Fowler Flaps and High Wings

Ophir

Well-Known Member
This pertains to Cessnas really. Does anyone know if the pitch up moment that occur with the application of a Fowler flap on a high wing is due to the change in center of pressure along the mean chord or it is due to altering the airflow across the empanage? Or both????
 

E_Dawg

Moderator
Gotta be the altered airflow over the tail because flap application tends to move the CP aft, which would actually cause the airplane to pitch downward.

Flaps are on the aft portion of the wing, and since the flaps are what adds to lift, the total effect is that of moving the CP aft.
 

Ralgha

Well-Known Member
Well, Cessna flaps are actually slotted flaps (says so in the POH!), but they cause the airplane to pitch up because they add drag to the top of the airplane, pullling the nose up.
 

Ophir

Well-Known Member
Both are great responses, thanks guys.

I think it is a combination of both of those reasons huh?

BTW, most Cessnas are Fowler. That is primarily what I fly beginning with a 1969, C182 and I can't remember ever seeing slotted flaps on one.
 

E_Dawg

Moderator
POH says slotted for the 172 and 152; that ASA aircraft book says they're slotted with 'fowler action over the first 10*'.

Depends on who you ask I guess
 

sorrygottarunway

Well-Known Member
oh gosh, the ol' fowler and slotted question... I got that on my checkride "Son, does this plane have slotted or fowler flaps"

Anyway, the pitching moment seems quite plausible due to an increase in drag. By the flaps extending and moving downward, you are increasing effective surface area as well as angle of attack. You'll also get a big increase in lift at the 0-10º transition (wich is why in the 152 10º are used for performance takeoffs).

In any case flaps are cool.
 

ERAU_Intern

New Member
Careful though. You aren't really increasing angle of attack with any type of flap. You are decreasing it. Which is what you WANT to do in order to be able to see the runway on your way down. You don't wanna have to come in Concorde style. What you are increasing is the camber of the airfoil. Which accounts ffor those extra "lifties" you were talking about.
 

EatSleepFly

Well-Known Member
[ QUOTE ]
Careful though. You aren't really increasing angle of attack with any type of flap. You are decreasing it. Which is what you WANT to do in order to be able to see the runway on your way down. You don't wanna have to come in Concorde style. What you are increasing is the camber of the airfoil. Which accounts ffor those extra "lifties" you were talking about.

[/ QUOTE ]

Huh?!?

AOA is the angle between the chord line and the relative wind. The chord line is the imaginary line running from leading to trailing edge of an airfoil. If you extend flaps, you change the position of the chord line such that you are increasing the AOA. Basic aerodynamics.
 
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