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Author Topic: Hartzell Prop SB "Flight Below 40C Prohibited"  (Read 478 times)

Mark S

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Hartzell Prop SB "Flight Below 40C Prohibited"
« on: July 05, 2021, 05:35:56 pm »
My airplane has a silkscreened placard on the panel. It reads "FLIGHT BELOW 40 C OAT PROHIBITED PER HARTZELL SERVICE BULLETIN #159"

I did a little digging into what that means and why--and its a real puzzle tracking it down.
The service bulletin 159 (should probably be 159A) is obsolete and superseded by a different service letter.
Then the reader is directed to "Manual 202A", but that document did not have an obvious answer.

I have encountered some -40 OAT in the winter, depending on which probe/sensor you look at. Operationally it would be nice to be able to terminate that restriction.

Mark S

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Re: Hartzell Prop SB "Flight Below 40C Prohibited"
« Reply #1 on: July 05, 2021, 05:53:11 pm »
I was advised to read up on the Propeller Owners Manual and look at the Maintenance Practices section.
It turns out the explanation is there, along with a Vol. 11 of Manual 202A
It is a function of the grease used.
Aeroshell 6 is the most common all purpose grease, and apparently used in all new production propellers since 1989 except for a few exceptions, notably the Piaggio P180. No limitations noted.
. . .but. . .
Aeroshell 5 has good high temp. properties and very little oil separation or leakage. It has the -40C limit. This product will limit the operator to flights warmer than -40C.
It is possible Aeroshell 5 was used (or mixed with other grease), on the aircraft at some time in the past, so the placard makes some sense.

Now, all I need to do is find the grease log entry and see what was used on the last overhaul. :)

Bruce Byerly

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Re: Hartzell Prop SB "Flight Below 40C Prohibited"
« Reply #2 on: July 05, 2021, 08:24:06 pm »
This one and the requirement to wear an oxygen mask above FL350 are occasionally ignored, or so Iím told. Not saying itís right but I remember pointing it out about 30 years ago and the PIC just said ďhuh, how ďbout that?Ē :P  I donít remember digging into it.