Does the Heavy Gunner perk affect the minigun on the vertibird?

I would think it would but I can't tell. Does the Heavy Gunner perk affect the damage of the mounted Minigun found on Vertibirds?

Yes, the perk does increase damage dealt by the mounted Minigun on Vertibirds. This is because, as seen at the very beginning of the game in Concord, the mounted Miniguns really are just mounted Miniguns.

From the wikia page for Miniguns:

Miniguns can be found as mounted door guns on Vertibirds or as a hand-held heavy assault and support weapon. It uses 5mm rounds as ammo.

And from the wikia page on the Heavy Gunner perk, the guns affected by this perk are:

• Minigun
• Gatling laser
• Missile launcher
• Fat Man
• Cryolator
• Flamer
• Broadsider
• Junk Jet
• Harpoon gun

A few users have also supported that this is the case in this thread:

User 1:

Yes its really just a regular minigun

User 2:

from my experience, yes:

1st time I tried it I had no big guns improvements and killing the behemoth was extremely annoying - took several passes from the vertibird and I had to reload several times

2nd time I tried it I had 4 ranks and the behemoth got annihilated in 1 pass

User 3:

Yeah it was a stupid decision to tie in the damage type of the vertibird minigun to heavy weapons.