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A diagrammatic representation of a fixed-wing airplane in phugoid. In aviation, a phugoid or fugoid (/ ˈ f juː ɡ ɔɪ d / ⓘ) is an aircraft motion in which the vehicle pitches up and climbs, and then pitches down and descends, accompanied by speeding up and slowing down as it goes "downhill" and "uphill".
The phugoid oscillation is a slow interchange of kinetic energy (velocity) and potential energy (height) about some equilibrium energy level as the aircraft attempts to re-establish the equilibrium level-flight condition from which it had been disturbed.
The motion is accompanied by slight lateral motion of the center of gravity and a more "exact" analysis will introduce terms in etc. In view of the accuracy with which stability derivatives can be calculated, this is an unnecessary pedantry, which serves to obscure the relationship between aircraft geometry and handling, which is the ...
Dutch roll is an aircraft motion consisting of an out-of-phase combination of "tail-wagging" (yaw) and rocking from side to side (roll). This yaw -roll coupling is one of the basic flight dynamic modes (others include phugoid , short period , and spiral divergence ).
[3]: 319 This greatly excited the phugoid motion, [3]: 291 and the aircraft pitched up, before pitching back down after power was reduced. When power was added again, the aircraft rapidly pitched up to 40°, and the airspeed dropped down to 108 knots (200 km/h; 124 mph) at 6:49:30 p.m., [ 3 ] : 1–6, 291 briefly stalling at 9,000 feet (2,700 m).
In flight dynamics, longitudinal stability is the stability of an aircraft in the longitudinal, or pitching, plane.This characteristic is important in determining whether an aircraft pilot will be able to control the aircraft in the pitching plane without requiring excessive attention or excessive strength.
This is to manage costs, but it also allows for simplicity of control by unsophisticated users of all ages. The downside of lack of elevator control is a tendency for the airplane to phugoid. To damp the phugoid oscillation naturally, the planes are designed with high drag which reduces flight performance and flying time.
Phugoid mode and "porpoising" mode are different ones. The first is a long period one, and the second is a short period movement as the change in AoA is. The airplane has three modes of oscillation.