Impact of dead radar on Bismarck's defence against Sworfish

[Siegfried]

On occaision much has been written on the impact on the Battle of the Denmark Straights of Bismarcks radar/s being out of action due to shock damage from a short battle with HMS Suffolk. Prinz Eugen took the lead to provide forward coverage since it was Bismarcks forward radar that had failed thus leading to HMS Hood mistakenly engaging the Heavy Cruiser instead of Bismarck. Overall however there was little inpact in the gunnery side of the Battle since neither side had a supeior radar and optical shooting was adaquet.

However a critical aspect of the Battle involves Bismark being hit by torpedos dropped from Swordfish torpedo bombers which she was unable to stop or shoot down. The impression I have is that Bismarcks FLAK was respected against high flying aircraft but that it was low flying ones that her systems couldn't effectively see.

Was Bismarcks radar still malfunctioning during her escape run? How would the non functioning radar have impacted her abillity to defend herself against the low flying torpedo bombers?

The attacks occured quite late in the day ie 8pm, one assumes under twilight conditions. How can I find out sunset times at the time and date of the Battle in order to evaluate visual conditions.

[Serg]

I'm not sure about twilight conditions but obviously the visibility was limited by low clouds, at a height of about 200 meters. According to Pursuit by Kennedy "Over Sheffield conditions were good for attack, with a cloud base of 2,000 feet rising to 5,000 feet. Coode led the striking force upwards with the intention of meeting them above cloud, there splitting up so as approach Bismarck from different directions, make it more difficult for her to avoid the torpedos. But unknown to him, Bismarck was sailing under what meterologists call a 'front', a wall of cloud reaching to beyound 10,000 feet and extending downwards almost to sealevel... At 700 feet the three planes plus another from No3 sub-flight that had accidentally joned them broke through the cloud to find themselves, not as they had hoped, astern of Bismarck but four miles ahead of her..."

[Dave Saxton]

Hi Siegfried,

1) Bismarck had three radar sets so it at least had the aft set and probably one of the forward sets during the Denmark St. battle and afterward. Tommy303 opined that the change in position was likely due to Luetjens wanting be able to use the foretop set to track and range the shadowers for Bismarck's guns because of its greater range (due to higher mounting height) and allowing the high foretop mounted forward radar of Prinz Eugen to monitor ahead.

2) If both forward sets were initially knocked out, then this was likely the result of tying the two forward sets together as one. This could be done with Seetakt and would have improved antenna gain.

3) The British eventually found that some of the radio mechanic ratings among the prisoners talked among themselves that the forward radar(s) was repaired late on the 24th or on the 25th.

4) The Bismarck was obviously using radar ranging when shooting against Vain's destroyers.

5) As far as I know lobe switching wasn't normally used by the KM big ships at the time of the Bismarck sorti due to typical inaccuracies of the rangefinder traversing mechanism. However, the radars could be used to range aircraft targets as well as surface targets.

6) A potential problem, and that there is evidence for occuring in the Bismarck case, was spectral reflection. This a little known but common problem of ranging low flying aircraft with radar at sea. What happens is that the target's echo reflection bouncing off the sea below the aircraft is picked up by the radar and causes an incorrect range measurement to be used in the firing solution calculations. The AA guns then shoot short of the target like they over estimate the speed of the attackers.