Twin tachs

Jim Burns wrote:

Is there anybody out there with any insight into this dilemma?

Thanks,
Jim

Hi Jim,
I have a dual needle tach in the 310 with electric tach generators on
each engine - no tach hour recorder. The plane has a hobbs meter that
is activated by a switch. It's not exactly a weight on wheels switch.
It is a microswitch activated by a small stainless steel flap on the
belly that is sensitive to airflow, similar to a stall switch. DC
power goes to the Hobbs, and the ground goes through the switch. It's
supposed to activate at a certain airspeed, but I know it has some
bounce due to airflow from propeller wash when taxiing and running up
the engines.

I previously had a Cessna single with both a Hobbs and Tach hour meter.
When averaged, I found that multiplying 1.15 times the Tach meter was
close to the Hobbs time. I've heard of others with planes on leaseback
that only had tach meters charging something like 1.1 or 1.2 times the
tach time.

Brian