MD11 Slats

[haztronic 1]

Just curious as to what the slats in the MD11 do. I just started getting into flying it (PMDG MD11) but never really knew what the slats did, hopefully I can get some good knowledge from avsim.

[altstiff 71]

The same as a flap, adding better lift at slower speeds. Slats are on the leading edge and not the trailing edge of the wing.

[ZachLW 37]

A slat does a few things. Off the top of my head:

• Allows higher angles of attack by "energizing" the boundary layer over the top of the wing and keeping air from separating from the top of the foil.
• Increases wing camber

[audiohavoc 24]

If you have time, try reading the manual. It is lengthy, but it is very good. The Angle of Attack training for the MD-11 is well done, and I recommend it as well. I had a good amount of hours in the MD-11, and I had spent time reading the manual and I still learned new things about the MD-11 from the Angle of Attack training.

[CoolP 283]

Just curious as to what the slats in the MD11 do. I just started getting into flying it (PMDG MD11)

Seems like you are getting to know and like her, huh? :( Great plane indeed. Big thumbs up on Shane's tip. I think the manuals and the optional AoA training help a lot and also cause the immersion to expand.Now on the slats, it's easier to divide the 'things on the wing' into two groups. The ones which allow you do fly a higher angle of attack (no, that's not the video folks) without stalling and the ones 'just' increasing lift. The slats are devices from the first group, with very little effect on the actual lift the wings produce. However, since you can fly that higher angle of attack with the slats extended, the cause of that higher AoA of course would be increased lift.Now the distinction on those two groups makes sense when you recall what you want to do with a plane. You want to land it rather slow (well, slower than cruise speed) and you may therefore need a combination of a safe (high) AoA and some extra lift. The lift portion comes from the flaps, on the trailing edge of your wings, the higher AoA, as said, is the slat part, therefore leading edge. On a modern jet, you will find a combination of both arrangements, whereas older versions of e. g. the 707 came with flaps only. Therefore, their ability to fly safe high AoA was reduced.Now slats only would be a theory thing since the now possible AoA increase also alters the body angle of the plane. This leads to a high amount of drag and also less tail strike clearance. So, that combo is a good way to go unless they introduce the flexible wing like on some prototypes, without actual devices to extend. Very fancy stuff.Now those things do very complicated things when looking closer. Stating this because you'll find a ton of docs on e. g. the slat effect (which often gets summarized as some 'easy' one, which it isn't at all). It's mainly a vortex getting generated, protecting the actual airflow over the main wing and therefore preventing a separation. As we know, that wing gives you the lift and you therefore want to protect that airflow. A common misconception is the thinking that the slats add some energy or even velocity to that airflow. The opposite is true, as shown buy Mr. Smith in 1975. He worked for the Douglas Aircraft Company, so maybe that's a hint. ^_^All the things you can extend on the MD-11 have a different effect on lift, the safely flyable AoA and drag. For instance, while you will gain a lot of lift from the first stages of flaps, their drag component increases over the added lift pretty soon, which leads to the engines spooling up to quite high values. That's why they avoid flying on high flap settings for long. It's a noise and fuel burn thing.Now the MD-11 needs rather high flap settings when slowing down for the approach and even ILS capture, which represents that other nature of hers and may also explain a bit how she received her role in today's economics.To conclude, the slat part is the first one for a reason and acts differently to the following flap extensions.