Lecture 8 Flashcards
Heat Engines
Utilize heat energy to produce the power for propulsion
2 Types of Heat Engines
Reciprocating
Gas Turbine
Engine definition
converts a source of energy into useful work
What is the source of energy in an engine?
Fuel
What is the work the engine produces?
Heat expands gases creating pressure against a piston in a cylinder. The piston causes the crankshaft to rotate
What is energy?
The capacity for doing work
Law of Conservation
Energy cannot be created or destroyed- only changed from one form to another
Kinetic vs Potential Energy
Energy of motion
Energy of position or stored energy
Normal Category G’s
+3.8 G, -1.52 Gs
Non acrobatic operations
Utility Category G’s
+4.4 Gs, -1.76 Gs
limited acrobatic operations
Normal Category G’s
+3.8 G, -1.52 Gs
non acrobatic operations
Positive G Loads
Centrifugal force acts in the same direction as WEIGHT- a downward force on the aircraft = you feel heavier
Negative G Loads
Centrifugal force acts in the opposite direction as WEIGHT- an upward force on the aircraft = you feel lighter
What is a G load?
(weight caused by aerodynamic load)/ (weight of the aircraft)
Static vs dynamic stability
initial response vs long-term response
Positive Static
Returns to initial position
Neutral Static
Stays in new position
Negative Static
Gets worse
Yaw stability
Stability about vertical axis
What maintains yaw stability?
Vertical stabilizer
How do sweptback wings increase yaw stability?
The wing hits the air at an angle, air gets more time to climb up camber, less effective at making lift and thus less induced drag
Pitch stability
Stability around the lateral axis
How does the tail contribute to pitch stability?
Camber on the bottom of the tail uses Bernoulli Effect on the
bottom of the horizontal stabilizer, and creates negative lift
How does negative lift contribute to pitch stability?
Weight / CG wants
to pull the airplane
nose down, but the
nose is being held
up by the force down
on the tail
Primary purpose of high lift devices?
Increase the maximum coefficient of lift of an airplane
Wing flap definition
a hinged, pivoted, or sliding airfoil usually near the trailing edge
What are wing flaps for?
Used for landing. Increases the lift, drag, or both by increasing AOA and camber
Split flap
Hinges a lower part of wing open.
Not good at producing lift, better for drag
Slotted flat
Most effective flap. Lift greatly increased. Drag only slightly. There is a small gap between wing and flap.
Fowler flap
Tucks into wing when retracted. Increases wing SA when deployed.
Leading edge flap
Moves forward and droops down.
Droop leading edge
Lowers AOA and raises camber as the air sees it.
Kreueger leading edge
Lower AOA, increase camber, more rounded leading edge
Aspect ratio equation
S^2/ A
High aspect ratio wings are good because?
produce less induced drag
Effective aspect ratio
gives the wings characteristics of a higher aspect ratio
Elliptical wing
good lift, drag, stall characteristics
Why does elliptical wing have good characteristics?
controls pressure differential and airflow along the span from root to tip
Why are elliptical wings expensive?
each wing station is a unique size
Winglets and sharklets do what?
reduce induced drag
When wing tapers in thickness…
CP moves less when AOA changes
Max Cl greater
Lift curve is greater since all the wing does not reach max lift at once
C(d) is lower (notable at low AOA)
When wing tapers in planform (chord)…
CP moves more when AOA changes
Max Cl greater
C(d) is lower (notable at high AOA)- reduced induced drag
When wing tapers in both thickness and chord…
decreased and increased CP offset one another
Max Cl greater
Cd is low at both high and low AOA
