The son of a Jewish businessman, Frankl scored his first victory on 10 May 1915 while serving as an observer with FA 40. That day, he shot down a Voisin with a carbine. For this feat, he received the Iron Cross, 1st Class. Later that year he became a pilot and scored nine victories flying the Eindekker with KEK Vaux. On 1 September 1916, he joined Jasta 4 and scored eleven more victories before he was killed in action on the afternoon of 8 April 1917. During a fight with Bristol Fighters, his Albatros D.III came apart in the air and went down near Vitry-Sailly.
When the Nazis came to power, Frankl's name was removed from the list of German World War I aviation heroes. After World War II, his name was reinstated to the list and in 1973, the Luftwaffe honored his memory by naming a barracks for him.