Yeah even the 11 sensors a side GHG was way superior to anything the allies had during the war. The irony of all this is that at the start of the war the US navy regarded all periscope attacks as too dangerous (subs could be spotted by aircraft). Thus standard US attack doctrine at the start of WW2 was a night,submerged, passive sonar attack. US sonars of the time could not support this doctrine and skippers who used these tactics did not hit their targets. Now a type XXI could have excecuted this attack (especially if it used 'Niebelung' active sonar.This sonar was used as the basis of the US BQQ-3a sonar.The BQQ-3a was an addition to the BQQ-1 intergrated sonar and was used to measure very accurately Doplar shifts in the targets motion).