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I am "almost" inclined to agree with you, Rusty. I have had my two pumps since 1998 and found that if you block off the pressure regulator you should get around 80 psi on a brand new pump. As they wear/age this no-flow pressure will slowly start to decrease. My "main" pump is now down to 60 psi while the back-up (only used for take off and landing) is still producing 80 psi.

However, I had to replace on of the original pumps after only 30 hours of test stand running. It simply would not produce pressure. I now wish I had taken it apart to see what the problem was. It was not the check valve, because pressure was maintained when the other pump was on. The pump could be hear running - so I suspect that the impeller had sheared a pin or something of the sort. So , my "however" is regarding the fact that most things have an "infant" morality period - which once you make it through provides a high probably of a long- long life. I suspect pumps are the same.

My point is having an "infant mortality" incident in a aircraft is far different than say - in a car (as we all know).

FWIW

----- Original Message -----

From: Russell Duffy

To: Rotary motors in aircraft

Sent: Monday, December 25, 2006 5:39 PM

Subject: [FlyRotary] Re: fuel pumps

A single pump system

is a non starter in aircraft.

Lynn E. Hanover

Hi Lynn,

Funny you should mention this, because I've actually been contemplating a single pump system on the single rotor. These pumps are quite reliable, and seem to give lower readings as they start to wear. I could probably argue that all the extra plumbing and wiring might cause more problems than it avoids.   Also, no one seems to mind running a single regulator, but that could fail just as easily.

One thing I keep thinking about is a conversation I keep having with a couple RV buddies. One guys wants an auto conversion, but only if it's as reliable as his car. The thought being that you get in your car and drive thousands of miles, and don't ever consider what whether the engine might break on the way there. Using a modern car as the reliability standard, you have to accept that there is only one of everything (ECU, fuel pump, etc).

BTW, just to let you know how abby-normal I think, I used to run both pumps all the time, just as I also run my boost pump (almost) all the time for the Lycoming. My logic is that I'd rather find out about a pump failure when I'm safely on the ground, checking them individually during my run-up.

I'm certainly not telling anyone to take out their backup pump, but I'm wondering if I might just leave mine out.

Cheers,

Rusty (attached pic for Lynn <g>)

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