If the average air-minded civilian is asked to define his conception of the manner in which aircraft may accomplish the destruction of naval surface craft his answer will undoubtedly be, “Why, with huge aerial bombs, of course.” A similar opinion seems to prevail in army circles as is evidenced by the following testimony recently given before a committee of the House of Representatives:
Mr. Collins: “What about battleships and cruisers?”
General Fechet: “Any battleship or cruiser can be destroyed by bombardment aviation.”
Even in the Navy those who are willing to admit that aircraft can menace the safety of surface vessels are generally inclined to disparage the potentialities of forms of aerial attack other than by means of heavy bombs dropped from high altitudes. This general belief is based partially on psychological reasons, but has its main foundation in the lack of information.
Anyone who has dodged a wrench falling from an upper grating of the engine-room or attempted to avoid the danger space of a bucket of paint dropped from aloft has been mentally impressed with the possibilities of danger from aerial missiles. Those who witnessed, or read accounts of, the bombing of the Ostfriesland and the Washington can realize that under sufficiently favorable conditions aircraft bombs can destroy the heaviest ship afloat. No such mental impressions or practical demonstrations of other forms of aerial attack have been widely enough published to influence the general opinion to any appreciable extent.
Roughly speaking, there are three different types of aerial attacks that can be delivered on surface vessels. The first has already been indicated. The second is by means of torpedoes launched from planes. The third is by means of fast, light planes using light bombs and machine gunfire. As this last form of aerial attack cannot be considered as constituting as great a menace to the safety of large surface vessels this discussion will be confined to the two more potent forms. It will be further confined to consideration of types of aircraft capable of operation from aircraft carriers.
Unfortunately for the purposes of direct comparison the service has not yet been equipped with types of aircraft designed exclusively for either bomb dropping or torpedo launching. Considerations of aerodynamical efficiency alone will eventually force a divergence in type. The efficient plane designed entirely for dropping heavy bombs from high altitudes is a large, heavy plane with a comparatively great wing span. The torpedo plane, not being required to lift a heavy load to any considerable altitude, can be a smaller, lighter, and faster plane of considerably lesser wing span. Consequently for a given amount of stowage and operating space on an aircraft carrier a larger number of torpedo planes may be provided than if the same allotment of space is devoted to bombing planes. In addition, the smaller size of the torpedo planes will render their handling on the carrier much easier; a point of no small military significance as will be appreciated by those who have served in the flight-deck crews of the carriers.
While it is very difficult to forecast even immediate trends in aircraft design, present limitations seem to indicate that the bombing plane cannot be considered as being capable of taking off from the deck of a carrier with a bomb weighing more than 2,000 pounds. Such a plane would be considered very efficient if it could lift this load to an altitude of 20,000 feet and have a maximum speed of 90 knots at that altitude. This type of plane would carry a crew of four; pilot, bomber, top gunner, and a combination lower gunner and radio man. The defensive armament of such a plane would include three machine gun emplacements: one covering arcs of fire forward and upward, one for fire upward and aft, and the third for firing through the bottom of the fuselage of the plane. The torpedo plane, on the other hand, could be developed to the point where it could attain a maximum speed of about 130 knots at sea level and still be capable of taking off from the deck of a carrier with a 21-inch torpedo. Its crew could be reduced to two men; pilot and gunner. The defensive armament of such a plane would consist of two machine gun emplacements; one for a free gun covering arcs of fire upward and aft, and the other for a fixed gun firing forward. Many may disagree with the more or less arbitrarily assigned performance figures but it is believed that fewer will find fault with the suggested tendencies of design.
