American Vengeance

The English were getting pretty tired of the word Stuka. They resolved to have a ship built that would make the slang contraction for Sturzkampflugzeug as obsolete a term as frigate or firelock. The British Purchasing Commission sent Vultee Aircraft, Inc, (now Consolidated Vultee) a set of basic specifications and only one general directive — build a ship that will put the Junkers Ju-87 and Noah's Ark in the same class.

Nine months after the blueprints came out of the drier, the first Vultee V-72 did 9-G dives over California. The British named it the Vengeance, and the Army, well pleased with its performance, stuck in a few modifications and put it into their fighting lineup as the A-31, later as the A-35.

The Vengeance was built with information earned at the cost of the enemy. The Germans, borrowing the theory of dive-bombing from the United States, designed their first job as a single purpose craft, allowing a lot of physical excrescences like fixed landing gear, flat radiators, etc, to slow its speed. Whatever armament it carried seemed to be chiefly to support crew morale. There were enough things wrong with the old Stuka to account for a 50-plus percentage of casualties. After the Battle of Britain, the English salvage heaps had more Stukas than the Nazi reserve pool.

In justifiable annoyance, the old Stuka was scrapped and snappy twin-engined combination types like the Ju-88 and Do-217 took its place. While these ships have shown themselves to be reliable craft, devoid of the basic faults of the Ju-87, they have at the same time washed out the basic virtues of the old single engine model — maneuverability that is native to a single thrust-line and good low-altitude performance.

The wings and tail of the old Stuka had a lot of good points — but its slowness, its short range, and lack of defensive armament made it a proverbial duck-in-shooting-gallery under the altered conditions of modern war. Furthermore, its liquid-cooled engine provedfar too vulnerable for an airplane that had to operate in the constant face of ground fire.

The Vengeance Benefits

The Vengeance is the product of all that was learned at the enemy's expense plus our own experience in dive- and attack-bombing. The ship that was built to out-Stuka the Stuka is a single-engined all-metal, low-wing monoplane powered by a 1,700-hp Wright double-row Cyclone engine. This is the first radical change from the Stuka idea. About a third of the Stuka class fell victim to engine failure due to slight damage to the liquid-cooling system. The glycol mixture, having little native surface tension, leaked out of minor radiator or pump breaks caused by flak or vibration.

The Vengeance is as clean as its function will permit, its fuselage shape follows the contour dictated by the engine, modified only by internal bomb considerations. A retractable landing gear has been incorporated, flush riveting has been used throughout, and enough armament has been provided so that the ship can deal with anything that cares to attack it.

The only palpable resemblance to the ancient Stuka is in the general wing form which proved to be the old Ju's best feature. This wing, in turn, was modified from a French Caudron's. The Vengeance's main surface is an all-metal, full-cantilever semi-monospar structure, comprising two inner and two outer panels attached to the fuselage and joined by an internal torque-box structure.

The ailerons are all-metal assemblies, conventional beam-and-rib structures covered with aluminum-alloy sheet. Static and dynamic balance and differential motion are provided. Trim tabs are controllable from the pilot's cockpit.

Slotted flaps extend from aileron to aileron, breaking only at the fuselage. These are hydraulically operated through a 60° range. A flap position indicator is located in the pilot's cockpit.

The lattice-type dive brakes are located on the upper and lower surface of each wing outer panel. Each upper assembly is linked to its corresponding lower unit to balance the air loads acting on each of them. Thus, comparatively little mechanical force is required to operate the hydraulic diving brakes.

The vertical and horizontal stabilizers are also all-metal structures; beams, ribs, stiffeners, and dural covering. Elevators and rudder, however, are aluminum-a11oy frames, fabric-covered. Tail units are also static and dynamically balanced and a controllable trim tab is on rudder and left-side elevator. An anti-boost tab fitted to the right-side elevator provides proper aerodynamic motion range.

The all-metal fuselage employs a composite structure comprising a semi-monocoque forward section and a monocoque aft section. The two are joined by bolted connections at four points corresponding to the aft termination of the longerons. The basic construction of both sections comprises a frame assembly of bulkheads and stringers covered with smooth aluminum-alloy sheets attached with countersunk rivets at flush joints. The cockpit enclosure comprises five light-alloy frames which support transparent panels. The windshield and the portion between cockpits are fixed. The forward sliding section telescopes over the fixed units. The rear sliding transparencies are under the fixed set. Behind this is a tiltable head arrangement which opens and permits free use of the flexible guns. An overturn structure, directly behind the pilot, extends to the top of the enclosure to protect the crew in the event of a nose-over. Suitable steel armor plate is installed for the crew's protection.

