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PBJ-1C: DESCRIPTION AND SPECIFICATIONS

Manufacturing Information: The PBJ-1C was manufactured by North American Aviation as the B-25C, exclusively at their aircraft plant in Inglewood, California.  As a note of reference, the B-25D and its naval variant, the PBJ-1D, was an identical aircraft—the only difference being that it was produced solely at the North American aircraft factory in Kansas City, Kansas.  This being the case, it is impossible to distinguish a PBJ-1C from a PBJ-1D without establishing the  aircraft's Bureau of Aeronautics Number (BuNo), or by examining the manufacturer's data plate for the corresponding AAF Serial Number.

Service Summary:  The Navy received a total of 50 PBJ-1Cs between 20 February 1943 and 19 April 1943.  All of these aircraft were from the 20 and 25 series production blocks.  These aircraft were primarily used stateside by the Marine Corps' Operational Training Squadrons, although two aircraft of this type were deployed to the Southwest Pacific and saw action with VMB-443.  The last PBJ-1C was stricken from the roles of the Bureau of Aeronautics on 31 January, 1946.

General Characteristics: The North American PBJ-1C medium bomber airplane was a mid-wing land-based monoplane powered by two Wright Cyclone engines.  Characteristic features of the aircraft included a tricycle landing gear, a gull-wing, and a double fin and rudder empennage.  In addition to .50 caliber machine guns, the PBJ-1C was also equipped to carry various types of bombs, depth charges, or an aerial torpedo.

Specifications: Basic PBJ-1C Models: North American B-25C-20 and B-25C-25.

Wingspan: 67 feet 6 inches.

Wing Area: 610 square feet.

Length: 53 feet 0 inches.

Height: 15 feet 9 inches.

Weight (Empty):  20,300 pounds.

Weight (Maximum Loaded):  34,000 pounds.

Performance: --------Maximum Speed: 247 knots (284 mph) at 15,000 feet.

Cruising Speed: 203 knots (233 mph).

Initial Rate of Climb:1,100 feet per minute.

Service Ceiling: 24,000 feet.

Range:  1,303 nautical miles (1,500 statute miles) with 3,000 pounds of bombs.

Crew: Five—Pilot; Copilot; Navigator-Bombardier; Radio-Gunner, and; Mechanic-Turret Gunner.  The three aircraft that saw service in the Southwest Pacific would have carried one or two additional crew members—an Armorer-Gunner to operate the tail gun, and sometimes a second Radio-Gunner.

Armament: Five .50 caliber M-2 machine guns—one in the nose in a flexible mount, two fixed mounted guns on the starboard side of the nose firing through holes cut into the Plexiglas glazing, and two guns in a Bendix Apmlidyne power-operated turret, aft of the wing.  The three C-model PBJs that were deployed for service in the Southwest Pacific undoubtedly had seven additional .50 caliber machine guns, bringing the total number of guns to twelve.  These additional machine guns were located as follows: One manually-operated gun in the tail, one flexible-mounted gun on each side of the aircraft in the waist position, and four fixed "package guns" (two guns per side) below the pilot’s compartment. 

Engines: Two Wright R-2600-13 Double Cyclones.  The engines were fourteen-cylinder, air-cooled, staggered, twin-row radials and were equipped with two-speed superchargers.  Due to the high compression ratio, the engine operated on 100-Octane fuel.  Individual flame-dampening exhaust stacks reduced the glare for night flying.  Under normal operating conditions, the engines developed a maximum of 1,700 brake horsepower (BHP) for take-off at 44.3 inches of mercury and 2,600 revolutions/minute (of the crankshaft, not the propeller).  The cylinders were numbered in a clockwise direction when looking from the rear of the engine forward to the propeller—Number 1 being the top cylinder of the rear row with Number 2 to its right in the front row.  Thus, all odd numbered cylinders are in the rear row and all even numbered cylinders in the front row.  Additional data on the engines is as follows:

Carburetors: Two Holley 1685HA carburetors.

Propellers: Two, three-bladed Hamilton Standard Hydromatic, full-feathering propellers with a diameter of 12 feet 7 inches.  The propellers were controlled by double-capacity governors and had pitch settings from 22 to 90 degrees.

Standard Fuel Capacity: 974 US gallons in ten self-sealing tanks located in the wings.

Additional Fuel Capacity: Additional fuel could be carried in three types of bomb bay tanks depending on the type of ordnance carried.  A maximum fuel capacity of 585 US gallons could be carried in bomb bay tanks, however using this type of tank would prevent the carrying of ordnance in the bomb bay.  See "Bomb Bay Configurations" for typical configurations of bomb bay tanks.