Even granting that the present compromise of design in which the two types are identical persists, there are certain comparative factors involving the two different forms of attack that merit consideration. It is almost universally conceded that the danger from anti-aircraft gunfire will force bombing planes higher than 10,000 feet. In the absence of the surprise factor, such as the sudden descent through a broken layer of clouds, a bombing attack from a lower altitude is almost certainly doomed to failure unless the anti-aircraft batteries of the target have been put out of action by strafing planes or other means. Some may consider the 10,000-foot altitude entirely too low and contend that a bombing attack from an altitude of less than 15,000 feet will be broken up by anti-aircraft fire. No matter which of the two figures is accepted bombing planes may be forced, by prevailing weather conditions, to attack from a dangerously low altitude. For example, on overcast days a fairly thick layer of clouds is very frequently found at an altitude of 5,000 feet above sea level or even lower. Bombing planes would be sharply silhouetted against such a background which, in conjunction with their low altitude, would make them comparatively easy targets. As still lower ceilings are often encountered an aerial bombing attack is sometimes entirely impossible. On the other hand torpedo planes can deliver an attack under almost any sort of weather conditions in which any aircraft operations at all are possible. Only in the very rare instances in which a low lying fog exists through which the tops of the targets are visible from clear sky above, would an aerial bombing attack be possible and a torpedo plane sortie impracticable. Therefore, the availability of a torpedo plane attack may be considered greater than one from bombing planes. It may be argued that the comparative disadvantage in availability of a bombing attack from this cause is somewhat compensated for by the fact that bombing planes can attack objectives ashore. However, objectives that might be considered as proper targets for bombing attacks from fleet aircraft that cannot also be attacked by torpedo planes are few in number. For example, what objectives ashore have been assigned as targets to the aircraft of the fleet in maneuvers? The answer is the locks of the Panama Canal and the Gatun dam. Is the possibility of a successful torpedo plane attack on these points, and particularly on the Gatun dam, so remote that a torpedo net or other means of defense is not needed?
In instances where weather conditions and other considerations permit of both forms of attack, which runs the greatest risk of being broken up by enemy action before its projectiles have been launched? Some will contend that neither form can hope to accomplish any tangible results and it must be admitted that this is true of unsupported daylight attacks in clear weather. But granting that both have the support, protection, and cooperation of fighting and strafing planes and that the two attacks are delivered during the heat of a general engagement, both have a reasonable chance of accomplishing definite results.
During the bombing attack these planes will be subjected to intensive attacks from hostile fighting planes. It is admitted that a formation of bombing planes has a certain inherent defensive ability against such attacks. However, the formation is not particularly well protected against fighting plane attacks from ahead and, to a lesser degree, from beneath. Fighting planes attacking from ahead and at the same altitude will force the formation to either turn or dive in order to bring any guns to bear. As any such loss of altitude is regained but slowly when the bombers are fully loaded and as altitude must be conserved in order that the bombing attack may not be broken up by anti-aircraft fire, it is probable that the usual maneuver will be a turn. By making repeated feint attacks the fighting planes, unless opposed by protective fighters, can force the bombing formation to turn entirely away from its objective or else accept the risk of fire from the fighters when none of the guns of the formation will bear. An aerial bombing attack, therefore, requires the protection afforded by an escort of fighting planes.
The formation of torpedo planes, during its approach, flies at low altitude and is protected from attack from beneath by the proximity of the surface. The torpedo planes can oppose fire from fighting plane attacks from ahead with their fixed guns. It might be argued that the bombing plane could be similarly equipped for the same purpose but even if this is done the advantage still rests with the torpedo planes for two reasons. The first is imposed by the nature of the two forms of attack. The bomb- mg planes must fly on a steady course for quite an appreciable period in order that the Proper dropping point for the bombs may be determined and reached. During this period any radical changes of heading would destroy the accuracy of the bombing. The torpedo planes are not so restricted. In their case it is only necessary to steady down in heading for a second or two. In fact zigzagging to avoid surface gunfire or to oppose aerial attacks is highly desirable. In addition the bomber is a heavier and larger type of plane and therefore less maneuverable and, even if equipped with a fixed gun, could not be expected to use it effectively. The torpedo plane being more maneuverable could use this weapon more effectively.
