# JASC 4900: Airborne Auxiliary Power Unit (APU) System

- Type: JASC system/component code (FAA)
- ATA chapter: 49 Airborne Auxiliary Power
- Title in the code table: AIRBORNE APU SYSTEM
- Service difficulty reports: 1,840
- FAA code table: https://www.faa.gov/sites/faa.gov/files/JASC_Code.pdf#page=43
- Page: https://openairdocs.org/jasc/4900

## What it covers

The airborne auxiliary power units (APU) installed on aircraft for the purpose of generating and supplying a single type or combination of auxiliary electric, hydraulic, pneumatic or other power. Does not include generators, alternators, hydraulic pumps, etc., or their connecting systems which supply and deliver power to their respective aircraft systems. Use this code for reports of a general nature with insufficient information to file in a specific JASC 4900 series code, or for reports which involve two or more APU systems. An entry "APU" is acceptable if no specific part is reported. The APU as well as aircraft make and model should be reported if known.

## Service difficulty reports (1,840, newest 50)

- [SDR AALA202610228350](https://openairdocs.org/sdr/AALA202610228350), Oct 21, 2026: Airbus A321211. APU. ODOR. AIRCRAFT WAS GROUNDED: DIRTY SOCK SMELL STARTED AFTER PUSH BACK AND CONTINUED THROUGHOUT THE AIRCRAFT DURING THE FLIGHT  (N186US)
- [SDR AALA202610124788](https://openairdocs.org/sdr/AALA202610124788), Oct 11, 2026: Airbus A321231. APU. ODOR. AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT DIVERTED TO MEM DUE TO THE FLIGHT CREW REPORTING A TOX (N934AA)
- [SDR AALA202610104335](https://openairdocs.org/sdr/AALA202610104335), Oct 7, 2026: Airbus A321231. VENT LINE. COKED. AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANTS REPORTED A CRAYON TYPE BURNING SMELL DURING APPROACH AND TAXI AFTER LANDING. SM (N932AM)
- [SDR DALA2026100805560](https://openairdocs.org/sdr/DALA2026100805560), Oct 4, 2026: Airbus A320212. APU. ODOR. ODOR - APU PLACED ON MEL FOR SMOKE/FUME EVENT AND REQUIRES APU WASH. PERFORMED W/C 4916-2001 AND W/C 4900-2001. CLEANED  (N369NW)
- [SDR YENA2026091800812](https://openairdocs.org/sdr/YENA2026091800812), Sep 16, 2026: Airbus A321231. APU. ODOR. FLT 323, JFK-LAX. IN FLIGHT, REPORTED CHEMICAL ODOR, APU ODOR EVENT SUSPECTED AFTER ENG RUNS CAME BACK WITH NO FINDINGS  (N967JT)
- [SDR DALA2026091105082](https://openairdocs.org/sdr/DALA2026091105082), Sep 10, 2026: Boeing 717200. APU. ODOR. BOARDING THE ACFT W/APU ON THERE IS A VERY STRONG DIRTY SOCK SMELL IN ALL AREAS OF THE COCKPIT AND CABIN, CORRECTIVE ACT (N927AT)
- [SDR YENA2026090800735](https://openairdocs.org/sdr/YENA2026090800735), Sep 7, 2026: Airbus A320232. APU. CONTAMINATED. FLT 1371, LGA-FLL. APU BLEED STRONG OIL ODOR IN FLIGHT DECK AND AFT CABIN. COMPLIED WITH INFO NOTICE 2017-T015 N AS TYPE (N584JB)
