It is a very useful system to use when "eyes down" time needs to be kept to a minimum (ie. low level fast jet).
Modern GA aircraft with fuel totalisers and gps charts etc etc would have no requirement to use this system
I would say that "Eyes down" time needs to be kept to a minimum whatever aircraft you are flying, be it FJ or Tiger Moth. I know that my instructor will want me to have my head in the chart as little as possible when navex-ing... aviate, navigate, communicate.
Also, with this manual system is all worked out, the pilot can keep a better personal idea of the fuel situation and does not need to rely on electronic gadgets which could go u/s at any time...
Bingo rings are good for keeping you on top of your fuel requirement, especially when you depart the original plan
Agreed -these are ideal for when you need to divert and are an instant indication of where you can divert to, according to the amount of fuel left. Give me a fuel circle any day.