Questions Flashcards
State conditions for hoarding frost to form
Away from clouds & precipitation, below 0 degrees c
Name 3 circumstances where hoar frost forms
On rapid descent from high cold, to warm moist clear air
After takeoff on frosty morning
Parked outside on clear winter nights or early morning
What effect will hoar frost have on the stalling speed of an aircraft?
Hoar frost Increases stall speed
What must be satisfied to achieve a minimum turn radius?
Wing loading must be low as possible
Air must be as dense as possible
What must be satisfied to achieve a maximum radius turn?
Wing loading must be as low as possible
Air must be as dense as possible
If we have a higher lift/drag ratio for an aircraft, the glide angle will have to be what to ensure maximum gliding range?
Smaller glide angle
Whats a manoeuvre envelope?
A graphic representation of the operating limits of an aircraft
What aircraft usually have a compressibility mach number?
Aircraft designed for subsonic or transonic flight
When all the limits are drawn together, they show the available range of manoeuvre for the aircraft at any height, the envelope shows:
A) basic stalling speed
B) available load factor at any height and speed
C) maximum EAS at any height
D) stalling speed at any height and load factor
What is the manoeuvre envelope used for?
To lay down design requirements for new aircraft
Illustrate performance of aircraft
Comparing capabilities of different types
What ate the axis of the manoeuvre envelope?
Vertical axis - load factor positive & negative
Horizontal axis - EAS
Why are aircraft designed to a bare minimum strength dependent on role?
Extra strength means more weight and in turn larger engines
What safety margin do aircraft have in relation to g?
50%
Maximum and minimum g limits?
-3g - +7g
Whats EAS?
Equivalent air speed limitation
(Maximum permissible diving speed)
Whats subsonic flow?
Air flowing at speeds less than at which sound travels
Pressure and temp remain constant (incompressible)
Whats the conservation of mass flow?
The mass of air entering a pipe and leaving it and passing any point must be constant.
A pipe using this is called a venturi
What is the effect of a Venturi?
An increase in the velocity of the air flow and decrease static pressure at the throat of the venturi
Why is a Venturi relevant?
An aerofoil is like the bottom half a Venturi an the low pressure caused acts as a suction which makes the wing lift upwards
Why can boullinis theory and conservation of mass airflow only be used for airspeeds below 150 m/s? And when are they irrelevant?
We assume temp and pressure are constant at subsonic speeds, this is not true but the margin of error is ignorable until 150m/s
At 340m/s, they are irrelevant
Whats upwash and downwash?
Upwash is the upwards flow of air before it goes over the aerofoil
Downwash is downwards flow of air after the aerofoil
How does downwash work?
The downwash air is deflected downwards from the shape of aerofoil which creates an opposite reaction force pushing the aircraft up
What factors affect total reaction?
Density
Velocity
Wing area
Angle of attack
Surface finish
Aerofoil shape
Span wise drift is progressively less pronounced from tip to root, what does this mean for transverse flow?
Transverse flow is strong at tips and reduces towards fuselage
In relation to polar curve coefficients, they depend on what 3 variables?
Angle of attack
Reynolds number
Mach number
Whats a polar curve?
A polar curve is a graph which contrasts the sink rate of an aircraft with its horizontal speed
Glide ratio = L/D
What are rectangular wings known to be in relation to stalling
Wing root stallers
Whats interference drag?
The mixing of two different airflows over different areas of aircraft
State which direction vortexes rotate for port and starboard side
Port - CW
Starboard - ACW
Aerodynamic effects of ice?
Drag increased, lift reduced
What are swept wings and what kind of aircraft are they used on?
Wing that sweep rearwards
Aircraft that fly in both transonic and sonic flight ranges
Whats a benefit and drawback of forward swept wings?
Higher angles of attack whilst maintaining airflow over wings
Difficult to fly
What are spins characterised by?
A high AoA
Low airpseed
High rate of descent
