I was watching a short program on the military channel showing the development testing of the F15. It showed a close up of the tail of the aircraft and the tail while it was being manipulated by the pilot. I saw something strange occur several times.
I understand that back pressure on the stick causes the elevator (or stabulator?) to move upwards. Down pressure causes the elevator to move down. However, the film clearly showed that not only do the elevators work in this manner, but there is also a contron input that causes the left and right memper to operate opposite to the other. Left up, right down, etc., much like the ailerons do.
My question is what input would create this situation and what what flight condition would it create? Is this unique to the F-15?
The F-15 and many other modern military aircraft are computer controlled. The computer takes what the pilot wants to do, and adjust the aircraft’s control surfaces to actually do it. This can result in some fairly complex movement in the control surfaces for a fairly simple control input by the pilot.
I heard one F-15 pilot describe how he maneuvered up for a refueling, and just gently guided the F-15 into place. It went very smoothly, and he was like “damn, I’m good” and then he looked back at the control surfaces and they were moving all over the place. It was the plane’s computer making it smooth, not him.
It not unusual for fighters with flying horizontal tails (the entire surface pivots) such as the F-15 or F-16 to use the tails to command some of the roll input. In this case, the two tails will move differentially in response to side stick input.
The F-15 has tailerons not elevators. The move together to act as elevators, and in opposite directions to induce roll. I am not certain of the exact setup on the F-15, but usually the ailerons are used in conjunction with tailerons at low speed to control roll, and only the tailerons are used at high speed.