US Navy: Naval Aviation Doctrine: Introduction to Naval Aviation, 1946 - Bombing Tactics
INTRODUCTION TO NAVAL AVIATION - RESTRICTED - ISSUED BY AVIATION TRAINING DIVISION OFFICE OF THE CHIEF OF NAVAL OPERATIONS U. S. NAVY. * JANUARY 1946 * OPNAV 33-NY-85; Chapter IX. Tactics and Flight Operations.
4. BOMBING TACTICS
The primary purpose of all aerial bombing tactics is to direct the maximum effective amount of fire power against a designated target.
There are a number of types of bombing attack, each with particular advantages and disadvantages and each designed to fit certain needs. In general, determination of the required type of bombing depends upon such factors as:
(1) nature of the target;
(2) nature of the ground and air defenses of the target and the target area;
(3) type of damage desired on the target;
(4) weather conditions over the target;
(5) distance to the target.
Different types of bombers necessarily are specialized - there is no such thing as an "all-purpose" aircraft, and this applies especially to bombers. A dive-bomber, for example, is relatively short-ranged and cannot be used against long-range targets. A long-range bomber may be able to carry bombs for thousands of miles, but the very design that gives it range makes it unable to stand the stress of a dive-bombing attack. A fighter-bomber is at home in either combat or bombing, but it doesn't do well at fighting while carrying bombs.
Naval bombing takes the following forms:
1. Dive bombing, a high-angle attack of 60° to 90°
2. Glide bombing, at an attack angle of 30° to 55 °
3. Low-level bombing, at minimum altitudes
4. Horizontal bombing, at level flight and usually from high altitude employing radar or an optical sight.
Dive Bombing
Dive bombing was developed long before World War II by the Navy as a means of "cornering" a rapidly maneuvering target. It is undertaken by specially designed aircraft capable of a sustained high-angle dive of 60 ° to 90 °, braked by dive flaps to maintain a constant medium speed during the latter stage of the attack.
The primary objective of dive bombing is the same as for other planes - to inflict maximum damage while being subjected to a minimum of antiaircraft fire. Attacks may be quickly launched, exploiting a high-speed approach to attain surprise. Accurate bombing of difficult targets, strongly defended positions, and ships is possible because the pilot literally "rides his bomb" to close range. The dive bomber presents a hard-to-hit target to enemy anti-aircraft gunners, due to the high angle of the attack, the rapidly changing altitude, and the con-usion likely to be caused at the focal point of the attack by the plane's dive. One of the principal drawbacks of dive bombing is its requirement of good visibility high above the target.
Peeling off into the dive
A miss
The four phases of a dive bombing attack are the approach, the initial dive, the aiming dive, and the get-away after the attack.
The approach is made in tight formation for air defense. During the flight to the target, an altitude of about 20,000 feet is gained if visibility and weather conditions are good. On sighting the enemy the initial dive is made - a shallow dive at high speed to take aircraft into position for the aiming dive. The aiming dive is started at almost 12,000 feet, with planes feeding into the target in rapid succession. In starting the dive, planes push over either straight ahead, peel off in a wingover turn, or make a simple nose down turn, to get lined up with the target quickly and smoothly. When the bomb is away, the pull-out must be made smoothly to avoid overstressing the plane and to reduce danger of collision with other attacking aircraft. Once the pilot has completed his mission, his immediate concern is to get out of range of automatic antiaircraft fire as quickly as possible, and to get to the predetermined rendezvous point for the join-up.
Typical dive bombing pattern
Glide Bombing
Glide bombing is similar in many respects to dive bombing, except that dive brakes, flaps, or other speed-retarding devices are not used, and thus the attack is delivered at rapidly increasing rather than constant speed. The glide angles developed in the attack vary from 30° to 55 °, depending on the tactical situation and the amount of stress the plane can take.
In a glide bombing attack a bomber makes a high-speed run on the target, using a short, fairly steep aiming glide to carry the bomb within short range of the target. After the bomb is released, the pilot utilizes the built up speed of the glide for a quick get-away.
