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White blocks at Flap positions on indicator

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White blocks at Flap positions on indicator

Old 16th Jan 2022, 13:39
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PFD
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Question White blocks at Flap positions on indicator

Hi all from sunny (sporadic) Banbury in UK. I have an on going question which the internet (and I've printed it all off, it's just not there) refuses to answer. As an aircraft ground engineer, it feels like a design/engineering thing. Why are there white blocks at the flap positions on the indicators? I feel like it's either for ease of pos identification or to allow for onload/offload flap positions?

Please put me out of my misery, I'm 64 and should be resting really

757-300 flap indicator
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Old 16th Jan 2022, 14:37
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Pre-digital? When flaps could be approximately the same, left & right, without undue worrying…

or, to account for (poor) pilot eyesight?

The gauges look familiar, and I think it’s for the situation when dealing with Flap drive failure checklist? “Flaps between 5 & 15?” etc. Anything in the white block counts as meeting the requirement.
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Old 17th Jan 2022, 05:23
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There is a speed limit opposite of each white block. Maybe it's done just to facilitate "flap position - speed limit" identification.

Last edited by Acie; 17th Jan 2022 at 06:23.
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Old 17th Jan 2022, 10:02
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It's to make it easier for partially sighted pilots.
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Old 17th Jan 2022, 13:17
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Originally Posted by PFD View Post
Why are there white blocks at the flap positions on the indicators? I feel like it's either for ease of pos identification or to allow for onload/offload flap positions?
The size of each block increases with increasing flap deflection. I would suspect the the size of the block shows the allowed indication error for a properly rigged aircraft.
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Old 17th Jan 2022, 16:00
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That and the small notch in the white block is the where each particular indication is correct.
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Old 17th Jan 2022, 19:16
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Rigging tolerance?
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Old 17th Jan 2022, 23:50
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Alternate flap position bands , to aid crew when using alternate flaps not to be confused with primary and secondary .
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Old 19th Jan 2022, 17:53
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Is it rigging tolerance between both sides, see the film on here about the flaps on YouTube.

Flight Controls
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Old 20th Jan 2022, 10:10
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The blocks were there in the 737-100/200 family, before limit speeds were indicated on the panel next to the indicator:


(from: Flight Controls)
Because of that, I tend to agree with the suggestion of rigging tolerances.
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Old 20th Jan 2022, 14:51
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Thanks all

Thank you all who have replied so far, honestly didn't realise there were two needles on that gauge.
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Old 21st Jan 2022, 16:39
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Yes 1.16 on the film shows them split

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