Inop fuel gauge on rental + long XC

[ChrisK]

The broken equipment / rental threads got me thinking about this, and as a renter...

Here's the scenario.

You check the plane out, do your runup, and everything is fine. You launch on your cross country flight and notice about halfway to your destination that one of your fuel gauges appears to be malfunctioning (fluctuating a lot but reading zero most of the time). You know that that tank should be almost full, and the other tank is reading almost full. What do you do? Turn around? Land? Continue?

 

[Jim Logajan]

(b) Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used.
Notwithstanding claims otherwise, why would the FAA use the highlighted words if it didn't intend them to have some level of precision appropriate to the task of aerial transportation?

 

[Jim Logajan]

Nothing in the wording of 23.1337 states any required accuracy, validity or positive indication of the INDICATION "SYSTEM" except for (ref.) 23.959 which is the unusable fuel reg.

I can see no way to interpret your claim that doesn't make those two sentences in 23.1337 effectively null and void of useful meaning. All because the FAA failed to specify accuracy?

By the way, I believe you used the word "calibrated" as a synonym for "labeled", which are quite different concepts.

 

[Jim Logajan]

In the absence of an accuracy spec, it only means the labels have to exist. We might want it otherwise, but who decides if a 1/4 tank error is excessive, whereas a 0.1 gal error isn't? Subjective requirements for measurements are problematic.

The FAA doesn't provide any quantifiable definition for "congested area" either, but that hasn't stopped it from successfully enforcing the regulation containing that phrase.

As to who gets to decide what is excessive error in any particular case - carried far enough, a judge. Otherwise the FAA. Everyone else has to try to anticipate what error would be seen as acceptable should something go wrong latter. The subjective nature of the regulation doesn't make it moot (though there are many regs where it would be nice if that was the case.)