Stalling, Spinning & Spiral Dives Flashcards
What is an aircraft stall?
The significant breakdown of streamline flow into turbulence over an aerofoil
When is an aircraft stalled?
When the critical angle of attack of the wings is exceeded
Why is stalling bad?
When an aircraft stalls, the lift production reduces and so no longer balances weight. Drag increases significantly
The aircraft will descend.
What is laminar airflow?
Smooth, streamline airflow over the wing
What is the transition point?
The point at which laminar airflow changes to turbulent airflow
What is the separation point?
Turbulent air separates from the upper surface of the aerofoil
What are the symptoms of a stall?
High nose attitude Low airspeed Stall stick postion Stall warning Buffet Mushy controls Nose drop Wing drop Inability to stop descent
What is the stall speed?
The speed below which an aeroplane will stall
Does an aircraft stall at a speed or an AoA?
An AoA
How does an increase in weight impact stall speed?
Increases stall speed
How does an increase in altitude impact stall speed?
No impact
Stall speed is an IAS which does not change with altitude
How does an increase in power impact the stall speed?
Lowers stall speed
How does an increase in bank angle impact the stall speed?
Increases stall speed
What impact does lowering flaps have on the stall speed?
Lowers stall speed
What impact does moving the CoG forward have on stall speed?
Increases stall speed
What impact can windshear have on stall speed?
Windshear can change the direction of the relative airflow causing the critical angle to be exceeded with no control input
What impact will frost and ice normally have on stall speed?
Normally, the critical angle remains the same and only the stall speed changes
The exception is hoar frost
What is hoar frost?
Where an aerofoil is covered in frost and/or ice
How does hoar frost impact stall speed?
Decreases the critical angle and increases the stall speed
Why does a wing drop in a stall occur?
The wing that drops has stalled first
Why should aileron input be avoided in a stall recovery?
May deepen the stall of the wing and the aircraft may enter a spin
How does a rectangular straight wing tend to stall?
Root first then spread outward Generally good handling Good aileron control Good stall symptoms Nose down at the stall
How does a swept back wing tend to stall?
Tips first then spread inwards
Poor handling
Can cause a wing drop
Can cause pitch up due to CoP moving forward, deepening the stall
What are some methods to improve stall handing characteristics?
Washout
Stall strips
Vortex generators
Wing fences
What is wing washout?
Wings have a lower angle of incidence at the tip than at the root. So the root will stall first
What does wing washout do?
Better aileron control
Early buffeting of the tail
Reduced chance of wing drop
What are stall strips?
Sharp edges strategically placed on the leading edge to cause certain areas to stall before others
What are vortex generators?
Small surfaces place on the upper leading edge to delay a stall
How do vortex generators work?
Create stable vortices on the upper surface of a wing
Delaying separation and so stall
What are the benefits of vortex generators?
Increase stall AoA and reduce stall speed
Increase control effectiveness
What are wing fences?
Vertical surfaces which run along the chord of the wing
What do wing fences do?
Minimise span-wise flow
Generally improve handling characteristics
When does a spin occur?
When one wing stalls more than the other wing
Usually when stalled uncoordinated
What happens in a spin?
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
What is autorotation?
When the roll and yaw in a spin is stable
Is the aircraft stalled in a spin?
Yes
Is the aircraft stalled in a spiral dive?
No
When does autorotation occur?
A spin
What are the indicators of a spin?
Low and steady airspeed
Steady rate of descent
Low g-forces
What are the indicators of a stall?
High and increasing airspeed
High increasing rate of descent
High g-forces
What is the stall recovery?
Reduce AoA
Apply full power
Maintain directional control with the rudder (until un-stalled)
What is the spin recovery?
Power to idle
Ailerons neutral
Rudder full opposite to the direction of rotation
Elevator forward
