Walter Demuth was born in Winterthur on November 24, 1925. After the compulsory school he began an apprenticeship as a mechanic in the Swiss Locomotive and Machine Works (Schweizerische Lokomotiv- und Maschinenfabrik) in Winterthur.
He worked for this company until February 1, 1947 when he was employed by Swissair as an engine mechanic. In the meantime he learned to fly with the Zögling sailplane on the Allmend of Frauenfeld with the famous Swiss glaciers pilot Hermann Geiger as an instructor. Much later, during his free time, he did the maintenance of small airplanes such as the Piper, the Auster, the Comte AC-4 Gentlemen, etc.
He was so fond of aviation that he decided to continue. On March 1, 1950 he was employed by Air Import as a mechanic. He was trained to do the maintenance of helicopters by Reinhold Günthard. Demuth then became chief-mechanic of Air Import and worked with Seppi Knecht, Roth, Ernst Bänzinger and Hans Hunger, the first Swiss helicopter mechanics.
In the meantime he also obtained the airplane private pilot licence.
In the Spring of 1954 he made the decision to become a helicopter pilot. He began the training on April 14, at the airport of Kloten using the Hiller 360 HB-XAB. His instructors were Albert Villard, Carl Bode and Sepp Bauer.
On May 7, at the airfield of Dällikon, FOCA’s examiner Heinrich Pfändler issued him the Swiss private helicopter licence n° 10.
Then on July 23, 1955 he received the commercial pilot licence. He continued to work as a mechanic and a commercial pilot on behalf of Air Import until the end of 1956.
By January 1, 1957, after the merger with Air Import, Demuth was employed by Heliswiss as a helicopter pilot. In the meantime he had logged about 250 hours of flight on the Hiller 360, UH-12B and C and the SO 1221 Djinn. This experience was mainly gained doing passenger, advertising, spray and ferry flights.
In January 1957 he was trained by Leo Kunz, the chief pilot of Heliswiss, on the Bell 47G and the G2.
On December 30, 1958 he obtained the licence as a helicopter instructor. In May 1963 he was trained on the Agusta-Bell 204B, the new turbine helicopter purchased by Heliswiss.
By January 1, 1964 he became chief pilot of Heliswiss. In the following years he was busy with the training of pilots, test flights of helicopters after their maintenance or repair works and their annual check, etc. In this function he also had the opportunity to test new helicopter types and models such as the Jovair MC-4, the Mil MI-4 Hound, the Wagner Sky-Trac, the Helitech-Sikorsky S-55T, the Sikorsky S-58T and many others.
In 1977 he was designated manager of Helitrade, a sister company which worked closely with Heliswiss, and was active in the buying and selling of helicopters, spare parts, aviation accessories, equipments, etc. For these reasons he considerably reduced his flying activity and then quit. Altogether he logged about 5'400 hours of flight mostly on the Hiller 360, the UH-12B, the SO 1221 Djinn, the Bell 47 series, the Agusta-Bell 204B, the Bell 206 Jet Ranger and the Hughes 500.