Window in aircraft door
 

On many commercial passenger aircraft, there is a small window in each door to the aircraft. In the event of a crash landing, one wants to be very careful not to open a door if there is a fire immediately outside.

I realise all the windows next to passenger seats gives plenty of visibility... but it seems strange that the person potentially opening the door (ie can be passenger, particularly if crew are injured) cannot see easily from the door itself but must go somewhere else first to look. This seems to go against human instinct, making it harder to check the safety of an emergency escape route as people, particularly if untrained for a scenario, often panic in emergencies instead of thinking rationally.

Is putting a sizeable window into aircraft doors just too difficult ? Or is there another reason ?

I would presume that it's something to do with being at the gate. The crew can see if someone is standing on the steps or on the pier before opening the door which swings outwards.

Indeed, they only need to see who or what is out there - in an evacuation, is there fire/water/danger?

Also, the main doors have much space taken up with the slides and a big window gives no benefit.

I'm really only guessing but you might be onto something with that last comment- in addition to the slide you've got to fit into the interior of the door structure all the moving cams/rollers/levers associated with locking/unlocking, plus maybe power assist...there might not be much room left to give a clear run through the internal structure that is big enough for a standard window.

Putting an appreciable-sized window in the door would immediately result in centre-row passengers all rushing to see the view. :O

Which is fine, until, the crew open the door without disarming the slide first....luckily, nobody was hurt on the airbridge.

I dare say that you have all seen images like this ...

https://cimg5.ibsrv.net/gimg/pprune....7f865fc67c.jpg