Turning in a car

Have you ever sped around a corner too quickly in a car? Or played "corners" as a kid?

• What do you feel as you go around the corner?
• In which direction does your body want to continue?
• Why don't we turn planes like this?

A body in motion continues in a straight line at a constant speed, unless acted on by an external force — Isaac Newton's first law

Turning in a car — continued

Most of us have never driven a car on a road like this, but maybe you've experienced something similar riding a bike on a special BMX track as a kid.

• Which direction is the force on the car passenger in this video?
• Why is this more efficient for the car turning the corner?
• Why don't we then have roads like this, if it's more efficient??

How is this turn similar to the turns we do in an aeroplane? How is it different?

Theory Overview

Learning Objectives

By the end of this lesson, our aim is to be able to:

• Explain the forces acting on the aeroplane in a banked turn — and why backpressure is needed to maintain altitude
• Describe the entry, maintenance and exit for a medium level turn, climbing turn, and descending turn
• Describe overbank and underbank tendency and why we hold aileron in a sustained turn
• Recognise the symptoms of a spiral dive and describe the correct recovery technique

As always, we'll then get to experience these medium level, climbing and descending turns in flight. We may demonstrate a spiral dive and recovery technique, but that's not something you'll be doing yourself yet.

Forces in a Turn

Lift in straight and level flight

In straight and level flight, lift acts straight up:

• Lift = Weight — altitude maintained
• All of the lift force is used to support the weight of the aeroplane
• If we adjust the power to speed up or slow down, we need to adjust the attitude to stay in level flight

Lift during climbing and descending flight

As we saw last lesson, when climbing or descending, although the weight is always straight down due to gravity, the lift no longer acts straight up:

• Lift = Weight component opposing the lift — constant climb or descent maintained
• All of the lift force is used to support the component of the weight opposing the lift
• We need to adjust the attitude to stay at a constant speed when changing the power to climb or descend.

What happens when we bank?

When we roll into a bank, the lift force tilts with the wings:

• The lift force is now split into two components:
  • Vertical component — still opposing weight
  • Horizontal component — pulling the aircraft into the turn (centripetal force)
• The vertical component is now less than the total lift
• If we don't increase lift, we'll sink — we're not supporting all our weight

Maintaining altitude in a turn

To maintain altitude in a banked turn:

• We need to increase total lift to restore the vertical component
• We do this by applying gentle back pressure on the control column
• In steeper banks, we may also need to add power to maintain airspeed
• The higher the bank angle, the more backpressure (and power) is required

Medium level turn: approximately 15–25° bank. At this angle, a small amount of back pressure is all that's needed — power is usually not required.

Turning Manoeuvres

What is a "coordinated" turn?

Why do we need to coordinate our use of ailerons and rudder when turning?

When we roll in one direction with the ailerons, the wing that gets lifted up also gets dragged backwards by the extra drag induced with the lift.

• This is another secondary effect of rolling which we didn't focus on in the first lesson, called adverse yaw.
• The plane that we're flying is designed to counter the effect of adverse yaw, so it's not so noticeable.
• You can read more about adverse yaw and how plane designs avoid it in BoldMethod's Adverse Yaw: How It Affects Your Plane.

Medium Level Turn — Entry

Entry sequence:

• Lookout — clear the area in the direction of turn before full scan from opposite direction
• Bank — apply aileron and coordinated rudder in the direction of the turn until 15–25°
• Balance — check the balance ball to ensure you're not skidding or slipping
• Back-pressure — apply gentle back pressure to maintain altitude
• Monitor ALAP: Attitude, Lookout, Attitude, Performance (particularly airspeed and balance ball)

Note: due to the aeroplane's stability around the longitudinal axis, you may need to keep holding slight aileron to avoid the aeroplane flattening out the turn automatically. This is the underbanking tendency at lower bank angles.

Medium Level Turn — Exit

Exit (roll-out):

• Anticipate the exit — start rolling out before reaching the desired heading.
• A good rule-of-thumb is 1/3 of your bank angle before the desired heading (e.g. 30° bank → 10° before desired heading).
• Bank — apply aileron and coordinated rudder to restore straight flight.
• Balance — check the balance ball to ensure you're not skidding or slipping
• Back-pressure — release back pressure as wings level

Climbing Turn

A climbing turn combines the climb entry (from lesson 3) with a turn:

• Establish the climb first and trim
• BBB — enter a gentle turn. Let the nose drop slightly to maintain speed (less climb)
• Keep bank angle shallower in the climb (10–15°): a steeper bank → less vertical lift → climb rate suffers
• Maintain climb power and climbing speed throughout
• On roll-out, BBB and recheck climb attitude and performance

Descending Turns — Powered

Powered descending turn:

• First establish the powered descent (Power Attitude Trim)
• Then enter a gentle coordinated turn with BBB, letting the nose drop a little to maintain airspeed.
• Monitor altitude loss throughout the turn
  • To reduce the rate of descent, add a little power and raise the nose slightly to maintain airspeed.
  • To increase the rate of descent, reduce the power a little and lower the nose slightly to maintain airspeed.

Descending Turns — Glide

Gliding descending turn:

• Establish the glide (throttle closed, glide attitude, trim)
• Enter a coordinated turn with shallower bank than level flight
• The glide descent rate will increase in a steeper bank — manage altitude carefully

In a future lesson on glide approaches, we'll learn other strategies to limit ourselves to very shallow turns during glides.

Underbanking and overbanking tendencies

More underbanking and overbanking

In a sustained bank, the aeroplane doesn't necessarily stay at the desired angle of bank on its own:

• The outside wing is travelling faster through the air (it traces a larger arc)
• Faster airspeed = more lift → the outside wing rises
• This tries to steepen the bank — called overbank tendency
• Below about 30° bank: the aeroplane's built-in stability tries to roll level (underbank tendency dominates)
• In a medium turn (15–25° bank): we hold slight aileron into the turn to maintain the bank angle

When climbing or descending there are more factors to consider. The following video from flight-club outlines these factors visually very well.

More underbanking and overbanking

Spiral Dive Introduction

What is a spiral dive?

A spiral dive is a dangerous, rapidly developing manoeuvre — not a spin:

• The aeroplane enters a steep, tight descending spiral with increasing airspeed
• Often develops from a steep uncoordinated turn, or from distraction (loss of control awareness)
• The aeroplane is not stalled — the wings are producing a lot of lift, which is what makes it spiral
• Pulling back on the control column will not recover — it tightens the spiral and overstresses the airframe

Recognising and recovering from a spiral dive

Recognition — the instruments tell the story:

• Airspeed: rapidly increasing (well above cruise)
• Altimeter: unwinding fast (descending)
• Turn coordinator/needle: hard over — steep turn
• Inclinometer ball: displaced (uncoordinated)

Recovery — in order:

1. Reduce power (throttle back)
2. Level the wings — aileron and rudder to roll out of the bank
3. Gently ease back pressure to pull out of the dive
4. Do not pull before the wings are level — this is the critical step.

Recognising and recovering from a spiral dive — sim demo

Recap

Let's check what we know

See if you can answer each from memory:

• When we bank the aeroplane, part of the lift is being used to turn the aeroplane. What must we do to maintain altitude — and why?
• In a sustained medium turn, does the aeroplane try to steepen the bank, or roll level? Why?
• How does the entry for a climbing turn differ from a medium level turn?
• What is the correct recovery sequence from a spiral dive — and what must you NOT do first?

Watch How does stall speed change in a turn again from the flight-club people for an excellent explanation of why our stall speed changes in a turn!

Arrival