AL 2005-06
3 August 2005
(Installed on A319, A320, A340, and Boeing 737 Aircraft)
Permanent Magnet Alternator (PMA) Failure
Transport Canada Civil Aviation (TCCA) is issuing this service difficulty alert to bring to the attention of the operators of these aircraft types, that an un-commanded in-flight shutdown (IFSD) may be prevented by the incorporation of the applicable software update in their engine full authority digital engine control (*FADEC) units.
*Note: The FADEC comprises many components, two of which are the electronic control unit (ECU) and the permanent magnet alternator (PMA).
History
In 2002, an Airbus A340-300 aircraft, equipped with CFM International CFM56-5C series engines, had an un-commanded IFSD on the #1 engine. The investigation revealed the root cause was a permanent magnet alternator (PMA) ball bearing failure. As a result of the rotor to stator contact due to the bearing failure, the PMA was unable to generate reliable electrical power for the ECU.
The ECU continuously monitors the PMA, and if the PMA fails to generate the required electrical power, the ECU will switch to other aircraft electrical power sources. In this incident, the ECU, being subjected to the intermittent nature of the PMA failure, remained in an endless loop switching between aircraft and engine power. With no reliable or consistent source of electrical power, the engine eventually shut itself down.
Reference: Transportation Safety Board (TSB) Report No. A02P0261.
FADEC software version 5.C.3.J, as introduced by CFM56-5C Service Bulletin (SB) 73-0126, November 2003 corrects this situation.
In the event of a power loss from the alternator:
- If the ECU sees a reapplication of power after not having power, it remains latched to aircraft power for the remainder of the flight; and
- A "NO DISPATCH" fault is then generated.
This failure mode logic was not part of the original certification software.
The same problem can also occur on the CFM56-5/-7 series engines.
Failure logic is addressed for these models in the following software versions:
| FADEC Software Version | Engine Series | Service Bulletin |
|---|---|---|
| 5.A.I | CFM56-5 | 73-0183 |
| 5.B.K | CFM56-5B | 73-0109 |
| 5.B.L | CFM56-5B | 73-0113 |
| 5.C.3.J | CFM56-5C | 73-0126 |
| 7.B.P | CFM56-7B | 73-0097 |
Transport Canada recommends operators with the above series engines installed on their aircraft to incorporate the appropriate Service Bulletin.
For further information, contact a Transport Canada Centre, or Mr. Robert Dixon, Continuing Airworthiness, Ottawa, telephone 613 952-4308; facsimile 613 996-9178 or e-mail dixonro@tc.gc.ca
For Director, National Aircraft Certification
R. William Taylor
Acting Chief, Continuing Airworthiness
Note: For the electronic version of this document, please consult the following Web address: https://tc.canada.ca/en/aviation/aircraft-airworthiness/aircraft-certification