Private Pilot Tutorial 4: Aerodynamics of Flight (Part 1 of 3)

tutorial for aerodynamics of flight this training tutorial will discuss aerodynamics flight in order for a pilot to safely execute maneuvers in flight it is important to understand the aerodynamic forces acting on an aircraft in flight the four forces acting on an aircraft in straight and level unaccelerated flight are thrust drag lift and weight thrust is the forward force produced by the powerplant propeller or rotor and is opposed by drag drag is the rearward retarding force caused by air that has been disrupted by the wings rotor fuselage and other protruding objects and opposes thrust weight is the combined load of the aircraft itself the crew the fuel and the cargo or baggage weight pulls the aircraft downward because of the force of gravity and is opposed by lift lift opposes the downward force of weight lift is produced by air flowing over the airfoil and acts perpendicular to the flight path through the center of lift in Strait level and unaccelerated flight the sum of the forces acting on the aircraft is zero this is for the most part true during climb and descending flight but things are a bit more complicated anytime the flight path of the aircraft is not horizontal lift weight thrust and drag vectors must each be broken down into two components for example during a glide part of the weight of the aircraft points forward and therefore acts as thrust or as the picture shows during a climb the weight can oppose lift and also thrust a pilot may hold an aircraft in straight and level flight at many different air speeds the pilot needs to coordinate the angle of attack with the speed of the aircraft for example if the plane is flying at a high rate of speed the angle of attack can be relatively low however if the rate of speed is low then the pilot must have a higher angle of attack this is caused by the amount of lift produced by the wings of the aircraft the higher the angle of attack the more lift is provided from the wing if a pilot can maintain a high angle of attack and a coordinated thrust level the aircraft can fly straight and level at low speeds level flight at even slightly negative angle of attack is possible at very high speed certain aircraft have the ability to change their direction of thrust rather than change their angle of attack such as the Harrier Jump Jet on the left and the osprey on the right these aircraft can point their thrust straight up without having to point their nose in that direction the Harrier jet uses vents to accomplish this and the Osprey can rotate its propellers to point up this allows each aircraft to hover over the ground or fly straight and level very slowly drag is the force that resists movement of an aircraft through the air there are two basic types parasitic drag and induced drag the first is called parasite because it in no way functions to aid flight while the second induced drag is a result of an airfoil developing lift parasite drag is any drag that is not caused directly from the aircraft producing lift it is broken down into three categories form drag interference drag and skin friction form drag is a drag that is caused by things like the cowling antennas and the aerodynamic shape of other components how quickly air flow rejoins itself is determined by the shape of the object it's flowing around as the picture on the left shows the best way to reduce form drag is to streamline as many of the aircraft components as possible interference drag comes from the intersection of air streams that creates eddy currents turbulence or restricts smooth airflow for example the picture on the right shows the intersection of the wing and the fuselage at the wing root this area has significant interference drag air flowing around the fuselage collides with air flowing over the wing merging into a current of air different from the two original currents skin friction drag comes from the surface of the aircraft not being completely smooth even though a surface may look smooth it has a rough ragged surface when viewed under a microscope this non smooth surface causes any interruption in air flow and more drag induced drag is the second basic type of drag when an airfoil produces lift there is always drag this drag comes from wingtip vortexes when the aircraft is viewed from the tail these vortices circulate counterclockwise about the right tip and clockwise about the left tip bearing in mind the direction of rotation of these vortices it can be seen that they induce an upward flow of air beyond the tip and a down wash flow behind the wings trailing edge this induced down wash has nothing in common with the down wash that is necessary to produce lift it is in fact the source of induced drag this down wash over the top of the airfoil at the tip has the same effect as bending the lift vector rearward therefore the lift is slightly aft of perpendicular to the relative wind creating a rearward lift component this is induced drag drag is the price paid to obtain lift the lift to drag ratio is the amount of lift generated by a wing or airfoil compared to its drag this also governs the airfoils efficiency aircraft with higher lift drag ratios are more efficient than those with lower lift drag ratios the lift drag ratio is determined by dividing the lift component by the drag component or above by dividing the lift equation by the drag equation L is the lift force and pounds CL is the lift coefficient P is density expressed in slugs per cubic feet V is velocity in feet per second Q is dynamic pressure per square feet and s is the wing area in square feet on the graph to the left the lift curve red reaches its maximum for this particular wing section at 20 degrees angle of attack and then rapidly decreases 15 degrees angle of attack is therefore the stalling angle the drag curve yellow increases very rapidly from 14 degrees angle of attack and completely overcomes the lift curve at 21 degrees angle of attack the lift drag ratio green reaches its maximum at 6 degrees angle of attack meaning that at this angle