A phugoid or fugoid /ˈfjuːɡɔɪd/ is an aircraft motion where the vehicle pitches up and climbs, and then pitches down and descends, accompanied by speeding up and slowing down as it goes "uphill" and "downhill." This is one of the basic flight dynamics modes of an aircraft (others include short period, dutch roll, and spiral divergence), and a classic example of a negative feedback system.
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. As speed decays, the nose will drop below the horizon. Speed will increase, and the nose will climb above the horizon. Periods can vary from under 30 seconds for light aircraft to minutes for larger aircraft. Microlight aircraft typically show a phugoid period of 15–25 seconds, and it has been suggested that birds and model airplanes show convergence between the phugoid and short period modes. A classical model for the phugoid period can be simplified to about (0.85 × speed in knots) seconds, but this only really works for larger aircraft.
CITIZENS OF OZ
Ev'ry day, more wicked!
Ev'ry day, the terror grows!
All of Oz is ever on alert!
That's the way with Wicked -
Spreading fear where e'er she goes
Seeking out new victims she can hurt!
A HYSTERICAL WOMAN
Like some terrible green blizzard
Throughout the land she flies:
AN OUTRAGED MAN
Defaming our poor Wizard
With her calumnies and lies!
ALLShe lies!
Save us from the Wicked!
Shield us so we won't be hexed!
Give us warning:
Where will she strike next?
Where will she strike next?
Where will she strike next!?
GLINDA
(spoken) Fellow Ozians - as terrifying as terror is, let us put
aside our panic for this one day: and celebrate!
(sung) Oh what a celebration
We'll have today
CROWDThank Goodness!
GLINDA
Let's have a celebration
The Glinda way!
CROWDThank Goodness!
MORRIBLE
Fin'lly a day that's
Totally Wicked-Witch free!
CROWD
We couldn't be happier
Thank Goodness!
GLINDA
Yes -
We couldn't be happier,
Right, dear?
Couldn't be happier
Right here
Look what we've got
A fairy-tale plot
Our very own happy ending
Where we couldn't be happier -
True, dear?
Couldn't be happier
And we're happy to share
Our ending vicariously
With all of you
He couldn't look handsomer
I couldn't feel humbler
We couldn't be happier
Because happy is what happens
When all your dreams come true!
MORRIBLE(spoken) And Glinda dear, we're happy for you! As Press
Secretary, I have striven to ensure that all of Oz
knows the story of your braverism:
(sung) The day you were first summoned
To an audience with OzAnd although he would not tell you why initially
When you bowed before his throne
He decreed you'd hence be known
As Glinda the Good - officially!
Then with a jealous squeal
The Wicked Witch burst from concealment
Where she had been lurking -surrpetitially!
PEOPLE IN CROWD
I hear she has an extra eye
That always remains awake
I hear that she can shed her skin
As easily as a snake!
I hear some rebel Animals
Are giving her food and shelter!
I hear her soul is so unclean
Pure water can melt her!
FIYERO
What!?
CROWD
Melt her!?
Please - somebody go and melt her!
FIYERO
(spoken) Do you hear that - water will melt her?! People
are so empty-headed, they'll believe anything!
GLINDA
(spoken) Fiyero! Oh - yes, thanks plenty, dearest! He's gone to
fetch me a refreshment. He's so thoughtful that way!
(sung) That's why I couldn't be happier
No, I couldn't be happier
Though it is, I admit
The tiniest bit
Unlike I anticipated
But I couldn't be happier
Simply couldn't be happier
(spoken) Well - not "simply":
(sung) 'Cause getting your dreams
It's strange, but it seems
A little - well - complicated
There's a kind of a sort of : cost
There's a couple of things get: lost
There are bridges you cross
You didn't know you crossed
Until you've crossed
And if that joy, that thrill
Doesn't thrill you like you think it will
Still -
With this perfect finale
The cheers and ballyhoo
Wouldn't be happier?
So I couldn't be happier
Because happy is what happens
When all your dreams come true
Well, isn't it?
Happy is what happens
When your dreams come true!
CROWD
We love you, Glinda, if we may be so frank
GLINDAThank Goodness!
CROWD
For all this joy, we know who we've got to thank:
Thank Goodness!
That means the Wizard, Glinda:
GLINDA
And fiance!
CROWD
They couldn't be goodlier
She couldn't be lovelier
We couldn't be luckier
GLINDA
I couldn't be happier
CROWDThank Goodness:
GLINDA AND CROWD
Today!