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When to use Aux Fuel Pump

sglynn

Well Known Member
I transitioned from carburetor engine to fuel injected on my RV. I'm flying in phase I testing. Question: When do you use the Aux Fuel Pump? I installed Andair's pump and filter. On my Piper carb engine I would use it:
1. During take-off
2. During landing in case go-around was needed
3. During changing tanks

On IO engine I'm using it to prime. Is that it? Should I use it with an IO-360 engine at the same places as with an O-360 engine? Isn't their a risk of flooding the IO engine with the extra pump running?

thanks
 
I have a different take on fuel pumps.

The hardest stress on an electric pump (or any motor) is when its turned on, due to the inductance of the motor and the resultant inrush current. Why do this? Just leave it on.

I have yet to replace a fuel pump on any of my own airplanes.

I make an exception starting an injected engine.
 
I have a different take on fuel pumps.

The hardest stress on an electric pump (or any motor) is when its turned on, due to the inductance of the motor and the resultant inrush current. Why do this? Just leave it on.

I have yet to replace a fuel pump on any of my own airplanes.

I make an exception starting an injected engine.

That makes sense but if I leave it on I don?t get the real GPH because it shows a real high usage. My pump is before the fuel flow sensor.
 
In addition to what others have said on when to use the Aux Fuel pump, I will add a few of mine that may or may not have been mentioned.

For Startup.
Any ground operation with a hot engine and hot ambient air temp.
Sometimes in climb depending on angle and power setting.
Anytime at or below 1,000 AGL.
 
SNIP

The hardest stress on an electric pump (or any motor) is when its turned on, due to the inductance of the motor and the resultant inrush current. Why do this? Just leave it on.

SNIP

How does this inrush stress harm or wear the pump?
 
How does this inrush stress harm or wear the pump?

If you watch a DC motor turn on with an oscilloscope one would observe a large spike in current due to the inductive reactance of the motor. Its nearly a DC short. That is hard on brushes and commutator wire insulation.

This really applies to any inductive load...for example, when do light bulbs usually burn out..? When you switch them on.
 
I use the boost pump for:

- starting
- take-off
- landing

I don't use it to change fuel tanks while airborne anymore; I just watch the fuel pressure after the switch...
 
So, help me sort this out.

Two pilots fly the same flight profile, in identical a/c, every day.

Pilot A: runs the boost pump to prime the engine (and verify operation), and turns it off until the next need for boost (either a mech pump failure in flight, or next start sequence).

Pilot B: runs the boost pump to prime, and never turns it off for the duration of the flight.

Both pilots follow the same methodology, every flight, until a pump fails.

Which pump was cycled more often?

Which has the higher probability of failing 1st?
 
I've installed a flowscan and a red cube right at the inlet of the carb. In both cases I fabricated a custom fitting and a bracket to support the red cube. Rock solid fuel flow readings.
 
Mean cycles between failure of the pump likely exceeds the lifetime airframe cycles by an order of magnitude

Turn it on and off whenever you think you need to.

Don't over think it

:D
 
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