September 1, 2022
By Kurt Allemeier
Share this post:
The Norden M9 bombsight was top secret and possibly over-hyped but definitely an important part of the United States Army Air Force’s daylight precision bombing campaign of World War II.
After World War I, military planners wanted to avoid any more trench warfare. Precision bombing was seen as a way to get at dug-in positions as well as attack manufacturing, power, and transportation infrastructure. Bombing during World War I was done with rudimentary bombsights that required luck and pilot skill to drop bombs on target.
The United States was developing a bomber fleet that flew higher and faster than any bombers before, so a bombsight capable of putting bombs on target was a necessity. Bombs dropped from 20,000 feet had to be dropped 2.5 miles ahead of the target.
The military turned to engineer Carl Norden who started developing a bombsight in 1921. Concerned about Norden’s temperament, military officials asked him to take on a partner. Ted Barth, who oversaw gas mask production during World War I, was recommended. The two partnered and Norden eventually sold his company to Barth, staying on as chief designer. By 1927, Norden had a prototype. The military took possession of a gyroscopic-stabilized bombsight, hyped mostly by propaganda as being able to put a bomb in a pickle barrel from 30,000 feet, in 1933.
Born of Dutch heritage in the East Indies, Norden studied at the Federal Polytechnic Institute in Zurich, Switzerland, before immigrating to the United States in 1904. Moving from job to job in the United States, Norden gained a reputation as a prima donna. Norden worked for Sperry as the company developed gyroscopes to improve the firing accuracy of warships, but what he thought was an insulting $25/week raise and his abrasive personality put him at odds with his bosses so he struck out on his own. Norden and Elmer Sperry Sr. feuded for years. Sperry tried to dispute many of Norden’s patents for several years, while Norden was derisive toward Sperry’s inventions. It is no wonder such a difficult man earned the nickname “Old Man Dynamite.”
Norden reportedly was “difficult to work with, self-centered, impatient, a perfectionist, and the highest ethical standard.” A devout Christian, he didn’t consider himself an inventor but a designer, noting that inventions come from God. Despite creating his namesake bombsight, his name doesn’t appear on the patent.
His work at Sperry earned him a number of contacts with the U.S. Navy who put him to work on several projects, finally leading around to a bombsight. The U.S. Navy was Norden’s only client.
In World War I, pilots used little more than sticks to try to show the range angle, a vertical line through the aircraft and the line of sight to the target at the moment to release their bombs. Dropping bombs on a target from a moving airplane had to take a number of factors into consideration to determine the range angle.
The timing of a bomb release required altitude, speed, humidity, air resistance on the bomb, and turbulence be factored into the computing. Norden’s bombsight was essentially an analog computer. Factors that weren’t part of the equation for when to drop the bombs were training, combat conditions like evasive maneuvers to avoid anti-aircraft fire and fighter planes, overcast conditions, and the bombsight itself.
Though he was working for the Navy, the U.S. Army Air Corps caught wind of Norden’s work in the early 1930s and wanted to test the bombsight. He had delivered a prototype to the Navy in 1930.
Norden tested several prototypes in the 1920s before testing an early production bombsight in 1931. That test, targeting a simulated battleship measuring 600 feet by 105 feet was successful, hitting the target with 10 of 12 dropped bombs. The bombsight, the most accurate of three tested but also the most difficult to use, had a pair of gyroscopes to provide a stable platform and utilized a rotating mirror that cancelled out ground motion to keep the target in the sight’s field of view.
The early trials showed the bombsight’s mechanism capable of putting bombs within 75 feet of the target. During training in 1940, the average Air Corps bombardier averaged putting bombs within 400 feet of the target, and that was at 15,000 feet. During combat in 1943, the accuracy decreased to within 1,200 feet of the target.
Thankfully, the Germans also struggled for accuracy in defense of their homeland as anti-aircraft crews fired, on average, 16,000 flak shells to knock down a single Allied bomber.
The Army Air Forces was committed to daylight precision bombing, working on the assumption that bombers flew too high and too fast for enemy fighters. The British, knowing that accuracy was an issue, preferred nighttime area bombing and wanted the Americans to follow their lead.
The serial number plate to the Norden bombsight on offer in the Oct. 4-7 Sporting and Collector Auction. This unit was made by Victor Adding Machine Co. Note it doesn't have Norden's name on it, only "U.S. Army Air Forces Bomb Sight."
