Originally Posted by
IO540
A sight gauge only tells you what you actually have, which is no good if you are enroute to somewhere and do not even know your precise fuel flow rate.
This is the system I refer to. It is very common in the better IFR tourers. I routinely land and fill up within 1-2% of the computed figure, and would never do my 900nm+ flights without it.
When I see bigger errors, it points to a pump which has been "adjusted" in favour of the airport, in a country where Weights & Measures inspectors are nonexistent
The biggest errors I have seen were ~ 5%, in Greece and Italy.
Anybody pushing to say 80% of their best dry-tank range, without this kind of equipment, is going to get their bum bitten eventually. Some stories I have heard have been truly scary, but the ones people talk about are the ones they got away with. Like one pilot who landed an old TB20 after a 1150nm flight with a few USG in the tanks.
I don't think many microlights do flight of significant distance, so they don't need to worry
It's really not that hard, if you have an accurate fuel gauge, you just track fuel consumption on your PLOG along with time and distance.
Having done quite a few multi-hour microlight trips, I reckon to be accurate to within a couple of litres of what it'll be at any point forwards once I've been flying for half an hour or so.
A light aeroplane, with the well known dodgy fuel gauges, does require more guesswork, or the sort of system you're talking about.
G