Aircraft technical Basics: TM 1-409, Aircraft Armament and Pyrotechnics, 1941: V. - Chemical Weapons used by Air Corps

Section V - CHEMICAL WEAPONS USED BY AIR CORPS

31. General.-A knowledge of methods of protection against chemical attack is of prime importance to any and all of the personnel of the Army. While offensive action is important, it follows that defensive measures must also be given great consideration. In general, protection is divided into two classifications, namely, individual protection and collective protection.

a. Individual protection.-Individual protection, as the term implies, concerns the protection of an individual person, and deals with pertinent equipment and procedures, that is, gas mask, gas mask drill, gas chamber, and protective clothing.

b. Collective protection.-Collective protection deals with the protection of a. group. This phase provides many problems because it covers numerous activities such as construction of gas-proof shelters; decontamination of grounds, buildings, supplies, munitions and equipment; protection of food supplies; provision and training of protective organizations; etc.

32. Agents and method of use.-a. The effectiveness of the airplane as a means of projecting chemical agents has been demonstrated. The following agents are suitable for such projection : HS (mustard), M-1, HS-M1, CNS, FS, FM, and PS.

b. The wide radius of action and potency of the chemical effects now possible with aircraft make installations and movements in rear areas much more vulnerable and important as military objectives.

c. The methods now being considered as feasible for dispersing chemical agents and smoke by aircraft are as follows :

(1) Spraying apparatus-nonpressure type.

(2) Bombs, chemical.

d. Although the development of apparatus and of aviation chemical tactics is still in an experimental stage, the work has been carried sufficiently far to demonstrate its physical, chemical, and military feasibility.

e. All chemical apparatus is designed to be attached in such a manner that it may be dropped by the pilot in an emergency.

33. Spraying apparatus.-a. General.-Liquid chemical agents are projected from airplanes as a fine spray or mist by means of the nonpressure spray tank.

(1) The area covered and the drift of the liquid particles depend upon their size, the altitude at which the liquid is released, and the direction and velocity of the wind.

(2) When FS smoke material is released from an airplane, a considerable portion of the material will eventually fall to the ground in the form of small droplets of sulphuric acid. Depending on the altitude of discharge and weather conditions, some of the material may also fall to the ground in the form of small droplets of undecomposed FS and hydrochloric acid. All these acids are injurious to most materials. These particles do not fall vertically but, depending on the altitude of release and the velocity of the wind, may drift unpredictable distances and in unpredictable directions before reaching the earth. Therefore, the. restrictions listed in AR 770-15 will be strictly observed when using FS in laying smoke with airplanes in peacetime operations.

b. Spraying apparatus (nonpressure).-(1) Various types of spraying apparatus have been standardized and discarded with the advent of newer types of airplanes. Both internal, or fuselage, and external, or wing, tanks have been tested with varying degrees of success. Either installation presents problems; for instance, with the fuselage installation it was found impossible to keep some of the spray from coming in contact with the airplane with the resultant corrosion caused by the various acids in the mixtures. In addition to the above, the fuselage tanks occupied space which might otherwise have been used for the carrying of bombs. On the other hand, the additional drag induced by wing tanks is very great, and slows the airplane down very appreciably. The last spraying apparatus standard for use by the Air Corps was the E6R9 chemical tank, a wing tank installation for use on single-engine attack airplanes. Since the attack airplane is now obsolete, a new type spraying apparatus is being developed for use on the light bombardment type airplane. However, at this time no information on this new development has been disseminated to the services.

(2) Since the principle of operation is the same for all nonpressure spraying apparatus, the E6R9 chemical tank is chosen as an example. This type of apparatus uses only the force of gravity. The apparatus consists of a streamlined tank, a discharge valve and discharge line, an air vent, and the necessary connections. Since no pressure is used, the tanks may be made of very light material. The apparatus has a very high chemical efficiency.

(3) When the valve is opened, the agent flows down through the discharge line and into the air. Here it is subjected to the natural shearing effect of the airblast and is broken up into very fine particles which drift with the wind. Due to the tendency of the minute droplets to remain in the air and to travel as a fine mist with the wind, the spray must be operated at very low altitudes, except under the special conditions such as sometimes exist at night or early in the morning. The width of the pattern varies directly with the wind velocity and with the altitude at which the chemical agent is released.

(4) The agents HS (mustard), M-1 (lewisite), PS (chloropicrin), FS and FM (smoke), and HS-M-1 mixture are all suitable for dissemination by spraying methods. CNS and CNB are mixtures of crystalline CN (a lachrymator) dissolved in volatile liquids, such as chloropicrin, carbon tetrachloride, benzine, and chloroform, which also makes them adaptable to the spray method. Due to the fact that these chemicals must be released from a very low altitude to insure maximum concentration and minimum volatilization, this type of apparatus is particularly suited to fast, low flying airplanes.

