Matt:

With all due respect, you have made some inaccurate assumptions.

1) I know how much fuel my tanks hold (usable) since I've run them dry to find out. One needs to do this in flight to find out.

2) I have verified that my rate of burn is very accurate. It will result in less than 1/2 gallon difference at any fill up.

3) I always plan a one hour reserve. I don't know too many pilots who would chide me as being risky on that count.

4) My on-board totalizer is very accurate.

5) I know within a 1/2 gallon how much fuel is on board before I start the flight.

6) I can check that the fuel burn IS what I think it is by running tanks dry.

7) I cannot recall a flight in the last ten years where the fuel remaining at landing was more than one gallon different than I calculated it would be.

You may not have that kind of accuracy. You may not trust it. YMMV, but my experience confirms the accuracy of the information I have on board. I get more use out of my airplane for my missions as a result. This has been true in the last four airplanes I have owned.

Walter


On Mar 4, 2005, at 12:39 AM, Matt Hapgood wrote:

Walter,
 
You said that "[you] think that a good pilot always knows how much fuel he has." 
 
I respectfully disagree and I think YOU are on the slippery slope.  I think a that a good pilot realizes that he DOESN'T know how much fuel he has, that he MAY have less than he thinks, and therefore plans conservatively. 
 
It's the pilot who thinks he has better information than he really does that is more likely to get dead than the conservative pilot.   In fact, I'm not sure I'd feel comfortable flying with someone who thinks they have more accuracy in their remaining fuel than than they probably do. 
 
Knowing how much fuel you have in flight requires knowing TWO things: 1) Burn rate, and 2) Starting usable fuel amount (and knowing how much fuel a specific flight will require adds in many more variables).
 
Unless I have TOPPED my tanks on a completely LEVEL tarmac, even perfectly accurate fuel flow doesn't really do much for me.  Because the bigger issue is "How much fuel did I have to start with" (does Tony D. come to mind?)? 
 
And here's the meat of the issue and where I think we really disagree:  Measuring fuel flow to +/- .2 GPH doesn't do squat.  5 hours in the air doesn't even equal a gallon.  It would be a minor miracle if you could look in your tanks, sitting on an average tarmac, and be within even 2 gallons of accuracy.  And if you think your fuel flow is +/- 1%, under the range of conditions in which you fly, then I certainly don't want to fly with you.  So, how accurate are YOU trying to be with fuel fuel flow and remaining fuel?
 
Go ahead and measure with a micrometer and cut with a hatchet.  I won't hold the piece of wood. 
 
And I CERTAINLY didn't say I don't CARE about how much fuel I have or how much I burn (please reread my post).  I am just realistic in recognizing that I don't have perfect information, so I'll be conservative. 
 
So I'll stick with my comment, which was:
 
"I personally don't really care whether I burn 8 GPH or 9 GPH in cruise.  I'm not going to fuel plan that precisely.  I can't.  I don't always know whether I will fly at 6,000' or 12,000' and that makes a WHOLE lot larger difference in fuel planning than leaning.  And just as in the car, I'd land and fuel up if I got lower on fuel than expected on a trip."
 
Maybe you turbo guys are different - no matter what altitude you fly you maintain the same cruise power setting.  It's just one number to remember.  But that's not the case for us normally aspirated guys.  My fuel flows vary significantly on EVERY flight.  I don't care to memorize every burn rate at every power setting.  I make conservative estimates for flight planning. 
 
Don't ask me my Lancairs burn rate - unless you just want a rough estimate, and I won't ask what the actual gas mileage of your SUV is (you'll probably reply that you drive a Honda Insight and I'll look really stupid).
 
If you don't want to fly with me, I'm not offended.  Happy flying.

Matt