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Analysis of the design features of a Boeing 747-8, Calculations of basic Aeronautical Engineering problems with data collected from various sources. An in-depth report on the design analysis of the Boeing 747-8 and its mission. (Venky, 2011. Boeing 747-8)http://2.bp.blogspot.com/-MbLERgS6ZCM/TVqYuazYg5I/AAAAAAAAACA/N3JAXo5nBgY/s1600/boeing%2B747-8.jpg
2. Manufacture and Operation
The manufacturer of the Boeing 747-8 is called The Boeing Company, one of the world's leading companies in aeronautical aircraft manufacturing. It is recognized as a multinational aerospace and defense corporation, the company is segregated into various divisions known as 'Boeing Capital', 'Boeing Commercial Airplanes', 'Boeing Defense, Space & Security', 'Engineering, Operations & Technology' and 'Boeing Shared Services Group' (Wikipedia, 2012. Boeing, 5 Divisions).
The Boeing Company has many manufacturing sites located around America, we are interested in the three major manufacturing sites where they assemble the aircrafts. In 1967 the Boeing 747 jumbo jet was the first to be assembled at the Everett, Washington site. The site at Renton, Washington did not manufacture the Boeing 747 family, instead it manufactures the Boeing 707, 727, 737 and 757. The final major manufacturing site is in South Carolina, here they manufacture parts for the 787 Dreamliner. The major manufacturing site is therefore located in Everett, Washington (Boeing, 2012. Commercial Airplane's).
There is a vast customer base for The Boeing Company, for instance the net orders from 34 customers for 2012 over each aircraft variant is 1056 aircraft. However we are focused on the operators and customers of the Boeing 747-8, according to the data found from Boeing, there are 13 different operators indicated from 2005-2012, ordering two variants of the Boeing 747-8 called the 747-8I and 747-8F. In total there has been 111 aircraft bought and 31 delivered. The operators are passenger airliner companies e.g. Air China, Korean Air, Cathay Pacific Cargo and Dubai Aerospace Enterprise, they will use the aircraft for either transport of passengers and luggage or cargo (Boeing, 2012. Commercial Airplane's).
3. Data Dossier
The following table (Figure 3.1) represents the parameters of the Boeing 747-8, this data is needed further into the coursework in Design Parameters and Variables section to work out basic calculations of Aeronautical Engineering problems with data collected from various sources.
Max Take Off Weight
Max speed (m/s)(or Mach Number)
274.48256 or 0.92 Mach
Altitude for max speed (m)
Typical cruise speed (m/s)(or Mach Number)
254.8128 or 0.855 Mach
Cruise altitude (or service ceiling)(m)
Stall speed (m/s)
Altitude for stall speed (m)
Weight for stall speed (N)
Number of Engines
General Electric GEnx-2B67
Max Thrust (kN) or power (kW) per engine
Altitude for max thrust or power (m)
Figure 3.1 (Boeing, 2012. 747 Family), (Supercritical Simulations Group, 2012. 747-8 QUICK REFERENCE PILOT GUIDE), (Wikipedia, 2012. Boeing 747-8).
4. General Arrangement
In this section I will identify the primary and secondary flight controls of the Boeing 747-8. Aircraft flight controls allow pilots to maneuver in the air and control altitude. There is three axis of motion; these are the lateral, longitudinal and vertical shown in figure 4.1. The lateral axis is coordinated from wing tip to wing tip, when the plane rotates about this axis it is called pitch. The longitudinal axis is directed from the nose to the tail of an aircraft and rotation about this axis is called roll. The vertical axis runs through the aircraft from top to bottom, rotation about this axis is called yaw. The first control surfaces I will look at are the primary flight controls; these are the main control surfaces responsible for the pitch, roll and yaw. Primary controls are usually recognized as hinged or trailing edge surfaces so they can move thus disturbing the air flow over them. Theses surfaces are called the ailerons, elevators and rudder (Wikipedia, 2012, Flight control surfaces).http://avstop.com/ac/flighttrainghandbook/image4js.jpg
Figure 4.1 (Avstop, 2012, Stability and Controllability).
