phugoid

The adjective is a learned borrowing from Ancient Greek φῠγή (phugḗ, “fleeing, flight; escape; retreat”) (ultimately from Proto-Indo-European *bʰewg- (“to flee”)) + English -oid (suffix meaning ‘having the likeness of, resembling’, forming adjectives and nouns). The word was coined by the British aerodynamicist and engineer Frederick W. Lanchester (1868–1946) in his book Aerodonetics (1908),^[1] the author mistaking the meaning of φῠγή (phugḗ) to be “flight” in the sense of “the act of flying”:^[2][3] see the quotations.

The noun is derived from the adjective.^[2]

• (Received Pronunciation) IPA^(key): /ˈfjuːɡɔɪd/

• Audio (Southern England):

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• (General American) IPA^(key): /ˈfjuˌɡɔɪd/

• Audio (General American):

  (file)

• Hyphenation: phug‧oid

phugoid (not comparable)

1. (aeronautics, aviation) Of the motion of an aircraft, missile, or other flying object: continuously oscillating in a vertical plane due to the object pitching up and climbing, thus slowing down; then pitching down and descending, thus speeding up.
   • 1908, F[rederick] W[illiam] Lanchester, “The Phugoid Theory—The Equations of the Flight Path”, in Aerodonetics: Constituting the Second Volume of a Complete Work on Aerial Flight , London: Archibald Constable & Co. , →OCLC, § 18 (Introductory), page 37:

     The Phugoid theory deals with the longitudinal stability, and the form and equations of the flight path of an aerodone.

phugoid (plural phugoids)

1. (aeronautics, aviation) The motion of an aircraft, missile, or other flying object continuously oscillating in a vertical plane due to the object pitching up and climbing, thus slowing down; then pitching down and descending, thus speeding up.
   • 1908, F[rederick] W[illiam] Lanchester, “The Phugoid Theory—The Flight Path Plotted”, in Aerodonetics: Constituting the Second Volume of a Complete Work on Aerial Flight , London: Archibald Constable & Co. , →OCLC, § 35 (The Time Period and Form of the Phugoid Path. Special Cases (continued).), page 63:

     As the amplitude of the phugoid is increased beyond the limits of the semicircle, there is a rapid shortening of the time period as shown by the manner in which the time curve falls away almost immediately after that critical form of flight path is passed. […] [I]f we select phugoids of greater and greater velocity, for a given aerodone the form of the tumbler curve approximates more and more closely to a circle of radius ${\displaystyle =2H_{n}}$.

   • 2016 November 2, Rob Taylor, “Malaysia Airlines Flight 370 likely in steep dive before crash”, in The Wall Street Journal‎, New York, N.Y.: Dow Jones & Company, →ISSN, →OCLC, archived from the original on 2023-03-26:

     As well as physical debris, the report drew on recent analysis by Australian defense scientists of burst frequency signals from Flight 370 to satellites that indicated the aircraft had been descending fast, likely in an automated series of swooping dives called fugoids.

• fugoid

• phugoid on Wikipedia.Wikipedia