Painting of lancaster with spinning bomb and special spot lights
Saturday, May 11th in Nanton the Bomber Command Museum of Canada held a special 70th anniversary commemoration of one of the greatest tactical air raids in World War Two history. The raid was an incredibly daring and dangerous plan and was the brain child of Barnes Wallis an aircraft designer for Vickers, Britain’s leading aircraft company at the time.
At the commemorative event that day was 89 year old Fred Sutherland from Rocky Mountain House who is one of only three crew still alive. Fred was the front gunner on the Lancaster bomber called N for Nancy that successfully breached the Edersee Dam in northern Hess, Germany. Of the 133 crew that flew the 19 Lancaster’s on that night 53 died in the raid. There were 30 Canadians in those crews, 15 of which returned safely to base. Seven of those fifteen were Albertans.
It was one of the severest blows suffered by Germany in the early days of the war. The raid and the device used that was designed by Wallis became known as the story of the bouncing bomb.
Just before WWII started Wallis committed his considerable skills and remarkable ingenuity as an engineer to the war effort he knew was about to begin. He set himself the task of trying to figure out where and how bombing could hurt Germany the most. He realized that the Nazi war effort was critically linked to coal mines, oil dumps and wells and to hydroelectric dams that controlled water levels in shipping channels. Wallis reasoned, by elimination, that the coalmines were too deep and the oil supplies of the Rumanian fields were too far away for raids.
The dams stood out in his mind, particularly the Mohne, the Edersee and the Sorpe. These three accounted for almost all the water supply that was needed to maintain the Ruhr Valley waterway and the Mittelland Canal. Barges shipping steel, coal and tanks traveled up and down these water highways feeding Germany’s monstrous arsenal of foundries and factories.
Wallis began by studying bomb aerodynamics, the behavior of explosives, fusing and aiming of bombs. He soon realized that bombs 20 times the largest existing size (500 lbs.) would not damage these significant concrete structures.
Barnes remembered then a 1935 engineering study that had looked into the mysterious shattering of concrete piles being driven into the riverbed of the Thames for the Waterloo Bridge. It revealed the shockwaves travelling back up the piles had caused an extension wave that the concrete couldn’t stand up to. His logic followed then that if you could place a bomb deep enough into the water in front of a dam the tamping effect of the water after an explosion would concentrate it and carry a much amplified “shock punch”.
Wallis began by building scale models of dams and testing them with charges. He discovered that a bomb would have to explode very close to the dams inside wall to carry a deadly enough punch. An abandoned Welsh dam about one fifth the resistance of the Mohne was tested with great success.
Barnes figured out the only way to place a charge properly would be to skip a bomb off the water over the torpedo netting at the dams, bounce it off the dam wall and have it drop down about 30 feet where water pressure would set it off.
He experimented with marbles and a catapult at a lake after remembering that old Navy trick of skipping cannon balls off of the water. It was during this simple experimentation that he discovered that a dimpled sphere traveled twice as far as a smooth one. Dimples diminish friction and create lift, a principle that Tiger Woods should be eternally grateful for. He also reckoned a way to keep the skipped bomb close to the dam wall once it reached it by putting a reverse spin on it, another golfer’s trick.
It took a great deal of planning and convincing of oft times skeptical High Command officials but eventually his logic and design won them over. A new squadron called 617 was formed with 133 men in 19 crews. Not one of them was told about the device or the targets and for months they did some pretty unusual flying training. Crews were told they had to learn to fly 60 feet off the ground with only moonlight to see by. Bomber windshields were replaced with amber glass and flyers wore blue tinted goggles so that daytime training simulated nighttime moonlit flying.
The calculations for the release of the spinning bombs dictated they had to be dropped at exactly 60 feet off the water and air speed had to be 240 mph only. For the number of skips to bring the bomb to the dam’s edge they had to be released from 467 yards out. The plane’s altimeters did not function at 60 feet so an ingenious spotlight set up was used. Spots located at specific angles on the nose and belly came together at exactly 60 feet over the water.
On the night of May 16th, 1943 the crews of Operation Chastise were finally briefed and took off on their deadly mission. They flew at an unbelievable 100 feet off the ground over Germany and 3 Lancasters were lost to cables and flak before they were even close to their targets.The modified Lancasters they flew had the 7 ton cylindrical bombs hanging from them on special mounts that would begin to reverse spin the bombs prior to their release, an action that “shook the living crap out of us”.
At 12:56 that night the fifth bomber on the Mohne run scored the hit that breached the dam and sent 200 million tons of spring runoff water down the valley. The Edersee was also eventually broken but the most critical target, the Sorpe earth dam, remained intact.
Nine hours later the remaining crews returned and were greeted by ground crews that were openly crying. Unbeknownst to the survivors ten planes and their crews had been lost in this incredibly dangerous mission.
