEM. LEAKING. AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANT REPORTED INTERMITTENT BURNING PLASTIC SCENT MID CABIN DURING CRUISE - MAINTENANC (N971UY)
- [SDR DALA2026080804585](https://openairdocs.org/sdr/DALA2026080804585), Aug 7, 2026: Airbus A321271NX. OIL SYSTEM. LEAKING. A MODERATELY STRONG OIL / MUSTY ODOR. ODOR PERSISTED UNTIL DESELECTING PACK 1. AT THAT POINT ODOR REDUCED BUT WAS STILL  (N501DA)
- [SDR DALA2026080804586](https://openairdocs.org/sdr/DALA2026080804586), Aug 5, 2026: Airbus A321271NX. OIL SYSTEM. LEAKING. FLIGHT ATTENDENTS REPORTED DIRTY SOCK SMELL AT GEAR DOWN THRU ENGINE SHUTDOWN, ODOR CAME AND WENT IN THE FRONT, BACK FA' (N549DN)
- [SDR DALA2026080404500](https://openairdocs.org/sdr/DALA2026080404500), Aug 1, 2026: Airbus A321211. OIL CAP. LEAKING. DIRTY SOCK ODOR, 6000-4000FT DEEMED TO DISSIPATE AFTER A MINUTE. FOUND OIL SEEPING THROUGH APU OIL FILLER CAP. REMOVED A (N375DN)
- [SDR AALA202608049301](https://openairdocs.org/sdr/AALA202608049301), Aug 1, 2026: Airbus A319115. VENT LINE. LEAKING. AIRCRAFT WAS GROUNDED: STRONG DIRTY SOCKS; MUSTY ODOR ON FLUGHT DECK. LESSENING WITH PACK 1 OFF. MAINTENANCE REPLACED TH (N9011P)
- [SDR I5PA2026072819301](https://openairdocs.org/sdr/I5PA2026072819301), Jul 28, 2026: Boeing 757223. SOLENOID VALVE. FAULTED. APU FAILED TO START DURING LANDING. R & R APU DEOIL SOLENOID VALVE IAW AMM. (N193AN)
- [SDR DALA2026073004411](https://openairdocs.org/sdr/DALA2026073004411), Jul 28, 2026: Airbus A330941. O-RING. LEAKING. ODOR IN CABIN DURING FLIGHT. REPLACED APU FILLER CAP O-RING PER A330 AMM 49-91. OK FOR SERVICE. (9202395) AIRCRAFT WAS G (N414DZ)
- [SDR YENA2026072800628](https://openairdocs.org/sdr/YENA2026072800628), Jul 25, 2026: Airbus A321231. OIL SYSTEM. LEAKING. FLT 524, LAX-JFK. TAXI OUT OIL ODOR WITH APU BLEED, DISSAPATED & ODOR RETURN ON DESCENT THRU 16000 FT FOLLOWED FROM ODOR (N944JT)
- [SDR UIEA2026072300640](https://openairdocs.org/sdr/UIEA2026072300640), Jul 23, 2026: Boeing 74747UF. APU. ODOR. BACK TO BLOCK DUE TO EICAS MESSAGE SMOKE CREW REST AND UNUSUAL SCENT DETECTED IN UPPER DECK. PERFORM FIRE TEST, NO SMOKE (N418MC)
- [SDR YENA2026070700523](https://openairdocs.org/sdr/YENA2026070700523), Jul 3, 2026: Airbus A320232. OIL SYSTEM. LEAKING. FLT # 375, PHL-FLL. INFLIGHT NOTICED DIRTY SOCK ODOR IN CABIN AFTER APU BLEED TURNED ON; COMPLIED WITH I/N 2017-T015-M.  (N618JB)
- [SDR YENA2026070700520](https://openairdocs.org/sdr/YENA2026070700520), Jul 2, 2026: Airbus A321231. OIL SYSTEM. LEAKING. FLT #316, SFO-JFK. DIRTY SOCK SMELL OUTOF 20,000 ON DESCENT IN FORWARD SECTION OF AIRCRAFT APU OFF.; PER INFO NOTICE 201 (N923JB)
- [SDR DALA2026070603931](https://openairdocs.org/sdr/DALA2026070603931), Jul 2, 2026: Boeing 737832. OIL SYSTEM. LEAKING. APU, PRIOR TO PUSH BACK WITH PACKS ON. A SMELL OF SMOKE ACCOMPANIED WITH A BANGING NOISE IT TAIL. AND VISIBLE SMOKE OBSE (N372DA)
- [SDR AALA202608127582](https://openairdocs.org/sdr/AALA202608127582), Jun 23, 2026: Airbus A321231. SEPARATOR. COKED. AIRCRAFT WAS GROUNDED: ON DESCENT, FLIGHT ATTENDANTS REPORTED A STRONG ODOR IN THE AFT HALF OF THE CABIN. IT WAS LIKENED (N908AA)
- [SDR AALA202608129232](https://openairdocs.org/sdr/AALA202608129232), Jun 23, 2026: Airbus A321231. TUBE. COKED. AIRCRAFT WAS GROUNDED: ON DESCENT, FLIGHT ATTENDANTS REPORTED A STRONG ODOR IN THE AFT HALF OF THE CABIN. IT WAS LIKENED (N908AA)
- [SDR AALA202608124014](https://openairdocs.org/sdr/AALA202608124014), Jun 23, 2026: Airbus A321231. MODULE. LEAKING. AIRCRAFT GROUNDED, DURING DESCENT, FLT ATTENDS REPORTED A STRONG ODOR IN AFT HALF OF CABIN. LIKENED TO ODOR OF EXHAUST.  (N908AA)
