Mystery Japanese item

[RH1941]

Hi guys first off thank you for looking. What I have here was given to me by a friend who has had it for years . We believe its from WWII because of the writing on the back . Can anyone identify what it is . Thanks again for looking . Gary

[Nick Komiya]

Those photos are horribly out of focus, but luckily I know what that is. That is an aiming scale for the Type 91 aerial torpedo. They are celluloid strips and each plane cockpit carried many of these strips in a box. When you found an enemy ship and wanted to mount a torpedo attack, you had to select the strip that matched your flight altitude and air speed (yours is for a height of 150 meters at an air speed of 160 km). You had to slide that into a mechanical sighting device, which allowed you to determine the torpedo drop-point.

Type 91s had a maximum range of 2000 meters, but to minimize misses, they got released at a range of 800 to 1000 meters away. But the torpedo travelling at 42 knots needed between 37 and 46 seconds to close that distance to target, so you needed to figure out in advance where the ship would be by the time the torpedo travelled that far.

If dropped from a high altitude, the torpedo would dive deep before slowly rising to surface, so releasing it at short range ran the risk of the torpedo missing the ship by passing it below the hull without impact, so you needed to select the right aiming scale for your speed and height. The other important variable of the enemy's speed had to be eyeballed and set referring to the dials on the strip.

[jeeplover]

that is very cool

[RussM]

Wow, that's a great piece of kit for an aviation or navy collector!

[RH1941]

Nick thank you so much for the help in identifying my item . Your knowledge of the Japanese military and its items is incredible. Thank you again . Sorry about the bad photos the glass over my camera on my phone has shattered. Trying to make an appointment to get a new phone . Gary

[Long Shot]

Your strip would fit in this sight:



Here's a different torpedo sight that just displays the degrees on a Kate B5N - the calculations would have to be determined from a reference, or training or another compute tool?

[Nick Komiya]

The Type 97 sight shown immediately below in B&W did not use interchangeable scales, while later models like the Type Zero sight shown at bottom used them.