I was looking at some photos today and came across this one:

enter image description here Image source

I noticed four little things in between the horizontal and vertical stabilizer. Could somebody explain me what those are?

  • $\begingroup$ From what I see, they are not antennae. I might guess that they are static-relievers but I may be wrong. $\endgroup$ Jan 26 '16 at 20:58
  • $\begingroup$ We also have this question which is very similar aviation.stackexchange.com/questions/24427/… $\endgroup$ Jan 26 '16 at 21:17
  • $\begingroup$ do you mean the metal plates over the fuselage? $\endgroup$ Jan 26 '16 at 21:23
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    $\begingroup$ Personally, looking at that picture I would asked about tube like formation on the back. $\endgroup$ Jan 27 '16 at 7:26
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    $\begingroup$ @JorgeAldo I would say that they are side-looking radar antennas. (this aircraft is part of the indonesian air force, probably a patroller/airborne radar station). $\endgroup$
    – Quentin
    Oct 17 '16 at 9:08

The objects are vortex generators. In general, vortex generators serve to introduce turbulence which helps to prevent flow separation. More information here:

This was to reduce elevator and elevator tab vibration during flight to increase their hinge bearing service life.

As mentioned on the site, you can see these on any 737 version from the original -100/-200 up through the NG. Better image from same site:

View of aft body vortex generators


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