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What is phugoid oscillation?
Phugoid (longer period) oscillations 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.
What causes Phugoid?
The phugoid has a nearly constant angle of attack but varying pitch, caused by a repeated exchange of airspeed and altitude. It can be excited by an elevator singlet (a short, sharp deflection followed by a return to the centered position) resulting in a pitch increase with no change in trim from the cruise condition.
What is spiral dive?
A spiral dive is a steep descending turn with the aircraft in an excessively nose-down attitude and with the airspeed increasing rapidly.
How can Phugoid motion be prevented?
A stable, decreasing phugoid can be attained by building a smaller stabilizer on a longer tail, or, at the expense of pitch and yaw “static” stability, by shifting the center of gravity to the rear.
What is short oscillation?
Oscillation is the process of moving back and forth regularly, like the oscillation of a fan that cools off the whole room, or the oscillation of a movie plot that makes you laugh and cry. Oscillation is from the Latin word oscillare for “to swing,” so oscillation is when something is swinging back and forth.
What is porpoising in aviation?
Landing an aircraft smoothly without waking the passenger in the back seat is one of the greatest feelings as a pilot. Porpoising can be caused by misjudging where the ground is, improper use of trim, forcing the aircraft onto the runway, or letting the nose drop prematurely.
When does the phugoid occur in an airplane?
When it occurs, it is considered a nuisance, and in lighter airplanes (typically showing a shorter period) it can be a cause of pilot-induced oscillation. The phugoid, for moderate amplitude, occurs at an effectively constant angle of attack, although in practice the angle of attack actually varies by a few tenths of a degree.
How long does a phugoid oscillation last on a jet?
A long period oscillation (eg Phugoid) is less dampened, can have periods a minute long (eg on a Jetstream: 40-50 secs) and continues for quite a while unless the pilot intervenes. One notable thing about the phugoig is that the angle of attack of the aircraft towards the airflow remains constant.
What kind of oscillation is porpoising phugoid?
Porpoising could be any up-and-down oscillation, from pilot-induced to anything else really. Phugoid is specifically an up-and-down oscialltion as long-period reaction to a perturbation.
What causes an unstable or divergent phugoid to form?
An unstable or divergent phugoid is caused, mainly, by a large difference between the incidence angles of the wing and tail.