Having had some minor experience, it the testing of ACES II seats and Martin-Baker Mk 16 seats for the JSF, perhaps I can shed some light on the realities of ejection seats. FYI, the ACES seat is in the A-10, F-15, F-16, F-117, and the B-1B. The MB seat is in the F-35, F-18, and nearly all European jets. First, all ejection seats are heavy. For the ACES II, about 250 lbs. ready to rock and the M-B Mk.16, just a few pounds lighter. Both use spigot guns to get the seat moving up the rails, and a rocket motor to provide the remainder of the ride. Both have headbox mounted parachutes and automatic inertia-real tighteners. Both also have leg restraints, but with the ACES seats that is an option. The standard maximum pilot weight for the ACES seat is 245 lbs for the pilot + his flight gear. The standard minimum weight for the ACES seat is 104 lbs + her flight gear. Yes, “her” because the only 104 lb USAF pilots I have ever met were female. The M-B Mk.16 has been qualified for the same pilot weight range. The acceleration onset rate is different for the two seats with the ACES exhibiting a 250 g/sec jerk (Yep, the third derivative is called “jerk” in the US and jolt by the brits) The M-B Mk.16 seat exhibits about 300 g/sec on the catapult stroke. This is a significant difference and caused many testing iterations to prevent injury to the 104 lb pilot. As some of you may be aware, female humans are different from male humans. In ejection seats this is a huge issue. Because female mass moment of inertias, sitting height CG, limb length, most significantly neck length are different than those of their male counterparts, the behavior of the seat on the rails and in flight may be acceptable to the male occupant, while injurious to the small females. All of the ACES seat testing that I have witnessed did not “injure” the 104 lb test mannequins that were used. The recorded force and moment data were within acceptable ranges. To qualify the M-B Mk.16 for the F-35 took extensive modification and retesting. The end result was that the 104 lb female forces and moments were brought within acceptable ranges. Ejecting from any aircraft is exposing the human body to the kinds of forces that can kill the seat occupant unless everything goes right.