Fuel pump questions

[Ken Mayer]

> > In-tank fuel pumps: Since the wiring is also submersed, would there be
> > any worry about the + and - wires shorting each other, causing a spark,
> > and destroying the fuel tank? (this is my dumb question)

The concentration of fuel vapor in the tank is above its upper explosive
limit, so it can't ignite. 

> > In-line or "booster" pumps: One person tells me you must run it
> > constantly with the main pump, otherwise there will be such a large
> > restriction in flow. 

Depends on the design of the pump.  Piper airplanes have a mechanical fuel
pump driven by the engine, and a separate in-line electric pump.  The
electric pump is off during normal flight ops.  It's turned on for
takeoff, landing, switching the tank selector, and emergency ops.  The
fuel pressure gauge reads ~5 psi with either or both running.

Ken
:-)