stability assignment

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School

Utah Valley University *

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3530

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Mechanical Engineering

Date

Apr 3, 2024

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docx

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Uploaded by CountRose15161

1. What control surfaces or features of an aircraft’s design provide longitudinal, directional, and lateral stability, respectively? Based on the Pilots Handbook of Aeronautical Knowledge (FAA, 1980) longitudinal stability comes from the elevator or the stabilator. Longitudinal stability is also known as pitch stability and the elevator is activated in an upwards or downwards attitude to combat the tendency of the aircraft to either pitch up or down, given whatever wind circumstances. Directional stability is controlled by the rudder on the vertical stabilizer. The aircraft might be subject to yaw in one direction or the other, like during take-off with the left turning tendencies. We use the rudder, deflecting it into the wind, to correct the yaw and bring the nose back to center. Lateral stability is controlled by the ailerons. The aircraft may be forced to roll one way or the other and to combat this instability we utilize the ailerons by deflecting them into the wind to provide correction. 2. Define Dutch Roll - The most insanely fun time of your life. A dutch roll is defined as a dynamically stable event, and a “series of out of phase turns when the aircraft rolls in one direction and yaws in the other” (Udis, 2015). It is an oscillation of an aircraft yawing and rolling back and forth, never staying in one position. Since it is considered a dynamically stable event, this means that the oscillations do get smaller and smaller over time. 3. Fighter jets are the most common example of a dynamically unstable designed aircraft. These designs have a center of gravity forced more aft making them significantly more unstable. “To make the plane more maneuverable, it had to be made less stable” (Rej, 2023). When the plane is designed to be unstable, movements away from the trimmed state at any given time are accelerated. The quicker response to small inputs on an unstable aircraft helps make larger angle changes, a lot faster. You can give an unstable aircraft a small input and it will react quicker and there will be a larger reaction. This is obviously important in fighter jets, as they need to be able to maneuver quickly to chase moving targets or run from opposing aircraft or missiles. References Pilot’s Handbook of Aeronautical Knowledge . (1980). . United States Department of Transportation, Federal Aviation Administration.

Rej. (2023, May 4). F-16: The first fighter jet designed to be unstable . War Bird Fanatics. https://warbirdfanatics.com/2023/05/04/f-16-the-first-fighter-jet- designed-to-be-unstable/ Udris , A. (2015, July 28). What is Dutch Roll, and how do you prevent it? . Online Flight Training Courses and CFI Tools. https://www.boldmethod.com/learn-to- fly/aerodynamics/dutch-roll/

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