- [SDR DALA2026061503566](https://openairdocs.org/sdr/DALA2026061503566), Jun 12, 2026: Airbus A320212. OIL SYSTEM. OVERSERVICED. SMOKE/FUME EVENT AFT GALLEY (10K THROUGH LANDING). C/A: PERFORMED INITIAL INSPECTION OF NR 1 , NR 2 ENG AND APU COMPARTM (N356NW)
- [SDR DALA2026061103520](https://openairdocs.org/sdr/DALA2026061103520), Jun 9, 2026: Airbus A319114. CONTROL VALVE. CONTAMINATED. FO SMELLED WET SOCK SMELL ON TAXI - IN WHEN SWITCHING TO APU BLEED. SMELLED IN FLIGHT DECK ONLY NOT IN CABIN. REMOVED LO (N346NB)
- [SDR SWAA2026060810070](https://openairdocs.org/sdr/SWAA2026060810070), Jun 7, 2026: Boeing 7378. LINE. LEAKING. PREVIOUS CREW REPORTS POSSIBLE SMOKE IN COCKPIT AFTER LANDING APU OIL SUPPLY LINE LEAKING AT THE LINE.<[01] OK TO CONTIN (N8790Q)
- [SDR AALA202606082338](https://openairdocs.org/sdr/AALA202606082338), Jun 7, 2026: Airbus A321231. MODULE. LEAKING. AIRCRAFT WAS GROUNDED: INBOUND CABIN CREW REPORTED A DIRTY SOCK / ROTTEN EGG SMELL ON DEPARTURE AND ARRIVAL BELOW 10K FE (N904AA)
- [SDR DALA2026060903441](https://openairdocs.org/sdr/DALA2026060903441), Jun 4, 2026: Boeing 717200. OIL SYSTEM. LEAKING. DIRTY SOCK ODOR ON GROUND AT GATE FROM BOTH PACKS INDEPENDENTLY ON APU AIR. T/S PER FIM 49-50 FOUND OIL INSIDE THE APU P (N937AT)
- [SDR DALA2026060403384](https://openairdocs.org/sdr/DALA2026060403384), May 31, 2026: Airbus A321271NX. OIL SYSTEM. LEAKING. FUMES - DESCENDING THRU FL190, CREW NOTICED A DIRTY SOCKS SMELL. O2 MASKS WERE DONNED AND AN EMERGENCY DECLARED. CORRECT (N589DT)
- [SDR DALA2026060203346](https://openairdocs.org/sdr/DALA2026060203346), May 31, 2026: Boeing 717200. OIL SYSTEM. LEAKING. FLIGHT ATTENDANTS REPORTED A MUSTY OR MILDEW SMELL DURING FLIGHT IN THE MID-CABIN. FOUND APU COMPARTMENT CONTAMINATED WI (N937AT)
- [SDR AALA202605283511](https://openairdocs.org/sdr/AALA202605283511), May 26, 2026: Airbus A321231. PRESSURE SWITCH. FAULTED. AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT DIVERTED TO PHL DUE TO THE FLIGHT CREW REPORTING WITH  (N116AN)
- [SDR AALA202605252810](https://openairdocs.org/sdr/AALA202605252810), May 20, 2026: Airbus A319112. OIL COOLER. LEAKING. AIRCRAFT WAS GROUNDED: DIRTY SOCK ODOR IN COCKPIT ON DESCENT WITH POWERS AT IDLE. DISSIPATES WHEN THRUST COMES BACK IN.  (N768US)
- [SDR DALA2026052103097](https://openairdocs.org/sdr/DALA2026052103097), May 20, 2026: Airbus A320212. OIL SYSTEM. LEAKING. CREW REPORTS MUSTY HAZE IN CABIN, APU RUNNING PACKS OFF. TURNED ON PACKS, MADE ISSUE WORSE. WOULD NOT DISSAPATE UNTIL PA (N356NW)
- [SDR AALA202605212742](https://openairdocs.org/sdr/AALA202605212742), May 18, 2026: Airbus A319112. O-RING. LEAKING. AIRCRAFT WAS GROUNDED: STRONG ODOR IN THE ENTIRE CABIN. MAINTENANCE FOUND APU OIL COOLING FAN LEAKING. REPLACED O-RING I (N705UW)

All 2,650: https://openairdocs.org/jasc/4990/reports.md

## Other codes in chapter 49

- [JASC 4900](https://openairdocs.org/jasc/4900): Airborne Auxiliary Power Unit (APU) System (1,839 reports)
- [JASC 4910](https://openairdocs.org/jasc/4910): APU Cowling/Containment (953 reports)
- [JASC 4920](https://openairdocs.org/jasc/4920): APU Core Engine (2,429 reports)
- [JASC 4930](https://openairdocs.org/jasc/4930): APU Engine Fuel and Control (1,087 reports)
- [JASC 4940](https://openairdocs.org/jasc/4940): APU Start/Ignition System (1,424 reports)
- [JASC 4950](https://openairdocs.org/jasc/4950): APU Bleed Air System (949 reports)
- [JASC 4960](https://openairdocs.org/jasc/4960): APU Controls (383 reports)
- [JASC 4970](https://openairdocs.org/jasc/4970): APU Indicating System (272 reports)
- [JASC 4980](https://openairdocs.org/jasc/4980): APU Exhaust System (164 reports)
- [JASC 4997](https://openairdocs.org/jasc/4997): APU System Wiring (226 reports)

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