My dad worked on the Lancasters, I posted on this thread (No 6# in 2010), dad was 90 then but died aged 96. In the last couple of years he started telling me about some of his wartime escapades. Having joined the RAF aged 18 he was training to be an aircraft electrician. When planes came in damaged the various parts were repaired by engineers, electricians etc. Then the whole plane had to be tested.
One of the Lancasters out on the lead up to the runway was fitted with anti submarine depth charges , these were huge and packed with high explosives, I think dad said there were two under each wing and two under the body so six in all. To do the wiring test a special switch had to be thrown which then prevented any bomb release mechanism from activating but showed the wiring was complete end to end. The bombs had to drop in a special sequence so it did not unbalance the plane. You would have thought they would test it before fitting bombs etc but seemingly not as they were under constant pressure to get planes back in the air asap
Dad was in training but for some reason the fellow in charge forgot to set the switch
Dad recalls standing there in horror as the mechanism began to whirr and one after another they heard thud, thud, thud as all six dropped one after another onto the concrete. He vividly remembered the plane tilting slightly, first one way then the other as the load altered
If these had been regular bombs it's possible it could have blown up the plane but depth charges had some kind of fuse which activated under water pressure.
The chap in charge was court marshalled, dad had to appear as well to give evidence but did not get into trouble himself as he was not actually in the cockpit when the switches were activated.