Vulnerability of Airships to Airplane Attacks

There is no belief more widely held than that which may be stated as, “Any airship will be immediately brought down if hit by a burst of machine- gun fire.” There is no belief which has less foundation in fact as recorded by past experience.

For two years during the World War, German airships raided France, Belgium, Russia, and England with absolute impunity insofar as airplane machine-gun attacks were concerned. A few ships were lost because of ground A.A. fire. They represented a very small percentage of the ships engaged in the airship offensive.

One explanation frequently offered is that the airplanes of the day did not have the ceiling of the contemporary airship. This is not true. Until the naval L-30 class appeared, there was no airship which had a loaded ceiling and few which had unloaded ceilings in excess of that of the defensive airplanes. The airship was hard to see at night unless illuminated, and searchlights were few. It could climb much faster than the defensive planes, a characteristic which it retains today. The greatest handicap for the defense was the lack of suitable armament.

The early airplanes carried two 20- pound high explosive bombs, two 16- pound incendiary bombs, and a supply of explosive darts for bombing airships in flight. There are only two cases recorded in which hits were obtained. In one, that of the LZ-37, the attacking pilot secured hits and set fire to the airship. In the other, the LZ-39, though hit several times, proceeded to her base despite one or more leaking cells, a few killed in the crew, and a propeller shot off. She was repaired in less than a week. Although damaged, her hydrogen was not set on fire and the “airtight subdivision” provided by the gas cells insured her flotation for the required period.

The same was true of the machine gun. Until an explosive ammunition was put into service no airplane attacks on airships with gunfire had been successful. Further, throughout the remainder of the war, no airplane machine-gun attacks on airships were successful unless they employed this special ammunition and set the airship’s hydrogen on fire.

On September 2, 1916, the German army airship SL-11 was brought down by a British defense pilot who was using the new Brock and Pomeroy bullets. This was the first airship, either raider or scout, to fall before the machine-gun fire of an airplane. By the end of the year four more Zeppelins were brought down by this means, all raiders. During 1917 only one raider was to fall, and in 1918 one more.

Thus one finds that of the 200 airships which were actually over English soil, the machine-gun fire of the defensive airplanes got 7, 5 in one period of 4 months before the airships changed their tactics. During the corresponding period it is interesting to note that airplane raiders suffered higher casualties. Approximately 424 German airplanes were over England during the war period. Fifteen of this number were brought down by the British airplanes.

At sea, during 1917, two airships were brought down by flying boats, one by an airplane launched from a cruiser. This was the first success for either type of plane although both had tried before. In every case the hydrogen of the airship was ignited by the new Brock and Pomeroy ammunition and the airship was lost because of fire. The airships were on scouting missions at the time and two of them were located because they did not restrict radio traffic to a minimum.

During 1918, a flying boat accounted for one scouting airship. A fighter which took off from a lighter towed by a destroyer got another. Again the airships were lost because of fire. There the record closes; 7 raiders and 5 scouting airships brought down in flames because of airplane machine-gun attacks with ammunition which could set their lifting gas on fire; one airship bombed by an airplane and again set on fire. In addition, just to complete the record, one must mention that 4 airships were bombed in their hangars and destroyed by fire. Here as in the air, unless the lifting gas was ignited, the ship was easily repaired.

Early in the war the British had performed experiments directed toward igniting the German airships’ hydrogen. They found that a hydrogen cell surrounded by an inert gas in an outer cell was completely protected. A Very’s cartridge was fired into the top and burned through to the bottom but the hydrogen did not ignite. For that reason many British officers thought that the German airships were “armored” with a layer of inert gas, possibly exhaust gas from the engines. Such was not the case but this was not demonstrated until the SL-11 was brought down.

U. S. naval airships are filled with helium. Helium is an inert gas and will actually extinguish a fire. Against machine- gun attacks, even with explosive bullets, our lifting gas is armored. The fuel supply is so widely dispersed that a hit which would cause a fire is unlikely. At any rate, heavy oil engines for airships are in sight. The new German passenger ship, the LZ- 129, is so powered. With heavy oil engines the last vestige of serious danger from machine-gun attacks disappears.

