The Federal Aviation Administration (FAA) issued an airworthiness directive (AD) on Thursday targeting specific Lycoming engines that are equipped with certain connecting rod assemblies.
WOW !! How does the parts inspection folks at Lycoming not verify the correctness of parts ? A simple bronze bushing and they canât ensure that it meets the specifications. !
So, the engine owners have to pay for their mistake. ?
This article would be a hell of a lot more useful if it specified which engine types are affected, or even included the AD number itself. Donât make your readers hunt for critical information.
check AD 2024-21-02. It looks like every model engine manufactured between the 2 dates.!!
After reading the AD, it seems like the only required action is to inspect the oil filter for bronze metal particles until the bushes are replaced. The oil filter should be inspected at every oil change anyway, so nothing to get excited about.
Well, it does cause some anxiety/frustration learning that there is an issue that could lead to an in-flight engine problem and unexpected repair costs - due to an apparant quality control issue at Lycoming.
Lycoming had issued a mandatory SB in 2017 on inspecting the bushing for wear and being displaced. see;
Unfortunately, there is no info on time in service for the reported failed parts.!
My question is can the bushing fail within the 50 hr oil charge interval ?
The cost analysis for this AD is amusing - 1 hour to remove baffles and exhaust so you can pull the cylinder and remove the piston pin in order to inspect the bushing. Plus, upon re-reading the cost analysis, the 1 hour is per engine so 4 or 6 cylinders removed in that 1 hour. Ridiculous.
Of course it could be another oil pump
Impeller odyssey. Or Crankshaft. Or piston pin cap orâŚ
Is the Franklin engine patent available? 
The affected parts are known to be installed on Lycoming Model AEIO-320 series, AEIO-360 series, AEIO-390 series, AEIO-540 series, AEIO-580-B1A, AIO-320 series, AIO-360 series, HIO-360 series, HIO-390-A1A, HIO-540-A1A, HO-360 series, IO-320 series, IO-360 series, IO-390 series, IO-540 series, IVO-360-A1A, IVO-540-A1A, LHIO-360 series, LIO-320 series, LIO-360 series, LO-360 series, LTIO-540 series, LTO-360 series, O-233-A1, O-235 series, O-320 series, O-340 series, O-360 series, O-435 series, O-540 series, SO-580 series, TEO-540 series, TIGO-541 series, TIO-360 series, TIO-540 series, TIO-541 series, TIVO-540-A2A, TO-360 series, TVO-435 series, TVO-540-A1A, VO-360 series, VO-435 series, VO-540 series, and VSO-580-A1A engines.
It would be interesting to find out if the oil specification for the motor had been change through those years, it maybe a element has been removed from the oil that is causing the failure,ie the new oil dose not have the properties to lubricate the bronze bush with the piston pin.
Many Lycoming engines use straight mineral oil for âbreak-inâ purposes with a new, rebuilt or overhauled engine. The operators should then switch to AD oil after âbreak-inâ has been accomplished. In those engines that use straight mineral oil beyond the normal break-in period (25 to 50 hours), a later switch to AD oil should be done with caution as loosened sludge deposits may clog oil passages. Oil screens must be checked after each flight until clots of sludge no longer appear.
Those Lycoming engines that are to be broken in with AD oil include all turbocharged models, the O-320-H and the O/LO-360-E.
Since modern FAA-approved ashless dispersant oils already include additives that make them superior to straight mineral oil, the use of additional oil additives in Lycoming engines has been very limited. The only additive approved by Lycoming is Lycoming part number LW-16702, an anti-scuffing, anti-wear oil additive. The policy governing use of this oil additive is spelled out in the latest revisions of Service Bulletins 446 and 471, and in Service Instruction 1409. These publications approve the use of LW-16702 for all Lycoming reciprocating engines except those that utilize a friction-type clutch and a common engine oil system for the transmission and clutch assembly. The use of LW-16702 is required in certain engine models. These models are the 0-320-H, O-360-E, LO-360-E, TO-360-E, LTO- 360-E, TIO and TIGO-541.
It was found that the bushing was not to spec. the OD was undersize, so there is not enough retention in the con rod. The bushing can move in the con.rod, causing wear and it looks like offset force from the piston, accelerating failure.
see; SB 632B
No enough interference on the bush will alway cause it to fail/spin in the rod housing - so there lays the problem !
What âoil filterâ? Oil filters were never standard on a lot of 4 cyl Lycoming engines. My O-320 does not have one.
A lot of us have added an STCâd oil filter.
The Tempest filter will catch 40 micron, [ 0.0015 inch] particles, while the oil screen has bout 1/32nd inch holes , stopping only âbigâ particles.
If you have an affected engine, SB480F lists that the max. number of bronze flakes is 5, in the filter or the screen,
See; https://www.lycoming.com/content/service-bulletin-no-480-f
So, it will require careful examination to find and identify the small particles.!
How do you check the screen after each flight?
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