Travis AIr Force Base Heritage Center









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Indoor Exhibits - Collections












The Jimmy Doolittle Air and Space Museum Foundation and Travis Heritage Center have an extremely interesting and wide variety of collections. Our weapons, engines, aircraft nose art, models, original photographs, aviation sculptures, military coins and uniforms are a delight to any craftsmen’s or artisans’ eye. The following represents an example of our holdings:

Armament:  PB4Y-2 Bow Turret (Model Number 250SH-3)

PB4Y-2 Bow Turret Restoration Crew
PB4Y-2 Bow Turret Restoration Crew:






















By Mat Voight
March 2001 Travis Air Museum News

This turret was originally designed by Boeing Aircraft corporation in 1940 for use on the Boeing XPBB-1 Sea Ranger.  It was built by the ERCO Company of Riverdale, MD and holds the distinction of being the first powered turret carrying twin .50-caliber guns to be specified for an American Naval plane.  In the XPBB-1, it was carried in three positions (nose, upper fuselage, and tail), but due to the changing strategic situation in the Pacific during WW II the contract for full-scale production of the XPBB-1 in Renton, Washington was cancelled in favor of the B-29 Superfortress.  However, the design of the 250SH turret proved satisfactory to the U. S. Navy and was soon adopted as a modification to the nose section of some PB4Y-1 Liberators.  These Liberators were essentially B-24D in every respect, but the addition of the new bow turret carrying 600 rounds of ammunition was credited with diminishing combat losses of the PB4Y-1’s. Beginning in early 1944, the U. S. Navy accepted a highly modified and improved version of the Liberator known as the PB4Y-2 Privateer.

This particular turret, a model 250SH-3, was built for the Privateer nose section.  It carried a total of 1300 hundred rounds of ammunition in three cases.  A total of 3000 ERCO 250SH turrets were manufactured.  Indications from particular equipment installed in this specific example show that it is in the serial number range of 982 to 1351.  A specific serial number cannot be determined as all data plates were removed after its service, probably while in the possession of the Aberdeen Proving Grounds where it may have been stripped of much of its equipment and modified with a makeshift sight.

The turret is a self-contained unit capable of operating independent of aircraft power if necessary.  Arc of fire was from 70 degrees below horizontal to 85 degrees above and 80 degrees to either side.  Empty weight is 561 pounds and fully loaded weight is 1131 pounds.  The turret diameter is 54 inches and is hydraulically driven on an internally mounted 1000 p.s.i. system.  As the rounds were fired, spent shell casings dropped into the chute below the guns and collected in the front of the turret where they could be removed after flight through the access panel on the front.  Belt clips were ejected sideways though chutes to leather bags that were also emptied after flight.  Armor plating included (two) 1/4 inch foot plates, a 1/2 inch plate covering the entire forward ammo box and a 1-1/2 inch armored glass gun sight.  It should be noted that, despite the appearance of cramped conditions, more equipment was installed in this turret than what is presently displayed. That equipment included a MK-9 gunsight, a turret control panel, belt collection bags, a hydraulic pump/motor under the seat, all hydraulic lines, arm rests installed on the side ammo boxes, a gun camera, the Plexiglas cover and of course, the gunner with his oxygen and communication gear.

Restoration was carried out by U. S. Navy personnel from VQ-3 Detachment Travis and entailed over 250 man-hours.  This turret is historically significant because it was installed on the PB4Y-2; the only 4-engine heavy bomber designed specifically for the U. S. Navy.  VQ-3 now flies the E-6 Mercury, the only 4-engine heavy jet aircraft designed specifically for the U. S. Navy.  A total of 736 PB4Y-2 Privateers were produced with 61 being lost to all causes during WW II.  A Privateer crew is also credited with being the first casualty of the Cold War having been shot down on a reconnaissance mission over Russia in 1948.

