Flap angles

I was leafing through the C172N POH for some flap settings yesterday and a
thought occured to me: there was a post here about some verions of the 172
having different full flap angles - some have 40 and 38 degrees. So i
wonder, how do they determine these angles for all flap settings when the
plane's still on the drawing board? Or is it an airfoil design thing? I've
noted that for example the Learjet 45 has first setting at 8 degrees. How do
they determine what is the right angle for each setting?

Triple Delta

"DeltaDeltaDelta" wrote in message
...
I was leafing through the C172N POH for some flap settings yesterday and a

If you read Russian (who knows, you might , check out this paper:
http://www.sla.ru/aviamaster/zipfiles/mexan_wing.pdf
it pretty much answers all your questions and more.

HECTOP
PP-ASEL-IA
http://www.maxho.com
maxho_at_maxho.com

They don't write the POH (AFM) until they've performance tested the
prototypes.

--
John T Lowry, PhD
Flight Physics
5217 Old Spicewood Springs Rd, #312
Austin, Texas 78731
(512) 231-9391

"DeltaDeltaDelta" wrote in message
...
I was leafing through the C172N POH for some flap settings yesterday
and a
thought occured to me: there was a post here about some verions of the
172
having different full flap angles - some have 40 and 38 degrees. So i
wonder, how do they determine these angles for all flap settings when
the
plane's still on the drawing board? Or is it an airfoil design thing?
I've
noted that for example the Learjet 45 has first setting at 8 degrees.
How do
they determine what is the right angle for each setting?

Triple Delta

Another option is to look for an aerodynamics course at a college
near you.

"John T Lowry" wrote in message link.net...
They don't write the POH (AFM) until they've performance tested the
prototypes.

I think he's asking why manufacturers designate the flap settings as
they do (not which setting should be used when). For example, the
G550 has flap settings of 0, 10, 20, and 39; his question is something
like "why 39 and not 40?" or "why do some 172's have 40 degrees of
flap avalible and others only have 38?" Or "why are flap settings not
evenly spaced?" Basically, how do they determine what flap intervals
should be available?

"why do some 172's have 40 degrees of
flap avalible and others only have 38?"


Dunno about 38, but the newer ones have 30, because full 40 degree flaps were
causing problems (which I can't recall) due to poor technique of some sort.

Might have something to do with slips with flaps, IIRC.

Jose

--
(for Email, make the obvious changes in my address)

"Teacherjh" wrote in message
...
Dunno about 38, but the newer ones have 30, because full 40 degree flaps
were
causing problems (which I can't recall) due to poor technique of some
sort.

at 40 deg they sucked for crosswinds and that probably ruined a student or
two complete with cross-control flutter, but were great for "carrier-deck"
landings

HECTOP
PP-ASEL-IA
http://www.maxho.com
maxho_at_maxho.com

On 16 May 2004 02:06:53 GMT, (Teacherjh)
wrote:


"why do some 172's have 40 degrees of
flap avalible and others only have 38?"


Dunno about 38, but the newer ones have 30, because full 40 degree flaps were
causing problems (which I can't recall) due to poor technique of some sort.

Might have something to do with slips with flaps, IIRC.

Jose

Yep, slips with flaps was part of it, but a nose high attitude with
full flaps on go-around is what bit most of the people before they
changed to 30.

z

Jose,

"why do some 172's have 40 degrees of
flap avalible and others only have 38?"


Dunno about 38, but the newer ones have 30, because full 40 degree flaps were
causing problems (which I can't recall) due to poor technique of some sort.

Might have something to do with slips with flaps, IIRC.

I'm always amazed at the amount of misinformation running around here.

Cessna switched to 30 degrees of flap deflection maximum on a heavier
model of the 172 because of rate of climb requirements during a balked
landing under the FARs. The earlier airplanes could meet the rate of
climb with 40 degrees, the newer ones could not, so flap travel was
limited to 30 degrees.

There is no problem with slips with full flaps on a 172, it's another
of aviation's old wives tales.

For an interesting descent rate, fly a Cessna O-1/L-19 (Model 305)
Bird Dog. It had 60 degrees of flaps available.

All the best,
Rick

Rick Durden wrote:

Cessna switched to 30 degrees of flap deflection maximum on a heavier
model of the 172 because of rate of climb requirements during a balked
landing under the FARs.

That's also the reason the 160hp Maule has only 40 degrees of flaps while more
powerful ones have 44 degrees. Even at that, max gross is 200 pounds less than the
180hp version.

George Patterson
I childproofed my house, but they *still* get in.