Two weeks ago I shared the first half of my lesson plan for steep turns. Today I will continue to share the last part of that particular lesson plan covering Va (maneuvering speed), weight impact, load factor and accelerated stalls, lastly rate and radius of turn. So as promised, here you go!
Why do we maneuver at the Va speed?
Va or your designed maneuvering speed is the speed at which the airplane will stall before it exceeds its designed limit-load factor.
- Full and abrupt aerodynamic control
- Lower weight lower maneuvering speed
- Heavier weight higher maneuvering speed
- It permits an aircraft to preform maneuvering training (such as steep turns) at or below calculated airspeed. This will allow the aircraft to stall (exceed the critical angle of attack) before it develops structural damage.
- The weight of the wings will exceed designed load limits when operating above Va resulting in structural damage.
The Impact of Weight Changes
- Heavier weight = greater AOA to produce sufficient lift to weight ratio
- Lighter weight = less AOA needed to produce sufficient lift to weight ratio
- Note* due to higher AOA of heavier aircraft it is closer to the C-AOA (Critical Angle of Attack)
Load Factor and Accelerated Stalls
- Load factor has a proportional relationship between lift and weight. The measurement for load factor is Gs—acceleration of gravity.
- Gs is a unit of measurement that is equal to the force exerted by gravity on a object at rest and indicates the force to which a object is subjected when it is accelerated. In other words, any force that is applied to an aircraft to change its flight path from a straight line produces some sort of stress on its structure. The resulting force that is created is the load factor.
- A 60 degree bank pulls 2 Gs— the weight of the aircraft is doubled.
- By increasing your load factor you also increase the stalling speed and make stalls possible at seemingly safe speeds.
- We use the normal category— limit load factor 3.8 to -1.5 Gs.
- The total lift has to increase substantially to balance the load factor or Gs
- As load factor increases, so does stall speed exponentially. An aircraft’s stalling speed increases at the square root of the load factor. Accelerated stall!
Rate and radius of turn
Rate of Turn
- The rate of turn (ROT) is measured in the number of degrees (expressed in degrees per second) of heading change by the aircraft.
- Airspeed increase = ROT decreases unless bank is added
- Bank angle increases = ROT increases unless airspeed is added
- “It is found that the horizontal component of lift is proportional to the angle of bank—that is, it increases or decreases respectively as the angle of bank increases or decreases. As the angle of bank is increased, the horizontal component of lift increases, thereby increasing the rate of turn (ROT).” (PHAK Ch. 5)
Radius of Turn
- The radius of a turn is directly proportional to the ROT as it is a function effected by both bank angle and airspeed.
- Airspeed increases = radius of turn increase
- “As the airspeed is increased in a constant-rate level turn, the radius of the turn increases. This increase in the radius of turn causes an increase in the centrifugal force, which must be balanced by an increase in the horizontal component of lift, which can only be increased by increasing the angle of bank.” (PHAK Ch. 5)
Student is able to maintain the entry altitude ±100 feet, airspeed ±10 knots, bank ±5°, and roll out on the entry heading ±10° of steep turn preformed.
Whenever you create a lesson plan, don’t forget to give credit and cite your sources!
PHAK Ch. 9 & 5
Private pilot Airmen Certification Standards
Airplane Flying Handbook
Commercial Pilot Practical Test Standards
If you have any questions or suggestions for improvement I’d love to read them in the comments below.
Question for current or previous CFI’s: What advice would you give a pre-CFI regarding creating lesson plans or preparation to becoming a CFI that you wish you knew before you started instructing?