In England, Verne writes in his diary . . . .
03-01-45 – 13th Mission ULM
Up again this morning and on a mission to Ulm, Germany. We carried nine 500 GPs and four M-17 incendiaries. Drop them by interval meter with 140 foot settings. Had very little flak at front lines and none over target. Took several pictures of the formation and members of the crew. Received a V-mail from Aileen. Dead tired tonight.
Combat Crew 87 flew the mission aboard unnamed Douglas, Long Beach, California–built B-17G #46901. Maj. James O. Gross was the pilot.
The Ulm mission was the 390th Bombardment Group’s 265th.
The first mission of March was designed to take out every factory and rail target in the city of Ulm.
The 390th’s part of the operation was to bomb the marshaling yard where twenty-five hundred wagons were passing daily. A heavy overcast forced the entire 418 bombers to use pathfinder. Results of the operation were not observed.1
The marshalling yard at Ulm was obscured by a 10/10 undercast. Bombing was by H2X from 22,400’.2
Notes & Commentary
1 United States and Albert E. Milliken. The story of the 390th Bombardment Group (H). [New York]: Priv. Print., 1947. p. 123.
2 “390th Group Intelligence Report – Ulm Mission of 1 March 1945”. 390th Bombardment Group (H) History, March 1945, Headquarters 390th Bombardment Group (H), 1 May 1945, microfilm B0426, Maxwell AFB, AL: Air Force Historical Research Agency, 1973, frames 1523 – 1529.
The interval meter (intervalometer) is the device that sent electric pulses to the bomb bay to drop the bombs. It was graduated not by times (e.g. drop a bomb every 2 seconds) but rather by feet (drop the bombs so that when the hit the ground they are each 140 feet apart). As such it was actually a computer that would take into account the speed and altitude of the plane to work out exactly when to drop the next bomb. It could be set for intervals of 7 feet up to 750 feet.
Thanks for the explanation of the interval meter (intervalometer). 42nd Bombardment Group (M) reports show this same device being employed on B-25s during low and medium-altitude missions in the South Pacific.