Mailing List flyrotary@lancaironline.net Message #6560
From: Ed Anderson <eanderson@carolina.rr.com>
Subject: Fuel Pump Master Switch?
Date: Wed, 17 Mar 2004 14:39:49 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Message
 
-----
Sent: Wednesday, March 17, 2004 1:03 PM
Subject: [FlyRotary] Re: mainfold hose

I was trying to think of a situation where I would want the master switch on, but not want the fuel pump on.  Maybe for an engine problem/shutdown, but still want to keep the radio and navs on ? 

 

Steve 

 

That's exactly what I was thinking.  I prefer to have both my pumps on separate switches, but I don't see any fire hazard in regards to leaving your pump on the master.  Like you said, if there's one switch you'll hit, it's the master.

 

Cheers,

Rusty (hope I don't get flamed <g>) 

 

No flames Rusty - just fire {:>). 

 

If I understand this discussion correctly, I can think of a number of reasons I might want my master switch on (on the ground) and would not want the fuel pump running.  But, I would presume in that case one could pull a circuit breaker to disable the fuel pump.  I would think you would hear the pump running - if not (and you canard guys might not) you might quickly run your battery down with that pump drawing its 5 - 9 amps with the Master on because you wanted to work on your intercom wiring,etc.

 

Here's a possible safety issue (may be far feched, but then that's the ones that get you).  You have your pump wired through your master power switch.  You fuel pump  malfunctions - say it shorts out and starts to draw a bunch of amps in that case, unless you have the pump on a circuit breaker (you do don't you?) , you would be forced to turn off the master switch - but wait that turns off your engine!

 

Your fuel pressure guage/alarm will give you the first indication of pump failure.  Then as it fall (rather quickly) below a certain level, the leaning of the mixture will cause the tone of the engine to change follow shortly by surging and stumbling followed even more shortly by engine stoppage.  It takes my system approx 3 - 5 seconds from the time the pump shuts off until the engine has stopped producing power. 

 

My personal preference is all critical subsystems require an overt action by me to either turn them on or turn them off.  I do not personally like machines/software that want to do important things for me as I have found they and I don't always agree on the needed action in all circumstances.  My suggestion is think hard about it before you  hardwire yourself into modes that may preclude you having full control over a situation.

 

 

But, then that is just my personal preference.

 

Ed Anderson

 

 

Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster