Bridges with the default durability are far too soft

[Charon]

Major bridges, especially steel girder bridges, were famously some of the hardest targets for bombers. They were hard to hit, yet were invariably targeted with 1000lb+ bombs, and frequently survived even direct hits from those.

 

This log from the 344th BG lists only two bridges targeted with 500lb bombs, likely the small bridges over canals here. The rest were targeted with 1000lb and 2000lb bombs.

 

The bridge at Thanh Hoa was famously hit by hundreds of bombs before finally being put out of use by 2000lb PGMs.

 

Yet in game, a direct hit from a mere 50kg bomb can destroy a span of this steel girder rail bridge (br_rw_dngrid, default durability 25000, loaded from the standard templates).

 

 

Please buff the durability values of all steel girder bridges so that they can survive single hits from 250kg bombs

 

Track:

bombtest.2023-02-02_20-00-03_00.zip

Edited February 7, 2023 by Charon

[Charon]

Mea culpa... I realize now that the durability (as obtained after 'reset durability to default values') in the editor is actually 50,000. The provided templates are too soft for some reason. Perhaps update them?

 

The values also seem a little low even when corrected, since spans can still fall to a pair of FAB-100s. Consider raising them a little more?

[Charon]

Here's a better track. A steel-girder railway bridge, with the 50000 durability value, brought down just by a near-miss from 2 FAB 100s, and another segment brought down by one hit and one miss.

 

 

bombtest.2023-02-03_19-31-44_00.zip

[Charon]

Further references:

 

Quote

When attacking bridges, I prefer to carry the heaviest bomb available. My plan is to hit the embankment or approach, leaving the span alone. On bridge attacks I favor glide-bombing at a 30 degree angle

Col Donald J M Blakeslee, 4th FG, quoted in "Down to Earth: Strafing Aces of the 8th air force", William Hess, p 106.

 

Quote

Anything less than 1000lbs is not too much good on bridges. On all the bridges we've bombed, we have only been successful in dropping one span. I'm sorry to have to admit that, but it seems to be the truth.

Col Joe L Mason, 352nd FG, ibid, p112.

 

Quote

The average bridge encountered in occupied territory can usually be damaged by skip-bombing with a 500-lb bomb and a delayed action fuse.

Col Thomas J J Christian Jr

361st FG, ibid, p119

 

Quote

The gruppe repeatedly attacked the Vistula bridges between Warsaw and Praga, as well as at Modlin, Wyszogrod, and Plock.

During these attacks, which were evaluated through photographs, it turned out that a lasting destruction of the bridges themselves was almost impossible. However, it was possible to achieve lasting effects by placing the weight of effort on the bridgeheads, thus rendering the bridge unusuable for a long time.

Photographic analysis of railroad and road bridges that had been hit with 500kg delay fused bombs showed that these bombs had sometimes only torn pieces out of the bridge or had simply fallen through the bridge leaving a more or less large ole without causing the bridge to collapse, which was the actual goal of the attacks.

As mentioned in section I, direct hits on bridges can only be achieved with some certainty when a dive against the wind is possible and no or only little AA defenses allow for a low release altitude.

[...]

In the case of stone bridges, fuse setting m.V. [with delay] only makes holes in the bridges, fuse setting o.V. does not cause stone bridges to collapse either.

On railway bridges, a fuse setting of o.V. results in the destruction of the tracks and such the inoperability of the bridge.

BArch, RL 7-1/12, Erfahrungsberichte der Fuhrungsstellen un unterstellten Verbanden uber den Einsatz in Polen, translated and reproduced in p236-238 of STUKA, The Doctrine of the German Dive-Bomber, by Christoph Bergs and Bernhard Kast.

 

Quote

19.05.42

[...]

Success: 1 hit (250kg) on the eastern bridgehead, 1 hit (500kg) on the eastern part of the bridge (above water), probably one further hit on the western third of the bridge.

Follow up report based on the impact pattern: there are 4 total hits on the bridge, namely:

eastward bridge joint destroyed

immediately next to this towards the west 50m bridge destroyed

in the eastern third of the bridge over the river, two adjacent hits which destroyed a bridge length of up to 28m.

[...]

Ordnance: 3 SC 500, 14 SC 250, 66 SC 50

[...]

The attacked bridge was a very strong bridge, same construction as bridge at Bogorodichnoye.

Mission report 567, p162 Bergs & Kast, translated from BArch, RL10/473a, Erfolgsmeldungen des IV. Fliegerkorps.

 

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In summary, pretty much everybody agrees you need at least 500lb bombs, with larger bombs preferred, and that even then it wasn't a sure thing. Targeting the bridge ramps was more reliable.