![]() ![]() "Vomit comet" aircraft in 0-G trajectory. G-acceleration (normally called "G-loading") is said to be 0 G. Note that there are no aerodynamic or thrust forces, so the vector sum of the aerodynamic and thrust forces is zero. Actual acceleration is 1 G downward, but "felt" acceleration is zero. So the acceleration component resulting from gravity is not "felt" by a pilot's nervous system, and does not deflect a G-meter, scale, or other similar instrument.Ī few examples make these concepts more clear:Īn imaginary aircraft in freefall in a vaccuum. Gravity can't be felt, because the force of gravity exerts an equal pull (per unit mass) on every molecule of an aircraft and contents, and so works from "within" to accelerate the aircraft and all the contents as a single entity without creating any stresses and strains within the aircraft and its contents. (The trajectory of the aircraft, of course, would change.) So in this sense, the G-force or G-acceleration actually has nothing to do with the pull of the earth's gravity.Īnother way to understand G-force or G-acceleration is to realize that the G-force or G-acceleration is the mirror-image of the "felt" component of the actual net force acting on an object or the net acceleration experienced by an object. (This is why we use a G-meter to avoid generating too much lift and pulling the wings off an aircraft during aerobatic maneuvering!) If the pull of the earth's gravity vanished, but the actual aerodynamic and thrust forces generated by the aircraft somehow stayed exactly the same, the G-force or G-acceleration would also stay exactly the same. Note the intimate relationship between the G-force or G-acceleration, and the actual aerodynamic and thrust forces generated by the aircraft. Expressed this way, the so-called "G-force" (which really would more properly be called "G-acceleration") is equal to the net vector sum of all the aerodynamic and thrust forces created by the aircraft, divided by the ratio of the mass (or weight) of the object in question to the total gross mass (or weight) of the aircraft, divided by the weight of the object in question. Normally however we talk about G-force by referring to the acceleration that would result from that force, but rather than using the usual units of acceleration, we use the units "G's", where 1 G is the acceleration caused by earth's gravity on an unrestrained object in a vacuum near the surface of the earth. Visualized this way, the units of G-force would be Newtons in the metric system, and pounds-force in the English system. In other words, the G-force applied to an object within in aircraft as an aircraft maneuvers could be said to be equal to the net vector sum of all the aerodynamic and thrust forces created by the aircraft, divided by the ratio of the mass (or weight) of the object in question to the total gross mass (or weight) of the aircraft. These forces are transmitted as stresses and strains through the structure of the aircraft to the pilot's seat, seat belts, etc and then are transmitted as stresses and strains to the pilot's body, as well as to all the other contents of the aircraft. The ultimate origin of these forces that the pilot "feels" is the aerodynamic forces created by the wings and other surfaces of the aircraft, and the thrust force created by the motor. So G-force describes the mirror-image of the force exerted on the contents of an aircraft by the aircraft due to the acceleration of that aircraft.įor a force to be "felt" by the pilot, the aircraft must "push" against the pilot's body, creating stresses and strains within the pilot's body. For example, if an aircraft is accelerating upwards at the start of a loop, the pilot "feels" an apparent force pulling him downwards into his seat more strongly than usual. "G-force" refers to the apparent inertial force that is "felt" by the pilot and the other contents in an aircraft as it accelerates. ![]()
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