Tail Loads and Stability
Natural longitudinal stability for an aircraft is achieved by having the Centre of Pressure behind the CG which has to be between forward and aft limits.. The nose down pitching moment is balanced by a down load from the tail.
If the CG gets to be too far forward there will be inadequate elevator to flare on landing. The stick will be against the rear stops and you will be wanting more. It's a very off putting feeling.
If the CG gets to be too far aft the A/C will start to run away in pitch, either up or down, at any small disturbance. The P51 Mustang is like this with a full aft fuselage tank or an F86 Sabre with 4 big jugs or any of those wrongly loaded aircraft that pitch up on take off and full forward stick is inadequate at the slow speed.. May they RIP and may others please learn from their mistakes.
So a 747 at/near AUW will have a down force from the tail of about 30 tonnes. What a waste. Yes, the wings have to overcome that load and there is significant.induced drag penalty as a result.
Along comes artificial stability with Fly By Wire and computers.
F16 Falcon was one of the first to benefit with its side stick control. Now the centre of pressure and the CG can be closely aligned resulting in the need for very little down or up force from the tail during cruising flight. The now inherent tendency to run away in pitch, up or down, has to be countered by the elevators which under command of the flight computers work hard to stop any pitching unless demanded by the pilot with stick force input. Result is an extremely manoeuvreable A/C in pitch with the elevators working in reverse to back off the tendency to over pitch. And a significant contribution to lesser induced drag. The US describes this type of aircraft as a Control Configured Vehicle. CCV. Wonder who dreamed up that one?
Don't know how far Airbus have gone in reducing tail down loads using artificial stability but they would just love to have zero tail load on the cruise.
Boeing will be trying to do the same. Big $$$$s at stake.
You can expect that auto balance will relieve the crew of any need for them to keep the CG near the C of P by proportional fuel feed from tanks.
First saw this auto balance in the RAF Vulcan and Victor. The Valiant required interminable crew attention managing fuel use from wing tanks which took the CG one way and fuselage tanks the other way. Must be a big problem with tankers off loading.