PHAK 5: Aerodynamics of Flight Flashcards
The four forces acting on an aircraft in straight-and-level,
unaccelerated flight are…
- Thrust
- Drag
- Lift
- Weight
What is thrust?
- Forward force produced by the powerplant/propeller or rotor.
- As a general rule, it acts parallel to the longitudinal axis. However, this is not always the case, as explained later.
What is drag?
- Rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects.
- As a general rule, drag opposes thrust and acts rearward parallel to the relative wind.
What is lift?
Force that is produced by the dynamic effect of the air acting on the airfoil, and acts perpendicular to the flight path through the CL and perpendicular to the lateral axis.
What is weight?
- Combined load of the aircraft itself, the crew, the fuel, and the cargo or baggage.
- Weight is a force that pulls the aircraft downward because of the force of gravity.
- It opposes lift and acts vertically downward through the aircraft’s CG.
In steady flight, what is the sum of thrust, drag, lift, and weight?
Zero
It does not mean the four forces are equal. It means the opposing forces are equal to, and thereby cancel, the effects of each other.
The sum of all upward components of forces (not just lift) equals the sum of all…
In straight, level, unaccelerated flight.
downward components of forces (not just weight)
The sum of all forward components of forces (not just thrust) equals the sum of all…
In straight, level, unaccelerated flight.
backward components of forces (not just drag)
In climbs and slow flight a portion of thrust is directed…
Upward and acts as if it were lift
In climbs and slow flight a portion of weight is directed…
Backward and acts as if it were drag
Relationship of forces acting on an aircraft.
What is 1?
Thrust
Relationship of forces acting on an aircraft.
What is 2?
Lift
Relationship of forces acting on an aircraft.
What is 3?
Drag
Relationship of forces acting on an aircraft.
What is 4?
Weight
Force vectors during a stabilized climb.
What is 1?
Flight path
Force vectors during a stabilized climb.
What is 2?
Lift
Force vectors during a stabilized climb.
What is 3?
Relative wind
Force vectors during a stabilized climb.
What is 4?
Thrust
Force vectors during a stabilized climb.
What is 5?
Center of lift (CL)
Force vectors during a stabilized climb.
What is 6?
Center of gravity (CG)
Force vectors during a stabilized climb.
What is 7?
Component of weight opposed to lift
Force vectors during a stabilized climb.
What is 8?
Rearward component of weight
Force vectors during a stabilized climb.
What is 9?
Drag
In glides, a portion of the weight vector is directed along the…
forward flight path and, therefore, acts as thrust.