Load Factor, Maneuvering Speed, & Stall Speed

https://www.boldmethod.com/learn-to-fly/aerodynamics/va-designed-maneuvering-speed-how-it-protects-aircraft/ - https://www.boldmethod.com/learn-to-fly/aerodynamics/why-aircraft-stall-speed-increases-with-bank-angle-aerodynamic-load/ - https://www.faa.gov/sites/faa.gov/files/07_phak_ch5_0.pdf

What is Load Factor?

Ratio of the lift being produced by the wings compared to the weight of the aircraft. It is measured in Gs (acceleration of gravity)

• Load Factor = Lift / Weight (expressed in number of "Gs")

What are “Gs” or “G-Force”?

A unit of force equal to the force exerted by gravity on a body

They are an acceleration of gravity

• Gs can be positive or negative

  • Ex of positive Gs: A sharp pull up and the resulting force pushing the pilot into the seat

  • Ex of negative Gs: A sharp push down and the resulting force lifting the pilot off the seat

What happens to the load factor as Gs increase or decrease?

• A load factor of 1 G is equivalent to normal gravitational forces

  • (at 1 G, a 200 lb. person weighs 200 lbs.)

• A load factor of 2 Gs is double

  • (at 200 Gs, a 200 lb. person weighs 400 lbs.), -

• A load factor of 3 is triple, etc.

• A load factor of 0.5 Gs is equivalent to half of the weight of the aircraft or person

What is “Factor to Safety”?

CFRs require an aircraft structure be capable of supporting 1.5 times their limit load factors w/out failure

• Some structural damage may occur under these loads still

What is Gust Factor?

The ratio between a peak wind gust and the mean wind speed over a specific period

• EX: If the winds are reported at 18 knots, gusting 30 knots, it means you have a gust factor of 12

How does load factor work @ Higher & Slower speeds?

• Slower speeds

  • The max allowable lifting force of the wing is only a little bit more than the amount needed to support the weight of the airplane. Therefore the load factor won't become excessive even if the controls are moved abruptly or if the airplane encounters severe gusts because it will stall before the load can become excessive.

• High speeds

  • The lifting capacity of the wings is so great that a sudden movement of the elevator controls or a strong gust may increase the load factor beyond safe limits.

Define Limit Load Factor?

The maximum safe load an aircraft is designed to withstand during normal operation without causing permanent structural damage

What is the Limit Load Factor for Normal Category Aircraft?

Positive Limit Load: 3.8G
Negative Limit Load: 1.52G

What is the Limit Load Factor for Utility Category Aircraft?

Positive Limit Load: 4.4G
Negative Limit Load: 1.76G

What is the Limit Load Factor for Aerobatic Category Aircraft?

Positive Limit Load: 6G
Negative Limit Load: 3G

How does Rate of Turn (ROT) change with airspeed?

The Higher the Speed, the Slower the ROT

The Slower the Speed, the Higher the ROT

Define Stall Speed

The minimum steady flight speed at which the airplane is controllable

Does load factor increase with bank angle?

Yes Load Factor does increase as our bank angle increases

What does an increase in load factor do to our stall speed?

Our stall speed increases

What happens to stall speed @ 45 degrees bank?

• Stall speed increases by 18-20% @ 45 Degrees Bank due to the 1.4 G's of load

What happens to stall speed @ 60 degrees bank?

• Stall speed increases by 40% @ 60 Degrees Bank due to the 2 G's of load

What is a Vg Diagram & what do we use it for?

The Diagram plots the load factor against the indicated airspeed, showing us whats Gs we can safely pull at certain Airspeeds

• Velocity VS Gs/ load factor

• Each aircraft has its own Vg diagram valid for its own weights and altitudes

Define Maneuvering Speed (Va) ?

Its the speed which you can move a single flight control, one time, to its full deflection, for one axis of airplane rotation only (pitch, roll or yaw), in smooth air, without risk of damage to the airplane

• Operating at or below Va does not provide structural protection against

  • Multiple full control inputs in one axis or

  • Full control inputs in more than one axis at the same time

• Va is set per aircraft in the aircraft specific POH

How do different weights affect Va?

When the manufacturer certifies Va, they do it at maximum gross weight.

• As your weight decreases, Va also decreases due to not having to have a higher AOA to maintain straight & Level Flight

Increased Weight → Increases AOA → Increases V_a