Unique Aerodynamic Characteristics of an Airplane - Essay Sample

A fixed- wing aircraft such as the airplane is an aircraft that uses wings to fly by generating lift from the shape of the wings and the automobiles forward airspeed. Fixed-wing aircrafts are different from rotary-wing crafts due to the fact that in rotary-wing aircrafts, the wings are mounted on a spinning shaft, forming a rotor thus flapping like the birds (Mooij, 2013). Airplanes have very unique characteristics that that enable them to fly and maintain balance in the air.

Is your time best spent reading someone else’s essay? Get a 100% original essay FROM A CERTIFIED WRITER!

Order now

To efficiently predict airfoil characteristics, it is important to analyze the experimental data to correctly determine the characteristics. Theoretically, conditions that affect an incompressible flow include the airfoil thickness ratio and the trailing edge angle (Xu & Wang, 2016). In the practical sense however, the factors influencing the boundary layer include the surface curvature, roughness or smoothness of the surface, the sharpness of the leading edge and finally the pressure gradients; all these factors significantly reduce the section lift-curve. Most airplanes are built with both horizontal and vertical stabilizers in the shape of an airfoil to stabilize the plane. Airplanes have an angle of attack which creates an aerodynamic force normal to the flow (Stengel, 2015). The shape of airfoils enables them to the required amount of lift, lessening the drag. The different airfoil designs play major roles in aerodynamics. At zero angle of attack, asymmetric airfoils can still generate lift while the symmetric airfoils are best suited for frequent inverted flight. Subsonic airfoils are characterized by a rounded leading edge that is naturally insensitive to the angle of attack (Mooij, 2013). Supersonic airfoils are however angular in shape and have sharp leading edges that are sensitive to the angle of attack.

The lift and drag forces are types of aerodynamic forces which greatly depend on the velocity of the flight, air conditions and the size and shape of the aircraft. While lift is the force perpendicular to the path of the flight, drag is however the force that moves along the direction of the flight path. The efficiency of an airplane is measured by the ratio of the lift force to the drag force. If the airplane produces a higher amount of lift as compared to the drag force, then the plane will have a large L/D ratio. Lift- to- drag ratios are mainly determined by calculations, flight experimentation tests and also testing in a wind tunnel (Xu & Wang, 2016). During cruise conditions, the lift force are usually equal to the weight hence the airplane can accommodate a large load while the thrust is equal to a drag during cruise conditions. Therefore, an aircraft requires a low thrust during a low drag condition (Stengel, 2015). The airplane is designed to produce a higher lift to drag ratio since the required lift is usually dependent on the aircrafts weight hence producing such a lift with a corresponding lower drag which saves fuel for the aircraft, improves the ease of climbing and produces an efficient glide ratio.

The main difference between a jet and a propeller is the engine structure. Turbo jet engines have enough power to generate the required thrust while burning large amounts of fuel during the process. Propeller engines are however best suited low flight speeds hence consuming fuel efficiently since they use most of the energy accelerating air. The two types of aircrafts also differ in terms of the distance covered. Propellers are best suited to cover shorter distances due to their ability to fly efficiently at lower speeds (Mooji, 2013). Their small size nature increases the rental opportunities for these planes especially from people purchasing private planes. Jets however fly over long distances and also accommodates many people. Private jets are more preferable for a time conscious person because of their speed and their ability to cover long distances (McRuer, Graham & Ashkenas, 2014). Propellers and jet are however similar due to the fact that they both have dimensionless coefficients used to determine their efficiency in terms of flight velocity. Both the performance of a jet and a propeller can be predicted using the small scale wind tunnel.

The low speed flight characteristic in an airplane is characterized by three pure and one impure stalling characteristic. A steady turbulent boundary- layer beginning at the trailing edge moving forward with a continuous increase in the angle of attack characterizes the trailing-edge stall. It mainly occurs on wings that have a more than 12 percent thickness. This type of stall also has a gradual rounding effect on the lift and curves the moment. A sudden local separation of flows close to the leading edge characterizes the leading-edge stall (Xu & Shi, 2015). The pitching moment curves and the lift for this separation pattern depicts a negligible variation in the lift-curve slope preceding the maximum lift and a sudden, large variation in lift after attaining the maximum lift. The thin-airfoil stall is whereby the laminar flow is separated from the leading edge giving room for a turbulent reattachment at a specific point along the flow which moves gradually downstream. The stall causes a general rounded lift-curve (Stengel, 2015). The combined trailing-edge and the leading-edge however can either produce a semi-rounded or a sharp lift-curve leading to a sharp and an abrupt decrease in lift.

