What is that device on an Su-27 pilot's helmet? While watching a YouTube video (2.5hrs), I noticed this device on the top of most Russian Su-27 combat pilot's helmet. A google search only shows it for a Su-27 and MiG-29, but apparently no other aircraft. It was not on any Chinese, Syria, Ukraine or Russian aerobatic pilots flying the Su-27. It appears to be at the wrong angle and has a metal plate that seems to exclude it from being some type of illumination.

What is this on a Su-27 helmet?
That is the mounting point for night vision goggles. The following image shows a helmet with NVG mounted.



Helmet mounted NVG; image from lemt.by

The USAF has helmets with different mounting and some of the modern pilot helmets (like BAE Striker II, for example) have an integrated night vision device.