Difference between 'slotted wing' and 'fixed slat'
Per Ardua ad Astraeus
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I'll start the furry ball rolling - to me, a Fixed Slat is a slat mounted on extensions from the leading edge whereas a Slotted Wing has slots 'built in' to the section. Memory fails me but I believe Handley Page had a machine with a slot built into the section - anyone recall?
Over to the dogs.........................
Over to the dogs.........................
Per Ardua ad Astraeus
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As you can see here (section 4) , the 'slot' can be at any point in the section, its function primarily is to re-energise the upper surface boundary layer with 'high pressure' air to improve attachment, in this case just in front of the flaps.
basic airfoil | slat | tr | 1933 | 0454 | Flight Archive
Southampton University cover it well at page 93 of this doc
basic airfoil | slat | tr | 1933 | 0454 | Flight Archive
Southampton University cover it well at page 93 of this doc
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From: Hamburg
Memory fails me but I believe Handley Page had a machine with a slot built into the section - anyone recall?
Per Ardua ad Astraeus
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From: UK
Hmm, I had that bit, but that is, in my book, a fixed slat unfortunately. I am still searching for an aircraft I recall from the dim and distant past which had a spanwise slot about 1 foot back from the L Edge - I thought it was HP but so far no sign of it. It was either a single or twin engined machine
Only half a speed-brake
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From: Commuting not home
These are fixed...
http://www.fliegerszene.de/2007/Let-...D-ESVU%20a.JPG
http://nd03.jxs.cz/492/665/f819d71a32_66283201_o2.jpg
http://www.fliegerszene.de/2007/Let-...D-ESVU%20a.JPG
http://nd03.jxs.cz/492/665/f819d71a32_66283201_o2.jpg
Last edited by FlightDetent; 13th January 2013 at 17:13.
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From: Denver
From an aerodynamic standpoint, they both do the same thing.
From a conceptual standpoint, I'd say a fixed slat is something separate bolted onto a given airfoil, whereas a slotted wing is an air channel cut within that airfoil.
In other words, take a given airfoil, and bolt something on the front of it to produce a slot, and that is a fixed slat. Take it off, and you are back to your original airfoil.
Conversely, take a given airfoil and cut a slot through it, and the overall external profile of the airfoil is still the same. Remove the slot (and the portion of airfoil ahead of it) and you no longer have the original airfoil.
From a conceptual standpoint, I'd say a fixed slat is something separate bolted onto a given airfoil, whereas a slotted wing is an air channel cut within that airfoil.
In other words, take a given airfoil, and bolt something on the front of it to produce a slot, and that is a fixed slat. Take it off, and you are back to your original airfoil.
Conversely, take a given airfoil and cut a slot through it, and the overall external profile of the airfoil is still the same. Remove the slot (and the portion of airfoil ahead of it) and you no longer have the original airfoil.
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From: uk
BOAC: the best I could find is this link:
Photograph of Aircraft G-ATBS
Slot quite clear on the wing outer section.
Did not also the G91 not have a wing slot?
Photograph of Aircraft G-ATBS
Slot quite clear on the wing outer section.
Did not also the G91 not have a wing slot?
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From: florida
Salute!
From the "lite" peanut gallery........
Slats seemed to be like those on the F-100. They didn't pop out until the AoA was above "x". Or were manually controlled.
Slots were permanently out there, or extended with gear/flaps down. Some really old planes had those like the Stinson and others. Possibly some of the ME-109 variants.
Then we had basic leading edge flaps like the A-7 and F-16 had. The A-7 ones came down with teh flaps. The Viper ones worked full time acoording to AoA and mach, but were fixed down at "x" degrees when gear handle was lowered.
From the "lite" peanut gallery........
Slats seemed to be like those on the F-100. They didn't pop out until the AoA was above "x". Or were manually controlled.
Slots were permanently out there, or extended with gear/flaps down. Some really old planes had those like the Stinson and others. Possibly some of the ME-109 variants.
Then we had basic leading edge flaps like the A-7 and F-16 had. The A-7 ones came down with teh flaps. The Viper ones worked full time acoording to AoA and mach, but were fixed down at "x" degrees when gear handle was lowered.
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From: Western USA
The DC-8 has slots inboard of each engine pylon that open and close with flap movement (closed when flaps up and open when flaps extended. Google it.
Slats, to me, are something different. Some are fixed and some are moveable/retractable.
Slats, to me, are something different. Some are fixed and some are moveable/retractable.
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From: USA
Like many terms use in aviation "slots" and "slats" can mean more than one thing according to applicability and historical pedigree! I'll stick to the common understanding of the terms as I've come to know them. While I have simplified my explanations somewhat, it's my hope that I've not strayed so far away from the objectively academic so as to promote any misunderstanding.
