ADY - Stalls, Spins and Stability Flashcards
What type of stall occurs when you are pulling out of a dive at high IAS
Dynamic or high speed stall
The definition of a stall is …..
That condition where an increase in AoA results in less lift
The downward component of the vortex at the wing tip causes what to happen ……
this causes the AoA at the wing tip to be less than at the wing root so the wing root will stall before the wing tip causing a much less pronounced wing drop
What type of aircraft are subject to dynamic stalls …..
Aircraft with high wing loading
Name 3 design features to minimise the stall …..
- Wash out
- Stall strips
- Elevator stops
The published stall speed in an aircraft’s flight manual is meant for …..
Usually the max all up weight when the aircraft is in level flight only
Name 3 factors that decrease the stalling IAS …..
- Flaps - Increase CL
- Power - has a component of lift to it
- CoG position - Moving aft is like reducing weight
Name 3 factors that increase the stall IAS …..
- Weight - more weight increases the stall speed
- Load factor - Is the same as a weight increase
- Ice or damage - Change the shape of the aerofoil and hence its lifting properties
It is impossible to enter a spin unless …..
the wings have stalled
In a spin the downward going wing moves …..
downwards and backwards
The rotation in a spin continues …..
while ever the wings are stalled
What happens to the rate of rotation once a spin has developed …..
it becomes constant
During a spin the balance ball will …..
Deflect away from the direction of the spin
During a spin the ASI will ……
give a very low and unchanging reading which is meaningless
Spin recovery requires you to do ……
- Unstall the wings
- stop the rotation with opposite rudder
The sequence and method is aircraft type dependant
Define Stability …..
Stability is the property possessed by an object which causes it to seek to return to its original position after it has been displaced
Dynamic stability - the object ….. .. ….. after a disturbance
returns to rest
Dynamic instability - the object makes no attempt to ….. .. …..
return to rest
Neutral stability - After a disturbance there is no further attempt to …..
diverge further from or return to rest
Longitudinal stability is in the …… area of motion
pitching
….. is the most important variable in controlling longituinal stability
CoG
When the CoG is ….. this has a ….. effect.
This effect is proportional to the …..
aft, destabalizing, arm from the CoG to the CoP
The ….. from the CoG to the ….. in the ….. ….. is a major influincing factor in longitudinal stability
distance of the arm, Cop, tailplane
3 design features that assist longitudinal stability are:
- Tailplane volume
- Orientation of the lift and weight
- Longitudinal dihedral
Longitudinal Dihedral: sometimes the taleplane has a smaller ….. .. …..
angle of incidence
The effectiveness of the tailplane depends on 2 things …..
- The distance from the CoG
- The area of the tailplane
Lateral stability is in which plane of motion?
roll
lateral stability and dihedral:
Describe how dihedral assist in lateral stability …..
In a side slip the AoA is greater on the lower wing. When there is dihedral on the wing this AoA is minimised picking up the wing providing better stability
Lateral stability:
Side slip results as the ….. component of the ….. lift vector in a roll
horizontal, inclined
Lateral stability:
Keel surfaces below the roll axis cause …..
lateral instability
Lateral stability:
Keel surfaces above the roll axis provide …..
Improved stability
In order to maintain manoeuverability in roll, lateral stability is usually …..
weak
The more stable an aeroplane is in lateral stability the …..
less manoeuvarable it will be
In a side slip on a swept back wing what happens to the lower wing …..
- The effective span is greatly increased
- The effective cord is reduced
- Much more air flows across the lower wing
What is anhedral …..
It is negative dihedral where the wings are set down and below the yawing plane. This takes away some of the excessive lateral stability to improve manoeuvrability
Define directional stability …..
the property that causes the aircraft to align its longitudinal axis with the direction of the relative airflow
Simply put - the property seeks to point the nose of the aeroplane into the wind
Relative airflow striking the surfaces forward of the CoG cause …..
Directional instability
Relative airflow striking the surfaces aft of the CoG …..
Create directional stability
What is the major contributor to directional stability …..
the surface area of the fin and rudder
Lateral stability is always ….. than directional stability
weaker
After a wing drop and no corrective action by the pilot, strong directional stability dominates providing a ….. into the direction of the sideslip potentially initiating a …..
yaw, spiral dive
A spiral dive is a …..
dynamically unstable condition where the nose is low and the airspeed is increasing
2 likely causes of a spiral dive are …..
- pilot incapacitation
- Non-IFR training
To correct a spiral dive …..
- Level the wings
- Pull up
What type of loads are present in a spiral dive …..
- Tortional
- Shearing
The primary reason for designing a wing with washout is …..
to ensure that the wing root stalls before the wing tip.
This happens as there is less AoA at the wing tip because of the washout
The dihedral on a high wing aircraft is usually less than that on a low wing design because the hgh wing design has a …..
stronger lateral stability.
remember that the wings are above the weight (lift above weight) so they are naturally more stable laterally
If no control inputs are made by the pilot, an aircraft which has rolled to the left from the level attitude will have a natural tendancy to ….
yaw to the left
remember after the roll the aircraft sideslips - this is yaw
spiral instability is the result of an interaction of …..
roll and yaw
this combination of stability (or not) would cause a spiral dive …
weak lateral and strong directional
Longitudinal dihedral enhances stability in pitch by providing an angle of incidence on the tail plane which is …..
less than that of the main wings
Compared with the upper wing, the lower wing of an aircraft in a spin is experiencing …..
more drag and less lift
A device which encourages the airflow to seperate from a wing surgace during the stall progression is a …..
stall strip
The primary reason for designing a wing with anhedral is …..
to reduce the leteral stability