c. Value of spraying.-The efficiency of dispersing chemical agents from airplanes by spraying apparatus lies mainly in the effective concentrations that can be accurately put down on personnel under conditions approaching complete surprise and the inadequacy of any practical protection against such an attack and the large amount of agent per tank which can be carried. The principal disadvantage of the spraying apparatus lies in the fact that the atomization increases the surface area of the liquid to such an extent that the persistency is greatly reduced. Chemical agents released by this method are not very efficient for contamination purposes. Another disadvantage is the fact that the airplane carrying the spraying apparatus must fly close to the ground when releasing the agent in order to provide a reasonable chance of striking the target and that the spray will not be too widely dispersed before reaching the ground.

d. Chemical tanks.-The model E6R9 chemical tank was developed by the Chemical Warfare Service for Air Corps use. The apparatus described is designated as airplane chemical spray tank E6R9, and is designed for either wartime or peacetime use for disseminating HS, FS, M-1, and other liquid chemical agents from airplanes. Operations is by electro-mechanical means, and the discharge of the contents is accomplished by the release of a closure plate from the end of the discharge line.

(1) The container used is a cylindrical tank with uniform ogival ends, and has a total capacity of approximately 23 gallons. A filling hole is provided at the front end of the container which also serves as a fitting for the vent mechanism when assembled for use. An opening is provided in the bottom at the rear of the container with a collar and beveled flange to which is attached the discharge line assembly.

(2) This apparatus is designed to be suspended at two points on the airplane chemical rack. Bracing against side sway is accomplished by four adjusting screws attached to this rack.

(3) In case of emergency the tank can be released from the chemical tank rack by means of a switch located in the cockpit of the airplane which operates a solenoid on the chemical tank rack.

e. Tactical uses.-Smoke screens and blankets are laid by light bombardment airplanes. Smoke may be used very effectively in this manner to screen bombing or other attacking airplanes from ground observation. Smoke clouds laid by airplanes may also be used occasionally to conceal the movements of fast moving ground forces

(1) Lachrymators are used for harassing or delaying the enemy.

(2) Vesicants, when dispersed by spraying, may be employed directly against personnel for casualty effect and for general harassing purposes. For neutralization purposes, the airplane spray is not as effective as bombs, due to decreased persistency.

34. Chemical bombs. a. Dissemination of chemical agents by means of bombs as compared with the nonpressure spray method, presents certain definite advantages which are enumerated as follows :

(1) Greater persistency due to the fact that the agent is not broken up into minute particles, thereby increasing the surface area of the liquid.

(2) Greater penetration, because the bomb is fuzed to burst on impact, which permits a better lateral spread than is obtainable with a liquid agent dropped from higher altitudes.

(3) The use of bombs permits greater safety to the airplane inasmuch as they can be dropped from high altitudes, thus eliminating the danger of small arms fire from ground troops.

b. Although larger bombs have been tested and some are now under development, the M46, 30-pound chemical bomb is standard for Air Corps use.

c. Chemical bombs are usually fuzed for instantaneous or super-quick action in order that an air burst is obtained, insuring minimum loss of chemicals into the ground. The booster charge may vary, depending on whether the bomb contains a persistent or nonpersistent agent. If a bomb contains a persistent agent, a larger booster charge may be used than if the contents were nonpersistent; the reason for this being that the nonpersistent agents are more volatile and would therefore evaporate and become ineffective in a very short time if spread thinly over a fairly large area. Persistent. agents, however, being much less volatile will remain effective over a longer period of time even though broken up into small droplets.

d. Chemical bombs containing a persistent vesicant may be used to great advantage in conjunction with demolition bombs as a means of retarding reconstruction of the target by the enemy, the chemical contents of the bombs contaminating the debris, thus rendering the process of cleaning up very difficult. Enemy strong points may also be neutralized and made untenable by the use of persistent agents in bombs; roads may be made impassable temporarily, thus slowing enemy troop and convoy movements.

e. The system of marking chemical containers and munitions applies also to chemical bombs. All chemical containers are painted gray and the nature of the contents indicated by colored bands running around the entire circumference of the container. Green bands indicate a casualty agent; one green band indicates a nonpersistent agent, two green bands, a persistent agent. A red band denotes a harassing agent; a yellow band, a screening smoke; and a purple band indicates that the contents is an incendiary. In addition to the bands, the symbol of the agent is stenciled on the container in the same color as the bands.

f. The various types of chemical bombs are separately discussed in TM 9-980.

35. Training-a. If a high percentage of chemical casualties is to be avoided, it is necessary that troops be well trained in gas discipline. Raw troops are prone to become panic stricken when unexpectedly subjected to chemical attack; this fear is not unreasonable when cognizance is taken of the fact that most people outside of the military service are in total ignorance of the actual facts concerning chemical warfare. The average civilian gathers his information from tabloid newspapers with a resultant distorted idea of the horrors of gas warfare; fortunately, it is possible to dispel such fears with a few simple lectures and drills.

b. Training of troops in gas defense should include lectures on the gas mask and protective clothing, different types of agents, and their odors (demonstrated by means of the gas identification set), and first-aid treatment for casualties from the various agents. Gas mask drill is important, and gas chamber drill should not be omitted since it demonstrates the ability of the gas mask to protect the wearer from noxious gases, and furthermore, the gas chamber dispels much of the fear of war gas inherent in untrained personnel. (See FM 21-40.)