Difference between 'slotted wing' and 'fixed slat'

[raikks]

Is there a difference between these two? Thx.

[BOAC]

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.........................

[DaveReidUK]

Is there a difference between these two?

In my experience, both terms are used pretty well interchangeably.

[BOAC]

This (http://naca.central.cranfield.ac.uk/reports/1933/naca-report-427.pdf) is the only reference I can find at the moment to the 'slotted wing'. As you will see there were lots of slots!!

[BOAC]

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 (http://www.flightglobal.com/pdfarchive/view/1933/1933%20-%200454.html)

Southampton University cover it well at page 93 of this (http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=70&ved=0CGwQFjAJODw&url=http%3A%2F%2Fwww.southampton.ac.uk%2F~jps7%2FAircraft%25 20Design%2520Resources%2FBrandt%2520Introduction%2520to%2520 Aeronautics%2FCh4Wing%26Airplane.doc&ei=ELHyUJTIMMib1AWekYGIAQ&usg=AFQjCNGewJV5GwZgRXXi-O3gC0JuoapE2A&sig2=a8ffqH7Z73nUvkWe3iHqGA) doc

[hvogt]

Memory fails me but I believe Handley Page had a machine with a slot built into the section - anyone recall?
According to Torenbeek/Wittenberg, your memory serves you right: "The development of wing flaps began in 1919 when the Englishman F. Handley Page invented the slotted slat at the wing leading edge which postpones stalling to a higher angle of attack." (Torenbeek/Wittenberg, Flight Physics, Dordrecht, 2009)

[BOAC]

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

[Meikleour]

Rollason Turbulent has a fixed slot aft of the leading edge!

[Onceapilot]

The remarkable Me163 rocket plane had fixed slotted outer wing sections .
Some versions of F4 had a fixed slat on their anhedral tailplanes.

[FlightDetent]

These are fixed...

http://www.fliegerszene.de/2007/Let-UH%20Z-37%20Cmelak%20D-ESVU%20a.JPG

http://nd03.jxs.cz/492/665/f819d71a32_66283201_o2.jpg

[BOAC]

I think the only likely 'candidate' so far there is the 163. I cannot find a planform of the Turbulent but I'm pretty sure like the 2 from FD those are 'fixed slats', not slots.

[Tinstaafl]

The tailplane on a Cessna C177 has slots.

[pattern_is_full]

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.

[Meikleour]

BOAC: the best I could find is this link:

Photograph of Aircraft G-ATBS (http://www.caa.co.uk/applicationmodules/ginfo/ginfo_photo.aspx?regmark=G-ATBS&imgname=G-ATBS001&imgtype=jpg)

Slot quite clear on the wing outer section.

Did not also the G91 not have a wing slot?

[gums]

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.

[Desert185]

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.

[DaveReidUK]

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

http://cdn-www.airliners.net/aviation-photos/photos/8/6/4/0083468.jpg

[raikks]

Thank you all for your answers. Definitely they are similar in operation, but I couldn't find a clear photo of a slotted wing.

[westhawk]

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

[WHBM]

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.
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.

[DaveReidUK]

or between trailing edge flap segments on a multi-segment trailing edge flap system such as Fowler flaps

Or, in the most basic form of (single-segment) Fowler flap, where the slot is simply the gap between the wing and the leading edge of the flap.

[Trent 972]

Grumman HU-16A (http://www.eaa1000.av.org/pix/albatross/albatross.htm) outer wing slots.

http://www.eaa1000.av.org/pix/albatross/slot.jpg

Each wing contains a slot from the tip float out to the wing tip. At high angles of attack, these slots help to keep the airflow attached to the outer portions of the wing so that the inboard portion of the wing will stall first. The benefit of this arrangement is that the ailerons should remain effective up to stall.

The slot is located such that at high angles of attack, high pressure air will be driven into the front of the slot, as shown by the arrows. The cross sectional area of the slot decreases as the air passes through it, additionally accelerating the flow through the slot.

[fdr]

FWIW, the DH-82 had H.P. automatic slats on some versions, and many also had a separate modification of a tail strake. The slats are similar to the A-4's design, popping out when the resultant force from the element gives a forward force relative to the tracks, and thereby driving the slat outboard. The Fieseler Fi-156 Storch had a fixed geometry LE slat AKA a slotted wing.

[westhawk]

Or, in the most basic form of (single-segment) Fowler flap

Yes indeed! Cessna has built a great many single engine airplanes so equipped. Apparently they are very fond of the single segment slotted Fowler flap design. Other than the occasional problems with worn rollers jumping track and jamming the flap (due to poor maintenance oversight) they do a great job.

[Lumps]

Check out the wing of a Helio Courier for all the goodies - AoA controlled slats (the inboard right hand slat quite often pops in at high power - high AoA flight, like take-off) spoilers for low speed roll control and loooong fowler flaps.

[barit1]

Some pre-1940 designs w/fixed slots:

Lockheed 14 (optional on this ship), and possibly the Hudson
Lockheed 18 Lodestar
Boeing B-17

Slots were difficult to anti-ice, and some operators closed them up (w/ performance penalty) to avoid this problem.

[D120A]

I learned to fly on a DH82A with automatic slats. It was a source of great mystery and wonder to me when they floated out at different times as the aircraft flew more slowly (with no slip, honest!) and they did so with no effect in roll or yaw as one deployed but not the other. Can current Tiger Moth operators comment on whether that is a common characteristic, or a was it just a sweetness of our particular aeroplane?

I assumed the former and wondered how difficult that was to achieve, and whether it was done using a wind-tunnel or through much tweaking during development flying.

[judge.oversteer]

Also early model NA F86, Canadair and CAC Sabres until they incorporated the famous 6:3 wing.

[DaveReidUK]

Also early model NA F86, Canadair and CAC Sabres until they incorporated the famous 6:3 wing.Off-topic, strictly speaking, as we're talking about fixed slats in this thread, but here's an earlier thread where the automatic slats on the F-86, Sabreliner, F-100, etc are discussed:

http://www.pprune.org/tech-log/501166-leading-edge-slat-forces.html

[D120A]

Thank you DaveReidUK, hadn't spotted that.

[AerocatS2A]

D120A, I spent a few years flying a Tiger Moth with slats and I never unlocked them, they just seemed a bit pointless to me and our other Tigers didn't have slats.

[GuilhasXXI]

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.
http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/statusicon/user_offline.gif http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/buttons/report.gif (http://www.pprune.org/report.php?p=7628670) http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/buttons/reply_small.gif (http://www.pprune.org/newreply.php?do=newreply&p=7628670&noquote=1)

This pretty much answers your question I guess..