It is important for pilots to determine control responses for the specific airplane they are using. They should be aware of what to do during climbs, takeoffs and landing when flying the planes at lower speeds to avoid stalls. During a specific airspeed, it is important to maintain a sufficient lift and ample control of the airplane during performance maneuvers. A minimum flight speed whereby the angle of attack is increased or the load factor may cause a sudden stall. Maneuver performance depends on a variety of factors such as the maneuvering load forced by turns, critical airspeeds and the location of center of gravity of the airplane (Mooji, 2013). When maneuvering at low flight speeds, it is important to take into consideration the outside visual reference and the indications on the instrument such as altitude and airspeed. When losing control of the airspeed, the plane should take control of the position of the centre of gravity to maintain altitude.

After stabilization of the power and the airspeed, turns maybe practiced to determine the characteristics of the airplanes control at minimal flight speeds.

The longitudinal axis of an airplane is usually a straight line passing through the cone of the aircraft. The center of gravity of the aircraft therefore lies either below or above the line. The lateral axis is however parallel to the aircrafts wings and lies along the crafts center of gravity. The aircraft, as controlled by elevators, pitches around the created axis (McRuer, Graham & Ashkenas, 2014). The axis perpendicular to the geometric plane created by both the lateral and longitudinal axes is known as the vertical axis. The linked set of surfaces causes rotation about one axis. However, stability is achieved as a result of two surfaces whereby one is in charge of moving the end points of the axis up and down according to the position of the aircraft. Therefore, provision of lateral rotation so that ailerons can achieve longitudinal stability is as a result of elevators. A plane is said to be vertically stable if it is stable both longitudinally and laterally (Xu & Shi, 2015). The plane may however be stable but in the direction hence it is important to consider the directional stability which maintains the longitudinal axis in a given direction along the geometric plane that had been formed by both the longitudinal and lateral axes. The rudder is therefore in charge of providing directional stability and controlling the yaw. It is also important to consider the aircrafts weight and center of gravity when analyzing stability. Most planes are stable when the center of gravity lies specifically on the center of the lift.

Early experimental crafts were fixed with turbojets to lower the speed of flight and a rocket engine to increase the speed of flight. Turbofans were later fitted with afterburners to make the flight speed supersonic and increase fuel efficiency by passing cold air in the engine area. Turbojet engines are however more desirable compared to the low bypass turbofans because when they reach supersonic speeds, they produce less nacelle drag. It is also important to limit the span of the wings to lower the drag effect which might lead to the reduction of the aerodynamic efficiency when flying at a lower speed (Mooji, 2013). For a supersonic aircraft, the aerodynamic design must be able to accommodate both ends of speed range since they land and take off at very low speeds. Using a variable-geometry wing has helped in solving the problem because of its ability to spread for low-speed and rises sharply backwards for a supersonic flight. This method is however not commonly used since it variates the longitudinal trim and also adds cost. The best method for the problem is the delta-wing design which is capable of attaining a high angle of attack during low speeds and is able to generate a vortex which increases lift thus lowering the landing speed (Stengel, 2015). During air flows, heat is generated by friction over the aircraft. This is because most supersonic aircrafts have been designed using aluminum alloys due to their cheap prices and the ease of using them but these alloys quickly loses their strengths at higher temperatures. Most supersonic aircrafts are designed to fly at subsonic speeds, exceeding the speed of sound only for a short period. The supersonic airlines designed to fly continuously at high speeds exceeding the speed of light and thus experience severe problems related to the designs.

References

McRuer, D. T., Graham, D., & Ashkenas, I. (2014). Aircraft dynamics and automatic control. Princeton University Press.

Mooij, H. A. (2013). Criteria for Low-Speed Longitudinal Handling Qualities: of Transport Aircraft with Closed-Loop Flight Control Systems. Springer Science & Business Media.

Stengel, R. F. (2015). Flight dynamics. Princeton University Press.

Xu, B., & Shi, Z. (2015). An overview on flight dynamics and control approaches for hypersonic vehicles. Science China Information Sciences, 58(7), 1-19.

Xu, Z., Yue, T., & Wang, L. (2016, August). Dynamic characteristics analysis for oblique wing aircraft. In Guidance, Navigation and Control Conference (CGNCC), 2016 IEEE Chinese (pp. 1039-1044). IEEE.