The fully retractable, hydraulically operated, main landing gear is provided with positive mechanical locks at both extreme positions. The Aerols swing back and up, simultaneously rotating a quarter turn to permit the wheels to lie flush within the wing when fully retracted. Hydraulic shock absorbers are built integral with the struts. The partially retractable tail gear operates in unison with the main gear. The landing gear is controlled through a hydraulic selector valve in the cockpit, and a hand pump is provided for emergency operation. Here, too, a cockpit position indicator is provided. The main landing gear is fitted with 36" smooth contour tires and fully enclosed disc-type hydraulic brakes. The non-steerable, full-swivel tail wheel is equipped with a 14.5" smooth contour tire, and with a centered-position lock controllable by the pilot.

The Vengeance is powered with a Wright Double Cyclone, fourteen-cylinder, geared, air-cooled, radial engine equipped with a two-speed, direct-drive supercharger. The propeller is a Hamilton Standard, three blade, constant-speed, non-feathering, fast-acting, hydromatic type. The oil system comprises a 25-gallon tank with warm-up hopper, oil radiator equipped with thermostatic relief valve, suitable ducts and controls and a standard oil dilution system for thinning the oil in cold weather. The oil tank housing contains a leak-resistant cell or liner to seal punctures resulting from bullets or other causes. The system is complete with baffles to maintain an oil supply to the engine in all flight altitudes. The fuel system consists of ten self-sealing fuel cells connected up to form four tanks. Two cells are housed within each inner and outer wing panel, and two additional ones are contained within the fuselage torsion box. A trap tank to insure fuel supply in all flight positions is located within the fuselage, aft of the fire wall, with a selector valve which bypasses fuel around the trap tank when desired. Incorporated into the system are several electrically-driven, immersed centrifugal fuel-delivery pumps, a solenoid-operating priming pump, an emergency fuel pump — manually operated from either cockpit, and the necessary components, such as pressure regulator valve, pressure gage, quantity gages, strainers, check valves, drain cock, etc. The six pumps connected to the four main fuel tanks force the fuel to the trap tank and these maintain the pressure in the trap tank. The remaining pump located in the top of the trap tank pumps the fuel out of the trap tank through the pressure regulator and into the carburetor. The left-side fuselage tank is considered the reserve supply. The fuel system incorporates an emergency firing cock for the destruction of the airplane. The total capacity of the fuel system is approximately 321 gallons.

The electrical installation of the V-72 is basically a 24V single conductor system. The only exceptions are in locations where a two-conductor system is necessary to prevent interference with the magnetic compasses or where equipment requires two wires. A 34AH, 24V, shielded storage battery and a 50A, 30V engine-driven generator constitute the power units. A battery disconnect switch, controllable from the ignition switch, is installed to permit isolating the battery.

A Stewart-Warner heating unit is installed in each cockpit, along with similar sets installed in each wing adjacent to the fixed gun installation. These constantly keep the guns at firing heat.

The radio installation consists of unit, antenna reel, receiver, provision for receiver and interphone amplifier.

The gunnery equipment comprises four .30-caliber fixed aircraft machine guns, wing-mounted outboard of the propeller disc. Ammunition stowage for 750 rounds per gun is provided. Two .30-caliber flexible machine guns are twin-mounted in the rear cockpit with stowage provided for 1000 rounds of ammunition per gun. The bombing equipment carried in the Vengeance consists of two 500-lb standard bombs carried within the bombbay as normal load. Also, two 250-lb standard bombs may be carried in the bombbay clearing the propeller blades; bomb-displacing gear is provided. All the bombs are electrically controlled from the pilot's cockpit and may be released selectively or in jettison.

The field service mechanics' prayer has been answered in the Vengeance in that all items requiring periodical service are accessible with the least amount of disassembly. The two-bay engine mount makes the accessory compartment a pleasure to work on.

Vengeance in Action

The thought in building the V-72 was to obtain correct aerodynamic features for an airplane capable of pulling out of fast dives, withstand shell fire, and carry the necessary armament of an attack ship. The speed of the V-72 dive bomber falls in the class of a low pursuit job and has the range of a light bomber.

The Vengeance is being called upon to perform both day and night bombing missions. While capable of high altitude performances, it is well-suited for low flying work. In bad weather it can bomb from low levels, working in or just under the clouds, picking out its objective. Low-level ground attack is another specialty of this versatile airplane.

This article was originally published in the June, 1943, issue of Air News magazine, vol 4, no 6, pp 44-48.
The original article includes 25 photos — 3 of the plane in flight and 22 on the assembly line.
Photos credited to Consolidated Vultee Aircraft Corp.

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