Dave wrote:

I had an interesting discussion with other pilots about converting my
Piper Cherokee 6 to all electric. This would basically require
replacing the AI and DG with electric AI and elec. HSI. So, then,
there would be no use for vacuum pump. But, one pilot said that the
certified elec. AI only allows for installation of the unit, and that
the FAA would *NOT* approve full removal of the vacuum instrument if
it was delivered and certified with the aircraft.

The key word in that last sentence is *if*. My Maule, for example, is certified
with no vacuum instruments at all. The vacuum system is listed as optional in the
owner's manual; in fact, I originally bought the plane with no system or instruments
installed.

I have not checked to see if electrical instruments are also listed as optional
equipment for the plane. If they are, I could replace my vacuum system with
electrical alternatives under the aircraft certificate. If not, I could still
replace the system, but there would be a significant amount of paperwork.

So, check the owner's manual for the Cherokee. If the plane was certified with
a vacuum system being optional, then it can be removed.

George Patterson
Great discoveries are not announced with "Eureka!". What's usually said is
"Hummmmm... That's interesting...."