A Plea: Please Get Dive and Torpedo Bombing Right

[charon]

Dive bombers and torpedo bombers played a key role in the Pacific war. No amount of skillful dogfighting is going to let a fighter pilot send a carrier to the bottom -- the bomber pilot can.

I know we're all salivating at the idea of screaming down on Akagi or Yorktown, but I've got opinions on the things that past sims have neglected, and I want you to not repeat those mistakes when you make your first bombers:

Bombs and Armor Penetration

When attacking ships, impact-fused high-explosive bombs were used to kill gun crews on the deck, and delay fused armor-piercing or semi-armor piercing bombs to penetrate the deck and cause more serious damage inside. The contrast in effect can be seen with the hits sustained on Yorktown at Midway. First a 242kg land-attack bomb that killed AA crews and left a hole in the flight deck, but which only started small fires below deck. Moments later, two 250kg SAP hits which penetrated the decks and exploded inside the ship, knocking out several boilers.

Cruisers and battleships have more armor and so the dive is even more important, to ensure that the SAP bomb has enough speed to pierce the armor, rather than just skipping off.

Please make sure to account for this. It shouldn't be enough to land just any hit with a bomb. Sinking capital ships out to require good hits, with the right bombs, the right fuses, and the right angles.  Ships deserve a damage model, even a simple damage model, just as much as planes do.

Dive Bomb Sights

Here's a picture from Ju 88 A-4 Werk Nr.0881478 at the Norwegian Aviation Museum. 

Notice something? That's right, the Schwenkplatt SP 1A. L.Dv 20/2, which describes dive bombing in the Ju 88, makes clear that the pilot should adjust the elevation of their reflex sight based on the wind and dive angle. The hold-over for the Ju 88 can be as much as 14° for some dive profiles (L.Dv 20/2, Tafel I), far too much for a hold-and-hope aiming strategy to be effective.

The Ju 88, as modeled in both CloD and in BoX, lacks the Schwenkplatt, so even though it has dive brakes and a contact altimeter, it is incapable of effectively aimed dive bombing.

The Pe-2 has a similar problem:

The reflex sight has an adjustment knob, but it can't be adjusted in game. The Pe-2 as modeled in BoX is incapable of effectively aimed dive bombing.

And the Ju 87:

Quote

Die Tatsache, das bei Sturzflugwinkeln zwischen 50° und 80° der Gesamtvorhalt fur Aufsatzwinkel und Windverbefferung ein Mass von 3 im allgemeinen uberschreitet, wurde bei der zum Schiessen ublichen Justierung des Reflexvisiers dazu fuhren, dass der errechnete Visierpunkt jeweils ausserhalb des Lichtkreises lage. Zur Abhilfe muss deshalb das Reflexvisier fur den Bombenwurf so justiert werden, das beim Zielen uber die Stachelspike bereits ein dem durchschnittlichen Aufsatzwinkel entprechender Borhalt gegeben ist, oder ein verstellbarres Revi benutzt werden.

Fur die Praxis ist es zweckmassig, der Justierung fur Ju 87 einen Vorhalt von 3° zugrunde zu legen. Hierdurch ist beim Zielen uber Gestachelspitze stets ein Vorhaltewinkel von 3°, beim Zielen uber den unteren Schnittpunkt der senkrechten Achse mit dem Lichtkreis ein Borhaltewinkel von 6° erreicht. Der obere Schnittpunkt der senkrechten Achse mit dem Lichtkreis ergibt ein Visierlinie parallel zur Justierachse und damit die Visierlinie fur das Schiessen mit dem starren Gewehr.

Due to the fact that at dive angles between 50° and 80° the total value of the lead and wind correction angle generally exceeds 3° would result in a calculated dive aiming point that lies outside the circle if the reflex sight is adjusted as for shooting. To remedy this, the reflector sight used for bombing must be adjusted in such a way that when aiming via the aim post, a lead angle corresponding to the average required angle is already used, or an adjustable reflector sight must be used.

In practice, it is advisable to base the adjustment for the Ju 87 on a lead angle of 3°. This means that a lead angle of 3°  is always achieved when aiming via the aiming post, and a lead angle of 6° is achieved when aiming at the point where the circle intersects with the vertical axis [aiming post]. The upper intersection point of the vertical axis with the circle results in a sight line parallel to the adjustment axis and thus the sight line for shooting with the machine gun.

L.Dv 20/2, p17. When the Ju 87 isn't furnished with an adjustable gunsight, it ought to be calibrated with a -3° offset such that the guns converge on the upper intersection between the vertical aiming post and the circle.

This adjustment isn't modeled in CloD nor in BoX, and while the Ju 87 is capable of diving steeply enough to still be effective, this omission handicaps it slightly and makes dive-bombing by-the-book a little more difficult.

US Navy Training Film: Introduction to Dive Bombing: "The sight is boresighted so the line of sight is below the line of flight. If this is done, the bomb will hit our point of aim when we release in a normal [65°-70°] dive".

I don't know specifically how the sight is calibrated on the SBD or on the D3A, I haven't spent time researching these particular bombers. But please please please, do a sanity check. If you get done modeling one of the dive bombers and find that to hit its target, with a historically correct dive angle and release height, requires holding the gunsight beyond the target and aiming by guesswork, stop and consider if that is plausible.

Evasion

Ships under attack don't generally sail in a straight line. Japanese ships, especially, relied heavily on aggressive turns to evade hits. American doctrine relied more on coordinated anti-aircraft fire (Shattered Sword Page 143-145), but even so they would maneuver to present hard targets to bombers and to evade torpedoes. Hiryū and Sōryū could even outrun American torpedoes outright.

Unless they're already crippled, hitting ships with torpedoes ought to require teamwork. Most aerial torpedoes were evaded. If a flight of torpedo bombers splits in two and attacks from right angles, they ought to present ships with an insoluble problem, but a lone torpedo attack should almost never achieve anything of consequence.

Yet I've not seen this implemented in a sim. Instead, ships usually sail straight forward like ducks in a shooting gallery.

Damage Control and Sinking

Usually in sims, ships get hit, counted as destroyed, and disappear under the waves in at most a few minutes. But often it took far longer in reality. Sōryū and Kaga were hit three and four times respectively and scuttled 9 hours later. Akagi was hit once and scuttled 19 hours later. Hiryū was hit four times and scuttled 16 hours later. Yorktown was hit 7 times before finally sinking 41 hours after the initial hits. Cruiser Mikuma was hit three times and sunk 7 hours later.

When capital ships are hit, they ought to take their time about sinking. Let them burn on the surface, or very slowly take on water and capsize.

Edited June 2, 2023 by charon

[Boom]

Great post charon!