Post-Annual Flight

Jay Maynard wrote:

On 2008-02-21, wrote:

I never use the fuel gauges for anything other than
passing reference, since we do everything by visual inspection and the timer
in our Garmin GTX-327 transponder.

How do visual inspection or your timer tell you if you've got an in-
flight fuel leak? That's an important reason for the fuel-gauge
requirement.


How does a fuel gauge that's so unreliable that you can't trust it to within
a quarter tank tell you whether you've got a fuel leak? That description
applies to every aircraft I flew during my primary training, late 1970s
vintage Cessna and Piper and Grumman products (this was in the late 1980s).
I was taught to verify the tank's level on preflight, and use time and
consumption per hour to figure usage.


It should tell you if the tank is empty. The fuel gauge is required to
read correctly for an empty tank. I use a timer and visual inspection
as my primary, but I also use the fuel gauges to verify that my fuel
burn is approximately what I expected it to be.

Jay's flight manual tells him to position the fuel selector on the
fullest tank (he's got four of them) in his pre-landing check list. If
I were in his shoes, I would plan my flight so that the tank with the
inop gauge was used early in the flight so that one of the others is the
fullest tank on landing. For take-off the same advice is in the AFM.
In that case, you have presumably just visually checked the fuel level,
so you can safely take off on the tank with the inop gauge. Still, as
the inboards are the "main" tanks and are supposed to be filled last and
used first (at least on a Six, which has the same fuel system), I'd be
getting that gauge fixed sooner than later.

I did have one of my tip tank gauges stop working about a decade ago for
the same reason (float fell off), and like Jay I put that off until the
annual, but I also didn't use the tip tank during that time the gauge
was broken and placarded it as tank unusable.