Lycoming IO360 “Roll-backs”

[PeytonM]

https://avbrief.com/faa-investigates-io-360-rollbacks/
I’m sure you’ve seen this already. One step away from an AD. And I’m in the final stages of factory rebuilt installation in my J! OMG!

[76Srat]

I'd love to hear from the experts on here about the specifics of the Avstar fuel servos and how broad those might be (if at all) in the IO-360-equipped Mooney fleet.  At first glance, I don't think there's much exposure.  But I've been wrong before when it comes to the FAA and its infinite wisdom and operator-friendly propensity to have very narrow application of its directives . . .

[kortopates]

I'd love to hear from the experts on here about the specifics of the Avstar fuel servos and how broad those might be (if at all) in the IO-360-equipped Mooney fleet.  At first glance, I don't think there's much exposure.  But I've been wrong before when it comes to the FAA and its infinite wisdom and operator-friendly propensity to have very narrow application of its directives . . .

Lycoming’s current‑production IO‑360 engines use AVStar fuel servos, not Precision Airmotive (RSA‑type) units.
Precision Airmotive RSA‑type servos are still widely used in the field and in overhauls, but new Lycoming engines ship with AVStar units.


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[PT20J]

Lycoming switched to AvStar some years back so if it was new, rebuilt, or overhauled  by Lycoming in the last 10 years or so, it will have an AvStar servo. 

[PeytonM]

Why are we just hearing about this now??

[76Srat]

It just seems dubious to me that the FAA would go the ACS route so quickly for what it essentially a fuel-starvation issue at idle in what I'm extrapolating to be mostly a training-based fleet.  Obviously, though not so obvious just yet to the larger public, there's been talk between the servo OEM, Lycoming and the FAA.  I could easily argue that any engine cutting out at idle in a training environment is because the student pilot forgot to enrich the mixture, fuel servo notwithstanding.  Again, easy to jump to all kinds of conclusions here and I'm certainly not trying to, but there's alot more going on than meets the eye here, so far.

 

[PeytonM]

I can confirm my factory rebuilt has the AvStar. Why are we just hearing about this now??

[N201MKTurbo]

I would imagine there have been SDRs about it. If you subscribed to SDRs you would already know about it. 
 

Go here and enter Avstar in the part make field.

https://sdrs.faa.gov/Query.aspx

[N201MKTurbo]

It seeme there is an issue with the idle mixture shaft. I read a few and they would not hold a consistent idle mixture.

[Shadrach]

On 12/17/2025 at 4:35 PM, kortopates said:

Lycoming’s current‑production IO‑360 engines use AVStar fuel servos, not Precision Airmotive (RSA‑type) units.
Precision Airmotive RSA‑type servos are still widely used in the field and in overhauls, but new Lycoming engines ship with AVStar units.


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Paul,

I’m confused by your post. I thought that the Avstar servo was the clone of the Bendix/Precision Airmotive RSA series. It’s my understanding that AVstar will overhaul Bendix/Precision Airmotive RSA servos.

[kortopates]

1 hour ago, Shadrach said:

Paul,

I’m confused by your post. I thought that the Avstar servo was the clone of the Bendix/Precision Airmotive RSA series. It’s my understanding that AVstar will overhaul Bendix/Precision Airmotive RSA servos.

The post was only about how pervasive the use of Avstar servo's are - they have entirely replaced in Bendix/Precision servo's in Lycomings production (as well as Flow dividers and injector nozzles) . But your comment is correct, AVSTAR, and many other fuel repair stations, will overhaul and both Bendix/Precision and Avstar servo's. But the Avstar is not a duplicate clone of the RSA servo but a FAA-PMA replacement for the Bendix/Precision servo's. It would probably be more correct to say Avstar matches Lycomings flow curves with their servo's. They utilize a different manufacturing process as well.