Fowler Flaps and High Wings

Ophir · December 11th, 2003, 15:29

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 · December 11th, 2003, 15:54

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 · December 11th, 2003, 15:57

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 · December 11th, 2003, 17:05

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 · December 11th, 2003, 17:16

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 · December 12th, 2003, 07:25

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 · December 12th, 2003, 08:35

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 · December 12th, 2003, 12:34

[ 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.

sorrygottarunway · December 13th, 2003, 23:49

yeah thats what I meant, the change in the chord line as the trailing edge of the wing "folds down"

EatSleepFly · December 14th, 2003, 18:03

Yeah, I know. I was referring to ERAU's post.

December 11th, 2003, 15:29	#1
Ophir Senior Member Join Date: Mar 2002 Location: was Ophir, CO, now in SLC! Posts: 1,477	Fowler Flaps and High Wings 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????

December 11th, 2003, 15:54	#2
E_Dawg Moderator Join Date: Apr 2002 Location: chicago Posts: 4,170	Re: Fowler Flaps and High Wings 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.

December 11th, 2003, 15:57	#3
Ralgha Senior Member Join Date: Dec 2003 Location: Fresno, CA Posts: 912	Re: Fowler Flaps and High Wings 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.

December 11th, 2003, 17:05	#4
Ophir Senior Member Join Date: Mar 2002 Location: was Ophir, CO, now in SLC! Posts: 1,477	Re: Fowler Flaps and High Wings 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.

December 11th, 2003, 17:16	#5
E_Dawg Moderator Join Date: Apr 2002 Location: chicago Posts: 4,170	Re: Fowler Flaps and High Wings 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

December 12th, 2003, 07:25	#6
sorrygottarunway Senior Member Join Date: Oct 2003 Location: DXR, Connecticut Posts: 1,170	Re: Fowler Flaps and High Wings 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.

December 12th, 2003, 08:35	#7
ERAU_Intern Junior Member Join Date: Apr 2003 Location: Knoxville, Maryland Posts: 244	Re: Fowler Flaps and High Wings 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.

December 12th, 2003, 12:34	#8
EatSleepFly Old Skool Join Date: Dec 2002 Location: ?? Posts: 4,600	Re: Fowler Flaps and High Wings [ 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.

December 13th, 2003, 23:49	#9
sorrygottarunway Senior Member Join Date: Oct 2003 Location: DXR, Connecticut Posts: 1,170	Re: Fowler Flaps and High Wings yeah thats what I meant, the change in the chord line as the trailing edge of the wing "folds down"

December 14th, 2003, 18:03	#10
EatSleepFly Old Skool Join Date: Dec 2002 Location: ?? Posts: 4,600	Re: Fowler Flaps and High Wings Yeah, I know. I was referring to ERAU's post.

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