The formation of torpedo planes, then, can oppose frontal aerial attacks with fire from their fixed machine guns. Their free guns aft would cover arcs of fire in that direction and upward arcs as well. Attacks from beneath would be impossible for reasons previously indicated. There remains only the possibility of diving attacks from above in the hopes that the free machine gunners would be unable to train and depress their guns quickly enough to oppose any effective fire. And in attacks of this sort the fighting planes would also be handicapped by the proximity of the surface. After a sharp dive at high speed planes lose an appreciable amount of altitude even after the controls are set for recovery from the dive. This squashing due to the momentum of the fighting planes would necessitate their starting recovery from the dive well before the altitude of the torpedo plane was reached. As the commencement of the recovery means that the fixed gun of the fighter would no longer bear and as this restriction would not apply to the free machine gun of the torpedo plane, it follows that the latter could continue fire during the period when the range was the shortest, while the fighter would have to cease fire at a comparatively long range. If the fighter persisted in the dive to fire at very close range it would run grave risk of crashing into the surface while recovering from the dive. For these reasons the torpedo plane formation stands a better chance of beating off attacks from hostile aircraft than does a similar group of bombers. In fact, it may be contended that a fighting plane escort would not be required by torpedo planes, although such protection is admittedly requisite in the case of bombing planes. Fighting plane pilots will probably object strenuously to this contention but at the same time they will admit that definite proof either way is lacking.
In addition bombing planes are exposed to attack from hostile aircraft for a longer period of time. With no great altitude to be gained, torpedo planes can proceed directly from their carriers to their objective. The bombing planes are faced with the necessity for attaining their bombing altitude, which, with the load that must be carried, requires a considerable time interval. Thirty additional minutes’ allowance for this feature of the bombing attack is not excessive. In addition, the fighting plane escort is required for a longer period, which, when the limited fuel capacity of these planes is considered, is of no small importance. Granting for the sake of argument that torpedo planes do require such escort, these fighters could he released for other activities one-half hour earlier than would be the case for the escort of a bombing group.
This extra time interval also imposes upon the officer in tactical command the necessity for choosing further in advance the moment for launching a bombing attack. Aside from this consideration this time interval imposes another comparative handicap upon the bombing planes. Assume that at the zero hour the torpedo planes can launch an attack in thirty minutes. The bombers will require an hour. Both groups will require thirty minutes to return to their carriers, the bombing planes, by gliding at full speed from bombing altitude, thus compensating for the higher maximum speed of the torpedo planes. Assume further that an hour will be required for both groups to refuel and re-arm on the carriers. The torpedo planes, as before, will be able to reach a position from which a second attack can be delivered in thirty minutes after taking off, while the bombers will again require a full hour. The torpedo planes will then launch their second attack two and one-half hours after the zero hour while the bombers will not be able to do likewise until three and one-half hours have elapsed. Therefore, the torpedo planes have what might be termed a greater rate of fire than the bombers.
But even if they concede the foregoing, proponents of the bombing plane contend that these planes have less to fear from surface gunfire than have the torpedo planes. They assert that the effectiveness of a splash barrage from the broadside batteries of surface vessels is such that it will form a more efficient bar to a successful torpedo plane attack than does anti-aircraft fire to a bombing attack. They also assert that anti-aircraft fire may be directed against torpedo planes in addition to that from the broadsides.
Considering first the bombing attack and its surface antidote, even the most rabid supporter of military aviation must admit that anti-aircraft gunnery has been improved immensely in recent years. There is no question as to its ability to break up a bombing attack if the planes come over low enough. The uncertainty lies in whether or not anti-aircraft fire will be effective at the greatest altitude from which accurate bombing is possible. While recent developments have greatly increased this altitude, still the bombing planes must fly on a steady course, at a constant speed, and in a fairly close formation for an appreciable period just prior to the release of the bombs. The constant course and speed are necessitated by the operating requirements of bomb sights. And as the size of the pattern of the bombs dropped varies directly with the dimensions of the bombing formation, it necessarily follows that these planes must be in a relatively close formation. A single anti-aircraft burst in the center of the formation during this period would probably destroy a majority of the planes within the group. While bombing planes may fly higher than the altitudes at which anti-aircraft fire is effective, by doing so they lessen the accuracy of the bombing and even then run the risk of having a single lucky burst destroy the formation.
