APU WHITE SMOKE

APU 131-9A / White Smoke from the APU Exhaust ATA:

49-80

FIN:

A/C Type:

A318 A319 A320 A321

Potential Impact:

Part Number:

3800708-1

Key Information:

Supplier:

Solution Benefit:

Linked Articles:

Linked Documentation:

4005KM Operational Reliability Line Maintenance

Ref:

49.80.00.002

First Issue Date: 03-SEP-2015

Last Publicatio Publication n Date:

10-DEC-2015

Status:

Open

Maintenance Cost Operational Reliability

Linked FAIR-ISP:

Engineering Support Fault Code/ECAM Warning:

First Issue Date:

03-SEP-2015

Model:

Last Publication Date:

10-DEC-2015

Status:

Open

Manufacturer:

Applicability: A320 family aircraft fitted with Honeywell APU 131-9A. Reference / Documentation: • Airbus TSM Task 49-00-81-810-889-A. Description Several Operators have contacted Honeywell in relation to events of white smoke from the exhaust upon APU shutdown. Smoke from the APU exhaust is covered by the Airbus TSM under task Ref. 49-00-81-810-889-A. This troubleshooting procedure focuses on the air/oil separator and recommends to replace the APU in case the issue cannot be fixed by replacing the separator. Detailed testing and investigation carried out in the Honeywell approved repair shops on APU returned with reports of white smoke revealed a severe obstruction of the gearbox vent tube by coked oil deposits. The obstruction of the tube results in an increase of the gearbox pressure beyond normal operating levels. This is believed to cause a reduction of the efficiency of the scavenge pump and eventually in oil leakage thru the turbine seal during shutdown. Oil leaking into the APU exhaust will burn due to the elevated temperatures and cause the white smoke observed. Consequence Obstruction of the gearbox vent tube may go unnoticed during the troubleshooting as per the current TSM task. This may eventually result in APU removal. Investigation Status The obstruction of the gearbox vent tube is caused by the presence of excess oil in the tube which eventually cokes due to the elevated exhaust temperatures. The failure mode responsible for the presence of oil in the vent tube is not fully understood at this time. Further investigations are currently underway to determine the root cause and to identify the relevant solution to the issue. Mitigation / Interim Plan As a mitigation and before APU removal is considered, Airbus and Honeywell have devised a procedure to remove and clean the gearbox vent tube and fitting. This procedure would allow to remove the coked oil deposits and to restore the balance of pressure in the APU gearbox without the need to remove the APU from the aircraft. The procedure will be included in the relevant aircraft documentation (AMM and TSM) next revision, and in the meantime, an advance copy can be provided on request to our Technical Publications department. Maintenance Information In case white smoke from the exhaust is noted upon APU shutdown, Airbus recommends initially following the current TSM procedure in task 49-0081-810-889-A.

If the troubleshooting procedures provided in the TSM cannot fix the issue, Airbus recommends all Operators to submit a query in TechRequest to our Technical Publications department requesting an advance copy of the removal, installation and cleaning procedures for the vent tube and fitting BEFORE proceeding with the replacement of the APU. Repercussions on A/C Operations Aircraft experiencing white smoke from the APU exhaust may be dispatched under MEL with the APU inoperative. The alternative procedure to remove and clean the gearbox vent tube may significantly reduce the time during which the APU is kept inoperative. Permanent Solution A final fix to the issue of smoke from the APU exhaust depends on the result of the root cause investigation. Currently, Airbus expects the root cause investigation to be completed within Q2 2016. Further information will be made available by means of regular updates to the present TFU article.

© Airbus SAS, 2015. All rights reserved. Confidential and proprietary document.The technical information provided in this article is for convenience and information purposes only. It shall in no case replace the official Airbus technical or Flight Operations data which shall remain the sole basis for aircraft maintenance and operation. These recommendations and information do not constitute a contractual commitment, warranty or guarantee whatsoever. They shall not supersede the Airbus technical nor operational documentation; should any deviation appear between this article and the Airbus or airline's official manuals, the operator must ensure to cover it with the appropriate document such as TA, FCD, RAS. Access to WISE is supplied by Airbus under the express condition that Airbus hereby disclaims any and all liability for the use made by the user of the information contained in WISE. It shall be used for the user's own purposes only and shall not be reproduced or disclosed to any third party without the prior consent of Airbus.