Ignition System Reliability

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CFMI Proprietary Information 13.1
Ignition System Reliability
CFMI Proprietary Information
The information (including technical data) contained in this document is the property of CFMI. It is disclosed in confidence and the technical data therein is exported
under a U.S. Government license GTDR. Therefore, none of the information may be disclosed to other than the recipient, or used for purposes other than to render
services to CFMI, without the express prior written authorization of CFMI. In addition, the technical data therein, and the direct product of the data, may not be diverted,
transferred, re-exported, or disclosed in any manner not provided for by the license without prior written approval of the U.S. Government.
CFMI Proprietary Information 13.2
Overview
• Fleet Experience
• Hardware Improvements
• Maintenance Recommendations
• Summary
CFMI Proprietary Information 13.3
Fleet Experience
• Ignition system is one of the top
causes of delays and cancellations on
the CFM56-3 engine program
• Ignition system reliability has been
improving with increased awareness
and new hardware
CFMI Proprietary Information 13.4
Hardware Status
• “Murphy-proof” leads have shown significant
improvement
- Reduced pitting and arcing at contacts
- Fewer misassembly errors
• New failure mode has been seen on new
“Murphy-proof” leads
- Inner seal failure resulting in electrical energy arcing
from the contact to the inner spring assembly
- Design changes are being evaluated
CFMI Proprietary Information 13.5
Hardware Status
Original Type 4
Ignition Lead with
WHITE silicone seal
CFMI Proprietary Information 13.6
Hardware Status
“Murphy Proof” Lead with
BLUE silicone seal
CFMI Proprietary Information 13.7
Maintenance Recommendations
• Replace ignition lead outer seal whenever the
lead-to-plug connection is separated
- Degradation of seal results in inability to reseal the
interface
- Note the seal is not interchangeable between the new
(blue) and old (white) Type 4 leads
• Polish the contacts when the lead-to-plug
connection is separated
- Unremoved pitting can lead to premature failure of both
igniter and lead
- Polishing tools available for the lead contact
- Unison tool kit P/N 11-10786-1 or P/N 137356
- Use 3/8” medium grit abrasive impregnated rubber rod
(Craytex or local purchase) for igniter plug contact surface
CFMI Proprietary Information 13.8
Maintenance Recommendations
Unison Contact Polishing Kit
CFMI Proprietary Information 13.9
Maintenance Recommendations
Apply Grease
DO NOT Apply
Grease to these
threads
Igniter Plug Maintenance
CFMI Proprietary Information 13.10
Maintenance Recommendations (Continued)
• Ignition component "soft-time"
- Study performed 1st Quarter 1993
- Airline input and experience considered
- Lead considered to be the major problem
- Exciter replaced to move aircraft although rarely
the problem
- Plugs are also cause of engine no-starts
- 2,000-cycle replacement on lead provided
alternating ignition is used
- 1,000-cycle replacement on plug (low energy)
- CESM 005 updated to reflect “remove and
replace” soft time recommendation
CFMI Proprietary Information 13.11
Summary
• Improper maintenance is still seen with original Type 4
lead
- Incorrect assembly or missing hardware
- Antiseize grease applied or not applied to proper locations
• New hardware improvements have proven to add life and
increase reliability of the entire ignition system
- Individual operators are reporting significant improvements with new
hardware
- Additional changes are being reviewed
• Unison has published a pocket-size Type 4 Ignition
Troubleshooting Guide
CFMI Proprietary Information 13.12
Summary (Continued)
• Operators are encouraged to incorporate hardware
improvements and/or "soft-time" replacement intervals
on older hardware
• Boeing has a Master Change available which provides a
kit of hardware and instructions to transfer the power
supply from the aircraft standby BUS to reach the left
exciter while the right hand side is inoperative
- The MMEL has been revised to allow dispatch with RH system
INOP provided the operator has an approved configuration for
the LH system to be powered by the aircraft BUS
• Dispatch reliability has exceeded 99.95% since
mid-1994 and is expected to continue to improve

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Ignition System Reliability