Jump to content

What's the reasons for using vision ports instead of periscopes?


curious1234
 Share

Recommended Posts

One thing to note about periscopes, a periscope could be removed for cleaning or swapping if needed from inside the vehicle.

For example, the driver's nighttime periscope on a M1A1 was stored inside until needed. These were good on the M1A1 and got better with the newer thermal camera'.

(23) Does the driver in the M1 Abrams tank only have the tiny rectangular windows in his hatch or does he also have internal monitors and cameras for visibility? - Quora

M113A1 had a older infrared periscope but I unfortunately never tried it.

Link to comment
Share on other sites

Vision blocks in certain types can also be removed. Both the side units on Ferrets and the front blocks (or vision or bullet screens) on WWII AFVs are replaceable. One of the many things I need to sit down and fab are more of the British ones with thick slabs of glass and a metal frame of the right shape/size to fit into the housing. 

And of course the post war periscopes can be replaced as well, but they were a more simple assembly. The WWII Mk IV types were two piece units. The upper portion is one part, the lower portion is another part. You undo a catch to swivel the lower portion out of the way and then you can withdraw/lower the upper periscope body from out/through the roof and replace it. 

Link to comment
Share on other sites

  • 2 weeks later...

There is one location that comes to mind where a vision port is preferable to a periscope, and that is the rear door of an IFV or APC.  A periscope would obstruct debussing troops, and any reduction in protection is negligible as it is not good practice to expose the rear to the threat.

Best,

Greg.

 

Edited by GJK
Link to comment
Share on other sites

These are the rear doors of the BMP. And there are periscopes built in. I can't see that these periscopes "would obstruct debussing troops". What do you mean by that?

1024px-Panzermuseum_Munster_2010_0665.thumb.JPG.2eb0d4dd8ac784ee14e6f3a65ca14029.JPG

Edited by Stefan Kotsch
Link to comment
Share on other sites

If you didn't have the depth of the fuel tank, you'd have the eyepiece sticking out into the doorway when you opened the door, which would potentially be a snagging issue.

For the BMP, it's not an issue as can be seen from interior views - the eyepiece is heavily recessed into the fuel tank outline.

Link to comment
Share on other sites

2 hours ago, DB said:

If you didn't have the depth of the fuel tank, you'd have the eyepiece sticking out into the doorway when you opened the door, which would potentially be a snagging issue.

For the BMP, it's not an issue as can be seen from interior views - the eyepiece is heavily recessed into the fuel tank outline.

I'm not sure what you mean precisely, are you envisioning something like the MT-LB's door? As in, this periscope is a snagging hazard for disembarking passengers?

mtlb-03.thumb.jpg.608f408e3ff164bdbce8268921d3dcb7.jpg

This seems to be a trivial issue which wouldn't be solved with a vision port anyway, since a vision port would have a considerable thickness of glass that has to protrude from the door.  

Link to comment
Share on other sites

It wasn't my original comment, but one attributable to GJK. I was agreeing that this isn't an issue for the BMP, for the reasons stated, but not all exits are equal, some are likely to be arranged such that what GJK said would be a potential issue.

Link to comment
Share on other sites

Hmm, ok but I'm still not sure what either of you have in mind. Maybe the idea is that putting a periscope in the hull ceiling directly in the path of the rear door will obstruct the passengers? But that is easily solved by embedding the periscope into the door itself, which works regardless of whether the door has spaced armour/depth or if it's just a single plate.

Link to comment
Share on other sites

On 12/17/2021 at 7:29 PM, Stefan Kotsch said:

These are the rear doors of the BMP. And there are periscopes built in. I can't see that these periscopes "would obstruct debussing troops". What do you mean by that?

1024px-Panzermuseum_Munster_2010_0665.thumb.JPG.2eb0d4dd8ac784ee14e6f3a65ca14029.JPG

The vehicles I have been in are Spartan, Warrior and FV432, none of which have the depth of door external to the hull which could be used for this arrangement.  This picture is interesting as I didn't remember it from the BMPs I've seen.  I think the last time was 8 years ago in Munsterlager in my defence!

Best,

Greg.

Link to comment
Share on other sites

On 12/20/2021 at 12:54 AM, Interlinked said:

Hmm, ok but I'm still not sure what either of you have in mind. Maybe the idea is that putting a periscope in the hull ceiling directly in the path of the rear door will obstruct the passengers? But that is easily solved by embedding the periscope into the door itself, which works regardless of whether the door has spaced armour/depth or if it's just a single plate.

Anything hull-mounted that intrudes into the door aperture is asking for equipment to get caught or someone debussing in a hurry to whack themselves on it.  I'm only 5'11" and was reasonably slight of build when I was serving but still thought getting in and out in a hurry with kit and weapon was a tight fit.

Fair point regarding a periscope in the rear door, but it seems unnecessarily complex compared to a vision port.  Not sure it would be possible on something like a M2/M3 Bradley or M113 with a ramp instead of a door?

Best,

Greg.

 

Link to comment
Share on other sites

18 hours ago, GJK said:

Anything hull-mounted that intrudes into the door aperture is asking for equipment to get caught or someone debussing in a hurry to whack themselves on it.  I'm only 5'11" and was reasonably slight of build when I was serving but still thought getting in and out in a hurry with kit and weapon was a tight fit.

Fair point regarding a periscope in the rear door, but it seems unnecessarily complex compared to a vision port.  Not sure it would be possible on something like a M2/M3 Bradley or M113 with a ramp instead of a door?

Best,

Greg.

 

Well, at the end of the day, the periscope is protecting the user by putting space between the objective window and the eyepiece. To get the same protection with a vision port, it would have to be a fairly chunky block of glass, which would probably protrude even further and pose a greater snagging hazard.

With a ramp, it does seem like an unsolvable issue. Seems that what they did on the Bradley (stick the periscopes into the ceiling) was pretty much the only way. Though they could have alleviated the snagging issue if they used periscopes with a folding eyepiece mirror, like the loader's periscope in Chieftain.

 

Link to comment
Share on other sites

Another example. The Chinese APC Type 63. The standard periscope is actually quite flat due to the vertical arrangement of the prisms. I suppose it's not a simple block of glass. Although that would not be a problem here.

Type63_YW-531.jpg.bb072b022fb6d76f525fdeab76d33d32.jpg

From toadmanstankpictures.

 
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...