The Douglas A-20 Havoc

Shakespeare, and millions of the bard's disciples, will argue that there is nothing whatsoever in a name, that roses would retain their sweetness under any arbitrary label. Perhaps this theory is correct. But when Sir William of Douglas led Baliol's legions at Berwick Castle in 1296 he established a previously undistinguished name as one of consequence in military annals. Nor did his heirs forfeit the dubiously honorable heritage. From James the First, who led the troops of Bruce at Bannockburn in 1314, down to James the Ninth, the Douglas name has appeared in more battle rosters than has any other Anglo-Saxon surname. There must be a score of German generals who wish the name had disappeared with passing of the last Douglas baron in 1857, for long before the Maginot Line became a monument to national stupidity, a modern Douglas was pouring powder and lead into lads of the Luftwaffe with a vigor which would shame the flesh-and-blood soldier who fostered the family's fame. This contemporary Douglas, known variously as the DB-7, the Boston, or the Havoc, has effectively restored the Black Douglas reputation to military annals — and its pilots say the best is yet to come.

Some combat airplanes make widely-publicized debuts, have a brief run of heroism, then pass quietly from sight in the face of tactical challenges. We have had several such planes; the enemy has had a great many. Other planes, in contrast, arrive over battle fronts with little ballyhoo, devastate everything the enemy cares to put on the firing line, undergo a few changes, then come in swinging on another front. The Douglas A-20 is a plane of that ilk. Although military security prevents revelation of current letter designations, it can be said that only the P-40 has served on so many fronts, on so many diverse war duties. And the P-40 has now run the gamut of possible design revisions — while the A-20's designers and Donald Douglas look to the continental invasion as their blaster's "coming of age." Thus, noone blames the citizens of Boston who have protested elimination of that city's name from the A-20 pedigree. But even the most ardent booster of clam chowder and baked beans will agree that Havoc is a nickname closer to the heart of this twin-engine terror of the skies.

Skin deep beauty

Everyone in America — and most of the people in England, Russia, and France — knows the Havoc superficially. No other plane has won newspaper tribute in more languages. But underneath that all-metal skin, which covers one of America's most beautiful large planes, lies a complexity, an all-around ruggedness, and an engineering brilliance known only to the men who fly and maintain this versatile warrior. Here, in its fighting heart, lie the elements of destruction which belie the ship's exterior beauty. Obviously, the major structural details cannot be publicized. The Havoc has performed so successfully that the enemy has not, in three years, learned all of the secrets of its battle brilliance. Hence, the brevity of text and structural analyses on succeeding pages constitutes no deliberate slight of this great plane. When more can be printed on the A-20 subject, newspapers and magazines will all give it the written tribute which has been on the lips of airmen in four allied countries for forty months.

General structure

A twin-engine attack bomber, carrying a crew of three or more depending on tactical arrangement and purpose, the A-20 has a wing span of 61' 4" and measures 47' 4" in overall length. When viewed on the ground, the A-20 is apparently lower than most ships of the light bomber type, though it measures 18' 1" in overall height. The fuselage is 27" high1, 49" wide, and clears the propeller by 9". Power from two Wright Cyclone GR-2600 radial engines drives three-blade Hamilton Standard Hydromatic propellers with a diameter of slightly more than ll feet. In general appearance, the A-20 is similar to the B-25 and the B-26 but is distinguished among modern aircraft by a tricycle landing gear, dihedral tailplanes. The main landing wheels carry 44-inch smooth contour tires by Goodyear while the nose wheel is shod with a 26-inch Hayes smooth contour tire. Dihedral angle of the tailplane is 10° as contrasted with a 5° angle in the mid-wing. With 550-gallon fuel capacity, using high-octane gas, the A-20's range, speed, combat loading, and ceiling are dictated entirely by operational purpose. Top speed is over 325 mph.

Care on delivery

Larger than an expensive yacht, more delicate than a fine watch, the A-20 asks for, and gets, special care from the moment it leaves Douglas or Boeing plants for the combat theatres. This begins, sometimes, with removal of wings and covering of the airframe with a tarpaulin when the plane is to be shipped by boat. But the A-20 is so urgently needed on so many fronts that the great majority are now flown to ferry stations throughout the world, to be taken over by Russian, British, or American pilots. Because ships are sometimes stored at these intermediate bases, an elaborate service ritual has been conceived by Army technicians. Here, then, is a maintenance procedure no less official than GI dungarees.

When the A-20 lands at a ferry station, all spark plugs are removed instantly, exhaust valves are sprayed with corrosion preventive compound, with spark plug holes permitting easy access. Four revolutions of the crankshaft then work the compound through valve guides before spark plugs are reinstalled after checking, cleaning, and replacement of defective plugs. Oil sumps are then drained while carburetors are thoroughly flushed with lubricating oils, propellers are coated with similar fluids, and unpainted engine parts are coated with petrolatum. The job is completed when propeller shaft parts are sprayed with melted rust preventive compound. When planes are to be stored under adverse weather conditions, or for more than six months under any circumstances, engines are, of course, removed entirely and a standard service and storage routine replaces this once-over-lightly.