It is true that torpedo planes, while attacking, may be subjected to anti-aircraft gunfire in addition to that of the broadside batteries. At first thought this might seem to indicate a greater difficulty in pushing home an attack. Such, however, is not the case. Considering first the anti-aircraft angle, it seems logical that the control officers of such batteries are apt to be much more alert for the appearance of planes at an altitude than for planes flying close to the surface. Therefore, other considerations being equal, a bombing group will be sighted by these officers earlier than would a torpedo plane formation. A psychological factor enters into this equation. A person ordered to watch the sky for the appearance of aircraft almost invariably looks too high. Even experienced aviators on board ship are apt to direct their gaze at too high an angle when expecting the appearance of returning planes.
Even granting that the torpedo planes are sighted at a considerable distance, anti-aircraft fire against these targets is not apt to be particularly effective. During the period that the planes are in range the formation of the torpedo planes is well spread, so much so that the gunners will be somewhat embarrassed by the multiplicity of targets. In addition, the design of anti-aircraft guns necessitates consideration of ease of operation at high angles of elevation. This involves a relatively greater height of the trunnions above the operating platform than is the case with the guns of the broadside batteries, so that when elevated the breech will not be so close to the deck as to interfere with loading operations. At angles of depression and even when level, unless these guns are fully automatic in action, the elevation of the breech is apt to introduce difficulties in loading operations. In fact, the very essence of anti-aircraft gunnery, i.e., high-angle, concentrated fire, militates against the successful use of these guns in repelling a torpedo plane attack.
There remains gunfire from the broadside batteries. Considered even singly the effectiveness of these guns for this purpose is open to question. Certainly these guns were not particularly successful at Jutland in breaking up destroyer attacks. The Nestor and Nicator in that battle ventured to within 3,500 yards range from a powerful division of battle cruisers and were not hit until after they had delivered their attack and were retreating. It is true that broadside batteries are far more effective now than they were at Jutland, but it may be questioned as to whether this improvement is sufficient to render them capable of destroying the smaller, far speedier, more numerous, and more widely dispersed and zigzagging targets afforded by torpedo planes. Much is heard of the probable effectiveness against torpedo planes of the laying down of a splash barrage, particularly from those who admit that it would be a difficult matter for these guns to score direct hits on torpedo planes. The theory is that by maintaining a rapid rate of fire and forming a wall of splashes at a range greater than that from which this form of torpedo attack would be effective, the torpedo planes would be denied access to the area within which they would constitute a menace. The origin of this theory was probably due to some of the pioneering torpedo drops from planes. Several years ago there were a number of instances in which operating personnel, through inexperience, launched their torpedoes when too close to the surface and the resulting splashes from the torpedoes threw the planes into contact with the surface and the planes were destroyed. It is believed that in accounts of these mishaps those without personal knowledge of aviation were mistakenly led to believe that the planes in question were destroyed by the torpedo splashes. What actually happened was that the torpedoes were dropped when the planes were extremely close to the surface, perhaps not over three feet. The splashy from the torpedoes took effect on the tail surfaces, elevating the tails of the planes so much that the pilots were unable to right their planes before their noses struck the water. Had these splashes taken equal effect when the planes were at an altitude of even as little as 20 feet, the pilots would have been able to avoid disaster. However, the splash from a 5-inch shell rises with much greater velocity and to a greater altitude than does a torpedo splash, although the relative density of the two columns does not appear to be greatly different. The writer is of the opinion that a splash from such a projectile striking a torpedo plane at an altitude of 100 feet would not materially damage the structure of the plane and, while it might throw the plane into a dangerous attitude, the pilot would have a fair chance of regaining control. For that matter it would be a simple matter for these planes to fly at a higher altitude than is attained by such splashes, without exposing themselves to aerial attacks from beneath, until just before launching their torpedoes when, of course, they would have to descend close to the surface.
