Originally Posted by
Check Airman
At my US company, flap 3 is “encouraged” but most people go with full. It’s at the discretion of the PF. My preference in your situation would be full. We do a few approaches to places where the glide slope is a bit steeper (maybe 3.3, I think), and flap 3 still works fine. I think the major hurdle would be getting stabilised earlier.
That said, 8kg of fuel is less than a rounding error on the gauges. The fuel bowser typically delivers a bit more than the number that’s dialled in. On my last flight, we were over fuelled by about 25 times the 8kg we’re thought to save with flaps 3.
The fact that you can't measure it doesn't mean it doesn't exist.
It will be measurable if a consequent number of pilots do this type of eco-flying.
(And, of course, if the fuel saving is not counterbalanced by longer taxi-in and/or more use of reverse thrust..)