- [SDR AALA202609089848](https://openairdocs.org/sdr/AALA202609089848), Sep 7, 2026: Airbus A319112. APU. ODOR. AIRCRAFT WAS GROUNDED: STRONG SOCK SMELL THROUGH 6,000 FT IN DESCENT WHICH CLEARED UP AFTER MAYBE A MINUTE - THE FLIGHT  (N748UW)
- [SDR AALA202609061034](https://openairdocs.org/sdr/AALA202609061034), Sep 3, 2026: Airbus A321231. PRESSURE SWITCH. FAULTED. AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO DFW DUE TO THE FLIGHT CREW REPORTING WITH  (N539UW)
- [SDR SOKF2026090401](https://openairdocs.org/sdr/SOKF2026090401), Sep 3, 2026: Airbus A320214. APU. ODOR. AIRCRAFT WAS PARKED AT MGA STATION DURING PASSENGER BOARDING FOR FLIGHT AV397 FROM MGA TO SAL WHEN, FOLLOWING APU START, (N689TA)
- [SDR AALA202609010725](https://openairdocs.org/sdr/AALA202609010725), Aug 28, 2026: Airbus A319112. VENT LINE. COKED. AIRCRAFT WAS GROUNDED: MUSKY SOCK ODOR LAST 15 MINUTES OF FLIGHT IN BOTH FLIGHT DECK AND CABIN - MAINTNENANCE FOUND THE  (N703UW)
- [SDR AALA202609013204](https://openairdocs.org/sdr/AALA202609013204), Aug 28, 2026: Airbus A319112. COOLING FAN. LEAKING. AIRCRAFT WAS GROUNDED: MUSKY SOCK SMELL LAST 15 MINUTES OF FLIGHT IN BOTH FLIGHT DECK AND CABIN - MAINTNENANCE FOUND THE (N703UW)
- [SDR YENA2026082600707](https://openairdocs.org/sdr/YENA2026082600707), Aug 26, 2026: Airbus A321231. APU. ODOR. FLIGHT 397, BOS-SEA, FLIGHT ATENDANTS REPORTED A FUEL/ OIL ODOR ON CLIMBOUT, MODERATE INTENSITY OCCURRING IN THE AFT GAL (N903JB)
- [SDR CALA2026082418860](https://openairdocs.org/sdr/CALA2026082418860), Aug 21, 2026: Boeing 767322. CONTROLLER. FAULTED. VIBRATION ON RT SIDE OF ACT, DID NOT FEEL IT BEHIND FIRST CLASS. WHILE STARTING BOTH ENGINES, FELT VIBRATION ONLY ON FIR (N674UA)
- [SDR YENA2026081400675](https://openairdocs.org/sdr/YENA2026081400675), Aug 10, 2026: Airbus A320232. APU. ODOR. FLT 1067, HPN-PBI, (DIVERTED TO JAX). COCKPIT ODOR EVENT ( PACKS ); COMPLIED WITH INFO NOTICE 20178-T015 ISOLATED FAULT  (N705JB)
- [SDR DALA2026081804717](https://openairdocs.org/sdr/DALA2026081804717), Aug 8, 2026: Airbus BD5001A11. APU. ODOR. FUME- DURING APU ON DEPARTURE, NOTICED WET DOG SMELL MOMENTARILY ON CLIMB. STRONG AROMA ON DECENT. DONNED O2 MASKS. DETE (N325DU)
- [SDR YENA2026080300642](https://openairdocs.org/sdr/YENA2026080300642), Jul 31, 2026: Airbus A320232. APU. ODOR. FLT 1098, MCO-BOS (AIRTURN BACK). DIRTY SOCK ODOR IN CABIN AND FLIGHT DECK, APU BLEED HAD BEEN ON FOR APPROX 10 MINS, OD (N613JB)
- [SDR DALA2026072904389](https://openairdocs.org/sdr/DALA2026072904389), Jul 29, 2026: Airbus A319114. APU. ODOR. CREW MENTIONED DIRTY SOCK SMELL THROUGHOUT ALL PHASES OF FLIGHT. TURN ON APU BLEED AND SMELLED FUMES AROUND MID CABIN. P (N351NB)
