The following quote is from G. Bristol’s book, Ace the Technical Piloting Interview:
[The] movement of the centre of gravity is due to a change in weight. The distribution of the aircraft’s weight can change for three reasons and thus cause the centre of gravity to move. The three reasons for a change in aircraft’s weight are:
- Fuel Burn
- Passenger Movement
- High Speeds*
*Note. This is so because the greater the speed, the greater the lift created. To maintain straight and level, the aircraft adopts a more nose-down attitude, accomplished by creating lift at the tailplane. This lift effectively reduces the weight of the tailplane section of the aircraft.
I was surprised to read that the centre of gravity (CG) changes with “High Speeds.” As I understand it, the horizontal stabiliser produces a downwards force to counteract the moment about the CG produced by lift acting through the centre of pressure.
Though the adoption of a nose down attitude at higher speeds to maintain straight and level does make sense due to the increased speed (assuming constant $ \rho $).
But I am still struggling with the sentence, “This lift effectively reduces the weight of the tailplane section.” I just can’t see how speed could change the actual CG.
Does the actual CG change at “High Speeds”?
(Though I do understand that aerodynamics is universal to all aircraft, if there are differences in discussion between light aircraft compared to turboprops and passenger jets, I would prefer the discussion to be more towards the latter, thank you)