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The MiG-35 has movable panels on the LERX (leading edge root extensions). There are a number of images around the web showing these panels deployed during slow flight and retracted otherwise.

When do they have to use these and what does the use of them change in the flight envelope?

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AEhere supports Monica
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George Geo
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  • That's more of a leading edge flap. – John K Oct 08 '19 at 13:46
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    Here may be a better picture, are you talking about those curved pieces at the root of the wing? – Ron Beyer Oct 08 '19 at 13:58
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    slats not flaps (flaps ar all the way from the root towards the tip of the wings). – George Geo Oct 08 '19 at 14:02
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    Those are Krueger flaps on the Leading Edge Root Extensions ( LERX ). – AEhere supports Monica Oct 08 '19 at 14:23
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    @George Geo source for your slat/flap definition please? – Jpe61 Oct 08 '19 at 16:16
  • @Mike Sowsun could you explain why you undid my characterization of these flaps and their location in favor of much more generic terms? If you are thinking these are not high-lift devices, please take note that the grey airframe in your photos, landing with them retracted, is bort 154, an older demonstrator which does not seem to have them. I have edited these particular images out and would like to also revert to the correct terms, unless you want to argue against that :) – AEhere supports Monica Oct 09 '19 at 07:43
  • They look like glove compartements for the ground crew to me. With the lid come loose. – PerlDuck Oct 09 '19 at 07:59
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    @PerlDuck that's one hell of a jam on that lid, if it stays open in flight. – AEhere supports Monica Oct 09 '19 at 08:02
  • @AEhere I have again added 3 photos showing 747, 712, and 702 landing or taking off without these panels extended. I don’t see how they can be called Krueger flaps when we have photographic evidence that they are not used in the “normal” way. – Mike Sowsun Oct 09 '19 at 15:02
  • @Mike Sowsun the "normal" way, please specify. Since you do not know whether the planes are taking off or landing, you hardly can judge the appropriate flap setting. In fact, you have, I bet, zero knowledge when it comes to flap settings on MiG-35 or any other russiang fighter jet for that matter, am I right? – Jpe61 Oct 09 '19 at 15:18
  • Yes, like most people I have zero knowledge of MiG-35 operations, and until someone who does answers this question, I just think it is better to call these "movable panels" instead of "Krueger Flaps". Krueger flaps are normally used for EVERY takeoff and landing and not left extended AFTER takeoff and landing. These clearly are not being used in like an airliner Krueger flap, so I consider it not to be normal. – Mike Sowsun Oct 09 '19 at 15:37
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    @MikeSowsun I am pretty sure your new images are of takeoffs based on the flap configuration. Also note that the image of two MiGs flying in formation was also taken at low speed (based on the vapours and the almost full flaps). I am inclined to call these Krueger flaps because out of Form, Fit and Purpose they seem to have the two first in common with them. The specific usage of flaps varies between airframes and loadouts, but I can see where you-re coming from. Do you also object to the LERX on a similar basis? – AEhere supports Monica Oct 09 '19 at 15:42
  • They probably are an unconventional use of the traditional Krueger flap, but it would be nice to get confirmation. I don't object to LERX as the MiG-35 clearly has LERX like many other aircraft. – Mike Sowsun Oct 09 '19 at 15:56
  • @Mike Sowsun the use of Kruegers could be seen as "normally" limited to only t/o and ldg, since we are used to seeing them only on airliners. Kruegers are used in high AoA situation, and airliners normally do not operate in such a condition outside the t/o and ldg phase. In general in modern fighters the control surfaces, be they whatever, are cotrolled by computers according to appropriate control laws. Should conditions demand so (high AoA for instance), any surface will be deployed as necessary regardless of the phase of flight. – Jpe61 Oct 09 '19 at 16:53
  • Usually if the Leading Edge is sharper then this type of flaps would help. – George Geo Oct 09 '19 at 16:59

1 Answers1

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The aerodynamic devices in question here were already present on MiG-29KUB which is a parent version of MiG-35: Wikipedia: MiG-35

The devices are in fact, as some have suggested, Krueger flaps, as Russian test pilot Pavel Vlasov describes in this article: The MiG-29KUB: in the Russian and Indian skies for 9 years

"It is a modern multirole plane with revolutionary fighting capabilities, with an increased payload and a longer list of weapons," said Pavel Vlasov, Honoured Russian Test Pilot, Hero of the Russian Federation, and General Director of the Gromov Flight Research Institute (and Head of the Flying Service at MiG until 2010). He noted at the same time that the MiG-29KUB featured a range of new solutions, such as Krueger flaps, a new flap design, a modern fly-by wire control system, and significantly improved piloting conditions

In addition to calling them Krueger flaps, this article also gives the devices the acronym LEVCON, leading-edge vortex controllers: SlideShare: Fulcrum Reloaded (see page 4)

The purpose of Krueger flaps is to increase the coefficient of lift of the wing, and to improve slow speed handling: Wikipedia: Krueger flap

After facts some speculation: the reason the Krueger flaps are not deployed in some of the pictures with gear extended is probably bacause they are not used in take off configuration, and the pictures most likely have been taken in t/o situation, not while the aircraft is landing

Jpe61
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    Nice work. Interesting that the aircraft has slats and flaps on its wing, and the "Kruegers" on its strake. One thing notably learned on this site is the undesirable characteristics of a sharp leading edge at higher AOA. They may have put a "flap" on there to "soften" the leading edge in situations where more maneuverability is needed. I would look for the computer, or pilot, to close it in situations where less change in AOA is anticipated. – Robert DiGiovanni Oct 10 '19 at 03:22
  • Nice find with that article. – AEhere supports Monica Oct 10 '19 at 14:17
  • Oh the things one can achieve with google and time to spare :) – Jpe61 Oct 10 '19 at 14:32