He competed in his first World Cup competition on January 27, 1982 in St. Moritz and immediately reached tenth place. Throughout the 1980s, Grandpaas often reached top positions, but mostly had to admit defeat to Matti Nykänen and Jens Weißflog . His first of a total of seven World Cup victories was on December 11, 1983 in Thunder Bay . At the 1984 Winter Olympics in Sarajevo , he reached eighth place on the normal hill.
The most successful season for grandpas was the winter of 1986/87. At the Nordic World Ski Championships (the only one in which he took part in his career) he won silver on the normal hill and in team jumping, as well as bronze on the large hill. He also won the overall World Cup for the only time in his career and in the meantime set a new world record for ski flying in Planica with 193 meters. The Pole Piotr Fijas shortly afterwards reached 194 meters.
After the winter of 1989/90, Grandpa ended his career.
Norway
Thunder Bay
Lake Placid
Oberstdorf
Štrbské Pleso