the most lift is obtained for the least amount of drag any angle of attack the aircraft operates at other than the lift drag max point will cause more drag therefore for the least amount of drag to lift the aircraft must fly with that angle of attack gravity is the pulling force that tends to draw all bodies to the center of the earth the center of gravity may be considered as a point at which all the weight of the aircraft is concentrated if the aircraft were supported at its exact center of gravity it would balance in any attitude this weight force acts downward through the airplane center of gravity in stabilized level flight where the lift force is equal to the weight force the aircraft is in a state of equilibrium and neither gains nor losses altitude if lift becomes less than weight the aircraft loses altitude when lift is greater than weight the aircraft gains altitude the pilot is able to control lift if the control yoke is pushed forward or pulled back the angle of attack changes and therefore the amount of lift changes as well for an aircraft to continue to produce lift the aircraft airfoil must be continually attacking new air on helicopters this is accomplished by the rotating blades in a fixed-wing airplane this is accomplished by the airflow over the wing the lift provided from the wing is proportional to the square of the aircraft's velocity lift and drag also vary directly with the density of the air density is affected by several factors pressure temperature and humidity at an altitude of 18,000 feet the density of the air has 1/2 the density of air at sea level in order to maintain its lift at a higher altitude an aircraft must fly at a greater true airspeed for any given angle of attack warm air is less dense than cool air and moist air is less dense than dry air lift varies directly with the wing area if the wings have the same proportion and airfoil sections a wing with an area of 200 square feet lifts twice as much at the same angle of attack as a wing with an area of 100 square feet for most situations the pilot controls lift and velocity to maneuver an aircraft as stated previously wingtip vortices are caused when the high pressure below the wing attempts to rejoin the low-pressure air around the wingtip causing a downward and outward vortex the above picture is a more detailed diagram of how this process looks on a wing the heavier and slower the aircraft the greater the angle of attack and the stronger the wingtip vortices wingtip vortices lead to a potentially hazardous condition called wake turbulence to avoid wake turbulence avoid flying through another aircraft's flight path rotate prior to the point at which the preceding aircraft rotated when taking off behind another aircraft avoid following another aircraft on a similar flight path at an altitude within a thousand feet and approach the runway above a preceding aircraft's path when landing behind another aircraft and finally touchdown after the point at which the other aircrafts wheels contacted the runway a hovering helicopter generates a downwash from its main rotors similar to the vortices of an airplane pilots of small aircraft should avoid a hovering helicopter by at least three rotor disk diameters to avoid the effects of this downwash wind is also an important consideration when dealing with wake turbulence because it can push around wake turbulence for example if there's a ten knot wind it will push the wake turbulence in the direction of the wind at a rate of 1,000 feet per minute if this is a problem pilots may also wait approximately three minutes for the wake to dissipate ground effect is a phenomenon that allows an aircraft to fly slower than normal a few feet from the ground when an aircraft in flight comes within several feet of the surface ground or water a change occurs in the three-dimensional flow pattern around the aircraft because the vertical component of the air flow around the wing is restricted by the surface this alters the aerodynamics of the wing mainly the fuselage and tail surfaces are also affected but ground effect mainly consists of the aerodynamic characteristics of the wing the reduction of the wingtip vortices due to ground effect alters the lift distribution of the wing and reduces the induced angle of attack and induced drag therefore the wing will require a lower angle of attack in ground effect to produce the same lift the reduction of induced drag due to ground effect means that less power is required to flight a certain speed most of the time ground effect will produce a higher pressure at the static source and the indicated airspeed will be lower than normally required when an aircraft is taking off the reverse happens from landing the aircraft taking off will require an increase in angle of attack to maintain the same lift experienced an increase in induced drag and thrust required experience a decrease in stability and a nose up change in moment and experience a reduction in static source pressure and increase in indicated airspeed this is something to consider on takeoff because it could mean a pilot attempting to take off will feel like the aircraft can lift off the ground prior to the recommended takeoff speed as shown above this could cause the plane to have poor initial climb performance and also in extreme cases prevent the aircraft from becoming airborne entirely axes of an aircraft will be covered more in depth in the flight controls chapter please help us spread the word about pilot training system and we look forward to further servicing your flight training needs

Channel: Pilot Training System

Views: 255,166

Keywords: Pilot, Pilot Training, Flight, Flight Training, Aviation, Aviation Training, Flying, Airplane, Aircraft, Plane, Introduction to Flying, Federal Aviation Administration, FAA, National Transportation Safety Board, NTSB, Aerospace (Industry), Aerospace Engineering (Industry), Private Pilot, Ground School, written, Pilots Handbook of Aeronautical Knowledge, PHAK, Aerodynamics

Id: jl2M9BopgM8

Length: 15min 13sec (913 seconds)

Published: Thu Jul 14 2016