Most commonly, a slot is a gap through which higher pressure air can flow from the lower airfoil surface to the upper surface. As the air passes through the slot it increases in velocity and is added to the airflow over the upper airfoil surface. This adds energy to the boundary layer airflow over the upper surface, thus increasing the critical angle of attack in the area behind the slot. By delaying the onset of airflow separation to a higher AOA, slots increase the maximum coefficient of lift attainable across a particular airfoil section.
Slots may be found placed slightly aft of a wing leading edge (fixed slot), between a leading edge slat and the wing leading edge or between trailing edge flap segments on a multi-segment trailing edge flap system such as Fowler flaps.
The fixed slot is typically placed along the outboard section of a wing leading edge. Placed as such, the critical AOA is higher in the outboard portion of the wing than the inboard portion, thus promoting inboard to outboard stall progression and maintaining aileron effectiveness to a higher AOA. This is especially useful in reducing the roll moment produced by asymmetrical stalls. Wing washout and and stall strips are two other methods available to accomplish similar results on a constant chord wing, though perhaps somewhat less effectively.
A slat may be fixed or moveable. A slat extends forward and downward into the airstream. If fixed, it is sometimes referred to as a leading edge "cuff". If moveable, slats may be actuated by a powered aircraft system such as hydraulic or electrical. Slat rails are placed at intervals along the wing span and oriented longitudinally to guide the slat along it's travel path. A slat is to a droop leading edge as a Fowler flap is to a plain flap. DLEs and plain flaps simply hinge down, increasing wing camber, while Fowler flaps and slats extend downward AND transit along the chord line. Both the Fowler flap and the slat increase the wing surface area in addition to increasing the airfoil camber as they extend.
Alternatively, slats may be actuated aerodynamically when high AOA causes an air pressure difference which acts to pull the unpowered slat out on it's rails to the extended position. Dynamic pressure pushes them back to the stowed position when the AOA is reduced enough. North American aircraft such as the F-86 Sabre and T-39/Sabreliner (NA-265) were equipped with such a slat system, sometimes erroneously referred to as "gravity slats". It's a matter of some interest that asymmetric deployment/stowing was not considered to be a significant matter of concern among pilots, though a slight rolling motion was not uncommon during deployment.
I hope that's helpful,
westhawk
Most commonly, a slot is a gap through which higher pressure air can flow from the lower airfoil surface to the upper surface. As the air passes through the slot it increases in velocity and is added to the airflow over the upper airfoil surface. This adds energy to the boundary layer airflow over the upper surface, thus increasing the critical angle of attack in the area behind the slot. By delaying the onset of airflow separation to a higher AOA, slots increase the maximum coefficient of lift attainable across a particular airfoil section.
Slots may be found placed slightly aft of a wing leading edge (fixed slot), between a leading edge slat and the wing leading edge or between trailing edge flap segments on a multi-segment trailing edge flap system such as Fowler flaps.
The fixed slot is typically placed along the outboard section of a wing leading edge. Placed as such, the critical AOA is higher in the outboard portion of the wing than the inboard portion, thus promoting inboard to outboard stall progression and maintaining aileron effectiveness to a higher AOA. This is especially useful in reducing the roll moment produced by asymmetrical stalls. Wing washout and and stall strips are two other methods available to accomplish similar results on a constant chord wing, though perhaps somewhat less effectively.
A slat may be fixed or moveable. A slat extends forward and downward into the airstream. If fixed, it is sometimes referred to as a leading edge "cuff". If moveable, slats may be actuated by a powered aircraft system such as hydraulic or electrical. Slat rails are placed at intervals along the wing span and oriented longitudinally to guide the slat along it's travel path. A slat is to a droop leading edge as a Fowler flap is to a plain flap. DLEs and plain flaps simply hinge down, increasing wing camber, while Fowler flaps and slats extend downward AND transit along the chord line. Both the Fowler flap and the slat increase the wing surface area in addition to increasing the airfoil camber as they extend.
Alternatively, slats may be actuated aerodynamically when high AOA causes an air pressure difference which acts to pull the unpowered slat out on it's rails to the extended position. Dynamic pressure pushes them back to the stowed position when the AOA is reduced enough. North American aircraft such as the F-86 Sabre and T-39/Sabreliner (NA-265) were equipped with such a slat system, sometimes erroneously referred to as "gravity slats". It's a matter of some interest that asymmetric deployment/stowing was not considered to be a significant matter of concern among pilots, though a slight rolling motion was not uncommon during deployment.
I hope that's helpful,
westhawk
Last edited by westhawk; 14th January 2013 at 08:06.
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The slots on the DC8 were an early modification for the DC8-12 model. many of the original DC8-11 were then converted, which would involve re-engineering the wings. Initial operations must have shown there was some issue which they overcame.
