Aerodynamics Flashcards
How can you recover from settling with power?
AIRSPEED
Large collective input
What is blowback and how is it compensated for?
Blow back is the raising of the nose because of the maximum amount of up-flap happening over the nose of the aircraft. It is compensated by cyclic feathering.
What is needed for dynamic rollover?
Pivot point
Rolling motion
Exceeding the critical angle
What is TAF and what is it the sum of?
Total Aerodynamic Force
It is the sum of lift and drag on an airfoil
What is transverse flow?
“Ariflow mullet”
Airfrlow is more horizontal in the front half, vertical in the aft half, causing the forward half of the rotor system to produce more lift.
Happens between 10-20 knots
Causes a right rolling motion
What 3 aerodynamic phenomenon cause the aircraft to pitch up and roll right?
Transverse flow
Dissymetry of lift
Gyroscopic procession
What is relative wind?
The wind parallel and opposite of the advancing blade
What is rotational relative wind?
How relative wind is made due to rotation of the rotor blades
What is resultant relative wind?
Rotational relative wind modified by induced flow
What is dissemetry of lift?
The difference of lift produced by the advancing blades compared to the retreating blades
Compensated with blade flapping and cyclic feathering
What is the difference in airflow during a hover IGE/OGE?
OGE requires a larger angle of incidence (more power) to hover because of induced flow. OGE also has larger wing tip vortices because the ground is not disrupting the airflow.
What is settling with power?
Vortex ring state
A condition of powered flight which an aircraft settles in its own downwash
Must have a vertical/near vertical descent > 300fpm
Slow forward airspeed (less than ETL)
20-100% of power applied
Conditions conducive to settling with power?
Formation flight
Masking/unmasking
Downwind approach
Not maintaining altitude during an OGE hover
Hovering above max hover ceiling
Steep approaches with high descent rate
What are the 3 types of drag?
Parasite- bolts/non lift producing components
Profile- frictional resistance of the blades
Induced- Incurred as the production of lift, decreases as airspeed increases
What is retreating blades stall?
A condition of flight where the retreating blade fails to produce adequate lift during higher airspeeds
3 sections
3 sections of retreating blade stall
Reverse flow- airflow flows the opposite way of producing lift
Negative stall- relative wind is above the chord line
Negative lift- the airfoil produces lift in the opposite direction
3 types of dynamic rollover
Up-slope
Down-slope
Level ground
What are the 3 regions of the blades during an autorotation?
Stall- inner 25%
Driving- middle 25-70%
Driven- outer 30% (produces the lift)
What is ETL?
Effective Translational Lift
Occurs when the rotor outruns its vortices and starts working in relatively undisturbed air
16-24 knots
Nose pitches up, rolls to the right
What is an autorotation?
A state of un-powered flight which the up-flow of air through the rotor system turns the rotor and produces lift
What are the 5 aerodynamic emergencies?
Dynamic rollover
Settling with power
Retreating blade stall
Compressibility
Ground resonance
What is translating tendency?
The aircrafts tendency to drift the right because of tail rotor thrust
Corrected by the MMU on the UH-60
What indicates you are experiencing retreating blade stall?
Vibrations
Nose pitching up, rolling left
What are the physical factors associated with dynamic rollover?
Main rotor thrust
CG
Tail rotor thrust
Cross wind
Ground surface
Sloped landing area
Low fuel
What are the human factors associated with dynamic rollover?
Inexperience
Innattention
Innapropriate control inputs
Failure to take timely corrective action
loss of visual reference
