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Date: Wed, 02 Mar 2005 18:09:47 -0500
From: Ernest Christley <echristl@cisco.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: fuel cutoff valve necessary?
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Ed Anderson wrote:

>Ernest, I could be wrong, but seems I recall somewhere that FAA requires a
>fuel shut off valve.  Someone else may know whether that is correct or not.
>For the reason you stated - Safety.
>
>Ed A
>
>  
>
I don't doubt that it is so, Ed, but putting the edicts from Federal 
agencies aside, I'd like to raise the question of whether it is safer. 

I mentioned two instance where a valve for a single tank system would be 
useful, an inflight fire and emergency landing prep.  In both instances, 
the pilot is required to remember to throttle back, turn off the boost 
pump and then turn off the manual valve under the worst of 
circumstances.  Unless it is very well practiced, most pilots will have 
to look around for the switches and knobs, taking their attention away 
from other duties.  If you're going in under partial power, you may not 
be wanting to give up that power until very short final, moving the list 
of task to the most dangerous times.  A throttle with a cutoff switch 
wired into it that would cut power to the pump after being pushed past a 
detent would accomplish three disjointed operations in one intuitive 
step, and leave the pilots thottle hand on the throttle.

Assuming that connections will be the weakest spot in any system, and 
that there actually is a pump that blocks flow when there's no power 
applied (I haven't tried to determine if there is),  I would argue that 
the pump IS the cutoff valve, and that adding a pilot operated manual 
valve actually reduces safety by needlessly increasing complexity and 
pilot workload.

Marc, is quite right that the fuel system is a pain to work on when the 
fuel can't be contained in the tank.  But does this argue for a pilot 
accessible fuel valve, or one directly at the tank exit?  I think it 
might be different issue from what I was first asking about, but 
interesting nonetheless.