Twin Commander

General Category => Engines => Turbine Commander Engines => Topic started by: Mark S on July 05, 2021, 05:35:56 pm

Title: Hartzell Prop SB "Flight Below 40C Prohibited"
Post by: Mark S 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The service bulletin 159 (should probably be 159A) is obsolete and superseded by a different service letter.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.
Title: Re: Hartzell Prop SB "Flight Below 40C Prohibited"
Post by: Mark S 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. :)
Title: Re: Hartzell Prop SB "Flight Below 40C Prohibited"
Post by: Bruce Byerly 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 I’m told. Not saying it’s right but I remember pointing it out about 30 years ago and the PIC just said “huh, how “bout that?” :P  I don’t remember digging into it.