As you can see in figure 4.2 the ailerons are located at the trailing edge of an aircraft towards the wing tips, they are operated in pairs and each one mirroring the others movement. When the pilot wants to roll the aircraft starboard, the right aileron goes up and the left one goes down thus if the pilot wants to maneuver the aircraft port, the left aileron will go up and the right will go down. Each movement will cause the aircraft to roll either positively or negatively (Wikipedia, 2012, Flight control surfaces).
As seen in figure 4.2 there is two elevators located on the trailing edge of the horizontal stabilizers, starboard side and port side. The elevators are operated in a synchronous state so when the pilot wants to maneuver the aircraft up he needs to pull back on his flight control stick, in succession this moves the elevators up. When the elevators are positioned upwards this produces a force acting down on the tail and causes the nose to pitch up. To maneuver the aircraft down the pilot needs to do the exact opposite (Wikipedia, 2012, Flight control surfaces).
Pictured in figure 4.2 the rudder is located on the trailing edge of the vertical stabilizers also known as the fin. The rudder differs from the ailerons and elevators because it is control by the pilots foot controls and not the stick. When the pilot wants to maneuver the aircraft starboard he will need to press on the right foot pedal positioning the rudder starboard and thus deflecting the tail port and the aircrafts nose to yaw starboard. The exact opposite of this would cause the aircraft to yaw port (Wikipedia, 2012, Flight control surfaces).
The second control surfaces I will look at are called the secondary flight controls, these control surfaces are used to adjust the primary flight controls and are also used in landing/take-off of an aircraft. The following surfaces are named spoilers, flaps and slats.
As seen in figure 4.2 the spoilers are located on the wing and in some cases (but not the Boeing 747-8) as an air brake they are located on the fuselage. Spoilers are flat surfaces on the wing and they are positioned perpendicular to the airflow. They provide a quick increase in drag, this are useful for lowering the aircrafts speed before landing. Spoilers are also used on aircraft like gliders that are low drag airplanes; they increase the drag of the gliders so the pilot is able to rapidly decrease altitude without gaining unnecessary airspeed (Wikipedia, 2012, Flight control surfaces).
In figure 4.2 of the Boeing 747-8 the flaps are located on the trailing edge of the wings on the inboard section of the wings. They deflect downwards in order to increase the curvature of the wing and the area thus increasing the maximum lift coefficient of the aircraft and reducing its stall speed. Flaps are deployed at low speeds and high angles of attack, such situations would be landing and take-off (Wikipedia, 2012, Flight control surfaces).
The final control surface located at the leading edge of the wings on figure 4.2. These behave similar to the flaps by effectively increasing the aircrafts wing camber, this allows changes to be made to the lift and also reduce the stalling speed. Slats can be either fixed or retractable (Wikipedia, 2012, Flight control surfaces).
General arrangement drawing
Figure 4.2 (The Unwanted Blog, 2011, 747-8).
5. Design Analysis
Intended Mission Types
The Boeing 747-8 family consists of two variants, the Boeing 747-8 Freighter (747-8F) and the Boeing 747-8 Intercontinental (747-8I). The 747 is a cargo aircraft and it carries half of the world's air freight, the 747-8F was launched by Boeing on November 14th 2005 in an attempt to keep their dominance in world air freight distribution. It was to replace the 747-400ERF as it had a larger pay load but a smaller range, this is important because the 747-8F is required to distribute machinery and indivisible loads. The mission the Boeing 747-8F has been designed for freight flights, we can see this because it is designed with a retractable nose for cargo to be loaded onto and it has been made to carry a heavier pay load to transport bigger objects. The second variant 747-8I is the passenger aircraft and was launched with the 747-8F, it has the typical three classes carrying up to 467 passengers at a range of 15,000 km. The design of the 747-8I helps it to carry 51 more passengers than its predecessors, two more freight pallets and also gives it 26% more cargo volume than the 747-400. If we compare the 747-8I with the 747-400 you will find that it is 30% quieter and 16% more fuel-efficient, this is important for passenger aircraft as it lowers the cost for airlines and passengers to utilize the aircraft. The mission the Boeing 747-8I has been designed for is passenger flights; we can see this in the design process, we would expect to see long distance flights being made with the 747-8I. The two variants have been designed with new engine technology and have been aerodynamically modified to allow longer ranges and increased cargo volume/passenger seats. Lastly there maybe another variant of the 747-8 as the United States Air Force are looking to replace the current Air Force One, Boeing VC-25 with the 747-8. South Korea is also seeking to make a purchase of the 747-8 as their presidential aircraft (Wikipedia, 2012. Boeing 747-8).
