What are these windows/portholes on the English Electric Canberra bomber? This may be an obvious question, but I don't know, which is why I'm asking here. I've searched "Canberra canopy porthole" and "window", but didn't get any information. There is a porthole of sorts on the left side of the canopy of this bomber, I'm wondering what it's for.


Photo source.

Here is a view from inside the cockpit:


Photo source.

There also appears to be a similar thing on the bottom of the nose of the aircraft, offset to its right. The following is a screenshot from a video game, as I wasn't to find a photo of this.



I'm tempted to say that this second one is to do with bomb sighting, however if it weren't there, the bomber would have just as good a view, wouldn't they?
It's called a "Direct Vision" (DV) window. The canopies are sealed shut, so the small DV window is provided as a way to open a small hole if required. For example, to communicate on the ground or in the event of icing or other canopy issues.

Edit: I wasn't able to find a formal source, but this page is fairly authoritative:

http://alverstokeaviation.blogspot.com/2016/08/english-electric-canberra-technical-tour.html