Stalling, Spinning & Spiral Dives

Question 1

What is an aircraft stall?

Answer 1

The significant breakdown of streamline flow into turbulence over an aerofoil

Question 2

When is an aircraft stalled?

Answer 2

When the critical angle of attack of the wings is exceeded

Question 3

Why is stalling bad?

Answer 3

When an aircraft stalls, the lift production reduces and so no longer balances weight. Drag increases significantly

The aircraft will descend.

Question 4

What is laminar airflow?

Answer 4

Smooth, streamline airflow over the wing

Question 5

What is the transition point?

Answer 5

The point at which laminar airflow changes to turbulent airflow

Question 6

What is the separation point?

Answer 6

Turbulent air separates from the upper surface of the aerofoil

Question 7

What are the symptoms of a stall?

Answer 7

High nose attitude
Low airspeed
Stall stick postion
Stall warning
Buffet
Mushy controls
Nose drop
Wing drop
Inability to stop descent

Question 8

What is the stall speed?

Answer 8

The speed below which an aeroplane will stall

Question 9

Does an aircraft stall at a speed or an AoA?

Answer 9

An AoA

Question 10

How does an increase in weight impact stall speed?

Answer 10

Increases stall speed

Question 11

How does an increase in altitude impact stall speed?

Answer 11

No impact

Stall speed is an IAS which does not change with altitude

Question 12

How does an increase in power impact the stall speed?

Answer 12

Lowers stall speed

Question 13

How does an increase in bank angle impact the stall speed?

Answer 13

Increases stall speed

Question 14

What impact does lowering flaps have on the stall speed?

Answer 14

Lowers stall speed

Question 15

What impact does moving the CoG forward have on stall speed?

Answer 15

Increases stall speed

Question 16

What impact can windshear have on stall speed?

Answer 16

Windshear can change the direction of the relative airflow causing the critical angle to be exceeded with no control input

Question 17

What impact will frost and ice normally have on stall speed?

Answer 17

Normally, the critical angle remains the same and only the stall speed changes

The exception is hoar frost

Question 18

What is hoar frost?

Answer 18

Where an aerofoil is covered in frost and/or ice

Question 19

How does hoar frost impact stall speed?

Answer 19

Decreases the critical angle and increases the stall speed

Question 20

Why does a wing drop in a stall occur?

Answer 20

The wing that drops has stalled first

Question 21

Why should aileron input be avoided in a stall recovery?

Answer 21

May deepen the stall of the wing and the aircraft may enter a spin

Question 22

How does a rectangular straight wing tend to stall?

Answer 22

Root first then spread outward
Generally good handling
Good aileron control
Good stall symptoms
Nose down at the stall

Question 23

How does a swept back wing tend to stall?

Answer 23

Tips first then spread inwards
Poor handling
Can cause a wing drop
Can cause pitch up due to CoP moving forward, deepening the stall

Question 24

What are some methods to improve stall handing characteristics?

Answer 24

Washout
Stall strips
Vortex generators
Wing fences

Question 25

What is wing washout?

Answer 25

Wings have a lower angle of incidence at the tip than at the root. So the root will stall first

Question 26

What does wing washout do?

Answer 26

Better aileron control Early buffeting of the tail Reduced chance of wing drop

Question 27

What are stall strips?

Answer 27

Sharp edges strategically placed on the leading edge to cause certain areas to stall before others

Question 28

What are vortex generators?

Answer 28

Small surfaces place on the upper leading edge to delay a stall

Question 29

How do vortex generators work?

Answer 29

Create stable vortices on the upper surface of a wing | Delaying separation and so stall

Question 30

What are the benefits of vortex generators?

Answer 30

Increase stall AoA and reduce stall speed | Increase control effectiveness

Question 31

What are wing fences?

Answer 31

Vertical surfaces which run along the chord of the wing

Question 32

What do wing fences do?

Answer 32

Minimise span-wise flow | Generally improve handling characteristics

Question 33

When does a spin occur?

Answer 33

When one wing stalls more than the other wing | Usually when stalled uncoordinated

Question 34

What happens in a spin?

Answer 34

The more stalled wing drops and this causes the aircraft to roll and yaw towards it This stalls the win further, causing an eventual stable rotation

Question 35

What is autorotation?

Answer 35

When the roll and yaw in a spin is stable

Question 36

Is the aircraft stalled in a spin?

Answer 36

Yes

Question 37

Is the aircraft stalled in a spiral dive?

Answer 37

No

Question 38

When does autorotation occur?

Answer 38

A spin

Question 39

What are the indicators of a spin?

Answer 39

Low and steady airspeed Steady rate of descent Low g-forces

Question 40

What are the indicators of a stall?

Answer 40

High and increasing airspeed High increasing rate of descent High g-forces

Question 41

What is the stall recovery?

Answer 41

Reduce AoA Apply full power Maintain directional control with the rudder (until un-stalled)

Question 42

What is the spin recovery?

Answer 42

Power to idle Ailerons neutral Rudder full opposite to the direction of rotation Elevator forward