Aerodynamic term I had not heard of until now

AggieMike88

AggieMike88

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The original "I don't know it all" of aviation.
Studying for CFI Written.... New word is "Phugoid"

Wikipedia explanation: https://en.wikipedia.org/wiki/Phugoid

A phugoid or fugoid /ˈfjuːɡɔɪd/ 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". 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.​


Test question was

If the airspeed increases and decreases during longitudinal Phugoid oscillations, the aircraft

... is maintaining a nearly constant angle of attack​
 
hmm can’t say I have either.
 
Yep the phugoid mode. It is a dynamic mode (dynamic stability). Learned about it in my Aerosytem Dynamics class.

Phugoid Mode
Short Period Mode
Dutch Roll
etc

It's been several years now, but I remember having to calculate stability matrices, eigen vectors, etc, which I guess mathematically described the dynamic stability of an aircraft. I don't remember much anymore though :(

The PHAK doesn't discuss Phugoid or Short Period modes. At least not in Chapter 5.
 
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That was the "Scientificy" word Jim Campbell used in every flight review of every aircraft he tested or claimed to test. I got bored with it 20+ years ago.
 
It's an engineering term that does not belong on a pilot's exam in my opinion. I was flustered with the IR written's obtuse questions, especially with the questions that had more than one correct answer where you had to select the answer that was "more correct".... smh. The material is difficult enough without trying to get slick with the questions.
 
At least I haven't yet seen "ahenway"
 
Like you, I had never heard of it before I started studying for the CFI written.
 
kath said:
Like you, I had never heard of it before I started studying for the CFI written.
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Might make for an interesting bumper sticker....

"Ask me about my Phugoid"

"I'm proud of my honors Phugoid"

"Don't laugh, it's Phugoid"​
 
PaulS said:
It's an engineering term that does not belong on a pilot's exam in my opinion. I was flustered with the IR written's obtuse questions, especially with the questions that had more than one correct answer where you had to select the answer that was "more correct".... smh. The material is difficult enough without trying to get slick with the questions.
Click to expand...

A CFI candidate is supposed to have a more in-depth level of knowledge than the average pilot, hence this question appearing on the CFI written.

That being said even the PPL writtens have gotten a little ridiculous with their questions. I have had several students recently coming back scratching their head on certain questions with multiple correct answers, or calculation questions where after doing all the math we came up with 120 for example, but the given answers are 118 and 122. Splitting hairs when having to use performance grid charts or sectionals.
 
I had a Cessna Cardinal that had significant, persistent phugoid oscillations. Bothered me for 2 years before a CFI taught me the term and how to handle them. Flying became much easier.


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...and the difference between that p thing and PIOs is?


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Maybe redo this well known SNL sketch...

140208_2723475_Nude_Beach_anvver_1.jpg


And substitute Phugoid for that.... other word

Bob: Hey guys!

Jack: Hey, Bob! Hey, your Phugoid looks great today.

Bob: Thanks, Jack. Yours too.

Ted: Hey, Bob.

Bob: Hey, Ted. How’s your Phugoid?

Ted: Not bad.

Bob: Good. Hey, I’d like you guys to meet Doug.

Jack: Hey, Doug.

Doug: Hey, guys.

Jack: Hey, pretty small Phugoid there, Doug.

Doug: Huh?

Ted: Yeah. You could pick a lock with that Phugoid.​
 
Bill Watson said:
...and the difference between that p thing and PIOs is?
Click to expand...

A PIO is you (the pilot) destabilizing things or amplifying the oscillations.

The phugoid is a measure of the airplane's own ability to damp out off-speed or off-pitch excursions (generally measured from when a steady state condition was disturbed). So, you're cruising along all trimmed out and you pull the yoke to a pitch-up which costs the airplane 10 knots. How many climb/descent cycles will it take until the airplane returns to steady-state?
 
giphy.gif


Nauga,
and the reason your slick airplane is a b***h to trim in cruise
 
Hi everyone.
Some of you guys have too much free time on your hands, but it can be fun to read.
Phugoid / slow oscillations are very likely the one things that we, pilots, encounter more often that anything in flying, and never really pay attention to it. Every time you level off, from climbs, descents.. there is this oscillation that occurs until the acft stabilizes / settles.
You can demonstrate it by trimming the acft and pitch up, pull up on the stick, and let go, observe, how the acft will oscillate, nose up, down, for a while and eventually stabilize. That also occurs when you get a gust, and or other external factors affecting the steady state the acft.
 
midwestpa24 said:
A CFI candidate is supposed to have a more in-depth level of knowledge than the average pilot, hence this question appearing on the CFI written.

That being said even the PPL writtens have gotten a little ridiculous with their questions. I have had several students recently coming back scratching their head on certain questions with multiple correct answers, or calculation questions where after doing all the math we came up with 120 for example, but the given answers are 118 and 122. Splitting hairs when having to use performance grid charts or sectionals.
Click to expand...

I teach 3 large ground school classes a year. The written test has changed a lot and continues to expand the topics. I blame the FAA’s decision to let the Embury Riddle type schools to influence the bank of test questions. While outdated questions have been purged, other questions beyond the knowledge required for a private pilot have been included.
 
drjcustis said:
I had a Cessna Cardinal that had significant, persistent phugoid oscillations. Bothered me for 2 years before a CFI taught me the term and how to handle them. Flying became much easier.


Sent from my iPad using Tapatalk
Click to expand...

Ah, the good ol' Cardinal Crowhop
 
Clip4 said:
I teach 3 large ground school classes a year. The written test has changed a lot and continues to expand the topics. I blame the FAA’s decision to let the Embury Riddle type schools to influence the bank of test questions. While outdated questions have been purged, other questions beyond the knowledge required for a private pilot have been included.
Click to expand...

One of my recent ones recalled several questions on constant speed propeller operations. It's been nearly 20 years since I took a PPL written, and I don't recall that being on there. I thought that was saved for complex/high performance endorsements.
 
midwestpa24 said:
One of my recent ones recalled several questions on constant speed propeller operations. It's been nearly 20 years since I took a PPL written, and I don't recall that being on there. I thought that was saved for complex/high performance endorsements.
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Not only questions on the CS operations, but the engine performance chart is for CS. Also there is a Vg diagram.
 
Clip4 said:
Not only questions on the CS operations, but the engine performance chart is for CS. Also there is a Vg diagram.
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Next they will be asking them about tailwheels! Oh the humanity!
 
midwestpa24 said:
One of my recent ones recalled several questions on constant speed propeller operations. It's been nearly 20 years since I took a PPL written, and I don't recall that being on there. I thought that was saved for complex/high performance endorsements.
Click to expand...

The CS prop questions on the private pilot airplane test have been there for at least 10 years now. I've always assumed they were included because no endorsement is needed to fly an airplane with a CS prop so a brand new private pilot would be qualified to fly it.
 
mondtster said:
The CS prop questions on the private pilot airplane test have been there for at least 10 years now. I've always assumed they were included because no endorsement is needed to fly an airplane with a CS prop so a brand new private pilot would be qualified to fly it.
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I've flown a square tail 172 with a manifold pressure gage. It was weird not having a prop control or gear lever . . . .
 
Having been formally trained using Aerodynamics for Naval Aviators, phugoid oscillation is one of the first topics covered in the study of Dynamic stability on the pitch axis. It mostly has to do with the ability of a stable system to self-dampen a naturally occurring oscillation. It is not unique to aircraft, by the way...
 
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