Total Drag Flashcards
What is Skin Friction Drag?
-Skin Friction is caused by air sticking to the surface as it passes the aircraft
What are the two sections of Parasite Drag?
- Skin Friction
- Form Drag
What is Form Drag?
- Form Drag is caused by air getting out of the way
- Form Drag can be reduced by changing the shape of the object
What is Induced drag?
- Induced drag is caused by the modification to airflow as it interacts with any LIFT- PRODUCING surface
- The main source of induced drag is spanwise flow deflection of airflow
What is streamlining?
-Altering the shape of the object to reduce drag
What design features keep drag low?
- Wheel spats
- Wing root fairings
- The streamlined cross-section for lift struts
How do you reduce induced drag?
-Keep wingtip as small as possible
What affects the amount of parasite drag experienced by aircraft?
- Speed
- AOA
- Position of flaps and undercarriage
What happens to parasite drag as speed increases?
Parasite Drag Increases
What is the rate that parasite drag increases with speed?
Parasite drag equals the square of the speed
What is spanwise flow?
Sideways deflection of airflow
What is an Eddie?
Deflected airflow from top and bottom surface meet at the tip to form small scale vortices
What two factors affect how much air spills across the wingtip and therefore the degree of vortex?
- Magnitude of pressure difference
- Time available for air to complete journey
At low speeds; is tip vortex and spanwise flow less or more?
Greater
Does Induced drag increase or decrease as speed increases?
Decreases as speed increases
What is Low aspect ratio?
- Short Span
- Long Chord
What is a high aspect ratio?
- Long Span
- Short Chord
Does a low or high aspect ratio wing have a higher stallin g angle?
Low aspect ratio wing has higher stalling angle
Does a high or low aspect ratio wing produce the most lift at the same Angle of Attack and Speed?
High Aspect ratio wing produces the most lift
What is wake turbulance?
-Vortices which trail behind large aircraft tend to create large amounts of roll or yaw for following aircrafts
Which direction do Vortices rotate from the left wing?
Clockwise
Which direction do Vortices rotate from the right wing?
Anticlockwise
How fast do vortices sink?
400-500fpm
When do Vortices tend to stabalise?
900 ft below flight path
At what height do vortices tend to stop sinking and move horizontally at about 3 or 4 knots?
At about 200ft
In stable conditions how long can vortices persist?
- Commonly 3 minutes
- At height; they may persist for 5 minutes
How far do the trails of vortices extend?
2-5 miles
Will vortices be present if no lift is being produced?
No
How far c an thrust stream and jet exhaust extend behind heavy aircraft?
500m
Are vortices more or less pronounced with flaps extended?
Less pronounced
What configuration creates the most wake turbualnce?
Slow speed and Flap extended
Separation standard reference?
AIP ENR 1.4 Para 9.2.2
Separation Standards for:
Light Aircraft landing behind Heavy aircraft
3 minutes
or
6nm
Separation Standards for:
Light aircraft landing opposite direction to departing heavy
2 minutes
or
6nm
Separation Standards for:
Light Aircraft departing after heavy
2 minutes
or
6nm
Separation Standards for:
Light aircraft taking off from mmre than 150m from heavy aircrafts commencement of takeoff run
3 minutes
or
6nm
At low speed what drag is higher?
Induced drag
At high speed what drag is higher?
Parasite Drag
If an aircraft is flown at the minimum total drag speed what will it achieve?
- Max range in nil wind conditions
- Best Air Nautical miles per gallon
- Least gallon per nautical mile
- Best lift/ drag ratio
- Best gliding range in nil wind conditions
What phases of flight are vortices present?
From lift off to touch down
Lateral drift rate of vortices once at ground level?
3- 4 knots
Minimum distance to avoid rotordownwash?
3 rotor diamaters
Wake turbulance is worst when….
A heavy aircraft is flying slowly