One of the main advantages of glide bombing is its flexibility. The pattern of the attack can be varied quickly to at almost any given situation; likewise, many different types of planes can glide bomb within their performance limits. The glide attack has been used by patrol planes, torpedo bombers, dive bombers, fighters, and fighter-bombers. It has been found particularly effective against small targets or those of low visibility, such as troops or gun emplacements difficult to sight from high altitudes. As aim can be corrected during the glide, the attack is useful against moving or rapidly maneuvering targets. Glide bombing necessarily starts from relatively low altitudes - too much speed would be built up in a long, steep glide without flaps - and frequently is used as an alternative to dive bombing when visibility over the target is too low.
As compared to dive bombing, the attack in a "clean" glide has some disadvantages. Vulnerability to antiaircraft fire is somewhat greater than that of dive bombing, so that glide bombing is not used, unless necessary, against strongly defended targets. The swift build-up of speed also requires caution on the part of the pilot to avoid overstressing the wings. Aiming allowances likewise are somewhat more complicated, and the pilot must be skilled in judging glide angles.
The phases of glide bombing are much the same as for dive bombing, although the tactics of each phase differ somewhat. The approach is made at a height enabling the attacking group to use clouds, sun lanes, and wind to the best advantage. With good visibility, at least 12,000 feet is required for good defense against enemy aircraft and to set the stage for a fast initial dive to attack position. If visibility is poor, the approach may be made from altitudes as low as 4000 feet. However, if the attack is made from too low a starting point, it loses the valuable assets of surprise and speed.
Where visibility permits, an initial dive brings the pilot into position for the push-over into the aiming glide at about 5000 feet. The attacking group maintains its defensive formations until it reaches this point, with divisions spreading out as they go into the inital dive and breaking up as they go into the aiming glide. Bombs are released at close range at the bottom of the glide, usually within 2000 feet of the target. Retirement is made at high speed to carry the plane out of the range of enemy AA fire.
Low-Level Bombing
Masthead, skip, or low-level bombing is another method of carrying a bomb right to the target, and dropping it so close that risks of a miss are reduced to a minimum. However, in this type of attack the bomb is dropped from level flight or in a very shallow glide (usually under 30°) at extremely low altitude - masthead height - and at high speed.
The bomb used in this form of attack must be fuzed for delayed detonation or the aircraft itself may be caught by the blast of its own bomb.
Masthead bombing normally is used when the weather is unsuitable for dive or glide bombing or in the case of targets that are particularly susceptible to this type of attack. It is also one means of attaining the vital element of surprise when the terrain is such that the bomber may "sneak up" on the target behind a screen of hills or ridges, to drop in almost at ground level and sweep the target with machine gun fire and bombs - all in less time than it takes for the AA defense to get its guns trained. A particularly appropriate target for masthead bombing is the unarmed or lightly armed ship; the bomb is dropped just before the bomber pulls up to pass over, and is aimed at the beam as the largest target. The bomb is dropped to penetrate at or below the water-line, producing a mining effect.
The approach procedure for low-level bombing is practically identical with that of glide bombing (except that the glide toward the target, usually started at about 12,000 feet, is 30° or less) and brings the plane over the target at almost zero altitude, in level flight, and at its highest allowable speed.
Horizontal Bombing
Horizontal bombing is done from steady level flight, usually relying on high altitude to reduce the probabilities of hits from enemy antiaircraft. It relies on the plane's own guns and its fighter escort, if any, for defense against enemy fighter planes.
This form of bomb attack is not used extensively by the Navy. While it is a principal weapon against "area" targets, such as industrial plants and railroad yards, and has attained remarkable accuracy by means of electronically operated bomb-sights, horizontal bombing is not accurate against mobile, fast, highly maneuverable seaborne targets.
Horizontal bombing, it is true, has been carried out against many targets by the Navy's large patrol bombers, and is a useful tool to destroy enemy shore bases, shipyards, and similar installations. It also has been used at times by carrier type aircraft, where area bombing was desirable and where defense against enemy aircraft required that our attacking groups remain in formation. Such bombing is done from the maximum altitude feasible under prevailing weather conditions to avoid detection by enemy defenses and to reduce the potency of their antiaircraft fire. The minimum altitude for horizontal bombing is the upper limit of effective automatic weapons fire, or about 4000 to 5000 feet.
