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Comment by hkwerf | Hacker News Reader

I've repeatedly heard stated that after a sufficient amount of force is applied to controls, "the link" between the controls is severed or deactivated, without any details regarding how this is done or what the actual effect is.

Here's an article stating exactly that: https://english.alarabiya.net/News/world/2022/04/28/Pilots-p...

> If opposing forces on the two columns pass a certain limit, the link between them is deactivated or “desynchronized” to prevent accidents in the case of one side getting jammed.

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It's a purely mechanical linkage. I've been trying to read the patent (US 5782436A). The USPTO has a new single-page web app. It's awful for finding by patent number, and worse when you want a full screen image of a drawing. It's clear that if one yoke is jammed and the other is moved with enough force, a spring loaded pin is forced out of a notch and the connection between the two yokes releases.

What's not clear is how the linkage still connects to the flight controls. The idea seems to be that the one which is moving wins. What is clear is that, if your side becomes disconnected, your yoke doesn't do anything. No wonder one pilot was frantic. It seems that you get reconnected by moving the disconnected yoke to agree with the one in control. Then the pin falls into the notch and the yokes are connected again. Not sure about that. You can see the pin and notch in the patent drawings.

This is independent of the fly-by-wire system. That's downstream from these mechanical devices.

I wonder if pilot training includes knowledge that yoke disconnection is possible.

> I wonder if pilot training includes knowledge that yoke disconnection is possible.

Probably, I've heard https://www.youtube.com/c/MentourPilotaviation talk about it as well.

They are trained in this. If disconnected, each yoke will control "their" half of the plane. This is mostly intended to maintain some level of controllability if one of the yokes were to get blocked or seized mechanically, this is not intended for human issues

If the linkage breaks, then each pilot gets to control the control surfaces on one side of the aircraft.

In the 777 it's a direct mechanical linkage between the controls, with a torque-driven breakout which temporarily severs the link if there's too much difference in the two pilots' inputs

That still leaves the question of how to interpret opposing inputs for the physical control surfaces, though

On the 757, the two control columns are linked with a roller bearing in a detent (notch). With enough torque applied, the bearing will come out of the notch and the columns can move independently.

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