On this video of Air North's gravel runway-equipped B737-200, there's what appears to be a small leading-edge flap (Krueger flap?) inboard of the engine. Refer to the screen shot below. What is this?

enter image description here


Notice in the video (and screen shot) that this device shows itself while no other flaps are extended.

  • 1
    $\begingroup$ Hard to say. Looks more like an access panel hanging down during servicing than a Kruger flap, which will be hinged at the front of the LE. $\endgroup$
    – John K
    Commented Jan 1, 2019 at 14:38
  • $\begingroup$ A closer view of a similar LE flap. I don't understand why the first answer by @TomMcW was downvoted, it seems to be the good one. $\endgroup$
    – mins
    Commented Jan 4, 2019 at 10:24

2 Answers 2


These are two leading edge Krueger flap surfaces at each side of the wing, you can see details about them according IPC and AMM documents I found over the internet:

LE Kruger slat

LE Kruger slat Mechanism

LE Kruger slat  Section

Regarding the Addendum, and why it seems that there is no other flaps deployed, I found a similar topic at Airliner.net Forum. As it is mentioned there, when is no hydraulic pressure, they can be extended by their weight:

...it has to do with the shut off valves and the actuators relaxing with no hydraulic pressure on them.

and also:

...Pressurize the system and they all move to their present commanded position

and another sidenote:

...Someone pulled that Krueger Flap to the fully extended position. When they droop because of no pressure on the system there in the mid positions.

and as final note, this issue is also mentioned in the AMM:

LE Flap Droop issue in the AMM

  • $\begingroup$ We have removed the images in your answer due to a DMCA complaint from Boeing. I realize this breaks your answer a lot. Please consider updating it in a way that makes it useful again without using copyrighted images. $\endgroup$
    – animuson
    Commented Aug 31, 2020 at 15:24
  • $\begingroup$ @animuson thanks for updating me. I found those documents on the internet. Now, I even can't see what images I had posted, and unfortunately, I don't remember them, to repost similar images. $\endgroup$
    – JetSonic
    Commented Sep 2, 2020 at 9:57

The 737-200 does have Krueger flaps inboard of the engines as seen in this photo

enter image description here source

It’s hard to really tell, but it looks like the outboard half of the flap is not entirely retracted.

  • $\begingroup$ Curious, where did you get that image? Is there a higher-res version available online? $\endgroup$
    – pr1268
    Commented Jan 7, 2019 at 5:31
  • $\begingroup$ Oh shoot! Did I forget to put a citation? I think it was on the site B737.com. I'll see if it's still in my browser history $\endgroup$
    – TomMcW
    Commented Jan 7, 2019 at 5:52
  • 1
    $\begingroup$ @pr1268 There. I added a citation link $\endgroup$
    – TomMcW
    Commented Jan 7, 2019 at 5:55

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