The Box Formation
At first, American heavy bombers flew in combat boxes of 18 aircraft with succeeding boxes following 1.5 miles (2.41 km) behind. To improve the defensive formation, this was replaced by the wing formation that combined three 18-plane groups. Also, instead of flying behind each other, the groups were positioned at high, medium and low level. The medium altitude group would fly slight ahead in the lead with the high squadron above and to the right with the low squadron beneath and on the left. The resulting 54 plane formation occupied a stretch of sky 600 yards long (549 m), a mile (1.61 km) or so wide and half a mile deep (.80 km). Other wings might fly identical formations to the target at six-mile (9.65 km) intervals.
This is the typical formation of 18 aircraft in a single squadron in a bomber stream. Bomber raids started as small intimate affairs. Usually moderate altitudes with a modest number of bombers, striking simple targets along the coast. As the numbers of available bombers increased the raids became larger and more daring. Some of the largest raids employed 1000 bombers to strike targets in Germany. This bomber stream could be as long as 100 miles (161 km) and as wide as 1 mile (1.61 km). At 180 mph (290 km/h) over the target an air raid could last from 35-45 minutes.
Each squadron in the bomber stream was composed of 3 flights of 6 aircraft each. Each flight had two elements of 3 aircraft each. In this formation the lead flight flew at the designated altitude. The planes in an element were separtated by 50' (15.2 m) horizontally, and each element was also separated by 50' (15.2 m). The high flight was 50' (15.2 m) behind and 50' (15.2 m) right of the lead flight. The low flight was 50' (15.2 m) behind and 50' (15.2 m) left of the lead flight.
This deployment of aircraft made it nearly impossible for a single fighter to get hits on multiple aircraft in a single pass through a squadron. Secondly, it also spread the attacking force out making it difficult for it to concentrate its fire. Thirdly, this opened up the gunners field of fire increasing their effectiveness.
Attacking A Flying Fortress
To reliably destroy a B-17, the attacker had to either break the integrity of the flight deck or explode the bombs in the bomb bay. Anything less only damaged the bomber. Hits on less vulnerable areas like the massive vertical stabilizer and rudder might cause the aircraft to slow but it would struggle on. Consolidated B-24 Liberators had a tendency to explode when hit but the B-17 rarely did.
Attacking a formation of American bombers from the rear was foolhardy due to the coverging fire from the bombers tail and ball turret gunners. Tail attacks also exposed the fighter pilot to additional fire due to the reduced closure speed. The standard fighter approach from 1000 yards (914.4 m) astern with an overtaking speed of 100 mph (161 km/h) took over 18 seconds to close the distance down to 100 yards (91.4 m).
Initially, head-on attacks were conducted with a flat angle of attack but this made judging the range to the target very difficult. German pilots were initially intimidated by the Fortress 104 ft (32 m) wingspan. The urge to open fire from too far away and to breakaway too soon for fear of collision looming large in the gunsight was overwhelming. Further refinement of the tactic showed that the optimum angle of attack when approaching from head-on was from ten degrees above the horizontal, what American bombers crews came to call "12 Oclock High." This greatly simplified the problem of estimating range and permitted a constant angle of fire similar to ground strafing.
When intercepting a bomber force, German fighter units initially flew a parallel course off to one side outside the range of the defensive guns. After reaching a point about 3 miles (5 km) ahead, either three or four plane groups peeled off and swung 180 degrees around to attack head-on in rapid succession. It was critical for the fighters to maintain some semblance of cohesion, or at least visual contact, so after each pass they could regroup for repeated concentrated attacks. That was the theory anyway. In reality, many pilots ended the first pass with a split-S manoeuver, inverting and diving down and away from the defensive fire above them.
With increased experience, German fighters began to make their head-on attacks using either in line astern or with the entire unit spread out abreast in the "company front" formation. The recommended procedure was to pull up and over the bombers and then from their position of advantage above, the German fighters were quickly able to launch another attack. It was critical for the fighters to maintain some semblance of cohesion, or at least visual contact, so after each pass they could regroup for repeated concentrated attacks. That was the theory anyway. The huge tail fin of the Fortress posed a collision risk and many German pilots preferred to break away below. Either they dipped the noses of their aircraft and passed close underneath, or rolled inverted and broke hard down with the "Abschwung" (Split-S maneuver.) This took them well below the bombers and valuable minutes were lost before they could gain sufficient height to attack again.
Attacks from above had the advantage of placing the vulnerable oil tanks (inside of the inboard engine nacelles) and wing fuel tanks (inside the outboard engine nacelles) directly in the attackers path.