In using helium for armor we have paid the usual price. For the same performance in cruising range, ceiling, and other tactical characteristics we must have ships considerably larger than an “unarmored” or hydrogen filled ship.

There remains the danger of airplanes bombing airships. The British found it extremely difficult even from very low differential altitudes. Also they found that it did not insure the sinking of the airship unless it could be set on fire. In addition they had to develop a special supersensitive fuse that would explode upon contact with fabric. The solid metal parts of a rigid airship represent a very small percentage of total area. Even today, unless sent out hunting for airships and nothing else, this would present a nice problem for the airplane commander. Such supersensitive fuses would not be very suitable for use against surface ships.

In the final analysis, however, it is not in any armor of helium, in the use of heavy fuel oil, or in the defensive gun power of the airship that reasonable invulnerability lies. All must be provided to meet modern conditions, true, but real safety lies in evasion of attack. Here the airship must borrow from the submarine and from the large surface ship.

Whenever there is a cloud layer within reach the modern airship may be expected to submerge in it and remain there except for very short periods. In the meantime a streamlined shape with large stabilizing surfaces will have been lowered from the airship. In this an observer will sit with full view of the surface. This “airship periscope” is smaller than an anti-aircraft sleeve target, it is not painted to increase visibility, and it leaves no visible wake. When such conditions exist the airship commander has no worries about attacking airplanes, or surface ships for that matter. Further, if those interested care to investigate aërological records, they will find that many sea areas in which the U. S. Navy is vitally interested have a high percentage of days in which the safety of invisibility could be utilized.

In clear weather the airship must borrow from the large surface ship’s tactics and utilize a screen of smaller units. Airplanes at sea must come from some place. The airship’s small planes can screen at such distance that a surface ship carrying airplanes will be sighted while still at such distance from the airship as to render the surface ship’s airplanes ineffective. Engineers have computed that an airplane taking off from an airship can fly with about 30 to 40 per cent greater wing loading than one taking off from the surface. This can be converted into fuel which means radius of action.

Unfortunately neither the sub-cloud car nor the airship-carried airplane had reached a stage of development which would allow the above to be definitely proved in operations with the fleet up to the time when the Macon lost a fin and three cells, and had to sit down. We do know what the Germans have done and we have done enough ourselves to know that the solution is simple.

Complete invulnerability will not be attained for the airship. It has not been attained for the submarine, destroyer, cruiser, or battleship, certainly not for airplanes. We can only expect, with intelligent handling and a proper conception of the problem, to keep our losses reasonably low. It is hoped that the common belief in the extreme vulnerability of airships to airplane attack, particularly machine-gun attacks, has been partly dispelled. The record would indicate that the percentage of losses has been quite low in the past; we believe it will be low in the future. War cannot be waged without risks.

[A General] requires to be endowed with a peculiar gift, which Napoleon calls “Divination," that is to say, something that partakes of the supernatural: this, in order that he may know what his enemy is doing. Moltke substitutes for this gift the duty of a General to take for granted that the enemy is capable of adopting wise and effective measures, and to arrange his plan of battle accordingly.

Even this, however, is no small undertaking. In order to carry it out a man must be possessed of a clear and impartial mind, so as not to fall into the error of suspecting the enemy of taking what appears to be his natural course, but which is, in sooth, only the creation of one's own wishes in the matter.

He who would win a victory must not recoil from the task of attempting at least to penetrate this veil of uncertainty. For this, decision and the power to carry it through are necessary. It would be wholly wrong to suppose that any good can come out of plunging into the depth of uncertainty. Before attempting to penetrate it one must first have formed a tolerably clear idea of what the enemy may reasonably be expected to do, so as to shape one’s course accordingly.—Von Stein, A War Minister and His Work.