B-J-J,
I'll try and tackle your drag question. Basically, there are two main types of drag on an aircraft. They are parasite drag and induced drag.
Induced drag is that drag caused by the production of lift. We all know about the pressure differences between the upper and lower surfaces of the wing. The air "spills" over the tips to fill in the void caused by the lower pressure above, thereby creating wingtip vortices. Looking at the wing spanwise (at the tip looking towards the fuselage), as the flow comes up and over the tips, it imparts a downward velocity on the flow leaving the trailing edge. This downward velocity component has the effect of tilting the lift vector rearwards (since lift is perpendicular to the relative wind). So, the lift from the wing now has a vertical component (to offset weight) and a horizontal component opposite the direction of flight. This horizontal component is drag. This drag force is not constant though. It depends on the lift coefficient (angle of attack), the planform shape of the wing, and the dynamic pressure (density and speed) of the airflow. Remember the FAA's "heavy, clean, and slow"? Well, the heavier the aircraft and the slower the airspeed, the higher the AOA will have to be to sustain the necessary lift. Flaps produce vortices of their own that tend to dissipate the main vorticies, so a clean wing will usually produce greater wake turbulence, but it varies with each wing and flap structure. "Ground effect" is something that we're all familiar with. As the aircraft approaches the pavement, the ground tends to dissipate the vortices, causing the lift vector to tilt forward. This reduces the drag and increases the lift at the same time. Some people will tell you that it is a "cushion of air" that causes ground effect. No such thing.
Basically, parasite drag is everything that is not induced drag. One exception is wave drag, but that's for another time. Parasite drag consists of skin friction drag (air viscosity), form drag, and several other types of less-significant drag. Form drag is the result of the shape of the aircraft and the size of the wake it produces. Flat plates held perpendicular to the airflow will exhibit lots of form drag, but very little skin friction drag. The opposite is true if you align the plate with the airflow. The classic example is sticking your hand out the window in a moving car. If your palm is forward, you will have much more drag (mostly form drag) than if your palm is down (mostly skin friction, but a much lesser value).
As a pilot, it's important to know when the aircraft will have the most drag. Parasite drag increases with airspeed (exponentially I might add!) and induced drag will decrease (mostly due to the lower angles of attack found at higher speeds). But as the aircraft slows, the parasite drag will decrease but the induced will increase. When the induced drag far overshadows the parasite drag, this is called the "backside of the power curve", meaning that more power will be required to sustain level flight as the aircraft slows.
Anyway, enough for now. This is a good discussion, let's have some more answers!
SuperD
I'll try and tackle your drag question. Basically, there are two main types of drag on an aircraft. They are parasite drag and induced drag.
Induced drag is that drag caused by the production of lift. We all know about the pressure differences between the upper and lower surfaces of the wing. The air "spills" over the tips to fill in the void caused by the lower pressure above, thereby creating wingtip vortices. Looking at the wing spanwise (at the tip looking towards the fuselage), as the flow comes up and over the tips, it imparts a downward velocity on the flow leaving the trailing edge. This downward velocity component has the effect of tilting the lift vector rearwards (since lift is perpendicular to the relative wind). So, the lift from the wing now has a vertical component (to offset weight) and a horizontal component opposite the direction of flight. This horizontal component is drag. This drag force is not constant though. It depends on the lift coefficient (angle of attack), the planform shape of the wing, and the dynamic pressure (density and speed) of the airflow. Remember the FAA's "heavy, clean, and slow"? Well, the heavier the aircraft and the slower the airspeed, the higher the AOA will have to be to sustain the necessary lift. Flaps produce vortices of their own that tend to dissipate the main vorticies, so a clean wing will usually produce greater wake turbulence, but it varies with each wing and flap structure. "Ground effect" is something that we're all familiar with. As the aircraft approaches the pavement, the ground tends to dissipate the vortices, causing the lift vector to tilt forward. This reduces the drag and increases the lift at the same time. Some people will tell you that it is a "cushion of air" that causes ground effect. No such thing.
Basically, parasite drag is everything that is not induced drag. One exception is wave drag, but that's for another time. Parasite drag consists of skin friction drag (air viscosity), form drag, and several other types of less-significant drag. Form drag is the result of the shape of the aircraft and the size of the wake it produces. Flat plates held perpendicular to the airflow will exhibit lots of form drag, but very little skin friction drag. The opposite is true if you align the plate with the airflow. The classic example is sticking your hand out the window in a moving car. If your palm is forward, you will have much more drag (mostly form drag) than if your palm is down (mostly skin friction, but a much lesser value).
As a pilot, it's important to know when the aircraft will have the most drag. Parasite drag increases with airspeed (exponentially I might add!) and induced drag will decrease (mostly due to the lower angles of attack found at higher speeds). But as the aircraft slows, the parasite drag will decrease but the induced will increase. When the induced drag far overshadows the parasite drag, this is called the "backside of the power curve", meaning that more power will be required to sustain level flight as the aircraft slows.
Anyway, enough for now. This is a good discussion, let's have some more answers!
SuperD