Steep turns consist of a single or multiple 360° turns in either or both directions, generally using a bank angle of 45° or 50° for training purposes. During the maneuver, pilots must maintain a constant altitude, airspeed, and bank angle.
When performing steep turns, pilots are exposed to:
As an airplane is banked, back pressure on the pitch control is applied to maintain level flight. The increase in lift results in more drag and a slower airspeed.
The turn also increases the load factor and stalling speed. Power must be increased to overcome drag and maintain a margin above the stall speed.
Load Factor | Drag | Stall Speed | Power Required |
---|---|---|---|
Increases | Increases | Increases | Increases |
The effects of torque and P-factor vary considerably throughout each phase of flight. Pilots must learn to compensate for these forces through the use of aileron and rudder inputs when appropriate.
In a steeply-banked turn, airplanes exhibit a tendency to continue rolling in the direction of the bank unless deliberate and opposite aileron pressure is held against the bank. The tendency to continue rolling is called overbanking.
Overbanking occurs due to differences in lift between the wings. The wing on the outside of the turn travels a longer path than the inside wing, yet both complete their respective paths in the same unit of time. Therefore, the outside wing travels at a faster airspeed than the inside wing, and, as a result, it develops more lift.
The design maneuvering speed (VA) is a structural design airspeed used to determine the strength requirements for the airplane and its control surfaces. When at or below VA, the pilot can move a single flight control, one time, to its full deflection, in smooth air, without risk of damage to the airplane.
Pilots should not interpret the maneuvering speed as:
The maneuvering speed (VA or VO) published in the AFM/POH is valid for operation at the stated weight, typically max gross weight. It decreases as the weight decreases.
Two concepts can explain the effect of weight on maneuvering speed:
When an airplane is subjected to an external force, such as the aerodynamic force from a control surface, it responds by accelerating (rotational acceleration) around one of its axes. This was stated in Newton’s Second Law of Motion, which can be written in the following way.
Acceleration = Force ÷ Mass
For a given control force, acceleration increases when weight (mass) decreases. Higher acceleration results in higher loads on the airplane structure. Therefore, as the airplane’s weight decreases, maneuvering speed must decrease.
Additional weight requires the aircraft to fly at a higher AOA to sustain flight. Since the heavier airplane is closer to the critical AOA (approximately 18°), it will stall more quickly following an abrupt pull-up or encounter with turbulence. This leaves it less susceptible to excessive load factors than the lighter airplane.
If not specified in the AFM/POH, the maneuvering speed for a lower operating weight can be approximated with the following formula.
VA1 = VA2 × √(Current Weight ÷ Maximum Gross Weight)
It can be approximated for airplanes without a published VA with the following formula.
VA = VS1 × √(Positive Limit Load Factor)
Load factor is the ratio of the total load supported by the airplane’s wing to the total weight of the airplane.
Load Factor = Lift ÷ Weight
As an airplane is banked, more lift is required to maintain level flight due to the inclination of the lift vector. Total lift must increase to maintain the same vertical component of lift equal to the weight. Therefore, load factor increases.
The following formula computes the load factor in a particular bank angle, represented by the Greek letter theta (Ø).
Load Factor = 1 ÷ cosØ
A stall that occurs at speeds greater than the 1 G stall speed is called an accelerated stall. In a constant rate turn, load factors increase as the bank angle increases. Pulling back on the pitch control also increases load factors.
An airplane’s stall speed increases in proportion to the square root of the load factor.
Accelerated VS = VS × √(Load Factor)
Bank | Load Factor | Stall Speed Increase |
0° | 1.0 G | 0% |
30° | 1.15 Gs | 7% |
45° | 1.41 Gs | 19% |
50° | 1.56 Gs | 25% |
60° | 2.0 Gs | 41% |
When the wings are banked, lift is separated into vertical and horizontal components. The horizontal component of lift causes the airplane to turn. Centrifugal force tries to pull the airplane away from the direction of the turn, counteracting the horizontal component of lift.
Lift: The greater the bank, the greater the rate of turn will be because more lift goes into the horizontal component. Total lift remains constant due to a decrease in the vertical component.
Drag: To maintain altitude in a turn, back pressure on the pitch control must be increased. As a result, drag increases, and additional power is needed to maintain airspeed.
The rate of turn is the number of degrees of heading change that an aircraft makes per second.
At a given airspeed, the turn rate increases if the bank angle increases. Likewise, if airspeed is held constant, the rate of turn increases if the bank angle is increased.
Rate of Turn = (1,091 × tanØ) ÷ KTAS
At a given bank angle, a higher airspeed makes the radius of turn larger because the airplane turns slower. The higher airspeed causes the aircraft to travel through a longer arc. To compensate for the increase in airspeed, the bank angle would need to be increased.
Radius of Turn = KTAS² ÷ (11.26 × tanØ)
Steep turns can be performed with or without trim. Using trim reduces the need for large control inputs and allows the pilot to keep a light feel on the controls during the turn.
If using trim, adjust it as the bank angle goes beyond 30°. During the rollout, apply forward pressure on the pitch control to prevent “ballooning” (gaining altitude) until the trim is reset.
Airspeed | Altitude | Bank | Rollout |
---|---|---|---|
±10 KIAS | ±100′ | 45° ±5° (SPT, PVT) 50° ±5° (COM, CFI) |
±10° |