Even granting that anti-aircraft and broadside battery gunfire will be effective against torpedo planes attacking singly, there are still two possibilities which may enable these planes to push home an attack despite this more or less questionable handicap. The first of these is a combined torpedo attack from both aircraft and destroyers acting in conjunction. In this case the torpedo planes can remain out of range during the approach of the destroyers and then, when the broadside guns are fully engaged with these targets, dash in and launch their attack. Even granting that the destroyers will fire their torpedoes at 10,000 yards and that the planes must be within 4,000 yards, the control officers of the guns will have only a short interval in which to sight these new targets and direct fire against them. The greater portion of this 6,000 yards can be covered by the planes at full speed (130 knots), and while the planes must slow down just prior to dropping, an average speed of 100 knots for the entire distance is not an excessive estimate. This would make the time interval in question less than two minutes. A single squadron of 18 torpedo planes would, during this interval, be separated into several groups with about 200 or 300 yards’ space between each group. Even granting that the planes are sighted just as the destroyers fire and that the shift in targets is made instantly, such a short time interval remains that it is very doubtful if fire could be more than opened against them before they would reach the dropping point. Certainly few of the planes would be destroyed from this cause, under such conditions.
Even this does not conclude the list of problems facing surface gunfire directed against these targets. Torpedo planes can approach almost unhindered under cover of a smoke screen laid by other aircraft. The planes can fly low enough so that they are hidden by this screen from their targets and yet high enough to evade most of the effects of a blindly laid splash barrage. In fact, under such cover the torpedoes may be dropped at almost point-blank range, although the planes are exposed only for a few seconds. The knowledge of such a protection with the resultant but momentary exposure to gunfire will have a great effect on the morale of torpedo plane personnel and makes for more accurate torpedo launching.
The bombing planes can expect no such assistance. There are no targets aloft to provide diversion of hostile gunfire and if concealment in the form of clouds is present it hinders accurate bomb dropping as much as it does anti-aircraft fire. Neither can these planes utilize the cooperation and support of surface vessels.
The relative accuracy of bomb dropping and torpedo launching from planes may now be considered. For this comparison the reports of gunnery practices are of little value. Although such reports on the whole seem to indicate a slightly greater accuracy for the torpedo plane, such a basis for direct comparison is obviously unjust to both sides. Torpedoes fitted with practice heads may be actually fired against capital ships; bombs may not. However, it is known that the accuracy of bombing falls off with increase of altitude with greater rapidity than does that of aerial torpedo launching with increase of range. General service opinion concedes a greater accuracy to the fire from torpedo planes. The same general opinion seems to prevail in the British Navy as is evidenced by the statement of Mr. Hector Bywater in the Baltimore Sun of April 24, 1929. In that publication, in discussing the then recent maneuvers of the British fleet, he states, “Of aerial bombing results I cannot speak from personal knowledge, but it is generally conceded that torpedo attack (from planes, as indicated by the context) is more to be dreaded.”
Proponents of the bombing plane will point out that as between torpedoes launched from a range of 4,000 yards and bombs dropped from 12,000 feet the targets will have four times as long an interval in which to avoid the torpedoes by maneuvering. They will further state that the time of the fall of the bomb from that altitude (about twenty-eight seconds) is so short that the targets can do little to avoid the bombs. They ignore the fact a maneuver started during the bombing approach would affect the accuracy of the bomb dropping far more than would a similar move affect the aerial launching of torpedoes. It is admitted that maneuvers to avoid torpedoes will be more radical than those to avoid bombs. It is undetermined, however, whether or not this is a positive disadvantage to the detriment of the over-all military worth of torpedo planes. In fact the imposing of radical maneuvers to avoid torpedoes upon enemy capital ships may be highly desirable. For example, in one practice attack a battleship was forced to change course sixty degrees and to stop both engines to avoid four torpedoes that finally passed just ahead of its bow. Had the course been maintained or, even with the change of course, had the speed been continued, all four torpedoes would have scored hits. If this maneuver had been imposed upon that ship during the heat of a general naval engagement it would have thrown that battle line into considerable confusion and would have resulted in the blanketing of the guns of at least one ship.