Oil Capacity: 76 US gallons in two self-sealing tanks located in the engine nacelles.

Flight Controls: Both the pilot and the copilot had a set of flight controls, consisting of a control column with a yoke and a set of rudder pedals.  The rudders, elevators and ailerons were controlled by a redundant cable system so that the loss of any one control cable would not seriously cripple the aircraft.  The rudders and ailerons were equipped with a combination booster and controllable trim tabs.  The elevators had controllable trim tabs which were set for no boost.  A bungee installed in the elevator control system reduced stick loads.  A locking system effecting all of the control surfaces simultaneously was controlled by a handle on the floor in front of the pilot's control column.  

Landing Gear: The landing gear was hydraulically operated with the main gear retracting into the engine nacelles and the nose gear into the fuselage.  Doors cover the gear openings in both the retracted and extended positions.  The swivel-type nose gear incorporated a centering device that operated when the strut was full extended (wheel off the ground).  A hydraulic shimmy damper on the strut resisted side loads that occurred on taxiing, take-off, and landing to prevent sudden movements of the wheel.  The nose wheel could also be released from the shimmy damper for the purpose of towing.

Wheels: The main wheels were of the smooth-contour type and were 47 inches in diameter.  The nose wheel was a smooth contour 30-inch tire and was equipped with a dual-seal inner tube for protection against blowouts and punctures.  In many aircraft, the smooth-contour type tires were replaced by tires with a cross-hatch diamond pattern tread.

Brakes: The main wheels were equipped with dual multiple-disc hydraulic brakes with a back-up air brake system for use in the event of a complete hydraulic failure.

Hydraulic System: A single high-pressure hydraulic system operated the tricycle landing gear, wing flaps, engine cowl flaps, bomb bay doors, and brakes.  The system was powered by two engine-driven hydraulic pumps, one of which would run the hydraulic system with sufficient pressure should the other fail.  The accumulators also retained a small amount of pressurized hydraulic fluid to permit one-way emergency operation of the wing flaps, cowl flaps, bomb bay doors, and brakes.  An emergency hydraulic system with a hand-pump and a selector valve was also provided to permit operation of the system in the event of the failure of both engine-driven pumps, or if the airplane was on the ground with the engines inoperative.

Electrical System: The electrical system was a 24 volt direct current, single-wire type, with the structure of the aircraft serving as a common ground return circuit.  Two engine driven generators supplied the power to the aircraft to operate various pieces of electrical equipment and recharge the batteries.  The batteries were only used when the generators were not operating, and each battery had sufficient capacity to operate the aircraft's electrical system.  An external power socket was located on the outboard side of the starboard engine nacelle aft of the firewall to permit an external power source to be used in starting the engines and operating the electrical system while the airplane was on the ground. 

Oil System: Each engine was provided with an independent oil system by the means of a self-sealing oil tank located in each engine nacelle.  Scavenged oil flowed through two oil temperature regulators and oil coolers in each wing where it was cooled by the air-flow entering a scoop just inboard of the engine nacelle, and exiting through apertures on the upper trailing edge of the wings.  The air ducts were equipped with full-closing shutters which were controlled by levers on the pilot's control pedestal.  Circulating oil was also used to supply the propeller feathering system.

Fuel System: An independent fuel system was provided for each engine with a cross-feed system to permit fuel to be transferred between tanks on opposite sides of the aircraft.  The main fuel supply was carried in four large self-sealing wing tanks, located between the fuselage and engine nacelle.  An auxiliary fuel supply consisted of six smaller self-sealing tanks installed in groups of three in each wing center section outboard of the main fuel tanks.  In addition to the main and auxiliary tanks, a 215 gallon self-sealing tank was normally mounted in the upper portion of the bomb bay, although this tank could be removed to accommodate larger larger loads of ordnance or a 585 gallon droppable tank.  When no ordnance was carried, a droppable 335 gallon metal fuel tank could be installed in the bomb bay beneath the the upper bomb bay tank.  Fuel flow was from the main tanks through a booster pump, to a fuel strainer, then to the engine-driven fuel pump that delivered fuel to the carburetors.  All main and transfer fuel feed lines were self-sealing.

Engine Fire Extinguisher System. A pressurized engine fire extinguisher system was installed incorporating a Carbon Dioxide cylinder.  Carbon Dioxide gas from this system could be directed from the cylinder to either engine via a selector valve, located on the fire extinguisher control panel in the cockpit.

