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LOAD FACTORS



A force applied to deflect an airplane from a straight line of flight produces a stress on its structure, this is called load factor.


At any given bank the rate-of-turn will vary with airspeed. At a higher speed the rate-of-turn is slower or a longer turn.


Since the aircraft we fly in for flight turning are in the Normal Category, the load factor range is from +3.8G’s – -1.52G’s. “G”- represents the pull of gravity.


As pilots, it is very important to keep in mind when looking at any load factor charts, and placards, they are for smooth air.


In a level turn at a 60° bank there is a 2G force put on to the aircraft. If the airplane weight is 2,600lbs. in normal level flight, now in a 60° bank the aircraft weights 5,200lbs.

Remember to maintain a level turn, back pressure on the elevator is required and a higher power setting.


The Private Pilot requirement only requires a max of 45° bank angle.



What about a non-level turn?

Turns are made by banking the airplane in one direction or the other, so the horizontal lift pulls the airplane from a straight flight path.


At a constant altitude, during a coordinated turn from straight and level flight the load factor is the result of two forces:

  • Centrifugal force

  • Weight (gravity)


The load factor put onto an airplane in a descent at a 45° bank would be, none (no load factor). No back pressure on the elevator is required for a descent.



Vg Diagram (picture)

We will just point out a few basic limits on this chart for Private Pilots. Each aircraft has its own Vg diagram that is valid at a certain weight and altitude.



Rough Air (turbulence) and load factor

In extremely rough (turbulent) air, as in thunderstorms or frontal conditions, it is wise to reduce the speed to the design maneuvering speed (VA). Regardless of the speed held, there may be gusts that can produce loads that exceed the load limits.


As a rule, when severe turbulence is encountered, the airplane should be flown well below VA as per the aircrafts POH and/or any placards. By doing this it is likely to cause structural damage to the airplane.


NOTE: Remember that the maximum “never-exceed” (VNE) placard dive speeds are determined for smooth air only.


References:




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