On this day 22 September 1917
On this day 22 September 1917 UB32 sunk by air attack.
U-boat UB 32 sunk by 2 x 230lb bombs dropped by Curtis Large America No.8695 from Dunkirk, escorted on its patrol by two Sopwith Pups. The crew of the seaplane was Flight Sub Lieutenants N A Magor and C E S Lusk & Leading Mechanic R A Lucas.
The crew reported seeing the explosions, wreckage and oil; wreckage and oil were seen and confirmed by the fighter escort. UB32 had sailed from Zeebrugge on 10 September and never returned. It was presumed lost. Although other sinkings were claimed, it is now known this is the only U-boat confirmed sunk by air attack alone.
Source:
Antisubmarine warfare in WWI, John Abbatiello