Air frame maintenance

Although less complex than the engine servicing, standard routines on the A-20 airframe are no less important to the final effectiveness of the ship in combat. Immediately after completion of the engine job, all unpainted metal parts, including the Alclad wing, tail, and fuselage surfaces, are sprayed with an accepted rust preventive compound. Control cables are then greased with a mixture of white lead and melted tallow while the entire hydraulic system is checked for leaks and filled with new fluid. All exposed sliding piston surfaces are then coated with castor oil, carefully covered with clean cloth or heavy paper and bearing surfaces are covered with petrolatum. The Goodyear and Hayes air wheels then enter the picture as bearings, grease seals, and wheels are removed and cleaned with gasoline, then dried with an air blast. Braking surfaces are washed with solvent and, if unpainted, are coated with a solution of metal, oil base, and primer — a coating which will be removed later before the ship goes into service. The balance of the magnesium wheel is then repainted with aircraft enamel wherever the factory finish has been chipped or worn. This latter procedure is repeated on braking plate, torque arm, shoes, and all other aluminum alloy parts, with special care exercised to prevent overlap on braking surfaces or linings. When axles have been cleaned and lightly coated with wheel bearing lubricant, the main landing wheels are reinstalled on the ship. Service routines on nose wheels follow the same general pattern with one exception. Knuckles are thoroughly cleansed with gasoline before getting fresh bearing grease. The tires are then washed, rubbed with glycerin until a uniform color is obtained, shock struts and bearings are greased and coated with rust preventive compounds, Aerol legs filled with new fluid. With removal of all pyrotechnic signaling equipment for storage with the local ordnance officer, removal of instruments for repair and checking before consignment to the Army instrument stock, storage of flotation gear, life rafts, and parachutes in special lockers which resist mildew and deterioration, the A-20 is all set for a pre-combat rest of as much as six months.

No less important to the A-20's success, after-flight inspections require considerably more elbow grease, plenty of brain work. As soon as the ship lands, bomb racks are checked, any remaining bombs in the bay are immediately removed. Armament is cleared and ejection mechanisms are checked for alignment with guns after all ammunition has been withdrawn. Guns are then cleaned, worn parts are replaced, reinstalled ordnance is checked for head space and free firing while flexible mounts are checked for free rotation. In sectors where guns are in constant use, a fire extinguisher is used to flush barrels with kerosene which runs down through entire mechanism, out through the open breech. When guns are checked, wires, lines, connections, filters are checked with engine accessory section cowling removed. Fuel and oil tanks are then filled to capacity while the propellers are cleaned with lubricating oil — after a thorough flushing with fresh water if the plane has been operating near salt water. Inside the plane, other mechanics sterilize mouth pieces, check pressure in cylinders if oxygen equipment has been used.

Regular servicing

Standard checkup and servicing procedures after twenty-five, fifty, and 500 hours of operation vary throughout the plane. For example, bomb racks get their first major inspection after fifty hours in a service routine which includes repair of cracks in brackets and linkage, security and condition of fittings, and replacement of loose or missing bolts and nuts. Defective indicator lamps are replaced when the bomb door hydraulic system is checked, repaired. After 500 hours, ball and needle bearings in the bomb door emergency mechanism are inspected, lubricated with grease. Gunnery equipment, on the other hand is surveyed carefully after twenty-five hours of operation, with loose and missing bolts being replaced, leakage in upper flexible gun stowage doors getting oil lubricating, driving spring mechanism in guns getting replacements for worn parts, muzzle groups and barrels undergoing inspection for defects.

This, briefly, is the maintenance picture on the hardest-hitting light bomber on the Allied air team. It would take several entire magazines this size to tell the entire service story — if military restrictions allowed wide circulation of such information. But this sampling should be adequate explanation of the unanimous respect for the A-20 in American, British, and Russian hangars — a respect which is echoed but not exceeded in flight operations rooms dotting the war fronts of the world. The first battling "Black Douglas" would like this modern Douglas which, in one week, boasts more conquests than the fifty-seven victories which he won in an entire lifetime.

This design analysis article was originally published in the October, 1943, issue of Air Tech magazine, vol 3, no 4, pp 20-27, 56.
The original article includes 11 drawings and schematic diagrams of various systems in the airplane. There are also a full-page full-bleed photo of A-20s in flight used as a background for the first page of text (plays Hell with the OCR program) and a plan-view photo used with a line drawing to illustrate hoist and jacking points.
Photos, drawings and diagrams credited to Douglas Aircraft.
The "fuselage is 27" high" statement is almost certainly in error — almost certainly a typographic error. The dimensioned drawing in the Aviation article [ PDF, 11.5 MiB ] shows a fuselage height of 82" at the cockpit.

Drawing/diagram captions: