Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Slow Flight and Stalling - Theory Part 2:

Performing and recovering from Stalls

CASA Recreational Pilot License (Aeroplane) — Lesson 5, Pre-flight theory part 2

All text and presenter notes in this briefing are licensed under Creative Commons BY-SA 4.0. More info

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Theory Lesson Overview — Part 2

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Learning Objectives — Part 2

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

  • Describe the correct recovery procedure for both an imminent stall and a fully developed stall, with and without power
  • Describe how flap, configuration and other factors affect the stall
  • Interpret instrument indications during a stall - what you expect to see if you stall when in cloud
  • Describe the HASELL check and complete it from memory
Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Waypoint 1 — Recovery Techniques

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Recovery from an Imminent Stall

The imminent stall is the easiest recovery — act the moment you recognise it:

  1. Reduce AoA — ease forward on the control column (the primary action)
  2. Apply full power — reduces height loss and helps regain flying speed
  3. Level the wings — with coordinated aileron and rudder, if banked
  4. Climb away — once flying speed is regained, establish a positive climb

Priority: reduce AoA first. Power alone will not recover a stalled wing.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Recovery from a Fully Developed Stall

If the stall is fully developed (nose has dropped, lift collapsed):

  1. Reduce Angle of Attack — relax the backpressure on the control column, allowing it to come forward until buffeting stops
  2. Apply full power — at the same time, smoothly apply full power
  3. Opposite rudder — if a wing has dropped, use the rudder (not aileron) to level
  4. Level the wings — with coordinated control inputs once flying
  5. Recover height — establish climb and regain lost altitude

Avoid the secondary stall: do not pull back aggressively when the nose drops — the wings may not yet be flying and a secondary stall can follow.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Recovering Without Power

We will also practise stall recovery without applying power:

  • Reduce AoA — ease forward to unstall the wing
  • Use rudder input to level wings until flying speed is regained
  • Accept the height loss — convert height to speed to re-establish controlled flight
  • Once flying speed is regained, ease back to recover from the descent, aiming for your minimum drag speed

Reducing AoA is always the primary recovery action — power assists but is not the first step.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Waypoint 2 — Effect of Power, Flap and Configuration

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Effect of Power on the Stall

Power affects stall speed and recovery:

Power setting Effect
High power Propeller thrust and slipstream over the inner part of the wings may delay the stall on that inner section only, which can mean the stall occurs first on the outer wing, causing a wing drop. Power also provides elevator and rudder authority (but not aileron)
Idle power No slipstream benefit — higher AoA required to maintain lift — stall speed is slightly higher
During recovery Full power minimises height loss and accelerates back to flying speed

Power may reduce stall speed — but power alone will not recover a stalled wing. Always reduce the angle of attack first.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Effect of Flap on the Stall

Flap affects both lift and stall characteristics:

  • Flap extended — increases lift at low speed, lowers stall speed (improves slow-speed performance)
  • Flap extended — also increases drag;
  • Flap extended — changes the nose attitude at which the stall occurs since the chord - the line from leading edge to trailing edge - now has a higher angle of attack for the same attitude, so that the stall happens at a lower nose attitude with flap than without flap
  • Flap retracted — higher stall speed; higher nose attitude needed to stall
  • Landing configuration stall — flap and slower speed typical of approach; a stall here is particularly dangerous due to the low altitude

We will practise a stall in approach configuration (flap extended) as well as from straight and level flight.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Other Factors Affecting Stall Speed

The stall always occurs at the same critical angle of attack, but the airspeed at which this happens varies with several factors:

Factor Effect on stall speed
Weight Heavier aircraft stall at higher speed (more lift needed → higher angle of attack at a given speed)
Load factor ('g') Increased 'g' (steep turns, pull-ups) raises stall speed — at 60° angle of bank level turn, stall speed × 1.41 - more about this on the following slides
Centre of Gravity A forward CoG means the elevator needs a greater downward force to balance which means the lift force needs to balance more than just the weight. A rearwards CoG makes recover from the stall more difficult
Dynamic loading Turbulence or abrupt pitch inputs increase effective 'g' and can stall the wing unexpectedly
Ice or wing damage Disrupts airflow, raises stall speed; can cause stall at much higher speed than placard
Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Load Factor and Bank Angle

Why do the 'g's increase?

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Load Factor and Bank Angle

The relationship between bank angle and stall speed is important to understand:

Bank angle Load factor Stall speed multiplier
0° 1.0 g × 1.00
30° 1.15 g × 1.07
45° 1.41 g × 1.19
60° 2.00 g × 1.41

At 60° angle of bank, the stall speed is 41% higher than in straight and level flight.

This is why a steep turn during slow flight - whether on take-off or the base-to-final turn - is dangerous: the aircraft can stall at a speed well above what the pilot expects.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Waypoint 3 — Instrument Indications

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Instrument Indications During a Stall

During one of the stall entries and recoveries, take note of the following instruments:

Instrument What to expect
Airspeed Indicator (ASI) Needle falls into or below the white/green arc; may fluctuate or indicate zero at the stall due to disrupted pitot airflow
Attitude Indicator (AI) High nose attitude on entry; nose pitches through the horizon on recovery
Altimeter Descending during the stall and recovery — note height loss
VSI Rapid descent rate at the stall
Balance ball Should be centred; any slip or skid increases risk during recovery

Pitot tube may be partially blocked during the stall — ASI may read incorrectly. Fly the attitude, not the instruments.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Waypoint 4 — HASELL and Recap

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

The HASELL Check

Before every stalling exercise, we'll complete the HASELL check:

Letter What to check
H Height — sufficient to complete the manoeuvre and recover (minimum is for recovery to be over 3000ft AGL)
A Airframe — correct configuration for the manoeuvre; no abnormal indications
S Security — harnesses fastened, loose articles stowed, no hatches or locks insecure
E Engine — temperatures and pressures in the green; carburettor heat applied and then off
L Location — not over a built-up area, aerodrome, or controlled airspace
L Lookout — 360° clearing turn (or two 90° turns) to check for other traffic

HASELL is not optional — complete it before any acrobatic manoeuvre

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Why HASELL Matters — the Lookout Turn

The 360° lookout turn (or two 90° turns) is critical because:

  • Before the stall, we may be climbing slowing — other aircraft cannot easily predict our path
  • The stall may involve a rapid pitch change and altitude loss — we need clear airspace below
  • Situational awareness (NTS1.2) requires us to know what is around us before entering any unusual manoeuvre

Never skip the lookout. If you see another aircraft during the clearing turn, wait or reposition.

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Summary — Full Lesson

Stalling — the key points:

Principle
Cause
Imminent symptoms
Fully developed effects
Recovery procedures
Factors affecting
Pre-acro safety check
Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Summary — Full Lesson

Stalling — the key points:

Principle
Cause Angle of attack exceeds critical angle — can happen at any speed
Imminent symptoms Low speed, high nose, mushy controls, buffet, stall horn
Fully developed effects Lift collapses, nose drops, possible wing drop
Recovery procedures Reduce AoA first; full power; level wings with rudder; regain height
Factors affecting Weight, 'g', flap, power, CoG, ice — all affect stall speed
Pre-acro safety check HASELL before every exercise; maintain coordinated flight
Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Objectives Check

Can you explain:

  • What causes a stall — and why it can happen at any speed?
  • The difference between an imminent and fully developed stall?
  • The correct recovery sequence?
  • What a 60° banked turn does to stall speed?
  • What HASELL stands for, and why the lookout turn is the last step?
Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Done

Slow Flight and Stalling — Theory Part 2: Performing and Recovering from Stalls

Questions?

Any questions before the pre-flight brief?

In Part 2, we're focusing on the recovery procedures rather than the aerodynamics of the stall, including how to practise stalls safely.

Click Direct-To to advance to Recovery Techniques.

This is the most important point of the whole lesson: the first action is always to reduce AoA. The instinct to pull back must be actively replaced with the correct response. Repetition in the air today is what builds the correct response.

Listen to this pilot's response for how he's recovering from the stall. The secondary stall is a common student error: the nose drops, the student pulls back hard, the wing is not yet flying, and a second (sometimes steeper) stall results. Insist on a smooth, deliberate pull-back after the AoA is clearly reduced.

This exercise builds the correct reflex: forward first, then power. If power is applied to a stalled wing without first reducing AoA, the nose yaws and the situation worsens.

Click Direct-To to advance to effects on the stall.

The landing configuration stall represents the most common fatal scenario: too slow on final approach, pulling back, inadvertently stalling. Connecting the exercise to the real-world scenario gives it meaning.

Note that 4 of 5 factors here are effectively a greater weight needing to be balanced by lift.

Turn the aeroplane to look head-on, then: - Note that the aeroplane is flying level and that the L balances W - gradually bank to 45 degrees - Note that the aeroplane is sinking - to restore level flight: - Add power to 82% and attitude to 10 degrees for stable flight at 45 bank. Actually, there's no need to restore level flight: as long as the aircraft has settled and is not accelerating, the vertical component of the lift should balance the weight. So we can test with 60 degrees too, which is simpler.

Use a concrete example: if Vs is 50 kt in straight level flight, at 60° AOB the stall speed is 50 × 1.41 = 70.5 kt. If you are flying at 75 kt on a steep base-to-final turn, you have very little margin. Originally had another slide following with this text and video, but removed for now: Again, it's not fun to watch (and we don't need to see the end - the video doesn't show the actual impact), but the report into this crash indicated that the **stall warning was activated but apparently ignored** during these turns. Note the **flaps which are still extended** in the first steep turn (so lower stall speed) are then retracted for the second steep turn. https://www.youtube.com/watch?v=XiId0z5EKtk

Click Direct-To to advance to instrument indications.

This may be important if a pilot is ever unfortunate enough to experience a stall while in cloud: knowing how to read the state of the aircraft can be crucial. The pitot system effect: during a nose-high stall, the pitot tube may point away from the relative airflow, giving an unreliable or zero reading. This is one reason the ASI alone should not be relied upon — the buffet, the feel of the controls, and the warning horn are equally important cues.

Click Direct-To to advance to HASELL and Recap.

Carburettor heat during HASELL: apply carb heat briefly to clear any carb ice before applying power for recovery — then turn it off before the exercise. During HASELL, the brief power reduction to check engine is also the moment to clear carb ice.