Search Radar: The primary function of the search radar was to locate shipping targets, including submarines running on the surface.  Early PBJs were fitted with the AN/APS-2 search radar in a radome located just aft of the bomb bay in the belly of the aircraft.  Produced by Philco and commonly referred to as George, this radar operated in the S-band and had a usable range of 13 nautical miles.  In later aircraft an improved version of radar, the AN/APS-3 was fitted.  Also produced by Philco, it was commonly referred to as Dog.  Operating in the X-band, the AN/APS-3 and had a usable range of 10 to 40 nautical miles.  The AN/APS-3 was mounted in a radome in the belly of the aircraft, aft of the bomb bay.

Radar Altimeter: Each aircraft were equipped with the AN/ARN-1 radio altimeter to permit flying at very low altitudes.  A pair of antennas for the AN/ARN-1 were located beneath the aft section of the fuselage.

Pilot's Gun Sight: The pilot was provided with a Type N-3B optical gun sight with a Type A-1 or A-2 combination gun-and-bomb head for sighting the nose guns.  This sight could also be used for minimum altitude bombing and had five stops which could be preset to predetermined bombing angles.  These settings provided a line of sight parallel to the flight path of the aircraft, to a bombing position in which the line of sight was from 1 to 14.5 degrees below the flight path.

Normal Bomb Load: 3,000 pounds.

Maximum Bomb Load: 5,200 pounds using external under-wing bomb racks.

Maximum Internal Bomb Load: 4,000 pounds.  See "Bomb Bay Configurations" for typical configurations of ordnance.

Bomb Bay Configurations:

One 2,000 pound bomb, or;

Three 1,000 pound general purpose bombs, or;

Twenty-Four 100 pound bombs, or;

Three 650 pound bombs, or;

Two 1,600 pound bombs, or;

Six 500 pound bombs, or;

Eight 250 pound bombs, or;

Four 1,000 pound armor-piercing bombs, or;

Two 1,000 pound bombs and a 215 gallon self-sealing bomb bay tank, or;

Four 500 pound bombs and a 215 gallon self-sealing bomb bay tank, or;

Four 325 pound bombs and a 215 gallon self-sealing bomb bay tank, or;

Two 1,600 pound bombs and a 215 gallon self-sealing bomb bay tank, or;

Two 650 pound bombs and a 215 gallon self-sealing bomb bay tank, or;

Twelve 100 pound bombs and a 215 self-sealing gallon bomb bay tank, or;

One Mk-13 torpedo (externally carried with bomb bay doors open), or;

A 335 gallon unprotected, droppable bomb bay tank, or;

A 585 gallon unprotected, droppable bomb bay tank, or;

A 215 gallon self-sealing bomb bay tank and a 335 gallon unprotected, droppable bomb bay tank.

Standard Color Scheme and Markings: PBJ-Cs were finished in the standard color scheme adopted by the U.S. Navy in February 1943—blue-gray on the aircraft's upper surfaces and white on the lower surfaces.  The National Insignia, consisting of a white star on a blue circular field, flanked by blue-bordered white rectangles, was applied to both sides of the fuselage aft of the wing, and to the upper surface of the port wing and the lower surface of the starboard wing.  The dimensions of these insignia was prescribed by Navy regulations which stated that the diameter of the blue field should be as large as possible without exceeding 75-percent of the vertical height at the point of application.  The regulations further specified that placement of the insignia on the wing should be one-third of the distance from the wing-tip to the fuselage.  All standard markings on the tail surfaces were applied using black 4-inch lettering and were placed at the mid-point of the vertical distance.  On the vertical stabilizer the markings consisted of the word "NAVY" followed directly below by the aircraft's Bureau Number, while the rudder was marked with the aircraft type, "PBJ1."

Unit and Individual Aircraft Color Scheme and Markings: PBJ-1C aircraft assigned to the operational training squadrons normally maintained the standard color scheme described above.  Most aircraft was identified with white lettering applied to the nose, just aft of the bombardier's station.  The aircraft's number usually consisted of the letters "MB" followed by a dash, followed by a two or three digit series of numbers.  These numbers were based on the last two or three digits of the aircraft's Bureau Number.  There is photographic evidence that at least one C-model aircraft (BuNo 35023) was stripped entirely of its paint, leaving the aircraft in an overall aluminum finish.  On this particular aircraft, the "MB" prefix was deleted and the aircraft's individual number, "023" was painted in black.  It is not known if other PBJ-1Cs were stripped of paint in this manner, although it is highly probable.  As for the three PBJ-1Cs that saw action in the Southwest Pacific, their color scheme would have been the standard two-tone scheme with the individual aircraft's number marked in a manner consistent with the system used by their respective squadrons while overseas. 

The aircraft depicted below represents the typical configuration, color scheme and markings of a C-model PBJ used for training in the United States.  This particular PBJ-1C operated from both MCAS Cherry Point and NAS Boca Chica and was lost when it was ditched on 29 February 1944 near Key West, Florida.