Jun 032011

The slideshow above reproduces “Preparation and Employment of the Fire Bomb,” a manual issued by The Chemical Warfare School at Edgewood Arsenal, Maryland sometime during late World War II. It provides step-by-step instructions for converting a drop tank into a napalm bomb, which is then mounted on a Republic P-47D Thunderbolt (serial no. 42-28610, for those interested in such details). Of interest is the equipment and techniques used in preparing the bomb; the candid shots of personnel, whose expressions range from boredom to mild amusement;  and detail shots of the mounting of the napalm bomb on the P-47D, which provide useful reference for modelers. The opening page of the manual is reproduced below.

1. Introduction

a. The droppable auxiliary aircraft fuel tank can be readily converted into an incendiary munition.

b. It is an effective weapon for use against personnel occupying gun emplacements, pill boxes, embrasures, caves, fox holes or truck convoys. Any material which is in part or entirely combustible, such as bridges, docks, railroad trestles, wooden surface vessels, small craft, warehouses and supply dumps make suitable targets for the Fire Bomb.

2. Preparation of Fire Bomb

a. To convert the gasoline tank into a Fire Bomb required only replacement of the standard filling cap with an E4R1 igniter.

b. If two igniters per bomb are desired an E3R1 igniter may be attached to the tail plug.

3. Fire Bomb Filling

a. Fuel may be a mixture of Napalm and any gasoline available.

b. A 6.1 percent by weight of Napalm (Eakins) In the gasoline-Napalm mix is recommended. At installations where other brands of Napalm are supplied, a sample mix should be made before the initial Fire Bombs are filled.

c. Time required for mixing of the solution varies with gasoline temperature, type of Napalm used, and the amount of air agitation.

(1) Gasoline temperature range for rapid mixing is from 70° Fahrenheit to 90° Fahrenheit.

(2) Mix depicted hereafter was made at 72° Fahrenheit using Eakins Napalm and required 4 to 5 minutes agitation per drum to gel.

d. After mix has gelled (tapioca stage) it should “cure” for at least 4 hours before using. This period of curing is necessary to permit the Napalm and gasoline to become a homogeneous mixture.

e. Once mixed the fuel may be left in the drums for extended periods without “breaking down” occurring.

4. Transferring fuel from Drum to Fire Bomb

a. Minimum pressure should be that which satisfactorily moves fuel from the drum into the Fire Bomb. This practice reduces the danger of bursting the drum. Pressure of 15 pounds per square inch was found sufficient to empty a drum through approximately 14 feet of hose and the quick opening valve into the Fire Bomb In 6 minutes.

5. Employment of the Fire Bomb

a. Reports from the field state that aircraft carrying the Fire Bombs prefer to come in at low altitudes (50 to 100 feet) and release the bombs in front of the objective, thereby throwing the contents forward onto the target.

b. Normally one bomb is released at a time as the area coverage is not markedly increased when both bombs are released simultaneously.

(1) Area coverage from one bomb is approximately 100 feet by 300 feet. The longitudinal axis being parallel to the line of flight.

All images from NARA Archives II, College Park, MD, RG 18


“Preparation and Employment of the Fire Bomb,” The Chemical Warfare School, Edgewood Arsenal, MD, in the files of the National Archives II at College Park, MD, RG 18

  2 Responses to “Preparing a Napalm Bomb for a Republic P-47D Thunderbolt”

  1. This is very nice material and rarely seen!!

  2. My father used to tell that 3 chemistry professors at Harvard discovered napalm early in World War II. He was then engaged by “the Army” to figure out how to manufacture it in usable quantities without blowing up Brooklyn. Obviously, during the War this was highly secret and this is the first time I have seen anything in writing confirming my father’s role in manufacturing World War II napalm.

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