AEIO-320 Oil Change Standards

[Bartman]

Hi all,

Yes, this is oil thread number three for the week because I keep being introduced to new information regarding the inverted oil system in my '79 8KCAB Decathlon and I just want to be sure that the complete and correct information is being posted here. Believe it or not, we pop up in search results very frequently and are quoted by AI so people come here for answers and this subject has a major effect on safety and cost-of-ownership so it's important to get it right.

This thread covers the Christen inverted oil system which was bought by Lycoming so there are Christen part numbers and corresponding Lycoming part numbers for the same parts. The earlier Bellanca inverted oil system isn't covered by this thread.

I wasn't aware of the existence of Lycoming MSB 480F which contradicts (some might say 'updates') the information in the Lycoming Owners' Manual for the AEIO-320 so I was ready to do oil changes at 25 hour intervals and to only inspect the sump suction screen at 100 hour intervals. Unless you've followed the breadcrumbs all the way to the end, you may draw incorrect conclusions, as I have, about what needs to be done.

The question is; what needs to be done to do a complete oil change on a Lycoming AEIO-320 engine with a Christen/Lycoming inverted oil system, and how often does it need to be done?

Here's what I can tell from everything I've read, at 25 hour intervals;

1. Drain oil from sump
2. Disconnect all three hoses from 3-way ball valve and drain oil from them
3. Disconnect inverted oil supply hose from breather tee
4. Remove/inspect suction screen in sump (requires removing the hose from the fitting)
5. Remove and inspect oil filter element
6. Reinstall suction screen tee and connect hose to fitting
7. Reconnect all three hoses to the 3-way ball valve leaving top hose disconnected at breather tee
8. Install new filter
9. Fill sump with new oil
10. Fill inverted oil supply hose with fresh oil and reconnect top of hose to breather tee

There is a warning about the sump plug being dislodged during inspection of the suction screen and how it can lead to loss of suction and severe damage to the engine if not installed correctly but this applies to horizontal-screen engines which is more likely to be the AEIO-360 series. Know which you have before proceeding with any of this.

This brings us back to an earlier question as to where the suction screen tee fitting should be mounted since the left rear sidewall location makes access very difficult, especially given that it has to be removed every 25 hours. The original drain location is also closer to the 3-way ball valve so the hose length can be reduced by about half which is desirable. Whichever location you choose, you have to ensure that the spot will keep the fitting submerged in oil during normal upright maneuvering which I think both the original sump drain location and the left rear sidewall do. I expect I'll be moving mine to the original sump drain location and using the unused port of the tee fitting as a sump drain.

Please let me know if you think any of this is incorrect or needs to be explained further in posts below.

Thanks for reading!

 

[Bartman]

AD 2024-21-02 states that it incorporates MSB 480F but does that mean the guidance of MSB 480F doesn't apply if your engine is excluded from the AD or does MSB 480F still apply outside of the conditions that made the AD necessary?

Dynamic Regulatory System

drs.faa.gov

 

[Bob Turner]

Guidance is just that - guidance - until an AD makes it mandatory. Following that SB is not required unless your engine was delivered with the faulty bushings.

As always, I could be wrong.

 

[Bartman]

A mandatory service bulletin isn’t mandatory? The AD says it incorporates the MSB but it doesn’t say it supersedes it, does that matter?

 

[Sully]

Mandatory SBs are not "Mandatory" for Part 91 operators.
But I would "Highly Recommend" adherence.
Does it apply to your engine? Yes
MODELS AFFECTED: All Lycoming direct drive.

 

[Bob Turner]

When Lycoming writes "mandatory" on an SB, they mean "highly recommended."

They cannot mandate anything - the Administrative Procedures Act specifies how an order becomes mandatory - in our case, it requires an AD.

We could have had an AD that simply applies the SB to all Lycoming engines. That has not yet happened.

It did happen on Cubs - the famous lift strut deal - and I believe our fuel injector line AD did that as well.

 

[Bartman]

It doesn't seem quite as onerous now that I've got my head wrapped around it and I know my inverted oil system is installed correctly. It'll be a little bit more of a project to do an oil change but it's a small price to pay for the experience you're getting in the air.