Lemain,
You said in your post #1683 above:
"I can't think of any reason why the industry should burden pilots with the task of running two units of measurement alongside each other, some 20% apart in magnitude (SG = 0.81). Can anyone else offer an explanation other than for the convenience of bean-counters?"
Well, actually, yes I can and it goes something like this.
When I land and shut down I look at the fuel gauge to tell me how much fuel I have left in the tanks. It is displayed in kgs because, when I do the performance calcs, I am interested solely in the weight of the fuel. I then work out the number of kgs I require to bring the total back to the required fuel load. Then, looking at the chart, I read off how many litres are needed and tell the crew member on the pump, the number of litres that they need to dispense before shutting off the flow. Once the refuel is done, I check to see that the expected number of kgs apprear on the gauge. It has absolutely nothing to do with keeping the bean counters happy - it has everything to do with ensuring that the aircraft is at the correct and expected weight which has everything to do with complying with PC1 operations.