[relix]

Make it broader - before take-off, pilots enter the expected destination (or expected distance). During cruising, computers keep track of how much fuel is being used (lost) per unit of time, and projects forward to see if they can still make their expected destination or not.

If the number does not reach within expected margins, then show an error.

This protects against leaks, but also miscalculation of fuel needed by the pilots, misfueling, or efficiency loss somehow.

[tlb]

Garmin G1000 units (popular in small planes) show this, as a circle around the current position, including fuel reserve. However, it depends on an accurate fuel level, which is mostly dead-reckoned from integrating fuel consumption. Measuring the actual fuel level in wing tanks is imprecise and the sensors sometimes get stuck and give bogus readings.

Perhaps the big innovation needed is accurate fuel quantity measurement.

[avereveard]

I think a plane can measure an approximation of weight loss from its own airspeed and angle of attack, won't give you exact weight measurement because weight at take off is an approximation, but might give a estimate of weight loss. Depends on the precision of the aoa sensor tho.

[cjrp]

Commercial airliners, and even some GA planes, have an accurate measure of fuel consumed using a fuel flow transducer.

[tlb]

Indeed, but that system will report nothing unusual when there's a leak directly from the tank, or in the pipe between tank and flow sensor (which I think is usually near the engine, downstream of a fuel pump) or if the tank wasn't filled to spec.

Any sensor has a failure rate. If the probability that a sensor has failed isn't dramatically lower than the probability of a leak, then the pilots will do just what they did in the incident and assume a bad fuel sensor reading rather than a leak.

Another failure mode of fuel tank sensors is short-circuiting and blowing up the plane: https://en.wikipedia.org/wiki/TWA_Flight_800

[t0mas88]

This already exists and in a much more advanced way. The flight management system calculates the expected fuel on landing based on the route, wind data, different fuel usage at altitudes etc.

It's not as simple as "fuel per time" because fuel usage and speed change massively with altitude.

What was missing here was a big warning to the pilots (that has since been added). But it's also standard procedure at all airlines to monitor fuel and required fuel calculations, which could have helped this crew if they did it earlier.

[spuz]

Fortunately this functionality is now in place in all Airbus aircraft thanks to this incident. I suspect the same is true on most commercial aircraft.