Operation ‘CHASTISE’ Mission Brief More than any other mission this would be a team effort, every member of the crew had a job to do…. The Rear Gunner.. On constant lookout for enemy aircraft and firing at enemy flak positions when in range The Wireless Operator.. Would switch on the belt drive to spin the mine, once mine is successfully released, fires a red flare to prepare the next plane for it’s ‘run’. The Navigator.. Looking out of the cockpit blister at the spotlights and calling height adjustments to the pilot. The Flight Engineer.. Hands on throttles controlling speed during attack. Pilot.. Keeping the plane steady and adjusting height according to Navigators instructions. Bomb Aimer.. Lining up the target and releasing the mine at the optimum point. Front Gunner.. Firing at dam defences as soon as in range to ‘keep their heads down’. Due to the scattered positions of the crew and the noise inside the aircraft, internal radio communications would be vital for a successful mission. The mission would be flown by 19 Lancasters in 3 waves The first wave, 9 aircraft led by Guy Gibson, and including his deputy Hopgood and both Flight Leaders. They would depart in 3 groups of 3 and would attack the Mohne Dam, 25 miles West of Dortmund. If this was breached with mines to spare, they would fly to the Eder Dam, 50 miles deeper inside Germany. These were curved, masonry ‘gravity’ Dams, at 450 yards distance and 60 feet altitude, the Upkeep mine would be spun backwards prior to release. It would then ‘skip’ across the water and on contact with the Dam wall, roll down the inclined wall to a depth of 30 feet were the barometric fuse would detonate. Barnes Wallis calculated it would take only 1 mine in contact with the dam wall to cause a breach. The second wave, 5 aircraft led by Flt Lt Joe McCarthy, ( due to a longer,more Northerly route to target, the second wave would actually depart before the first wave.) they would attack the Sorpe Dam, 6 miles Southwest of the Mohne. This was an undefended target, a straight concrete core with earthwork banks on either side. This would require the aircraft to fly along the dam and drop the Upkeep, without spinning it, as near the centre as possible. These Upkeeps were fused to explode at a depth of 25 feet, the idea being 5 concentrated strikes to blow the top off the dam rather than cause a breach. The third wave of 5 aircraft, would depart individually starting 2 hrs after the first and second waves. They would be diverted on route to a target as and if required. Three additional dams, the Ennepe, Bever and Lister were also briefed as possible secondary targets, although these were of far lower capacity than the primary targets. With a few more details covered, the briefing wound up and crews retired to the mess to while away the last couple of hours. At 21:00 hrs Flt Lt Hutchison fired a red very light into the darkening sky, this was the pre-arranged signal for the first and second wave aircraft to start their engines..... OPERATION 'CHASTISE' WAS UNDERWAY............. As McCarthy, Wave 2 Leader, started his engines, Glycol coolant poured from the starboard outter Merlin.This aircraft was going nowhere! he ordered his crew to grab their gear and get to the 'spare',fearing another plane may have problems and beat them to it.With the clock ticking, there was no time to wait and the other planes began to roll, with Flt Lt Bob Barlow now leading in ED-927 / AJ-E getting airborne at 21:28, followed by Les Munro in ED921 / AJ - W at 21:29, Vernon Byers in ED934 / AJ - K at 21:30 and Geoff Rice in ED936 / AJ - H at 21:31. Gibson now prepared to lead the First Wave off........