Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

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Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Julian Mills » Wed Sep 21, 2016 10:08 am

Hi All

I know that the Luciole does not make it in to the SSDR class due to the stalling speed being above 35Kt

However could the Luciole wing be manufactured with a FIXED LEADING EDGE SLAT within the current wing plan profile ?

Slats can improve wing lift by *40% but at the cost of slightly extra drag at high speeds.

Are there any other factors other than the stalling speed that would exclude the Luciole from being in the SSDR class ?

Is there anybody up to speed with Xfoil software or similar who could look at this to see if it is really possible to increase the Cl max by adding fixed slats to the Luciole wing to get the stalling speed below 35Kt ?

Julian Mills

* Mechanics of flight (9th edition A C Kermode)
---------------------------------------------------------------------------------------
The stalling speed has been calculated from Lift=1/2* q* V2 *Cl *S
Typical Cl max values have been use for the relative wing config
It looks like sub 35 Kt stall speed could be possible !!!!

MAUW_____Wing area_____Wing Config____Cl max____Stall speed
200 kg_____4.6m2________Clean__________1.2_______47 Kt
200 kg_____4.6m2________Flap___________1.8_______38 Kt
200 kg_____4.6m2________Flap & Slat_____2.25______34 Kt

The table above was added (7 Oct 2016)

Julian Mills
Last edited by Julian Mills on Fri Oct 07, 2016 1:23 pm, edited 13 times in total.
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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby dmcnicholl » Wed Sep 21, 2016 5:39 pm

What would be the weight penalty of that modification? There's not a lot to play with if you still want to get into it and fly.
You might say, "so what?" "It gets it under SSDR which allows a max take off mass of 300kg, so there's loads of scope and I can do what I want" but that still wouldn't raise the MAUW of the design.
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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Julian Mills » Wed Sep 21, 2016 6:51 pm

As always with these thing the devil is in the detail.

One thing is for sure, it would be unwise to increase the MAUW

Yes there would be a weight penalty of may be around 5Kg.

At the end of the day only pilots below a certain weight could fly the Luciole with full fuel.

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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Nick Allen » Mon Oct 03, 2016 9:58 am

How far off is the stall speed? I don't have the LAA article to hand, but I thought it was very close to 35kt. Would it not be worth considering vortex generators before attempting to add slats?
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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Julian Mills » Mon Oct 03, 2016 10:26 am

Vortex generators may help for a reduction of 1 or 2Kt at most.

I have Google the stalling speed for the Luciole and it would seem to be 36Kt (65kph)
http://www.flying-directory.com/popup_i ... t&id=54243
or
http://www.revolvy.com/main/index.php?s ... 20Colomban
87 km/h (54 mph or 47 kts).

Can any Luciole pilot confirm what is the true stall speed or minimum steady flight speed in the landing configuration is at MTOW from the LAAs point of view.


Julian Mills
Last edited by Julian Mills on Tue Oct 04, 2016 3:37 pm, edited 1 time in total.
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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Nick Allen » Mon Oct 03, 2016 1:05 pm

I've seen 65kph quoted -- that's 35.09kt: isn't that 35 within the limits of ASI accuracy!? Perhaps you should talk to Richard Teverson (though his luciole.co.uk website seems not to be working at the moment).
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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Ian Melville » Tue Oct 04, 2016 12:31 pm

IIRC CAS is reguired for the SSDR stall speed, slightly more difficult reading to get for the average builder.
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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Julian Mills » Tue Oct 04, 2016 3:27 pm

Ian Melville wrote:IIRC CAS is reguired for the SSDR stall speed, slightly more difficult reading to get for the average builder.


Ian, can you give any more detail why this is more difficult for the average builder please ?

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Re: Luciole, FIXED LEADING EDGE SLAT, reduce stall speed ?

Postby Ian Melville » Tue Oct 04, 2016 5:08 pm

Apart from some maths, you will also need a swivelling pitot.
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