At around 50 seconds on the linked video you can see the serrations on the trailing edge of the B52's spoiler.

What purpose does it have, and what gives it advantage/disadvantage over the standard spoiler? I've only seen serrated trailing edges on wind turbine blades.

enter image description here

  • 2
    $\begingroup$ I don't know for sure, but it's most likely to reduce a burble or vibration by diffusing the air flowing around the TE of the spoiler (I doubt it would be only to reduce noise). $\endgroup$
    – John K
    Nov 5 '18 at 4:49
  • $\begingroup$ Are you talking about these en.m.wikipedia.org/wiki/High-lift_device $\endgroup$
    – Ali Erdem
    Nov 5 '18 at 6:09
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    $\begingroup$ Maybe it is one geometric solution to tune the lift/drag curve of those spoilerons along the whole deflection range. (providing more drag than expected at low deflection angle) $\endgroup$
    – qq jkztd
    Nov 5 '18 at 14:14
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    $\begingroup$ @JohnK - I seem to recall this as well. With a straight rear edge you can get flutter and have to design for that, but the serrations spoil the resonance. $\endgroup$ Nov 7 '18 at 21:24

The comments above by John K. and Maury Markowitz are on the right track. The serrated trailing edge of the spoilers has an effect on vortex shedding. It is called that because it is a vortex-shaped airflow that is shed from the rear of an airfoil or other surface.

On modern jet engine nacelles the serrated edges at the rear reduce noise. However, on the B-52 the most likely reason for this feature on the spoilers is to reduce the possibility of vortex shedding inducing vibrations that could cause the wing structure to resonate due to the harmonic oscillation of the vortex. This is also known as flutter. My guess is that at some point in the life of the aircraft design it was determined that this was (or could be) an issue, and this was the solution.

If you think about the last time you flew on an airliner where the pilots deployed the spoilers while still in flight, you may remember the vibration generated by them. That is the consequence of vortex shedding, and that is what the serrated edges are designed to minimize on the B-52.


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