Steep Turns Overview:
- Steep turns consist of single to multiple 360° and 720° turns, in either or both directions, using a bank angle between 45° and 60°
- Steep turns help pilots understand:
- Higher G forces experienced during a turn
- An airplane's inherent overbanking tendency when the bank angle exceeds 30°
- Significant loss of the vertical component of lift when the wings are steeply banked
- Substantial pitch control pressures
- The need for additional power to maintain airspeed during the turn
Steep Turns Performance Review:
- To fully appreciate steep turns, a full review of turn performance is required
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Turn Performance Review:
- When banking an airplane for a level turn, the total lift divides into vertical and horizontal components of lift
- To maintain altitude at a constant airspeed, the pilot increases the angle of attack (AOA) to ensure that the vertical component of lift is sufficient to maintain altitude
- The pilot adds power as needed to maintain airspeed
- For a steep turn, as in any level turn, the horizontal component of lift provides the necessary force to turn the airplane
- Regardless of the airspeed or airplane, for a given bank angle in a level altitude turn, the same load factor will always be produced
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Rate and Radius of Turns Review:
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Rate of Turn:
- The rate depends on a set bank angle at a set speed [Figure 2]
- The standard rate of turn is 3° per second
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Speed & Rate of Turn:
- If the aircraft increases speed without changing the bank angle, the rate of turn decreases
- If the aircraft decreases speed without changing the bank angle, the rate of turn increases
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Bank Angle & Rate of Turn:
- If the aircraft bank angle increases without changing airspeed, the rate of turn increases
- If the aircraft bank angle decreases without changing airspeed, the rate of turn decreases
- Speed and bank angle, therefore, vary inversely to maintain a standard rate turn
- This is important in the instrument environment, such as when holding or on an instrument approach
- A rule of thumb for determining the standard rate turn is to divide the airspeed by ten and add 5
- Example: an aircraft with an airspeed of 90 knots takes a bank angle of 16° to maintain a standard rate turn (90 ÷ by 10 + 5 = 14°)
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Radius of Turn:
- The radius of turn varies with changes in either speed or bank [Figure 2]
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Speed & Radius of Turn:
- If the speed increases without changing the bank angle, the radius of turn increases
- If the speed decreases without changing the bank angle, the radius of turn decreases
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Bank Angle & Radius of Turn:
- If the speed is constant, increasing the bank angle decreases the radius of turn
- If the speed is constant, decreasing the bank angle increases the radius of turn
- Therefore, intercepting a course at a higher speed requires more distance and, therefore, requires a longer lead
- If the speed is slowed considerably in preparation for holding or an approach, a shorter lead is needed than that required for cruise flight
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Load Factor Review:
- The load factor is the vector addition of gravity and centrifugal force
- When the bank becomes steep as in a level altitude 45° banked turn, the resulting load factor is 1.41
- In a level altitude 60° banked turn, the resulting load factor is 2.0
- To put this in perspective, with a load factor of 2.0, the effective weight of the aircraft (and its occupants) doubles
- Pilots may have difficulty with orientation and movement when first experiencing these forces
- Pilots should also understand that load factors increase dramatically during a level turn beyond 60° of bank
- Note that the design of a standard category general aviation airplane accommodates a load factor up to 3.8. A level turn using 75° of bank exceeds that limit
- Because of higher load factors, steep turns should be performed at an airspeed that does not exceed the airplane's design maneuvering speed (VA) or operating maneuvering speed (VO)
- Maximum turning performance for a given speed is accomplished when an airplane has a high angle of bank
- Each airplane's level turning performance is limited by structural and aerodynamic design, as well as available power
- The airplane's limiting load factor determines the maximum bank angle that can be maintained in level flight without exceeding the airplane's structural limitations or stalling
- As the load factor increases, so does the stalling speed
- For example, if an airplane stalls in level flight at 50 knots, it will stall at 60 knots in a 45° steep turn while maintaining altitude
- It will stall at 70 knots if the bank is increased to 60°
- Stalling speed increases at the square root of the load factor
- As the bank angle increases in level flight, the margin between stalling speed and maneuvering speed decreases
- At speeds at or below VA or VO, the airplane will stall before exceeding the design load limit
- The load factor is the vector addition of gravity and centrifugal force
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Overbanking Review:
- In addition to the increased load factors, the airplane will exhibit what is called "overbanking tendency"
- In most flight maneuvers, bank angles are shallow enough that the airplane exhibits positive or neutral stability about the longitudinal axis
- However, as bank angles steepen, the airplane will continue rolling in the direction of the bank unless deliberate and opposite aileron pressure is held
- Pilots should also be mindful of the various left-turning tendencies, such as P-factor, which require effective rudder/aileron coordination
- While performing a steep turn, a significant component of yaw is experienced as motion away from and toward the earth's surface, which may seem confusing when first experienced
- Before starting any practice maneuver, the pilot ensures that the area is clear of air traffic and other hazards
- Further, distant references should be chosen to allow the pilot to assess when to begin rollout from the turn
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Coordination Throughout Turns:
- A slipping turn results from the aircraft not turning at the rate appropriate to the bank being used, and the aircraft falls to the inside of the turn [Figure 3]
- The aircraft is banked too much for the rate of turn, so the horizontal lift component is greater than the centrifugal force
- A skidding turn results from an excess of centrifugal force over the horizontal lift component, pulling the aircraft toward the outside of the turn [Figure 3]
- The rate of turn is too great for the angle of bank, so the horizontal lift component is less than the centrifugal force
- The ball instrument indicates the quality of the turn and should be centered when the wings are banked
- If the ball is off-center on the side toward the turn, the aircraft is slipping, requiring added rudder pressure on that side to increase the rate of turn
- Also, reducing the bank angle without changing the rudder pressure will help coordinate the turn
- If the ball is off-center on the side away from the turn, the aircraft is skidding, requiring rudder pressure on that side to be relaxed to decrease the rate of turn
- Also, increasing the bank angle without changing the rudder pressure will help coordinate the turn
- The ball should be in the center when the wings are level; use rudder and/or aileron trim if available
- The increase in induced drag (caused by the increase in the angle of attack necessary to maintain altitude) results in a minor loss of airspeed if the power setting is not changed
Steep Turns Procedure:
WARNING:
All procedures are GENERALIZED.
