106 Through Exam 2 Flashcards
Define flight controls
a moveable airfoil that can be manipulated by the pilot
Normal category
non acrobatic operations
+3.8 - -1.52 G
Utility
limited acrobatic
+4.4 - -1.76
Acrobatic
unrestricted
+6 - -3G
Why do positive Gs make you feel heavier
centrifugal force acts in the same direction as weight
When is the stability of the aircraft?
the time between manipulation of the flight controls
Static stability
will the aircraft return if displaced
dynamic stability
how the aircraft will return if displaced
What does dihedral do
contributes to stability in the roll axis
helps restore wings level
Yaw stability is around what axis
vertical
what contributes to yaw stability
vertical stabilizer
swept back wings
How do swept back wings help with yaw stability
back wing has less frontal area: less lift, less drag
front wing has more frontal area: more lift, more drag
pitch stability is about the ____ axis
lateral
Flap which hinges down
Split flap
hinge of trailing edge leaves gap between wing and flap
slotted
extends out and down
inside wing when retracted
Fowler
only wing to increase surface area when deployed
winglets and sharklets do what
reduce induced drag
straight taper characteristics
CP moves more with AoA
max Cl greater
Cd lower
why is thickness taper combined with planform taper
Decreased Cp movement from thickness taper offsets increased cp from planform taper
mean aerodynamic chord
way of measuring chord length on non rectangular wings
high wing pros
better lift/drag ratio
better lateral stability
shorter landing distance
Low wing pros
easier to build
better roll maneuverability (less lateral stability)
shorter take off distance
Tee Tail advantages
allows for flow of air over rudder at high AoA
horizontal stabilizer is out of the way of engines
keeps horizontal stabilizer and rudder out of main wing downwash
Vee Tail advantages
decreases interference drag
decreases pressure and skin friction by combining “ruddervator”
Why do fighters have two tails?
stabilization in event of damage and reduce the height needed for full flight control
What do flying wires do
transmit lift back to fuselage
what do landing wires do
transmit downward impact of landing, or negative G loads, on wings back to fuselage
what do interplanetary struts do
transmit lift loads and landing loads between top and bottom wings
what do cabane struts do
support top section of wing above fuselage and transmit lift loads of wing roots to fuselage
what is the Center Section
airfoil shaped section above fuselage to which upper wings attach
when does interplanetary interference become a problem
when gap is less than one chord length apart
What is decalage (fixed wing)
Angle of difference between upper and lower wings of biplane
When one of the wings set to a higher angle of incidence than the other
What did the NASA AD-1 demonstrate and who was the designer
an aircraft wing can be pivoted obliquely from zero to sixty degrees in flight
Burt Rutan
Ruddervator (V tail) advantages
lighter
less wetted surface
reduced drag
increased stealth
canted surfaces reflect radar away from surface and engine mounting reduces infrared signature
improve safety and cabin noise reduction
Ruddervator disadvantages
more complex control system
have to be structurally more robust
control forces required for operation are higher
What is the tandem wing aircraft
both wings left up, no horizontal stabilizer pulling down
Tandem wing disadvantages
very difficult pitch stability
very limited CoG
What type of aircraft did the wright brother’s make? (in respect to wings)
biplane canard
What’s the difference between a tandem and canard
tandem: two full wings
Canard: main wings and smaller wings that can only carry 25% of weight
Canard characteristics
both wings provide lift (more efficient)
canard stalls before main
not as stable as conventional aircraft
Conventional tail characteristics
best pitch stability
Drag from horizontal stabilizer
interference drag (tail surfaces to fuselage)
Pressure drag from horizontal and vertical stabilizer
Flying wing characteristics
no horizontal tail - drastically reduced drag
sharp swept back wings for yaw stability
What are split rudders
split control at wingtips for rudders
What are elevons
ailerons moved inboard and combined with elevators
As air approaches the speed of sound…
it becomes compressible
What is the mach number
the speed of the aircraft in relation to speed of sound
Define Subsonic
any region below transonic
define transonic
first evidence of localized sonic or supersonic airflows and begins at critical mach number
ends when all flows around aircraft are supersonic
Define sonic
speed of sound
define supersonic
any speed faster than speed of sound
define hypersonic
any speed above Mach 5
where plasma begins to affect the airflow
How does drag react in transonic flight
drag rises quickly at Mcrit then drops off when fully supersonic
Normal shockwave characteristics
perpendicular to direction flow
air slows from supersonic to subsonic
pressure, temperature, density increase BEHIND shock
air flow direction does not change
tremendous drag
Oblique shock wave
generated by nose and leading edges
shock inclined to flow direction
supersonic speed to lower supersonic speed
airflow changes directions ACROSS shock
pressure, temperature, density increase THROUGH shock
creates some drag
Supersonic lift
Caused purely by AoA
shock produced at leading edge
shock going down is stronger than shock going up
(pressure jump down is larger than pressure jump up)
causes greater pressure under the airfoil
describe the supercritical wing
long flat upper camber with downward turn near trailing edge
keeps airspeeds constant across wing
lowest pressure concentrated around highest camber
smaller pressure differentials spread out over bigger area of wing which keeps lift produced the same
supersonic aircraft have a _____ overall cross-sectional area and ____ aspect ratio
larger, smaller
this creates smooth transitions from wings to fuselage cross-section
What is the Whitcomb area rule
essentially a series of tests looking at different factors in order to get reduced drag between Mach ,75 and 1.2
Why is wing sweep beneficial when supersonic
keeps wing tips out of the shock waves
(if the shock wave contacts the wing tips, airflow over the tips and ailerons can be disrupted)
For a helicopter in hover, the forces
are all acting vertically
What does the collective stick do (left of pilot)
increases (or decreases) AoA of all main rotor blades together in order to increase lift
What does the cyclic stick do (in front of pilot)
changes blade pitch at only one part of rotating cycle
tips rotor disk forward and moves helicopter forward
Why do helicopter rotors run at a constant rpm
increasing rotor speed to get more lift takes too long (changing pitch is instantaneous)
rotor blades need centrifugal force to hold them straight out or lift forces will fold up and break the blades
In North America, the main rotor spins ____ as viewed from top
counter clockwise
Moving the foot pedals____
changes the pitch of the tail rotor
If tail rotor quits, the helicopter____
spins around in a circle in the opposite direction of main rotor
what is translating tendency
in a hover, the sideways thrust of the tail rotor tries to drag the helicopter sideways - if uncorrected, drifts to right
