Maintenance Briefing Notes Best Practices IDG case damage IDG damage due to low oil level operation Preamble As part of an overall safety management system, Airbus has processes in place where significant, or safety related in-service maintenance events are investigated by a panel of multi-disciplinary experts. The purpose of the event investigation process is to continuously improve our product, but also to share the lessons learned with the customers community in order to improve awareness to manage the risks from events caused by human actions that may affect flight safety, or cause personal injury, and damage to components. Maintenance Briefing Notes, Page 1
The Airbus Maintenance Briefing Notes will be dedicated to share maintenance errors related events and their consequences. Sharing the Airbus world-wide return of in-service events, in particular concerning maintenance errors, could help operator and maintenance organizations identify and understand multiple contributing factors to errors and violations. This should not be understood to put the blame on the maintenance mechanics who are working often in a challenging and stressful environment. The maintenance error in this context is defined as a human action that unintentionally deviates from the required, intended, and expected action. Whereby the violation is a human action that intentionally deviates from company or regulatory policies and procedures. What happened The following operator report is just one example of similar other reports: Event details: During A/C pushback the pilot started ENG 1. IDG & Fire Loop messages lit and ENG 1 was shut down without discharging fire extinguisher. Aircraft returned to Gate (awaiting confirmation of pilot actions). At the gate, LH Fan cowl opened for inspection, revealed Kevlar plastic wrapping on LH of fan case damaged by high temperature oil with localised sooting also visible. An Engine dry crank carried out, and line engineer reported IDG oil leak from oil out tube of IDG to IDG ACOC. Engine Maintenance History: One flight prior the event, A/C returned to the base with IDG1 OIL LO PRESSURE" and "GEN 1 FAULT. Maintenance found that IDG has been over serviced IDG oil drained out, IDG1 reconnected, and engine run successfully performed. Maintenance Briefing Notes, Page 2
Why did it happen The first warning IDG OIL LO PRESSURE has been confirmed as an IDG internal failure. As per the recommended procedures, flight crew disconnected the IDG (in flight). According to the manufacturer, a sudden disconnection can result in an inaccurate oil level indication, due to oil being potentially trapped in the sump. Once on ground, the IDG has been serviced and re-connected. This reconnection is not permitted according to maintenance procedures. When an IDG is in a failure condition, such as an oil leak in this case, its reconnection can lead to over-damage. As per the shop investigation report, operation of the IDG with this oil leak condition led to increased internal failures, up to a damage of the IDG housing. This damage enabled an oil to leak out from the IDG on hot engine parts, leading to the fire warning, and to replace the engine before next flight. A combination of un-intentional maintenance errors can explain this event: A continuing leakage of the IDG was not detected Maintenance documentation was not respected: the IDG was mechanically re-connected, despite the (non-detected) oil leakage Maintenance Briefing Notes, Page 3
Lesson learned Procedures as laid down in the AMM and TSM should be strictly adhered to: AMM: A300-600/A310: 24-11-00 Pb 01 Operation of the generator drive section A320 Family/A330/A340: 24-21-00 Pb 01 Operation/control & indicating, Disconnection of the IDG. TSM: 24-20-00-810 Pb 201, Low oil pressure of the Integrated Drive Generator 1 (2) The Trouble Shooting Manual recommends that in the case of an IDG low oil pressure warning, the IDG is replaced before further flight, in order to avoid more IDG, or consequential damage to engine parts. Further Reference: Operators Information Transmission (OIT), Ref.: 999.0069/13, dated 10 Oct 2013 Subject: ATA 24 IDG Disconnect We appreciate receiving feedback to this issue of the Maintenance Briefing Notes. Uwe Eggerling Senior Director Safety Engineering & Maintenance Airbus Customer Services Mailto: uwe.eggerling@airbus.com Maintenance Briefing Notes, Page 4
This Maintenance Briefing Note (MBN) is part of a set of Briefing Notes that provide an overview of the applicable standards, techniques, best practices, human factors, suggested company prevention strategies and personal lines-of-defense related to major threats and hazards that may affect maintenance. This MBN is intended to enhance the reader's safety awareness but it shall not supersede the applicable regulations and the Airbus or airline's maintenance documentation; should any deviation appear between this MBN and the Airbus or airline s maintenance documentation, the latter shall prevail at all times. In the interest of aviation safety, this MBN may be reproduced in whole or in part - in all media - or translated; any use of this MBN shall not modify its contents or alter an excerpt from its original context. Any commercial use is strictly excluded. All uses shall credit Airbus. Airbus shall have no liability or responsibility for the use of this MBN, the correctness of the duplication, adaptation or translation and for the updating and revision of any duplicated version. Airbus Customer Services Maintenance Engineering Services 1 Rond Point Maurice Bellonte - 31707 BLAGNAC CEDEX FRANCE Maintenance Briefing Notes, Page 5