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.

enter image description here Photo source.

Here is a view from inside the cockpit:

enter image description here 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.

enter image description here

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?

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    $\begingroup$ A blown, spherically shaped plexiglass dome will never have the optical qualities of a flat piece of glass, especially with the production technology of the late Forties. So yes, the nose cone window is for bomb aiming. $\endgroup$ – Peter Kämpf Nov 8 '18 at 18:44
  • $\begingroup$ You beat me to it w/ your comment Peter-- was in process of adding to my answer $\endgroup$ – quiet flyer Nov 8 '18 at 18:49

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:


  • $\begingroup$ Note the wires going to it-- it is heated, don't you think? If it opens, can you identify where the handle or latch is? So perhaps it is heated AND it can be opened? $\endgroup$ – quiet flyer Nov 8 '18 at 17:22
  • $\begingroup$ Is this both the case for the canopy one and the one on the lower nose? Would you open the port/window completely? If so I'd imagine enormous amounts of wind entering the cabin. @quietflyer Yes, I did notice the wires. Not sure what they're for. $\endgroup$ – Zebrafish Nov 8 '18 at 17:24
  • $\begingroup$ @quietflyer It certainly makes sense to be heated. It looks pretty clear that the bottom is hinged (7 O Clock our image), with a secured (thumbscrew) handle at the top (1 O Clock) $\endgroup$ – Dan Nov 8 '18 at 17:25
  • $\begingroup$ I'm thinking that part of the reason it exists, is so it can be heated more strongly than the plexiglass could be. In other words it is glass and can take the direct heat of a heating element that would melt the plexiglass. This answer could be improved by incorporating that idea. $\endgroup$ – quiet flyer Nov 8 '18 at 17:27
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    $\begingroup$ That's a very interesting link. In that model the bottom flat window seems to be for bomb sighting. It is also centred, as opposed to the offset ones to the side in my images. $\endgroup$ – Zebrafish Nov 8 '18 at 17:33

Re the upper "porthole"-- it sure looks like a heated panel for clear vision in extreme icing. Note the resemblance to a "hot plate" in King Air etc. It is undoubtedly glass and can be heated by a heating element (note the wires) to much higher temperatures than the perspex canopy could tolerate. Note that there is one on each side, and this aircraft has side-by-side seating in the cockpit. As has been noted in another answer, it appears to have a hinge and a thumbscrew latch, so it could be opened if needed (e.g., a/c is heavily iced up and electrical power has been lost or can't keep up with the icing-- or just to talk to someone on the ground.)

Your question also references the flat panel on the transparency on the lower part of the nose. It is not clear from the photos whether this is heated or not; it's almost certain that this larger flat panel could NOT be opened. However you'll note that it is very common for aircraft to include a flat glass panel for aiming a bombsight or as a window for a camera in the case of a reconnaissance aircraft. The curved perspex of the rest of the transparency will always have some optical distortion. Note that until fairly recently, many fighter aircraft had a flat windscreen in front of the pilot. Again part of the reason for this was to prevent optical distortion as the pilot looked through the gunsight. If this weren't an issue, the thick armored flat glass of the windscreen could have been "faired" more smoothly by an additional curved piece of perspex in front of it, but this was only rarely done.

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    $\begingroup$ I'm not a Downvoter, however, "Probably a (guess)" is a very poor answer. $\endgroup$ – abelenky Nov 8 '18 at 17:32
  • $\begingroup$ Well, I don't think so. Anyone who's seen a "hot plate" in a King Air etc would note the strong resemblance but it's only appropriate to note that one doesn't actually know this for a fact. $\endgroup$ – quiet flyer Nov 8 '18 at 17:34
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    $\begingroup$ If we are waiting for a design engineer or pilot to provide a definitive answer we might be waiting a long time. A credible, well reasoned educated guess goes a long way towards generating useful discussion and enhancing understanding. $\endgroup$ – Michael Hall Nov 8 '18 at 17:46
  • $\begingroup$ Was starting to type the additional info as saw your comment Peter $\endgroup$ – quiet flyer Nov 8 '18 at 18:57
  • $\begingroup$ This is a good answer now. It also answered another question that was in my mind, why do fighter aircraft have a flat glass front portion on the canopy given that it sacrifices aerodynamics. I think maybe because it's usually thick bulletproof glass, but the view distortion reason seems true also. $\endgroup$ – Zebrafish Nov 8 '18 at 19:20

the DV window was used by aircrew , open the dv and stick your hand out, to indicate to the ground crew that the aircraft in now depressureised and that it was safe to open the side door (strike wing RAF Akrotiri)

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    $\begingroup$ Hi. Can't they just see a thumbs up from behind the canopy? (There must be something else to it, preferably with a reference to back up any claim.) $\endgroup$ – ymb1 May 26 at 12:19

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