By the summer of 1943, the Germans had deployed the Focke Wulf FW 190A4, a dedicated bomber killer armed with two 7.9mm machine guns and four 20mm cannons. With all guns functioning, a three-second burst fired about 130 rounds of ammunition. The Luftwaffe estimated that it took an average of 20 hits from the 20mm cannon to destroy a B-17. Analysis of gun camera film revealed that the average German pilot scored hits with only 2 percent of the rounds fired, thus on average, 1000 rounds were fired to score the 20 hits required.
Seeking to stem the armada of Allied bombers, the Germans tried dropping pre-set bombs on them timed to explode when they were at the same height as the stream. The Germans also employed 210mm, tube-launched, spin-stabilized rockets employing 248-pound (113 kg) projectiles with 80-pound (36.3 kg) warheads (a version of the German Armys "Nebelwerfer"). The warheads were time fused to detonate at between 600 to 1200 yds (549-1097 m) from the launch point. To inflict damage the rocket need only explode within 50 ft (15.2 m) of the target although the warhead would also detonate if it struck a bomber. Often an exploding B17 caused enough damage to adjacent planes to bring down another or even two. Although not particularly accurate, the rockets served well to break up the formation. The added weight and increased drag of the installation severely degraded the performance of the German fighters and made them vulnerable to Allied fighter escorts.
With the advent of American long-range fighters, the Germans were forced to change tactics again. The need to inflict damage on the bombers was ever increasing and to accomplish this their planes needed additional and heavier armament. The weight of these additions decreased the performance of their fighters such as to make them easy victims if Allied Fighters were encountered. The Luftwaffe's answer was the "Gefechtsverband (battle formation) consisting a "Sturmgruppe" of heavily armoured and armed FW-190A8s escorted by two "Begleitgruppen" of light fighters, often Bf 109Gs. The task of the light fighters was to engage the escort while the heavy fighters attacked the bombers. It was a great theory but difficult to employ. The massive German formations were unwieldy and took time to assemble. They were often intercepted by Allied Fighters and broken up before they reached the bombers but when they did make it through the results could be devastating. With their engines and cockpits heavily armoured, the Sturmgruppen pilots braved the storm of fire and attacked from astern.
Later in the war, the Germans introduced the Mk 108 30mm heavy cannon capable of firing 600 11-ounce (330 gram) high explosive rounds per minute. Three hits with this weapon were usually sufficient to bring down a Flying Fortress. On the other hand it was a low velocity weapon and its effective range was shorter than the 20-mm cannon forcing German pilots to fly even closer to get hits.
The jet propelled Me 262 introduced in the last year of the war was 100 mph (161 km/h) faster than contemporary piston-engine fighters and well armed with four 30mm cannons. In a head-on attack, its 350 yards (320 m) per second closing rate was too fast to allow accurate aiming or to allow optimum use of its short-ranged armament. To overcome this, German Jet pilots used the "roller coaster" attack. Approaching from astern at about 6000 ft (1,829 m) above the bombers, the jets pushed over into a shallow dive starting about 3 miles (5 km) away. They quickly built up speed such that the escorts could not follow them. Diving down until they were about a mile (1.61 km) behind and 1500 ft (457.2 m) below, they pulled up sharply to bleed off speed, leveling off at 1000 yds (914.4 m) astern in position to deliver an attack.
Desperate to inflict massive losses on the American Bomber stream and force a month long bombing pause, the Germans concocted a plan for a massive ramming attack. Late in 1944, Oberst Hans-Joachim Herrman proposed using 800 or so high altitude Bf-109Gs stripped of armour and armament to reduce weight for such an attack. Lightened in this manner, he calculated the planes could reach 36,000 ft (10,973 m) well above the American escort fighters ceiling. German pilot losses were predicted to be around 300, more or less what was lost in a normal months fighting. Aircraft losses would be much higher of course, but by this point numbers of aircraft were not the Luftwaffes problem. Trained pilots and especially fuel were. Fully trained fighter pilots were too valuable to be wasted in these attacks, so volunteers were called for from the training units. The first ramming unit, "Sonderkommando Elbe" formed in April 1945, flew a single mission with 120 aircraft. Its inadequately trained pilots were unable to inflict much damage. Fifteen bombers were rammed but only 8 were destroyed.
"Fips" Phillips, a 200+ Eastern Front Ace wrote the following while in command of JG 1 defending against American Bombers over Northern Germany:
"Against 20 Russians trying to shoot you down or even 20 Spitfires, it can be exciting, even fun. But curve in towards 40 fortresses and all your past sins flash before your eyes."
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