How accurate must fuel gauges be for VFR flight? All Private Pilots should know the acronym TOMATO FLAMES for the Minimum Equipment List (MEL).

On that list, F means Fuel Gauges.But what exactly is required of fuel gauges?

Yesterday, my rental plane came with a note that the fuel gauges were swinging wildly, and bouncing to zero occasionally.   I planned a 90 minute flight, starting with full fuel, so there was no real risk of running out of gas.I decided the fuel gauges probably didn't meet the spirit of TOMATO FLAMES, but I admit that I don't know what the exact requirement is.

How accurately do the gauges have to work to be legal?
The indicator must be calibrated to read zero when that tank is actually empty of all usable fuel (in level flight).  Bouncing is fine as long as they do not bounce when the tank is actually empty.

See regs:


23.1337
91.205