The declared fuel emergency of 200kg.
Seems to me that’s running on fumes. I know in general measuring equipment can be inaccurate when measuring at the extreme of the measuring range.
When he declared his emergency, what he actually said was that if he had to fly the arrival, he'd be landing with 200 kgs. By not flying the arrival, and taking as direct a route as possible, he would have landed with more, though how much more is hard to work out. I'd guess at about 1,000 kgs. That's still an extreme figure. I don't understand how he got so low, as even if the airport he was using for his diversion calculations was suddenly snatched away from him, he still should have been planning to get to the end of the runway with:
a) Fuel to fly from present position to the start of the approach, plus 10%
b) Fuel to fly the approach
c) 30 minutes holding
plus
d) Fuel to go around and fly to the alternate
c) Fuel to fly the approach there
By my maths, he was somewhere around 6-7 tonnes short of what he should have had. Which really means he should have made the decision to divert much earlier, and probably should never have joined the holding pattern at all.
In your aircraft is there a point at which displayed fuel is inaccurate?
It would be interesting to know the actual inaccuracy. The tolerance is catered for by the min fuel at the end of the runway, which is a regulatory requirement of 30 minutes.
We monitor the fuel in a couple of ways. One by looking at what the fuel system says, but also by comparing the recorded fuel burn with the start fuel. Any divergence from the planned fuel, that we can't explain (by different altitude or wind to the plan) will also cause us to delve into the system. Generally, the difference peaks at around 1-1.5 tonnes in the middle of the flight, but then they close up again, mostly being close to equal at low fuel states. I'd take that as meaning that the system has been tweaked to ensure as much accuracy as possible at low fuel states.
I understand if displayed fuel is this the aircraft should have already been on the ground.
If the weather had been nice, he should have been on the ground with about 3 tonnes. As it wasn't, then he should have carried about 6-9 tonnes over the fence (depending upon which alternate you use). The numbers just don't make that much sense, so something else has happened to confuse the issue. Basically, he should have landed in Muscat as he passed by....