Leading Edge Slat Forces

[nzhills]

Hi
Regarding the title, I wanted to be explicit about what I was talking about and I am using the American nomenclature. Coz, slats are unpowered devices in my world, but America does not think so, (long live Frederick Handley Page).
Anyway, what sort of forces would be required to extended a 'slat' prior to landing on something like a 767?
Mark

[Capn Bloggs]

In our world, slats are not unpowered. Mine are hydraulicly operated. As to the forces required to extend them, I'll leave that to the experts!

[MarkerInbound]

Mine are too. Since it's a 3000 psi system, I'd say less than 3000 psi.

[BOAC]

nz- perhaps to clarify?

There are 'slots' (fixed') and 3 sorts of slats that I know of::-
1) Fixed
2) Automatic
3) Powered

[Crabman]

Where is your "world"? Can I have one of my own?

I'm not sure what America does or doesn't think about "slats" (or did you mean "slots"). I'm pretty sure that a typical American (of the USA variety) doesn't think much about "slats" (or "slots"). If and when he does, he would probably allow for "slats" to be powered or unpowered.

You might want to sit down for the next part. Despite your fervent prayer, Frederick Handley Page has passed on.

[de facto]

I'm not sure what America does or doesn't think about "slats" (or did you mean "slots

How about the last but not least sl:Ets?

[DaveReidUK]

There are 'slots' (fixed') and 3 sorts of slats that I know of::-
1) Fixed
2) Automatic
3) Powered

What's the difference between a slot and a fixed slat ?

[Avionker]

As I understand it a slot is a fixed device and a slat is retractable. Therefore you get the advantage of a slot at low speed, without the drag penalty at higher speeds.

A "fixed" slat is in fact a slot.

[rogerg]

Automatic - the slat lies flush with the wing leading edge until reduced aerodynamic forces allow it to extend by way of aerodynamics when needed. Sometimes referred to as Handley-Page slats.
Had them on the Tiger Moth and the North American Sabreliner, Which had NA Sabre wing.
Two types I have flown

[grounded27]

Ref: AA flt191 and un controlled deployment of slats as a result of broken hyd lines when #1 engine departed the aircraft. So I would say yes slats are hydraulically controlled and deployed under most normal circumstances.

[BOAC]

Re slats and slots - my understanding from many years ago is that a slot is a channel cut in the wing section near the leading edge whereas a fixed slat is an aerofoil section fixed and extended forward from the leading edge. Therefore they are NOT the same. However, "that is not important right now".

[DaveReidUK]

Therefore they are NOT the same.

Hmmm.

That aside, for the sake of completeness we should also include the slotless slat, aka DLE. :)

[Avionker]

And let's not forget Krueger flaps and variable camber Leading Edge flaps....

[BOAC]

DLE - emptied Google looking for that. A new one for me. Any link? What about the slatless slot?

Time, perhaps, to ask if a deployed slat creates a slot - no, I thought not.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

[mike-wsm]

BOAC Droopy Leading Edge?

http://i1165.photobucket.com/albums/q594/mike-wsm/pprune/patents-1-1-1_zps80310083.png

USP 4,200,253

[BOAC]

Did have, but went private and it was sorted.

[DaveReidUK]

BOAC Droopy Leading Edge?

Correct. If he'd been a BEA guy, instead of a BOAC one, he'd have remembered them. :O

[nzhills]

Wow, where to start.

I'd chosen the technical forum for a technical discussion. Instead every participant bar one has commented on terminology. Thank you OK465, you are correct. I should have referred to them as leading edge devices.

MarkerInbound, thank you for your contribution. 3000 psi is a measure of pressure not force. Additionally, the leading edge devices are generally powered by a torque tube running behind the fixed leading edge. This can be powered by a hydraulic motor, usually in the left wing root, which will have 3000 psi powering it. But how much power does the hydraulic motor put out?

There are publications out there that refer to Handley Page Slats as being unpowered leading edge devices. This is what I have learnt. I am confronted with Boeing SRM's that refer to beams as chords, straps as chords, stringers as chords. Yet I learnt a chord is a measurement of distance between the leading and trailing edges of a wing. I suppose this is another example of the golden rule, he that hath the gold maketh the rules.

I think that Lachmann also referred to his leading edge devices as slats, (quick Jeeves look up Lachmann).

My comment "long live Fredrick Handley Page" should have read "long live the memory of Frederick Handley Page". An independant thinker ostracised from British aerospace.

After all that, does anyone know the sort of forces invovled in extending the leading edge devices at say 160 knots?

[Wizofoz]

nz,

You're still not being clear- do you mean LEDs as found on modern Jets, in which case the answer is "3000psi of hydraulic power", or unpwered slats, as in a Tiger Moth, in which case the answer is "Spring Pressure".

If it's the latter, the slats are spring-loaded open. When there is sufficient airflow, the pressure forces them them shut. They can also be locked shut mechanically

Not going to happen a 160kts as the Tiger would have shed it's wings by then!

Someone mentioned the Sabre liner, and by inference the F-86 having unpowered slats? I wasn't aware of that, but would be interested to know if that is the case.

[BOAC]

Thanks, mike- yes, although I did not work for either BEA or BOAC I am familiar with a Drooped Leading Edge (but, like Google, not with 'DLE'.which is, I think, either a skin condition or a French airport:)) It was DR's "the slotless slat" that threw me.

NZ - if this really bothers you, why not try the '1/2 rho Vsquared S' using a flat plate coefficient? Or you could just use <3000psi? Since basic sprung automatic slats 'pop out' due to low pressure at the l edge, I suspect the forces are not great.

I believe the slatted F-86 (before they adopted the 'f c e l e a ' for DR:)) had automatic slats, but whether sprung or hydraulic I know not

[autoflight]

Even if not very much force is required to deploy slats, in an airliner the hydraulics give control of all positions and ensure symetrical operation of each wing. To be sure to get this result, I guess a fairly large force is used.

[BOAC]

Not forgetting, of course, a 'controlled' retraction which requires a motive force.

[DaveReidUK]

but whether sprung or hydraulic I know not

There's a reference to the Sabreliner's slats being sprung in this thread (post #8):

http://www.pprune.org/tech-log/9511-warbird-q-bf109-leading-edge-automatic-slots.html

so presumably the same applies to the F-86 variants that had slats (not all did).

[Owain Glyndwr]

After all that, does anyone know the sort of forces involved in extending the leading edge devices at say 160 knots?

The Triumph Gear Systems website gives maximum operating torque and rpm for their B767 leading edge actuator as:

Inboard 18,800 in.lb @ 2.2216 rpm
Outboard 12,000 in lb @ 2.345 rpm

[mike-wsm]

If the actuator arm is six to ten inches long, then Owain's answer can be converted to a force in the range 1,000 to 3,000 lbf for that particular aircraft. This is the capability, ie the force available to meet all eventualities. The actual force required under normal operating conditions may be much smaller.

Every design will differ and I suspect assessment of the required force is very much a wind tunnel issue.

The use of slats and their effect in extending the Cd curves are well described here:
Anatomy of a STOL Aircraft (http://www.zenithair.com/stolch801/design/design.html)

[MarkerInbound]

On the 727 there are 7 actuators in each wing moving the LEDs. No torque tube drives.

[Yobbo]

The DC-8 had slots which opened when flaps were selected.They were located inboard of the engine nacelles. Their function was to improve the airflow around the nacelle.If one or more failed to open a extra 10-15 kts was added to Vref if my memory serves me correctly.Failure to open on the ground was a no go item.