As a teenager, Neumann apprenticed under the master auto mechanic Meister Schroth, who followed the traditional Prussian lifestyle of "First the work, then the pleasure."
In 1935, Neumann entered the well-regarded technical college Ingenieurschule Mittweida and earned very high grades. With other students from the college, he learned to construct and pilot a one-person glider. His experience as an engine mechanic, an aircraft designer, and as a practical engineer would prove very useful in his career.
A few months later, on 1 September 1939, Germany invaded Poland. On 3 September, the United Kingdom declared war on Germany, and all Germans in Hong Kong were rounded up and interned in La Salle College, Kowloon, a Christian Brothers High School for boys. Neumann was interned in the school together with some 100 Germans for several months. The British in Hong Kong considered any German citizen a potential "fifth column" and revoked his passport. No embassy would talk to him.
Luckily, Neumann had a chance meeting with W. Langhorne Bond of the Chinese National Aviation Corporation. The company arranged for Neumann to enter China without a passport. He flew to Kunming, capital of the remote Yunnan province, and there he contacted the Chinese Air Force. Soon after he met Colonel Claire Lee Chennault, who had established the Chinese Air Force with Madame Chiang Kai-shek.
As the war with Japan progressed, the Chinese Air Force became the American Volunteer Group, nicknamed the "Flying Tigers." Neumann helped the effort against the Japanese in many important ways. He led dangerous supply convoys, he performed all types of mechanical repairs on P-40 aircraft, he translated to and from Chinese, he assembled a working enemy Zero from crash parts to assess its flight characteristics, and he even directed bombing attacks from the ground while disguised as a Chinese coolie.
Eventually Neumann was dispatched to Washington, D.C., where he met Clarice, who would later become his wife. Yet for all of Neumann's heroism in China, as a German he was still considered an enemy combatant. It took an act of the United States Congress to correct this. After the war, he was finally permitted to work for Douglas Aircraft Research.
In the year that followed, the Chinese Communist army was taking over China. The Neumanns had no choice but to attempt to return to the United States. They chose an unusual route. Instead of flying or sailing across the Pacific, Clarice suggested that they drive over the Asian continent towards North Africa. Thus began their incredible and dangerous journey to Tel Aviv. Most border crossings were dangerous, because by 1948 most countries in Asia were undergoing political turmoil. Finally, after a journey of many thousands of miles on poor roads by Jeep, they were able to conventionally return to New York City.
A major success for GE was his guiding the design and development of the huge high-bypass turbofan jet engines (or simply called "fanjets") that now power the largest commercial aircraft.
The Gerhard Neumann Museum in Niederalteich, Bavaria, honors his contributions to aviation.
His autobiography "Herman the German: Just Lucky I Guess chronicles his life.