Load Factors in Flight
Load factors and safe flight. "The witness saw pieces of a plane fall out of the bottom of a nearby thunderstorm"...this is related to phrases like, "separation in flight" and "exceeded the designed stress limits of the aircraft" as frequently reported in too many accident reports.
The strength of an airplane is measured by the total load its wings can support without sustaining permanent structual damage. In curved flight - all types of turns, pullups from dives or when abrupt or excessive back elevator is used-the load factor increases because of the buildup of centrifugal force.
Remember the steep turn instruction when you had to perform a left and right 360 degree steep turn for your instructor without losing altitude? You could feel the buildup of G-forces in your rear end and the pooling of blood trying to respond to the increased Gs.
The increase of the load factor occurs at a startling rate once the bank of the aircraft has passed 45 degrees. At a 60 degree bank the load factor is 2 Gs. Twice what the load factor is in straight and level flight. At a bank of 70 degrees, a mere 10 degrees more, the load factor is 3 Gs and at 80 degrees the load factor increases to the structural failure stage of almost 6 Gs.
Since most aircraft rated for "Normal Category" are limited to 3.8 Gs the danger from rapidly increasing G forces in planned and unplanned (read in a "thunderbumper") is obvious. Yes, you can rationalize that a plane is engineered for a safety factor 50 percent above the specified load limit for the Normal Category aircraft but it is foolish to insert yourself into a deadly game of G Force versus Structural Failure.
The limit above is the point at which wings and engine decide to leave the plane. Before the above limit is reached you can expect some damage to the aircraft. The more excess the more damage until you reach the engineered limit.Think about the aircraft you rent. If the G load was exceeded on a prior flight in a rented aircraft the 50 percent engineered safety factor may be considerably reduced. Structural failure may occur at a G force of 3.9 Gs, for example. Renting? Do a careful preflight.
If you encounter rough air or unusual vertical gusts, immediately slow the plane down to its specific "maneuvering speed" at which it will still continue to fly with a safe margin above a stall but, in rough air, it will sustain the least amount of structual damage. This speed is about 1.7 times the stall speed of the aircraft your flying.
