How does this Bell 206 cyclic control linkage work?

Question

I'm studying the Bell 206 Maintenance manual to understand how the pilot's control inputs get converted to swash plate movements.

This diagram seems to explain the cyclic well, but I can not figure out how the lateral stick movement is transformed.

Here is an example of how the crank mixer is operated by the cyclic (Y bar 9)

The forward-aft movement of 12 (the stick) causes member 10 to rock back and forth, moving 9 back and forth, which operates the mixing cranks at the end (connected to 7 and 8).

However, it looks like the stick can't mover laterally at all, since 10 can't move laterally (?) I can't figure out even why 10 has a provision for motion in the vertical plane in the first place.

Perhaps I'm misunderstanding how 12 moves? I'm assuming it pivots around the base (15).

A more detailed view of the linkage:

Thanks!

Does this answer your question? How do a helicopter's cyclic and collective transfer commands to the swash plate? — Pilothead, Feb 05 '22 at 02:10
I have read those answers thoroughly. I understand the principle. I wish to know how this particular design works. There is something about the lateral motion of the stick here I do not understand, since the linkage 10 looks like it will lock any lateral motion. — Kaushik Ghose, Feb 05 '22 at 02:17
You should provide a link to your source, both for attribution and so people can see any related material. Different views sometimes clarify operation. — Pilothead, Feb 05 '22 at 02:23
That's good, and your second illustration shows the spherical bearings at 5 and 16. — Pilothead, Feb 05 '22 at 12:44

Pilothead · Accepted Answer · 2022-02-05T12:37:42.610

4

9 is a rigid structure held in a single plane by three links, two forward (one is the cyclic) plus one at the rear. It replicates the cyclic position in the rear link (and incidentally in the other forward link) and cannot by itself cause a differential motion in 7 and 8, which is the rear link's job.

The picture is insufficiently detailed. The links (view C) at the ends of 10 use spherical bearings to allow lateral motion. 10 does not move vertically, it moves laterally which moves 9 laterally which imparts a tilt to the poorly illustrated link at the back of 9 which moves 7 and 8 differentially. An axial twist in 10 is the same motion as 10 and 9 fore and aft, and is the means by which that occurs. The pivots are the bottom spherical bearing in view C and similar attached to cyclic.

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edited Feb 05 '22 at 12:37

answered Feb 05 '22 at 02:29

Pilothead

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@jim An axial twist in 10 is exactly the same motion as 10 and 9 fore and aft, and is the means by which that occurs. The pivots are the bottom spherical bearing in view C and similar attached to cyclic. 9 is a rigid structure held in a single plane by three links, the two forward already mentioned plus one at the rear. It replicates the cyclic position in the rear link and cannot by itself cause a differential motion in 7 and 8, which is the rear link's job. – Pilothead Feb 05 '22 at 05:20
Ok. That’s an interesting linkage, but I think I’ve got it now. Thanks. – Jim Feb 05 '22 at 06:34
Very nice explanation - thank you for finding that picture of the linkage. I understand now! – Kaushik Ghose Feb 05 '22 at 12:45

How does this Bell 206 cyclic control linkage work?

1 Answers1