Bombardiers, sworn to secrecy about the Norden bombsights workings, required as much as 18 weeks of training. The sight head was installed prior to missions, and removed and stored in a secure site between missions. The bombardiers agreed to destroy the instrument in the event their plane was shot down.
The Norden bombsight was difficult to use and the slightest computational error — altitude or air speed — could throw off accuracy of a bombing run. Identifying the target through the viewport in overcast skies as the plane shimmied and shook made targeting tough, too. The difficulty of the task and the bombardier’s station in the plane, in the Plexiglas-covered nose of the aircraft as it takes on anti-aircraft and dodges fighters, made it difficult to recruit the best candidates.
Using the Norden bombsight, the bombardier on the Enola Gay, put its atomic bomb within 800 feet of its target in Hiroshima, while the bombardier of the Bockscar landed its atomic ordnance 1,500 feet from its target at Nagasaki.
To improve accuracy, the Army Air Corps identified the best bombardiers in each squadron and designated them lead bombardiers. On missions, following bombardiers — or toggeliers — would drop their bombs following the lead bomber.
A combat box formation for bombers was also devised that provided for greater field of fire to fend off fighters. The arrival of long-range fighters like the P-51 Mustang helped in defending the bombers and allowed for less defensive maneuvering. Once air superiority over the continent was achieved, bombers could fly at lower altitudes, also improving bombing accuracy.
Carl Norden wasn’t a fan of electronics, so his bombsight was mostly mechanical in nature. That made the design more difficult and the manufacturing process slower. The Navy started taking delivery of the bombsight in 1932 and the Army in 1933. Just over 100 were made annually in the early years of production before manufacturing stepped up in the war years.
The bombsight had two main parts – the sight head and the stabilizer. The sight head had the controls and knobs the bombardier used to keep the target sighted and compute the release. The stabilizer housed the gyroscopes that provided the stability.
The M-9 bombsight, introduced in 1943, offered improvements that gave the bombardier control over the aircraft in the final moments of the bombing run and also included filters to cut down on glare and haze.
The bombsight was considered top secret for a time. The name of the company never appeared on the factory where the bombsights were produced. Bombardiers had to swear to protect it. Photos of the bombsight weren’t allowed. When the sight head was removed from a plane it was accompanied by armed guards and stored in a secure location.
As more bombardiers were trained on it and technicians had to repair it, the number of people who had to know about the bombsight became so large it was too difficult to keep it top secret. After a time and enough bomber losses, it was assumed that the Germans had recovered a bombsight and deduced how it worked.
It turns out the Germans knew about the bombsight before the start of World War II. Herman W. Lang, a German-born naturalized U.S. citizen was employed at the Norden factory as a draftsman and inspector in the 1930s. He was a Nazi storm trooper during the early 1920s before immigrating to the United States in 1927. While employed by Norden he copied plans for the bombsight that were smuggled to Germany via an ocean liner. His copied plans were incomplete so he traveled to Germany to finish the bit of espionage.
The German government paid Lang 10,000 Reichsmarks. Part of a sizeable Nazi spy ring in New York City, he was eventually betrayed. He was among 33 convicted and was sentenced to 18 years in prison for espionage. Lang was deported to Germany in 1950.
The Germans did build a mockup of the bombsight and compared it to their bombsight, the Lotfernrohr 7, and found their sight easier to use.
Installed in legendary planes like the B-17, B-24, and B-29 bombers, the Norden bombsight was a key to taking the Allies’ fight to the manufacturing, transportation, and military infrastructure of the Axis powers. While not as accurate as its hyped-up marketing claimed, it was as much a mainstay of the United States’ strategic bombing strategy as the planes that carried it. A sight head to a Norden bombsight is available in the Oct. 4-7 Sporting and Collector Auction.
The Politics, Pickle Barrels, and Propaganda of the Norden Bombsight, Museum of Aviation
Not so Secret Weapon: The Norden Bombsight, by C.G. Sweeting
The Norden Bombsight: Was it Truly Accurate Beyond Belief? By Roaul Drapeau Warfare Hitstory Network
The Unconventional Genius of Carl Norden, from America’s Pursuit of Precision Bombing, 1910-1945 by Stephen L. McFarland
The Norden Bombsight and the U.S. Naval Proving Ground, by Robert V. Gates, Air Power History, Summer 2020
Please login to post a comment.