Does thrust increase lift? Why does thrust decrease with speed? What are the factors affecting thrust? Why does the thrust of a turbojet increase with airspeed? How does humidity affect turbine engine performance? What two factors determine the amount of thrust produced by a propeller?
Which is the greatest force on a propeller? How do you calculate propeller efficiency? How do you increase thrust on a propeller? Which is better a 3 or 4 blade prop? What is the most efficient propeller design? How do you fly a constant speed propeller? Why did the B 36 have pusher props? Are any B still flying? Was the B used in Korea?
Which is bigger B 52 vs b36? How many b52 are still flying? What is the largest bomber ever built? How many b29 are still flying? How many b52 bombers were shot down in Vietnam? The air resists the motion of the aircraft and the resistance force is called drag.
Drag is directed along and opposed to the flight direction. Like lift, there are many factors that affect the magnitude of the drag force including the shape of the aircraft, the "stickiness" of the air, and the velocity of the aircraft. Like lift, we collect all of the individual components' drags and combine them into a single aircraft drag magnitude.
And like lift, drag acts through the aircraft center of pressure. Thrust To overcome drag, airplanes use a propulsion system to generate a force called thrust. The direction of the thrust force depends on how the engines are attached to the aircraft. In the figure shown above, two turbine engines are located under the wings, parallel to the body, with thrust acting along the body centerline. On some aircraft, such as the Harrier, the thrust direction can be varied to help the airplane take off in a very short distance.
The magnitude of the thrust depends on many factors associated with the propulsion system including the type of engine , the number of engines, and the throttle setting. For jet engines, it is often confusing to remember that aircraft thrust is a reaction to the hot gas rushing out of the nozzle. The hot gas goes out the back, but the thrust pushes towards the front.
The motion of the airplane through the air depends on the relative strength and direction of the forces shown above. If the forces are balanced, the aircraft cruises at constant velocity. If the forces are unbalanced, the aircraft accelerates in the direction of the largest force.
Note that the job of the engine is just to overcome the drag of the airplane, not to lift the airplane. A 1 million pound airliner has 4 engines that produce a grand total of , of thrust.
Otherwise, if the AOA is decreased too fast, the aircraft will descend, and if the AOA is decreased too slowly, the aircraft will climb. As the airspeed varies due to thrust, the AOA must also vary to maintain level flight. At very high speeds and level flight, it is even possible to have a slightly negative AOA. As thrust is reduced and airspeed decreases, the AOA must increase in order to maintain altitude. Any further increase in the AOA will result in the wing stalling. Therefore, extra vigilance is required at reduced thrust settings and low speeds so as not to exceed the critical angle of attack.
If the airplane is equipped with an AOA indicator, it should be referenced to help monitor the proximity to the critical AOA. Some aircraft have the ability to change the direction of the thrust rather than changing the AOA. This is accomplished either by pivoting the engines or by vectoring the exhaust gases. It opposes or overcomes the force of drag. As a general rule, it acts parallel to the longitudinal axis.
However, this is not always the case, as explained later. Drag—a rearward, retarding force caused by disruption of airflow by the wing, rotor, fuselage, and other protruding objects. As a general rule, drag opposes thrust and acts rearward parallel to the relative wind. Lift—is a force that is produced by the dynamic effect of the air acting on the airfoil, and acts perpendicular to the flight path through the center of lift CL and perpendicular to the lateral axis.
In level flight, lift opposes the downward force of weight. Weight—the combined load of the aircraft itself, the crew, the fuel, and the cargo or baggage. Weight is a force that pulls the aircraft downward because of the force of gravity. Relationship of forces acting on an aircraft. Force vectors during a stabilized climb. Make flight training easier, less expensive, and more enjoyable.
Master all the checkride maneuvers. Learn the "stick and rudder" philosophy of flying. Prevent an airplane from accidentally stalling or spinning. Land a plane quickly and enjoyably.
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