- [SDR YENA2026071400574](https://openairdocs.org/sdr/YENA2026071400574), Jul 13, 2026: Airbus A320232. APU. ODOR. FLT 2144, PBI-EWR. DIRTY SOCKS ODOR WITH APU ON. C/W INFO NOTICE 2017-T015M IDENTIFIED AS TYPE 1 APU , ACCOMPLISHED LEVE (N618JB)
- [SDR AALA202607150312](https://openairdocs.org/sdr/AALA202607150312), Jul 12, 2026: Airbus A319132. SENSOR. LEAKING. AIRCRAFT WAS GROUNDED: MUSTY SOCK SMELL DURING DESCENT AT 18,000'. FLIGHT CREW DID FUMES REMOVAL PROCEDURE AND FUMES DIS (N818AW)
- [SDR UIEA2026062400535](https://openairdocs.org/sdr/UIEA2026062400535), Jun 27, 2026: Boeing 7478F. DUCT. BROKEN. APU BLEED DUCT EXIT FLANGE FOUND BROKEN. APU BLEED DUCT REPLACED PER CUSTOMER REQUIREMENT EA-1949A004 APU LOAD COMPRESSO (N868GT)
- [SDR AALA202606284611](https://openairdocs.org/sdr/AALA202606284611), Jun 23, 2026: Airbus A321231. FCU. LEAKING. AIRCRAFT GROUNDED: ON DESCENT, FLT ATTS REPORTED A STRONG ODOR IN AFT HALF OF CABIN. LIKENED TO ODOR OF EXHAUST. IT DISS (N908AA)
- [SDR CALA2026061917188](https://openairdocs.org/sdr/CALA2026061917188), Jun 14, 2026: Airbus A319131. APU. ODOR. MUSTY SOCK SMELL FROM PACKS W APU BLEED RUNNING OILY MUSTY SMELL WITH PACKS RUNNING ON APU. PLACED APU ON MEL MEL 4910B  (N840UA)
- [SDR YENA2026052800490](https://openairdocs.org/sdr/YENA2026052800490), May 27, 2026: Airbus A320232. APU. ODOR. FLT#39, FLL-SJO. "CABIN ODOR ON DESCENT ( APU SYSTEM )" OPEN (N623JB)
- [SDR FDEA202605020532](https://openairdocs.org/sdr/FDEA202605020532), May 2, 2026: Boeing 7673S2F. APU. FAULTED. WHEN I TRIED TO SWITCH FROM EXTERNAL POWER TO APU POWER, THE APU WOULDN T HOLD THE LOAD. EVERYTHING IN THE COCKPIT FLICK (N156FE)
- [SDR AALA202604303690](https://openairdocs.org/sdr/AALA202604303690), Apr 26, 2026: Airbus A321231. APU. CONTAMINATED. AIRCRAFT WAS GROUNDED: FLIGHT ATTENDANT REPORTED A VERY STRONG PLASTIC NAIL POLISH SMELL IN THE AFT GALLEY. MAINTENANCE  (N995AN)
- [SDR AALA202604284928](https://openairdocs.org/sdr/AALA202604284928), Apr 26, 2026: Airbus A321231. APU. CONTAMINATED. AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO GND DUE TO THE FLIGHT CREW REPORTING THAT  (N145AN)
- [SDR CALA2026050415934](https://openairdocs.org/sdr/CALA2026050415934), Apr 24, 2026: Boeing 777222. APU. FAULTED. ON TAXI OUT SMOKE STARTED TO COME INTO THE COCKPIT. AFTER THAT THE LT PACK FAILED AND RAN THE CHECKLISTS. SMOKE CLEARED  (N794UA)
- [SDR HNAA2026042300354](https://openairdocs.org/sdr/HNAA2026042300354), Apr 23, 2026: Emb EMB145LR. APU. ODOR. STRONG CHEMICAL SMELL ENTERED COCKPIT AND CABIN WHILE APU RUNNING. R & R APU IAW WC 49-80-05, OPS CK GOOD NO ABNORMAL SM (N660CL)
- [SDR HNAA2026041500285](https://openairdocs.org/sdr/HNAA2026041500285), Apr 15, 2026: Emb EMB145LR. APU. ODOR. STRONG ODOR IN COCKPIT, NO REPORT FROM PREVIOUS CREW. NEW CREW REPORTED CHEMICAL ODOR WHEN ARRIVING TO THE A/C 1M MIN LA (N928AE)
