The process of Boeing-747
The Pratt & Whitney JT9D high-bypass turbofan engine was developed for the 747.One of the principal technologies that enabled an aircraft as large as the 747 to be conceived was the high-bypass turbofan engine. The engine technology was thought to be capable of delivering double the power of the earlier turbojets while consuming a third less fuel. General Electric had pioneered the concept but was committed to developing the engine for the C-5 Galaxy and did not enter the commercial market until later. Pratt & Whitney was also working on the same principle and, by late 1966, Boeing, Pan-Am and Pratt & Whitney agreed to develop a new engine, designated JT9D, to power the 747.
The project was designed with a new methodology called fault tree analysis, which allowed the effects of a failure of a single part to be studied to determine its impact on other systems. To address concerns about safety and flyability, the 747’s design included structural redundancy, redundant hydraulic systems, quadruple main landing gear and dual control surfaces. Additionally, some of the most advanced high-lift devices used in the industry were included in the new design, in order to allow it to operate from existing airports. These included leading edge flaps running almost the entire length of the wing, as well as complex three-part slotted flaps along the rear. The wing’s complex three-part flaps increase wing area by 21% and lift by 90% when fully deployed compared to their nondeployed configuration.
How airplanes works
Lift is a force on a wing (or any other solid object) immersed in a moving fluid, and it acts perpendicular to the flow of the fluid. (Drag is the same thing, but acts parallel to the direction of the fluid flow). The net force is created by pressure differences brought about by variations in speed of the air at all points around the wing. These velocity variations are caused by the disruption and turning of the air flowing past the wing. The measured pressure distribution on a typical wing looks like the following diagram:
- A. Air approaching the top surface of the wing is compressed into the air above it as it moves upward. Then, as the top surface curves downward and away from the airstream, a low-pressure area is developed and the air above is pulled downward toward the back of the wing.B. Air approaching the bottom surface of the wing is slowed, compressed and redirected in a downward path. As the air nears the rear of the wing, its speed and pressure gradually match that of the air coming over the top. The overall pressure effects encountered on the bottom of the wing are generally less pronounced than those on the top of the wing.C. Lift componentD. Net forceE. Drag component
When you sum up all the pressures acting on the wing (all the way around), you end up with a net force on the wing. A portion of this lift goes into lifting the wing (lift component), and the rest goes into slowing the wing down (drag component). As the amount of airflow turned by a given wing is increased, the speed and pressure differences between the top and bottom surfaces become more pronounced, and this increases the lift. There are many ways to increase the lift of a wing, such as increasing the angle of attack or increasing the speed of the airflow.
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