757 flap indicator

[darshanpatelh]

Hello been on the type for a few months now, and noticing a few interesting things(to me). One of which is the white arc inside the flap indicator around each flap position. The Arc spans on what it seems like 3 different widths, but not in a linear way. Up,1,5 looks the same and 15,20,25 same, but the arc on 30 looks similar to the first 3. Systems Manual states the Flap Disagree and Asym should indicate the relative positions of either flap when the hydraulic power is cut. I don't quite understand the reason for the white arcs to be there and their function. If anyone has insight over this, I would greatly appreciate the knowledge.


Regards,




Flap Indicator Pic

[darshanpatelh]

farm4.static.flickr.com/3178/3099143869_83633174c7_b.jpg
Flap Indicator Pic Reference

[AerocatS2A]

I don't fly it, only a guess, but looking at pictures of the indicator I would think it is the range for normal indication. So the needle should sit somewhere in the white arc for each position. The width of the arc would then be a function of the range of allowable error in the indication.

[darshanpatelh]

I don't fly it, only a guess, but looking at pictures of the indicator I would think it is the range for normal indication. So the needle should sit somewhere in the white arc for each position. The width of the arc would then be a function of the range of allowable error in the indication.
Thanks AerocatS2A

[Rudder Sir]

If it's similar to the 737, there may be a small index within each arc that denotes the exact flap position on that airframe. This is used in the 737 when setting the flap using the alternate system - I.e. you hold the extended/retract switch until the flap pointer matches the index within the arc for the desired flap position.

[AerocatS2A]

Thanks AerocatS2A
Eh, now I've looked at your close up picture, I don't think I'm right. It looks like the indicator should sit right in the middle of each arc where the indent is.

[darshanpatelh]

Yes I agree with your observation. There is a notch with a range on either side.