- [SDR DALA2026040802231](https://openairdocs.org/sdr/DALA2026040802231), Apr 7, 2026: Airbus A320212. APU. CONTAMINATED. DIRTY SOCK ODOR AFTER APU BLEED SELECTED. OPENED APU COMPARTMENT, SAW SIGNS OF OIL ON APU AND APU DOOR IAW AMM 49-00. RU (N373NW)
- [SDR DALA2026040602166](https://openairdocs.org/sdr/DALA2026040602166), Apr 5, 2026: Airbus A320212. APU. ODOR. AT 15000 FEET ON DESCENT DIRTY SOCK SMELL ALL WAY UNTIL SHUTDOWN. FLIGHT ATTENDANT SMELLED IT. FO PUT MASK ON AS PRECAUT (N373NW)
- [SDR DALA2026040802227](https://openairdocs.org/sdr/DALA2026040802227), Apr 4, 2026: Boeing 717200. APU. ODOR. CREW REPORTS ON TAXI IN APU START HAD FUEL FUMES THROUGHOUT CABIN. REPLACED APU. (1528181) (AIRCRAFT GROUNDED) (N948AT)
- [SDR WX0A2026033032772](https://openairdocs.org/sdr/WX0A2026033032772), Mar 27, 2026: Airbus A319111. APU. ODOR. (AIRCRAFT NOT GROUNDED) AFT FA'S REPORT A CHEMICAL OR DIRTY SOCK OR DIRTY SOCK SMELL ON APPROACH INTO KJKA. THEY REPORTE (N320NV)
- [SDR YENA2026032300330](https://openairdocs.org/sdr/YENA2026032300330), Mar 21, 2026: Airbus A320232. APU. CONTAMINATED. FLT 610. SDQ-JFK, ( APU BLEED AIR SUPPLY SYSTEM ) FA'S REPORTED FUMES SIMILAR TO HYD FLUID ON T/O FROM SDQ THAT STARTED  (N652JB)
- [SDR WX0A2026031632756](https://openairdocs.org/sdr/WX0A2026031632756), Mar 16, 2026: Airbus A320214. APU. ODOR. (AIRCRAFT NOT GROUNDED) DIRTY SOCK SMELL ASCENDING THRU FL 210. DISSIPATED ON ITS OWN WITHIN A FEW MINUTES / PERFORMED T (N206NV)
- [SDR YENA2026031600307](https://openairdocs.org/sdr/YENA2026031600307), Mar 13, 2026: Airbus A320232. APU. CONTAMINATED. FLT 259 BDL-FLL. DURING BOARDING ODOR IN CABIN AFTER TURNING APU BLEED ON.; COMPLIED WITH I/N 2017-T015 M. IDENTIFIED SO (N561JB)
- [SDR SWIA2026031175509](https://openairdocs.org/sdr/SWIA2026031175509), Mar 11, 2026: Cndair CL6002B19. A/C PACK. ODOR. INTERMITTENT ENGINE OIL ODOR IN CABIN/COCKPIT DURING CRUISE/DESCENT FROM VENTS. WENT AWAY AFTER BLEED SOURCE SWAPPED TO  (N983SW)
- [SDR AALA202603131549](https://openairdocs.org/sdr/AALA202603131549), Mar 10, 2026: Airbus A321231. PRESSURE SWITCH. FAULT MESSAGE. AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT DIVERTED TO ICT DUE TO THE FLIGHT CREW REPORTING THAT  (N933AM)
- [SDR AALA202603121549](https://openairdocs.org/sdr/AALA202603121549), Mar 10, 2026: Airbus A321231. APU. ABNORMAL. AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT DIVERTED TO ICT DUE TO THE FLIGHT CREW REPORTING THAT  (N933AM)
- [SDR YENA2026031100286](https://openairdocs.org/sdr/YENA2026031100286), Mar 3, 2026: Airbus A320232. APU. ODOR. FLT 1142 PBI-BDL, AFTER ROTATION AND THROUGHOUT THRUST REVOLUTION OIL ODOR IN COCKPIT. CABIN CREW DID NOT NOTICE THE ODO (N519JB)