6. Design Parameters and Variables
In this section I will calculate the design parameters and variables using basic aeronautical engineering concepts. I will be obtaining results for the aspect ratio, wing loading, thrust loading, air density and speed of sound at cruise altitude, cruise mach number and speed, lift coefficient at cruise, drag coefficient at maximum speed and lift coefficient at stall.
6.1, In order shown above, I need to find the aspect ratio of the Boeing 747-8, to do this I would use equation 1. In order to solve that, what we need to do first is calculate the planform area, this is shown in equation 2.
The variable 'AR' is the aspect ratio, 'S' is the planform area, 'b' is the wingspan, '' is the tip of the chord and '' is the root chord. An illustration in figure 6.1.1 shows how to find the wingspan, tip chord and root chord.
From (Boeing, 2012. 747 Family) the wingspan of the Boeing 747-8 is 68.45m, from (Peter Gilchrist, P.G. 1998. Boeing 747-400) the root chord is equal to 16.56m and the tip chord is equal to 4.06m. We now have our variables, we can plug them into equation 2 to get our planform area.
We can know plug equation 3 into equation 1 to yeild the aspect ratio, thus.
6.2, Secondly in the list I need to find the wing loading at maximum takeoff weight, from (Wikipedia, 2012. Wing Loading) there is a relationship between speed and lift, the faster you go the more lift you get per unit area of wing. This tells us that a wing that is smaller can carry more weight providing the take-off and landing speeds are increased. It making the wing smaller you decrease the aircrafts maneuverability. The standard way to work out the wing loading of an aircraft is the maximum loading take-off weight over the wing area, shown in equation 5.
According to Boeing (Boeing, 2012. 747 Family) the maximum take-off weight is 447,696kg, the wing area is found from the data dossier and its value is , I now need to put these quantities into equation 5, thus.
6.3, Next on the list is calculating the thrust loading at maximum thrust and maximum take-off weight. The thrust loading of a aircraft is a dimensionless product and it is a direct indication of the performance of the engines. This quantity changes with gravity gradient or difference in weight due to consumption of fuel, this type of experiment should be done in a controlled enquirement in order to get dependable results. The way I am going to calculate this is by dividing the maximum thrust in Newtons and the maximum take-off weight in Newtons (Wikipedia, 2012, Thrust-to-weight ratio), this is shown in equation 7.
So from the data dossier we can get a value for the maximum thrust at 296000N and a value for the maximum take-off weight 448000kg, putting these into equation 7 yields.
6.4, This section looks at the air density and speed of sound at cruise altitude, if cruise altitude is unknown then assume it is 80% of the service ceiling. Air density is the mass per unit volume of the earths atmosphere, it is a function of altitude meaning it decreases when altitude increases, this is the same with air pressure. There can be other factors that effect the air density and air pressure such as temperature. With equation 9 one can determine the air density at any altitude and temperature.
The variable '' is the air density, 'p' is the pressure at a given altitude 'h', 'M' is the molar mass of dry air equal to 0.0289644kg/mol, 'R' is the universal gas constant equal to 8.31447J/(molâˆ™K) and 'T' is the temperature at a given altitude 'h' (Wikipedia, 2012, Density of Air). 'M' and 'R' are constants, 'p' and 'T' are variables I have to deterimine. Equations 10 and 11 show how to calculate 'p' and 'T'.
The constants '' is the sea level standard atmospheric pressure equal to 101.325kPa, '' is the sea level standard temperature equal to 288.15K, 'g' is earths gravitational constant equal to 9.80665, 'L' is the temperature lapse rate equal to 0.0065K/m and 'h' is the altitude at cruise equal to 10668m (Wikipedia, 2012, Atmospheric Pressure).
We now have all the information we need to work out equations 10 and 11, thus.
Now that we have calculated our values of 'p' and 'T' we can substitute them into equation 9 and get our air density at cruise altitude, thus.
