RPM Guage markings

simonlowther · Post by **simonlowther** » Tue Apr 13, 2021 5:21 am

Hi all,

My 120 is fitted with a C85-12, it has a yellow range on the Tach at 2075 - 2300; I can not find any reference as to why this is present and what damage is risked operating in this range. Does anybody know what the story is with this.

Much thanks
Si

Post by **6643** » Tue Apr 13, 2021 6:53 am

Back when the McCauley 1A90 props were first certified there was a restricted range and a required placard stating to avoid continuous operation in that range. In 1949 McCauley issued Service Bulletin 13 rescinding the restriction and calling for removal of the placard.

8342 · Post by **8342** » Tue Apr 13, 2021 6:58 am

Does Cessna Service letter SLN-15 apply?

Rick

Post by **6643** » Tue Apr 13, 2021 7:05 am

8342 wrote: ↑Tue Apr 13, 2021 6:58 am Does Cessna Service letter SLN-15 apply?

I would have to say "No, not as of the issuance of McCauley service bulletin 13." Cessna was just passing on McCauley's installation information in SLN-15. Interesting there doesn't seem to be any updated bulletin from Cessna, though.

simonlowther · Post by **simonlowther** » Tue Apr 13, 2021 9:11 pm

Great info, much thanks.

Si

simonlowther · Post by **simonlowther** » Wed Apr 14, 2021 2:24 am

Now found the SB in the resources section of the website. All good thanks.

Si.

a64pilot · Post by **a64pilot** » Wed Apr 14, 2021 10:00 am

Don’t feel bad, for I guess the last 15 years or so that I’ve had the airplane, I’ve been staying out of the avoid range,I only learned it’s been rescinded the other day, now it’s ingrained as habit

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RPM Guage markings

RPM Guage markings

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