Lecture 8 Flashcards
Heat engines utilize _____ to produce the power for _____.
heat energy
propulsion
What two types of engines are heat engines?
Reciprocating (piston) engines
Gas turbine (jet) engines
What is “work” in a piston engine?
Heat expands gases creating pressure against a piston in a cylinder
The piston moves down causing the crankshaft to rotate
What is energy?
The capacity for doing work
Energy cannot be _____ or _____.
created
destroyed
Energy can be _____ from _____ to _____.
transformed
one kind
another
What is kinetic energy?
Energy of motion
What is potential energy?
Energy of position or stored energy
Describe how potential energy changes to kinetic energy in an aircraft
Potential energy (stored fuel) transforms into kinetic energy (moving fuel)
_____ –> _____ –> _____ = thrust
Chemical energy (fuel)
Heat (combustion)
Mechanical (rotation)
When a mixture of gasoline and air is ignited the _____ of the molecules _____.
kinetic energy
increases
What is a normal category aircraft?
Used for non acrobatic operations
Lowest amount of G’s
Most restricted
What is a utility category aircraft?
Limited acrobatic operations
Median amount of G’s
Both normal and utility fit in this category
What is a acrobatic category aircraft?
Unrestricted operations
Highest amount of G’s
For positive G loads, centrifugal force acts in the _____ as weight and makes you feel _____.
same direction
heavier
For negative G loads, centrifugal force acts in the _____ as weight and makes you feel _____.
opposite
lighter
What is load factor?
Ratio of the total load supported by the wing compared to the weight of the aircraft
As you _____ the bank on the aircraft, the G force on the aircraft _____.
increase
increases
What are the two kinds of stability?
Static stability
Dynamic stability
What is static stability?
The initial tendency of an aircraft to return to its original position when it’s disturbed
What is dynamic stability?
How an airplane responds over time to a disturbance
Describe positive static stability
When the nose pitches up, the nose lowers and returns to its original attitude immediately
Describe neutral static stability
When the nose pitches up 5 degrees, and stays at 5 degrees
Describe negative static stability
When the nose pitches up, and continues pitching up until stall
Describe positive dynamic stability
If the nose pitches up, it will go up and down until it returns to its original altitude
Describe neutral dynamic stability
If the nose pitches up, it will continue to go up and down steadily
Describe negative dynamic stability
If the nose pitches up, it will continue to go up and down with worsening pitch until it reaches stall
The aircraft must be stable around _____ axis.
all three
Dihedral contributes to _____ in the roll axis and to the restoring of _____. Wings are angled _____.
stability
“wings level”
up
Anhedral or negative dihedral can improve _____ in planes with a very low _____ due to heavy cargo.
roll rate
center of gravity
_____ maintains yaw stability.
Vertical stabilizer
Explain how swept back wings increase yaw stability
The wing moving forward presents more frontal area straight into the wind, increasing lift and induced drag
The wing moving backward has less frontal area and not in straight relative wind, producing less lift and less induced drag
What makes the airfoil on the tail of an aircraft different?
The camber is on the bottom, like an upside-down airfoil
Creates lift in a downward direction
High pressure above, low pressure on below
What is the purpose of an upside-down airfoil?
Weight wants to pull the airplane nose down, but the nose is being held up by the force down on the tail
Tail makes negative lift (tail down force)
What is a wing flap?
A hinged, pivoted, or sliding airfoil near the trailing edge of the wing
What is a wing flap designed to do?
Increase lift, drag, or both
Used primarily for landing
Increase AOA and camber
What is the primary purpose of high lift devices?
Increase the maximum coefficient of lift of an airplane
Describe a plain flap
A simple hinge causing the entire trailing edge to droop
No “slot” created
Which type of flap is the most effective?
Slotted
Describe a split flap
A flap hinges to the lower portion of the wing open, the trailing edge does not droop
Used for making drag
Not good at producing lift
Describe a slotted flap
The most effective at increasing lift
A hinge moves the flap out down, leaving a gap between the wing and the flap
Greatly increases lift
Drag is slightly higher than a plain flap
Describe a fowler flap
Tucks up inside the wing and extends outward and downward, leaving a gap between wing and flap(s)
The only flap that increases the wing surface area
Called slotted fowler flaps when there are multiple slots
What do leading edge devices do?
Lowers the AOA
Increases camber
Makes a more rounded leading edge
What is aspect ratio?
Span divided by chord
What kind of wings have a higher aspect ratio?
Gliders (longer and thinner)
High aspect ratio produces less _____.
induced drag (smaller wingtip vortexes)
What does it mean to give a wing an “effective aspect ratio”?
To give the wing characteristics of a higher aspect ratio
What does an effective aspect ratio do?
Prevents the airflow from under the wing from rolling off the tip of the wing and creating a rolling vortex by making the wing seem to have a higher aspect ratio
What are some things that can give a wing an effective aspect ratio?
Drooped wing tips
Fuel tanks
Missile launchers
Winglets/Sharklets
Forward swept wings
What do winglets and sharklets do?
Reduce induced drag
Taking away drag increases thrust
What is the difference between winglets and sharklets?
Nothing but the company that uses them (Airbus versus Boeing)
What are the pros of combining a taper in thickness with a taper in planform?
Maximum CL is greater
They offset each other’s negative effects and both add to the maximum CL*
What is Mean Aerodynamic Chord?
Finds the chord length of a non-rectangular wing
(Chord root + Chord tip) /2
