https://aviation.stackexchange.com/q...mig-29-cockpit
Q: What is the purpose of the “Mirror-Thing” over the Mig-29 Cockpit?
A: The periscope replaces the rear view mirror on the two-seaters version
because the instructor seat (aft) is not high enough, contrary to other training
aircraft, to see the runway. The runway is projected on a second mirror inside
the cockpit (that's why it's named a periscope and not a mirror):
Note how the projected part of the image fits very well into the direct view of
the exterior.
An opening is created in the canopy when the top mirror is deployed. From below
this is what it looks like (not exactly the same model):
The bottom mirror unfolds down to instructor eyes height:
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