Always fly per Pilot Operating Handbook procedures,
observing any relevant Standard Operating Procedures (SOPs)
- Perform clearing turns
- Select a prominent visual reference point ahead of the airplane and out toward the horizon
- Adjust the pitch and power to maintain altitude
- Trim as necessary
- Maintain heading and note the pitch attitude required for level flight
- After establishing the manufacturer's recommended entry speed, VA, or VO, as applicable, the airplane should be smoothly rolled into a predetermined bank angle between 45° and 60°
- As the bank angle is being established, generally prior to 30° of bank, elevator back pressure should be smoothly applied to increase the AOA
- Considerable force is required on the elevator control to hold the airplane in level flight
- The decision whether to use trim depends on the airplane characteristics, speed of the trim system, and preference of the instructor and learner
- Simultaneously, power sould be applied
- as the AOA increases, so does drag, and additional power allows the airplane to maintain airspeed
- Remain coordinated
- Remember parallax error
- As the bank angle is being established, generally prior to 30° of bank, elevator back pressure should be smoothly applied to increase the AOA
- Rolling through 30° of bank, increase power to maintain airspeed
- Increase pitch to maintain altitude
- Trim as necessary
- Pull back on the yoke will increase rate of turn but do not allow the aircraft to climb
- Reference the visual point selected earlier and roll out 20-25° before entry heading
- Through 30° of bank, decrease RPM
- Decrease pitch
- Trim nose down
- Return to wings level on entry heading, altitude, and airspeed
- A good rule of thumb is to begin the rollout at 1/2 the number of degrees of bank prior to reaching the terminating heading
- For example, if a steep turn was begun on a heading of 270° and if the bank angle is 60°, the pilot should begin the rollout 30° prior
- While the rollout is being made, elevator back pressure, trim (if used), and power should be gradually reduced, as necessary, to maintain the altitude and airspeed
- A good rule of thumb is to begin the rollout at 1/2 the number of degrees of bank prior to reaching the terminating heading
- Immediately roll into a bank in the opposite direction
- Perform the maneuver once more in the opposite direction
- Upon rolling out after the second turn, resume normal cruise
- Trim as necessary
- Complete the cruise checklist
Steep Turns Common Errors:
- Failure to adequately clear the area
- Inadequate back-elevator pressure control as power is reduced, resulting in altitude loss
- Excessive back-elevator pressure as power is reduced, resulting in altitude gain, followed by a rapid reduction in airspeed and "mushing"
- Remember, the aircraft stalls at a higher airspeed when in high angles of bank
- Inadequate compensation for adverse yaw during turns
- Inadequate power management
- Inability to adequately divide attention between airplane control and orientation
- Inadequate pitch control on entry or rollout
- Failure to maintain constant bank angle
- Poor flight control coordination
- Ineffective use of trim
- Ineffective use of power
- Inadequate airspeed control
- Becoming disoriented
- Performing by reference to the flight instruments rather than visual references
- Failure to scan for other traffic during the maneuver
- Attempting to start recovery prematurely
- Failure to stop the turn on the designated heading
Steep Turns Case Studies:
- National Transportation Safety Board (NTSB) Identification: CEN20LA357:
- The NTSB determines the probable cause(s) of this accident to be: The pilot's failure to maintain airspeed while maneuvering at low altitude, which resulted in an aerodynamic stall and collision with terrain
Conclusion:
- Remain mindful that performance calculations are usually more optimistic than performance in reality
- As PilotWorkshops state: "Steep turns demonstrate turn performance while practice division of attention, orientation, comfort with higher G-forces, overbanking tendency, and learning the control inputs required to maintain altitude at a constant airspeed during the turn"
- Consider actual versus realized performance when doing any performance calculations
- Consider practicing maneuvers on a flight simulator to introduce yourself to maneuvers or knock off rust
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