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RE: Flaps
Actually flaps are extended for takeoff and landing, and retracted for level flight. I believe that there are at least four "notches" of flaps: 5 degrees, 10 degrees, 15 degrees and 20 degrees. I believe the first extention of flaps occurs a few miles from touchdown along with the landing gear.
RE: Flaps
There are four types of flaps: plain, split, Fowler, and slotted.
The plain flap is a section of the trailing edge of the wing is rotated downward. This is the kind of flap on DC9s.
The split flap is the underside of the wing trailing edge is rotated downward. This is the kind of flap that is on DC-3s.
The Fowler flap is a section of the wing trailing edge that extends rearward as it rotates downward. This kind of flap is on DeHavilland Dash 8s.
The slotted flap, sometimes also referred to as a slotted Fowler flap, is a multi section piece of the trailing edge that extends rearward as it rotates downward. The multiple sections separate as the flap extends forming slots to improve the airflow. This kind of flap is typical on all Boeing jets since the 727 with the exception of the 747SP. The 707s and 720s were built with plain flaps and the 747SP had Fowler flaps.
The plain flap is a section of the trailing edge of the wing is rotated downward. This is the kind of flap on DC9s.
The split flap is the underside of the wing trailing edge is rotated downward. This is the kind of flap that is on DC-3s.
The Fowler flap is a section of the wing trailing edge that extends rearward as it rotates downward. This kind of flap is on DeHavilland Dash 8s.
The slotted flap, sometimes also referred to as a slotted Fowler flap, is a multi section piece of the trailing edge that extends rearward as it rotates downward. The multiple sections separate as the flap extends forming slots to improve the airflow. This kind of flap is typical on all Boeing jets since the 727 with the exception of the 747SP. The 707s and 720s were built with plain flaps and the 747SP had Fowler flaps.
RE: Flaps
In addition to the types of flaps that Ex-Pratt has correctly elucidated, a correction is in order as far as flap positions mentioned by another poster. There is no industry standard set of positions...they vary by aircraft, and the positions themselves are not really indicative of any degrees as such, rather they are arbitririly numbered "units". Some planes, like say the 737 have 1,2,5,10,20,25,30,40 units, with the kreuger flaps extending fully at any position other than up. The l/e slats will extend to mid and then full extension at certain other flap settings (automatically). The sequencing of the fore,mid (main) and aft flaps are done via a series of cams,rollers/carriages,detents. Wild stuff to watch-- it'll blow your mind if you could see it while it's all "opened up". That's just the 737-200. Some like the 767 have flaps that are, in effect, fowler flaps but do not roll on tracks extended by jackscrews but are "hung" via geared linkage. DC-9's are funny. They're are as Ex-Pratt pointed out simple hinged flaps extended with linear hydraulic actuators...but they're hinged in such a way that they act like fowler flaps in the lower (numerical) settings. Not exactly "one size fits all" is it! Hope I answered your question without confusing you even more. 
RE: Flaps
Yes, those are found on the MD-80's too.
For use on optimal flap setting take-offs.
But DC-9's don't have plain flaps. Not even a Cessna 152 has plain flaps anymore. Both have fowler flaps.
The Cessna even has a slotted fowler flap.
Also if I'm not mistaken, the DC-3 had plain flaps, while the DC-2 had split flaps. Don't know for sure though.
The MD-80 has single slotted fowler flaps. 727 have double slotted fowlers while the 747 has tripple slotted fowlers.
I also didn't know that they're referred to as units as in the aircraft I fly the AOM still uses degrees and the degree symbol is typed at every selector position.
OH ! Hehe, there's one more type of flap. Well, only in it's name though. It's not really a flap as we all know it.
Anyone care to guess?
Regards,
Dash8
For use on optimal flap setting take-offs.
But DC-9's don't have plain flaps. Not even a Cessna 152 has plain flaps anymore. Both have fowler flaps.
The Cessna even has a slotted fowler flap.
Also if I'm not mistaken, the DC-3 had plain flaps, while the DC-2 had split flaps. Don't know for sure though.
The MD-80 has single slotted fowler flaps. 727 have double slotted fowlers while the 747 has tripple slotted fowlers.
I also didn't know that they're referred to as units as in the aircraft I fly the AOM still uses degrees and the degree symbol is typed at every selector position.
OH ! Hehe, there's one more type of flap. Well, only in it's name though. It's not really a flap as we all know it.
Anyone care to guess?
Regards,
Dash8
RE: Flaps
I can confirm that the DC-3 had/has split flaps....All they are about good for it to increase the drag of the airframe.
A slotted flap is just that it has a slot or slots in it that allow air to flow past and attach to the backside of the flap.
A fowler flap is designed to increase the surface area of the wing when it deploys. it moves aft and down at the same time causing more surface area on the wing. The Lockheed Electra was great for it. I can remember riding into Adak on one. The flap would move mostly aft on the first two or three notches the pilot would select. But when he selected that last one it would stop moving aft and rotate down quite severly. Wild show to watch.
Techincally the 727 has triple slotted, fowler flaps. The flaps have motion simular to the fowler flaps, but have slots built into them to allow air to slip past and keep the airflow attached to the back side.
This just shows that a flap can have several different elements from different design types
A slotted flap is just that it has a slot or slots in it that allow air to flow past and attach to the backside of the flap.
A fowler flap is designed to increase the surface area of the wing when it deploys. it moves aft and down at the same time causing more surface area on the wing. The Lockheed Electra was great for it. I can remember riding into Adak on one. The flap would move mostly aft on the first two or three notches the pilot would select. But when he selected that last one it would stop moving aft and rotate down quite severly. Wild show to watch.
Techincally the 727 has triple slotted, fowler flaps. The flaps have motion simular to the fowler flaps, but have slots built into them to allow air to slip past and keep the airflow attached to the back side.
This just shows that a flap can have several different elements from different design types
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- Guest
RE: Flaps
I believe that flaps are extended or (retracted) at least 10 miles from touch down point .But it does not always go that way. The pilot may retract the flaps as far as 20 miles from the area. It all depends on the aircraft you are flying. For example an ordinary apporach from the NW to ORD (OHARE) may require flaps way before the lineup of the runway.
Best wishes 727 Rules!
Best wishes 727 Rules!
RE: Flaps
L-188
The 727 trailing edge flaps do not have slots built in to them but are actually 3 piece (fore flap, mid flap, aft flap) flaps which during extension seperate forming the slots. And during retraction become essentially one large assemby forming the trailing edge.
The 727 trailing edge flaps do not have slots built in to them but are actually 3 piece (fore flap, mid flap, aft flap) flaps which during extension seperate forming the slots. And during retraction become essentially one large assemby forming the trailing edge.
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