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Reading about the Douglas C-133, I see this:

The second issue discovered was stall characteristics gave very little warning to the crew. The left wing was found to stall before the right wing. The fix was simple, a small strip of metal was attached to the right wing causing it to stall at the same time the left wing would stall.

The issue affects the whole type. What would cause one wing to reliably stall before the other?

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    $\begingroup$ It has to have something to do with the fact that all four engines turn in the same direction $\endgroup$ – TomMcW Oct 4 '17 at 20:34
  • $\begingroup$ Interestingly enough, this article (which Wikipedia cites), says that "Cameras... clearly showed the right wing stalling before the left—in fact, the left wing usually didn’t stall at all" airspacemag.com/military-aviation/… $\endgroup$ – Cody P Oct 4 '17 at 23:18
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In general, aircraft aerodynamics can be affected from manufacturing tolerances or consistent asymmetries.

The reason can be due to any asymmetry in the wings or fuselage shapes, or wing-to-fuselage fixtures.

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  • $\begingroup$ Are you suggesting their jigs were crooked? $\endgroup$ – Adam Oct 4 '17 at 17:32
  • $\begingroup$ Exactly. The consistent asymmetry might be the result of a fixture being asymmetric, or a mould or template. $\endgroup$ – Gürkan Çetin Oct 4 '17 at 17:34
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For any design, a skidded turn stall is an example of one wing stalling before the other. This would be characteristic of a handling error rather than a design issue.

In an aircraft not in balanced flight, particularly in a skid (nose inside the radius of turn) the fuselage will somewhat mask the airflow on one wing causing it to stall before the other.

We used to teach these to instructors at altitude when I was a standardization pilot in the Navy, for the T-34C, to illustrate the disorienting rolling moment that occurs when one wing stalls.
Close to the ground this kind of stall could be lethal
(Please view the whole video, the narration by the instructor is very good).
The video example shows a rapid loss of about 700' with an instructor knowing it was coming. He calls it a "base to final skidded stall" that he describes as causing "an incipient spin."

This is a form of a cross control departure. A college classmate of mine died in a cross control departure in the landing pattern, in a T-2 over 30 years ago during flight training.

(I just discovered that the Navy now prohibits cross control departure training in the T-45C jet trainer which IIRC was part of the OCF syllabus in the T-2. I also found it missing from the T-6B syllabus, which I must say surprises me).

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    $\begingroup$ Sure, but if you did the maneuver the other way then the other wing would stall first, correct? The C133 writeup implies that the problem was systemic for the whole fleet. $\endgroup$ – Adam Oct 4 '17 at 17:32
  • $\begingroup$ I'm curious about the C-133 case in particular. I'm only assuming it's a design issue if the fix was a piece of hardware. $\endgroup$ – Adam Oct 4 '17 at 18:43
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In a non-design respect, sharp yawing pressure during a stall can result in one wing stalling more than the other. That causes a spin. If you're looking for a design that can do it, a square of metal near the top of the camber can increase the turbulent airflow to match or exceed the other wings'. Any difference of the wing shape, airfoil size, or airfoil shape between one wing and the other can also result in one wing stalling more easily than the other.

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