Fundamentals of Bombing Aim
Accuracy in all types of bombing depends in large part upon the pilot's understanding and use of the physical forces that govern the flight of the plane and the path taken by the bomb. Navy bombing, in particular, depends heavily on the pilot's flying and aiming ability. Dive bombing, glide bombing, and low-level bombing are all aimed by the eye of the pilot - through a fairly simple sight - and by the way he flies the plane, and not on complex electrical sighting devices. In effect, in most Navy bombing attacks, the pilot carries the bomb to within short range of the target. Likened to bowling, we could look at it this way. We could rig a sighting device at the end of the alley that would compute all of the factors involved and would aid accuracy; but a simpler way to assure a strike every throw is to carry the ball right down to the pins and let it go at point-blank range.
Detailed and voluminous technical books have been written to explain the effects of the various forces affecting the course of a bomb and how to utilize them in aiming. Also, numerous manuals have been necessary to aid in teaching the special techniques of each particular type of bombing. All that can be presented here is a brief summary of the factors involved.
Certain of these factors result from the flight of the aircraft, others from the forces acting on the bomb as it falls through space.
The pilot's problem is (1) to aim the plane toward the target, (2) to establish a line of sight in relation to the target, (3) to release the bomb at the proper point and instant, and (4) to bring its trajectory on the target. Because of the effect of wind drift, attitude of the plane, and target motion (to mention a few of the things involved), the pilot may not put his sights on the target at all - but on an aiming point in space some distance away from it. This isn't as confusing as it may seem when it is remembered that the same tiling is done with a rifle in "leading" a moving target for motion or elevating the sights for long-distance shots.
The aircraft in turn gives thrust and velocity to the bomb. That is, when a bomb is released it starts out in the same direction and with the same speed as the plane. So to aim the bomb the plane must be aimed. This would be simple enough if a plane flew exactly in the direction it is pointed. But it doesn't. Cross wind causes a plane to drift. Different speeds, loadings, and angles of dive cause the plane to vary in its attitude - to fly nose-up or nose-down in relation to its flight path. This naturally throws the line of sight either up or clown, and the effect must be known and compensated for in sighting.
Then the instant the bomb is released, gravity begins to pull it toward the earth, and air resistance begins to slow its velocity, causing its trajectory, or path to bend downward. Thus, even if the flight path of the plane were aimed straight at the target, the bomb would fall short. The pilot has to allow for this drop or trail in sighting. The amount of trail of a given bomb varies with its initial velocity, the slant range to the target. and the angle of dive. This latter is important because the steeper the angle, the less the trail; obviously, if a bomb was released from a plane in a 90° dive, the force of gravity is in the same direction as the initial thrust of the bomb, and the bomb would fall straight down with no trail at all. The pilot must make allowance in his sight for these various effects; "elevating" the line of sight to compensate for the amount of trail of a given bomb released at a given altitude, speed, and dive angle.
Fortunately, the pilot doesn't have to do all of this arithmetic while his plane is roaring down on a target. The computations are made by expert ballisticians and are presented in sighting tables, which show the total or net allowance that should be made for various angles, speeds, and ranges for each type of aircraft and bomb. The pilot has been trained to make several different "standard" attacks, each with a given angle, speed, and slant range, each of which has a given aiming allowance.
This leaves only wind drift and target motion, if any, to be accounted for. This is done by "rules of thumb" in which the pilot has been versed. The amount the wind will drift a bomb depends on speed of the wind and the time the bomb takes to travel from the point of release to the target. The amount of distance the target will move while the bomb is falling depends on the target's speed.
The pilot knows that with It given "standard" attack, the line of sight should be moved into the wind (upwind) a certain distance for each knot of wind, and that a target should he "led" by a certain amount to compensate for gravity. In actual practice, the apparent motion the pilot sees - or the relative motion between the airplane and the target - gives the pilot all the clue he needs to estimate accurately the amount and direction of lead for wind and target motion combined.
