2008 02 22
IO-240 fuel system contamination
There have been a number of rough running/unstable engine events and engine shutdowns occurring on Diamond Aircraft (DA) model DA20-C1 powered by the Teledyne Continental Motors (TCM) IO-240-B series engine.
Uncommanded engine shutdowns have occurred during various phases of training flights (stalls, spins and sideslips). Engine idle instability and sputtering at low power have also occurred during the critical approach phase and after landing. Engine fuel related problems have occurred both on the IO-240-B13/B17 equipped with the altitude (aneroid) compensating fuel system and the IO-240-B3 engine with the manual leaning fuel pump.
Subsequent to these events, TCM and DA have conducted a detailed examination and analysis of the fuel system components (engine mechanical fuel pump, throttle valve/fuel metering unit, fuel manifold flow divider and injector nozzles). Mild to severe foreign contaminants were discovered in some of the failed components. As in all fuel injected TCM engines; if the fuel flow is interrupted or sufficiently reduced by contaminants the engine will run lean and may even shutdown.
Some fuel system components have very small passages and tolerances; therefore any time that a fuel system is “opened” for maintenance action, there is a significant opportunity for contamination to be introduced. Maintenance personnel should take every precaution to minimize this hazard especially during “fuel set-up” procedures or fuel system component changes. It is also possible that contaminants are being introduced to fuel system components during ”flushing” procedures or any time that fuel system maintenance is performed.
In an effort to minimize fuel system/engine instability, TCM have very recently issued Service Bulletin SB07-9 titled “IO240B Inline Fuel Filter Reorientation”. In conjunction with SB07-9, TCM have also issued Service Information Directive SID07-10 titled “IO240B Fuel System Component Installation” to further minimize the possibility of fuel system contamination.
In order to address in-flight shutdowns and/or engine instability on aircraft equipped with the altitude compensating fuel system, Diamond Aircraft Company has recently issued Mandatory Service Bulletin (MSB) DAC1-73-05 Rev 1; titled “Operating Limitations with Altitude Compensating Fuel Systems” dated December 14, 2007. Furthermore, Transport Canada Civil Aviation (TCCA) has issued AD CF-2007-27R1 mandating the above MSB and also specified changes now listed in Revision 23 of the DA20-C1 Aircraft Flight Manual.
TCCA recommends that owners, operators, maintainers and other responsible persons comply with all maintenance related information provided by the respective Type Certificate Holders. Additionally, it is recommended that all owners, operators and maintenance facilities ensure that their work environment is kept to the highest level of cleanliness. Good housekeeping practices need to be an inherent part of the workplace culture. Even tiny airborne particles can contaminate an open fuel system or fuel system components.
Malfunctions, defects and failures occurring on aeronautical products should be reported to TCCA, Continuing Airworthiness via the Service Difficulty Reporting (SDR) Program. Should you have any questions, please do not hesitate to contact Mr. Barry Caldwell at telephone 613-952-4358 or firstname.lastname@example.org
For Director, National Aircraft Certification Philip Tang
Acting Chief, Continuing Airworthiness
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