The speed of sound at cruise altitude can be calculated by equation 15, 'c' is the speed of sound in an ideal gas at cruise altitude, 'Î³' is the adiebatic index equal to 5/3, '' is the air density and 'p' is the pressure (Wikipedia, 2012, Speed of Sound).
Imputting the constants and the answer we got from equation 12 and 14 yeilds.
6.5, This section closly relates to the previous section, I need to find the cruise mach number and speed, to do this I need to know the speed of sound at cruise altitude which I have calculated in equation 16. To calculate the mach number at cruise altitude we use equation 17.
The variable 'M' is the mach number at cruise altitude, the constant 'V' is the velocity of the moving aircraft at cruise altitude equal to 254.8128m/s and the constant 'c' is the speed of sound at cruise altitude equal to m/s. We can input our values, thus.
6.6, Now I need to calculate the lift coefficient of the Boeing 747-8 at cruise, aerodynamicists use the lift coefficient as a way to model complex shapes in wind tunnels in order to theoreticaly design a shape, inlination and some flow conditions on lift. The following equation 19 is a rearranging of the lift equation (NASA, 2012, The Lift Coefficient).
The variable '' is the lift coefficient, 'L' is the lift force, '' is the free stream air density equal to 0.3795999993, '' is the free stream velocity equal to the mach number multiplied by the speed of sound at altitude '' and 'S' is the planform area (Wikipedia, 2012, Lift Coefficient).
Equation 19 can be simplified further to make it easier to calculate. I can see the quantity '' is equal to the dynamic pressure '', this yeilds.
Substiting equation 20 into equation 19,
Now, I have a nice simplified equation for the lift coefficient, however I can do more. If the Boeing 747-8 is at cruise altitude doing steady and level flight then it must mean that the lift force must be equal to the weight force of the aircraft. This means we can replace 'L' with a known quantity 'Weight' in Newtons, thus.
I can now input our constants into equation 22, 'Weight' is equal to 4270295.93585N, '' is to be determined from equation 20 and 'S' the planform area from the data dossier is equal to I need to calculate '' and substitute the answer into equation 24, this is defined in equation 23.
I now have all the quantities to calculate the lift coefficent using equation 22, thus.
At low altitudes you would expect the lift coefficient to be higher than this but because we are at high altitude the dynamic pressure is much highter so lift is lower.
6.7, Now, I need to calculate the drag coefficient of the Boeing 747-8 at maximum speed. Again in fluid dynamics like the lift coefficient, the drag coeffiecient is a dimensionless quantity. Aerodynamicists use the result to determine the drag or resistance of an object in a fluid such as air or water. It is derived from the drag equation, if the coefficient is low or high this governs how aerodynamic or hydrodynmaic the drag is on the object (Wikipedia, 2012, Drag Coefficient). The drag coefficient is defined in equation 26.
The variables '' is the drag coefficient, 'D' is the drag force, 'S' is the planform area equal to and '' is the dynamic pressure, assuming the aircraft is at cruise altitude travelling at maximum speed then we need to calculate '' using equation 23.
From equation 20 we can calculate the dynamic pressure, substituting our value from equation 27.
6.8, The final section I have to calculate the lift coefficient at stall. This is similar to section 6.6, I need to calculate our new dynamic pressure at stall altitude and air density at stall altitude. Firstly I will calculate '' like I did in section 6.4, this means we need to calculate pressure and temperature at stall altitude using equations 10 and 11. Then I will calculate '' using equation 23, this means I need to calculate the speed of sound at stall altitude and the mach number.
Calculating '', In equation 29 all the constants are the same, I only change the altitude 'h'.
= 84318.06712 Pa
I can now use the results from equation 29 and 30 to calculate equation 9 and work out the air density.
Calculating '', using equations 15 and 17 we can solve equation 23.
Using the results from equations 32 and 33 I can input them into equation 23 and I can deterime '', thus.
So I can now calculate my new dynamic pressure '' with the results obtained by equations 31 and 34, I then substitute the findings into equation 20, thus.
Now, I have calculated all the variables we need to solve equation 22 at stall speed and altitude using the results obtained from equations 35, thus.