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Change from mechanical to electric fuel pump? printer friendly version
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JamesB
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Posted Saturday, May 31, 2014 @ 11:53 AM  

I've been thinking about switching from the stock VW mechanical fuel pump to an electrical fuel pump on my RF5B.

Has anyone done this? Satisfied? Which pump did you choose?

Advantages:
- Newer parts/technology in the pump
- Simpler fuel plumbing
- Fuel lines further from the exhaust

Disadvantages:
- Losing electrical power/stopping fuel flow in flight.
- A mechanical pump allows for hand propping if you have no battery power.

Scenario 1: Drained power during soaring, can't restart.
This would probably be the case with mechanical or electric pumps for me. If I'm restarting, I'm probably at about 2,500' at the end of the day and have lost lift. Although 2,500' gives me landing choices if the engine doesn't start, it's not high enough to build enough speed for an "air start" for the engine. So, I'm probably landing out either way.

Scenario 2: Loss of alternator during a flight.
Then I think you'd shut down all unnecessary electrical loads, just as you always would, and proceed to the next appropriate airport. The fuel pump doesn't consume much power. It would unlikely make a difference.

Scenario 3: Hand propping a dead airplane.
It's hard to imagine my hand propping the RF5B -- or being somewhere there's no source of charging for the battery.

Thoughts?

Jorgen
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Posted Sunday, June 1, 2014 @ 02:40 PM  

Hi James,
thanks for posting your thoughts and sharing your engine adventure with the insert- been there, done that. Just got back from a half hours 4 soaring so I'm with fresh impression from an airstart- that would of course be more adventurous with an electrical fuel pump. Regarding mechanical vs electrical fuel pump I think the disadvantages outweigh the advantages of a switch, but I have limited (=too few seasons) experience of the battery requirements of the 5b. I would be concerned with low battery after soaring (which is what a 5b excels in) but maybe a modern battery would reduce that risk?

May the 4's be with you/ Jörgen

JamesB
First Sergeant

Gender: Male
Location: Near Seattle, WA; USA
Registered: Oct 2006
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Posts: 257

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Posted Monday, June 2, 2014 @ 09:13 AM  

One option might be to add a small backup battery just large enough to drive the pump for a reasonable amount of time.
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