Metrowest Daily News 7/23/09: Take a trip aboard a B-17 Flying Fortress this weekend. Bill Gilmour was flying in a B-17 over Berlin in 1944 when the enemy shot down the “metal monster” of an aircraft, forcing him and his crewmates to parachute from the plane. Captured as a prisoner of war, he was held by the Nazis in Austria for 14 months and came home an American hero, honored with the Purple Heart and a presidential citation. Now, 65 years later, the Wayland resident, 86, clearly remembers the 23 intense missions he participated in and the extraordinary machine he flew on. One of these World War II-era B-17s, the Liberty Belle, among close to 13,000 built and only 14 that are still flying, has landed at the Lawrence Municipal Airport in North Andover. This particular Flying Fortress took to Massachusetts skies for the first time Monday for press tours, and will be available for public flights this weekend.