In the mid-1930s, Nazi Germany had a problem. Its twin-engined medium bombers, such as the Heinkel 111, had a range of perhaps 1,500 miles. However, the Luftwaffe's single-engined fighter plane, the Messerschmitt Bf 109, had a range of only 400 miles (it wasn't until mid-World War II that fighters carried drop tanks). Before 1939, airpower enthusiasts believed "the bomber will always get through" enemy air defenses, but the Germans also realized they needed a fighter capable of escorting bombers all the way to the target and back.
Their solution was the Messerschmitt 110, a twin-engined fighter that looked more like a small bomber. With a range of 1,500 miles for the early models such as the Bf 110C, it was far more heavily armed than single-engined fighters, with up to four cannons and four machine guns firing to the front, plus a rear gunner with a machine gun to ward off attacks from behind. Remarkably, with a speed of around 350 miles per hour, the Bf 110 was also as fast or faster than many early World War II fighters.
Yet there is never a free lunch in aircraft design. Carrying all that extra fuel meant a bigger, heavier aircraft. A bigger, heavier aircraft required two engines and two propellers, which added even more weight. The result was that the Bf 110 weighed more than four tons, or twice that of the Bf 109.
That the heavy fighters were called zerstorer (destroyers) was emblematic of the confidence the Germans placed in their heavy fighters. They were considered the elite of the Luftwaffe arm, and they lived up to that reputation in 1939, flying against 230-mile-per-hour Polish biplanes, or unescorted British bombers flying over Germany.
Then came the Battle of Britain. Until the summer of 1940, the Luftwaffe had mostly supported the ground troops by striking nearby targets in Poland and France, against poorly prepared opponents and within range of Bf 109 escort. Now they were tasked with a strategic bombing campaign that sent them deep over British territory from bases in France and Norway. The Bf 109 was a formidable single-engined fighter, but its range was so short that it could only spend ten minutes over London before returning to base, leaving the bombers to be picked off by Royal Air Force interceptors.
Needing long-range escorts, the Luftwaffe confidently committed its elite Bf 110 units. Dogfighting slow Polish biplanes was one thing: RAF Hurricanes and Spitfires, equal or nearly equal to the top-line German Bf 109, was something else. Now the price was paid for the Bf 110's range and armament; against modern single-engined fighters, the German aircraft lacked maneuverability and acceleration. Instead of protecting the Heinkels and Stukas, the German fighters had to protect themselves, sometimes by forming defensive circles in which the Bf 110s formed an aerial merry-go-round to keep RAF fighters from attacking each aircraft's rear.
The Luftwaffe began the Battle of Britain with 237 Bf 110s—and lost 223. Among the victims was Bf 110 pilot Hans-Joachim Goring, the nephew of top Nazi and Luftwaffe chief Hermann Goring.
That wasn't the end of the Bf 110 story. In North Africa and Russia, it became a useful ground attack aircraft (as did British heavy fighters like the Bristol Beaufighter). Equipped with newfangled aerial radar, the Bf 110 found life as a deadly night fighter, hunting unescorted RAF Lancaster bombers in the darkened skies over Germany. Armed with extra cannons and unguided air-to-air rockets, the Bf 110 also took a toll of U.S. B-17 and B-24 bombers flying unescorted deep-penetration raids into Europe in 1943. But as an air superiority fighter, the day of the Bf 110 was over.
That message was emphatically delivered in 1944 by the U.S. P-51 Mustang, a single-engined fighters, that could fly 450 miles an hour, to a range of 1,600 miles, while still remaining highly maneuverable. Against marauding American Mustangs and Thunderbolts over Germany, the Bf 110 again became the hunted instead of the hunter.
The arrival of the Mustang also announced the bankruptcy of the heavy World War II fighter. American aircraft design genius (and in the Mustang's case, a British engine) created a fighter with speed, maneuverability and range. It lacked the armament of a Bf 110, but so what? A Mustang was much more likely to be blazing away at a Bf 110's tail rather than the other way around.
The heavy fighter concept still lives today, but in a mutated form. When we speak of the "heavy" F-15 and "light" F-16, we mean a highly capable but very expensive aircraft, versus cheaper but less capable light fighters.
Changes in aircraft technology and weapons have also removed the need for a World War II-style heavy fighter. In those days, fighters were only armed with cannon and machine guns, which meant speed and maneuverability were needed to get into a firing position on an opponent's tail. Today, an aircraft like the F-35 can sacrifice speed and maneuverability in return for sensors and air-to-air missiles that—theoretically at least—will give it the first shot. Where extra fuel once required a bigger aircraft to carry it, aerial tankers allow a fighter to enjoy longer range without the bulk.
But the Bf 110 concept still resonates in illuminating how quickly a clever technological fix becomes obsolete. In the late 930s, when the RAF was still flying biplanes like the Gloster Gladiator, the Bf 110 must have seemed as cutting-edge as an F-22 compared to a Korean War F-86. Yet if German planners had really considered the problem, they might have realized that advances in aircraft and engine technology would result in single-engined aircraft with the Bf 110's range, but not its handicaps.
In the end, the "destroyer fighter" concept was sunk.
Image: Messerschmitt Bf 110G. Wikimedia Commons/Public domain