- [SDR CALA2026030314213](https://openairdocs.org/sdr/CALA2026030314213), Mar 1, 2026: Boeing 737824. APU. SMOKE. APU WILL NOT HOLD ELECTR ICAL POWER, GROUND CREW SAW A PUFF OF SMOKE FROM APU. FUMES IN FLT DECK STARTED APU IAW 49-11-0 (N36280)
- [SDR YENA2026022500238](https://openairdocs.org/sdr/YENA2026022500238), Feb 25, 2026: Airbus A320232. APU. CONTAMINATED. FLT #1367 HPN-PBI. "AFT INFLIGHT SMELLED DIRTY SOCK SMELL AS SOON AS WE TOUCHED DOWN AND TAXIED TO THE GATE. THIS WAS AF (N562JB)
- [SDR HNAA2026022500157](https://openairdocs.org/sdr/HNAA2026022500157), Feb 24, 2026: Emb EMB145LR. APU. ODOR. AFTER LANDING DURING APU START, JET FUEL SMELL IN FLT DECK AND IN CABIN FOR APPROX 20 SECONDS. APU AUXILIARY POWER UNIT  (N690AE)
- [SDR DALA2026030801598](https://openairdocs.org/sdr/DALA2026030801598), Feb 23, 2026: Airbus A320212. APU. ODOR. ON TAXI IN, FLT ATTENDANTS NOTIFIED PILOTS OF A SMOKEY HAZE IN THE CABIN. IT WAS DESCRIBED AS SMELLING "FRUITY" AND LIKE (N370NW)
- [SDR KC8A202602230014](https://openairdocs.org/sdr/KC8A202602230014), Feb 22, 2026: Lear 45LEAR. APU. ODOR. 5 MINUTES AFTER TAKEOFF, AIRCRAFT CABIN FILLED WITH WHITE SMOKE. SMOKE SMELLED LIKE OIL. NOT ELECTRICAL. AIRCRAFT RETURN (N453CK)
- [SDR YENA2026022300234](https://openairdocs.org/sdr/YENA2026022300234), Feb 20, 2026: Airbus A320232. APU. ODOR. FLT # 1169 JFK-JFK. " AFTER ENG 1 START ODOR DETECTED IN AFT GALLEY AND ROW 16. DIRTY SOCK SMELL. SMELL PERSISTED ON APU (N703JB)
- [SDR WX0A2026022032735](https://openairdocs.org/sdr/WX0A2026022032735), Feb 19, 2026: Airbus A319111. APU. ODOR. (AIRCRAFT NOT GROUNDED) DIRTY SOCKS SMELL ON DECENT @ 12/L FT APU OFF AT TIME CONTINUED TO LAND. PERFORMED TASK CARD 21- (N309NV)
- [SDR YENA2026021700208](https://openairdocs.org/sdr/YENA2026021700208), Feb 17, 2026: Airbus A320232. APU. ODOR. FLT 438, MCO-BDL . STRONG OIL ODOR DURING CLIMBOUT & CRUISE, WENT AWAY FROM 35000 FT TO LANDING ,SMELLED A LEVEL 2 OIL O (N643JB)
- [SDR YENA2026021700206](https://openairdocs.org/sdr/YENA2026021700206), Feb 14, 2026: Airbus BD5001A11. APU. ODOR. FLT 994, DEN-BOS. DURING TAXI IN FLIGHT CREW AND CABIN CREW SMELLED ELECTRICAL/METALLIC ODOR. THIS WAS SHORTLY AFTER APU (N3289J)

All 1,840: https://openairdocs.org/jasc/4900/reports.md

## Other codes in chapter 49

- [JASC 4910](https://openairdocs.org/jasc/4910): APU Cowling/Containment (954 reports)
- [JASC 4920](https://openairdocs.org/jasc/4920): APU Core Engine (2,430 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 4990](https://openairdocs.org/jasc/4990): APU Oil System (2,651 reports)
- [JASC 4997](https://openairdocs.org/jasc/4997): APU System Wiring (226 reports)

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