In a message dated 1/9/2004 10:29:53 AM Central Standard Time,=20 gary21sn@hotmail.com writes:

It would seem the line from the fuel pump to the header tank will hav= e=20 fuel in it because of header tank slosh back from taxi, turns, climb and=20 turbulence, etc. unless a check valve is in the line. =20

Rob, et al,

Hmmmm...

Let me describe my setup and experience.

1. Automatic "header full" system keeps the header tank between 8.25 an= d 9=20 gallons at all times. Lower level sensor must remain at the lower leve= l=20 for about 15 seconds before the pumps are started (avoiding start/stop cycle= s in=20 turbulence). This assures me of about 1 hour flight time in case of=20 complete power failure, etc. Indicators show the header full and anoth= er=20 for "timer running."

2. Both pumps (located in the stub wings) are simultaneously=20 engergized. There are check valves at each header entry point for= a=20 variety of safety reasons - siphoning, negative pressure, etc. The win= gs=20 are emptied evenly meaning that lateral trim does not change thru the flight= =20 unless I throw the passenger out.

3. Each pump has its' own pullable breaker and manual on/off=20 switch. This allows for non-automatic operation. There is no fue= l=20 selector for KISS.

4. VM EPI 800 fuel probes are in all three tanks. They are very=20 accurate. All tanks produce a warning (I have annunciator lights) when= =20 they are below 4 gallons. I would be gasping for air if the header fal= ls=20 below 4 gallons (ask the Don about this). The Gallons indicator shows=20= zero=20 (by design) when below 2 gallons. There is a fuel totalizer runni= ng=20 off the fuel flow sensor, generally 2-3% high, that is another low fuel warn= ing=20 source.

5. The automatic system is manually turned off when the header do= es=20 not refill after dropping to 8 gallons and the wings have been zero for a wh= ile.=20 This probably means the pumps are running "dry" for no more than 15-20=20 minutes. Slosh, etc. probably means the pumps are not really dry for t= hat=20 length of time. I have flown in this condition about ten tim= es=20 (including the Kitty Hawk to Dayton race leg, 10 minutes before=20 crossing the finish line) and the pumps are still working. The wings h= ave=20 been emptied in level flight with not much more than a cup of fuel remaining= in=20 each wing as later measured on the ground.

6. The panel is placarded "Do Not Take Off With Less Th= an 8=20 Gallons In The Header." There is no experience maneuvering when t= he=20 header contained less than 4 gallons, although the header is throughly=20 baffled.

In flight I cannot hear the pitch of the pumps change when thay run dry= =20 because of their stub wing location - perhaps you can hear them as they are=20 under the seat. Maybe you could hook up an aural sensor switched into=20= the=20 audio panel or use a stethoscope, checking heart rate and pump pitch, w= hen=20 you think the wings are dry.

Scott Krueger=20 AKA Grayhawk
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL=20 (KARR)

"...as we know, there are known knowns; there are things we kn= ow=20 we know. We also know there are known unknowns; that is to say we know there= are=20 some things we do not know. But there are also unknown unknowns - the ones w= e=20 don't know we don't know." D. Rumsfeld