How many times does Fred Allison try to escape captivity?

It seems from the text that Fred Allison tried to escape one time.

The prisoners made an impromptu unsuccessful dash for freedom when a fellow inmate shot a guard. We don't know for sure, but we can assume that Fred Allison was one of the prisoners that attempted to escape. Dig, Allison's oldest and best friend, managed to break free by stealing an aircraft from a nearby airfield, but it does not appear that Allison was involved.