The next point to be considered is the relative effectiveness of the bomb hit and the torpedo hit. The 2,000-pound bomb, previously indicated as being the largest size that, for the immediate future, can be used by carrier bombing planes, has between two and three times the weight of explosive carried by the war head of the aircraft torpedo. Obviously as between single hits from the two weapons, both ideally placed, the bomb hit will be far more effective. But while the torpedo hit is always located so that the explosion takes place directly against the under-water skin of the ship, the same is not true of all bombs that inflict damage. Even though near hits of bombs do considerable damage by mining effect; for this effect to be marked, the point of impact must be close to the side of the target to equal the effectiveness of the torpedo hit. It is generally conceded that bombs striking close to the side of the target are more effective than direct hits, but the area within which this effectiveness exists is comparatively narrow in width. In fact, it may be argued that a group of four bombs taking effect on a capital ship will, by reason of some of the bombs striking the water too far away from the side of the ship to take full effect, not do greater damage than that caused by four torpedo hits. However, the greater weight of the explosive in the bomb makes it difficult not to admit a slight superiority in effectiveness to the bomb hit. Obviously, if the weight of the bomb could be increased this advantage of the bombing plane would be correspondingly augmented. But with the many arguments in favor of carriers smaller in size than the Lexington and Saratoga and the probability that future carriers will be of smaller size than those huge vessels, the take-off space available will be decreased and not enlarged. Therefore it is difficult to see how a heavier bomb can be used in the absence of some device such as a catapult to assist in launching planes thus heavily laden. And the introduction of such devices would naturally lead to other complexities. Shore-based planes, on the other hand, are not so limited with respect to the space available for taking off. Neither are such planes restricted in size as are carrier planes. A 4,000-pound bomb or even heavier for such planes seems quite practicable.
In summation, and considering types of planes capable of being developed in the immediate future, we find that a greater number of torpedo planes can be utilized for a given allotment of carrier space. These torpedo planes, in addition, can be handled on the carrier more efficiently than the correspondingly lesser number of bombing planes. Torpedo planes can attack under weather conditions in which a bombing attack is impracticable. Bombing planes are less capable of defending themselves against hostile aircraft than are torpedo planes. In addition they are exposed to such attacks for a longer period of time. The time for launching a bombing attack must be selected further in advance than must one for a torpedo plane attack and torpedo planes can attack oftener in a given interval of time. Torpedo planes can attack almost any logical target. Bombing planes run greater risk of destruction from surface gunfire than do torpedo planes. A bombing attack is more apt to be broken up by combined hostile efforts than is a torpedo plane attack, as the latter can attack in conjunction with destroyers and under cover of an aerially laid smoke screen. In addition, and this is a point that has not been brought out before, torpedo planes can, by such cooperation with surface vessels, increase the effectiveness of the surface torpedo attack. And in such combined attacks torpedo planes may be able to push home their effort almost unopposed by hostile gunfire. Bombing planes just prior to bomb dropping must fly on a steady course, at a constant speed, and in a close formation. Torpedo planes may steer erratic courses at high speed until the instant of torpedo launching and can attack in a widely spread formation. Therefore a torpedo plane attack has a better chance of being pushed home. Torpedoes can be launched from planes with greater accuracy than can be obtained in bombing. As against the foregoing the bombing planes can claim but two slight advantages. Their targets have less chance to avoid their projectiles by maneuvering and the bomb hit is more effective than the torpedo hit.
Subject to the development of planes designed exclusively for torpedo or for bombing missions, it seems logical to conclude, in the unfortunate event of war within the next five years, that a greater over-all military efficiency would result from the elimination of the high altitude, heavy bombing plane from the complement of aircraft carriers, and the substitution therefor of an additional and greater number of torpedo planes. However, the foregoing should not be construed as meaning that, during the time of peace, the development and operation of bombing planes as a distinct type should be limited in any manner until their possibilities and limitations have been definitely determined.