Gun-Bomb-Rocket Sights

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Oct 15, 2018

I'm new to this forum. Long story follows:

I was learning about W.W.II torpedoes and their design problems (most of which are well known) then discovered an elephant size problem. The range (how far it goes on its own power) exceeds the useful range (maybe where the hit probability is less than 10%) by over an order of magnitude. This means a lot of time and money was spend for nothing. By the end of W.W.II the range was over 10,000 yards but hits out more than 1,000 yards almost never happened (Ref: Pig Boats). Since the Ford Instrument Co. made the Torpedo Data Computer as well as the Gun Director for Battleships I started looking to see if there's a similar problem with big naval guns, and as far as I can tell Battleships (aka Iron Castles for admirals) can NOT hit a moving ship at anywhere near their 35 mile range.

I came across the Norden Bomb Sight while learning about gyroscopes
and the fact that the US Navy developed it and gave up since it did not work. But the Army put it into production, where it did not work. They gave up on precision Horizontal Bombing and went to Carpet Bombing. What did work for the Navy was dive bombing. So I started looking for dive bombing sights, but none were to be found. It turns out that what are called "Gun Sights" on early planes, like the Douglas SBD Dauntless is in fact the 3X rifle scope which was used for both bombs and guns. Note a dive bombing sight points forward just like a gun sight, not down like the sight for horizontal bombing.
Mk 20 Mod 4 Gun-Bomb Sight

More modern Sights, like the Mk 20 Mod 4 were used for all the ordinance on the Skyraider which includes Guns, Bombs plus 2-3/4" and 5" rockets. So a Gun-Bomb-Rocket Sight.
This sight was also used on the AC-47 Spooky Gunships.
Mk 20 Mod 4 Gun-Bomb Sight

I'm still trying to understand the function of the 3 Reticles and how the "Mills" knob is used. The exact "Mils" knob appears on the F4 APQ-72 sight. I'm guessing that for each type of ordnance there's a Mills setting changing the vertical angle of the aim point. I suspect that the filter color is independent of the Reticle when the reticle wheel is assembled.

I have a Navy Mk. 18 Gun Sight on the way and there will be a new web page about it. Learning more about it brought me to this forum.

Have Fun,

PS Trivia: While looking for dive bombing sight patents I discovered the problem caused by using a conventional bomb rank on the center line of a propeller dive bomber. Since the bomb has a much lower drag coefficient than the airplane as soon as it is released it starts going faster than the plane and will fly through the propeller, not a good thing. So special bomb racks are used to move the bomb far enough away from the propeller disk so that does not happen.

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