Discussion
Match each longitudinal characteristic with the mode it belongs to.
List I
A. Period of about ninety seconds
B. Damping ratio near 0.6
C. Large angle-of-attack perturbation
List II
P. Short period
Q. Phugoid
Select the correct match.
Answer: A
A ninety-second period can only be the phugoid; a damping ratio of 0.6 and a large incidence excursion both belong to the short period. So the pairing is A-Q, B-P, C-P. Reading the period as a short-period figure would require the mode to last a minute and a half, which contradicts its name. Attributing a damping ratio of 0.6 to the phugoid overstates its damping by more than a factor of ten. And a large incidence perturbation is precisely what the phugoid does not have, since it proceeds at nearly constant angle of attack.
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