Engine:  R-2600-13

Travis Air Museum Engine Room: R-2600-13 B-25 engine on the rightTravis Air Museum Engine Room: R-2600-13 B-25 engine on the right
Travis Heritage Center Engine Room: R-2600-13 B-25 engine on the right

The following has been excerpted from the North American Aviation Field Service Manual for B-25C and D):

The Wright Cyclone, Model C14B, carries the Army Air Forces designation R-2600-13. The "R" stands for radial type of engine, "2600" stands for the number of cubic inches piston displacement, and the "13" is the model number.

The engines are air-cooled, static, staggered, twin-row radial type having two speed superchargers. Owing to the high compression ratio of 6.9:1, the engine operates on 100-Octane fuel. No other fuel may be used except in the event of an emergency, when a fuel of the next highest Octane rating may be used.

Under normal operating conditions, the engines develop a maximum of 1700 BHP (brake horsepower) for take-off at 44.3" Hg. (manifold pressure - in inches of mercury - of the fuel-air mixture in the engine intake pipes after passing through the supercharger) and 2600 RPM (revolutions per minute of the crankshaft, not the propeller).

The cylinders are numbered in a clockwise direction when looking from the rear, or anti-propeller end, forward to the propeller end. Number 1 cylinder is the top cylinder of the rear row. Number two is 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.


  • Model:  R-2600-13 (Wright Cyclone Model C14B)
  • Type:  Static Radial, Air Cooled, Double Row
  • Number of Cylinders:  14
  • Bore:  6.125 in.
  • Stroke:  6.312 in.
  • Piston Displacement:  2603
  • Compression Ratio:  6.90:1
  • Blower Gear Ratio:  7.06:1 and 10.06:1
  • Blower Diameter:  11.00 in.
  • Rated RPM of Crankshaft:  2400
  • Rated BHP/RPM at 6700 ft:  1500/2400
  • Rated BHP/RPM at 13,000 ft:  1350/2400
  • Take-Off BHP/RPM:  1700/2600
  • Rotation of Crankshaft (from anti-propeller end):  Clockwise
  • Rotation of Propeller (from anti-propeller end):  Clockwise
  • Propeller Reduction Gear Ration (crankshaft to propeller):  16:9
  • Average Weight of Engine:  1978.50 lbs.
  • Overall Length of Engine:  63.10 in.
  • Overall Diameter of Engine:  54.26 in.

Continue with Nose Art:  “Sack Time”



History of Travis AFB








Basic Trainers
     BT-13 “Valiant”
     T-37 Simulator
     F-100 Cockpit Trainer








Early Years
     Wright Brothers








World War I
     94th Aero Squadron
     Stars and Stripes








Inter War Years
     Spirit of St. Louis
     Cessna AT-17 Bobcat








World War II
     Flying Tigers
     “The Hump”
     Piper L-4 “Grasshopper”
     CG-4 Combat Glider
     Tuskegee Airmen
     Doolittle Raid
     “Fat Man” Nuclear Bomb








Cold War
     Berlin Airlift
     The “Candy Bomber”
     Candy Bomber Honored








Korean War
     Korean War Gallery
     Korean War: “In Field”
     Korean War: “On Base”
     Korean War Stories
     Truman’s Secret Visit
     Flying Cheetahs
     Rescue Mission
     SAC Air Crews
     Travis Crash
     Operation Starlift








Vietnam War
     Vietnam Exhibit
     The Nurses
     Bringing Them Home
     Operation Homecoming








Modern Flight
     Strategic Airlift
     C-141 “Starlifter”
     Lockheed C-5 “Galaxy”
     Aerial Refueling








Space Exploration
     Aerojet General XLR73
     Mercury Spacecraft
     Project Gemini








Humanitarian Missions
     Stinson L-5 “Sentinel”
     EMEDS Unit
     Operation Babylift








     AGM-28 Hound Dog Missile
     PB4Y-2 Bow Turret
     Engine: R-2600-13
     Nose Art
     Military Coins
     Military Uniform Collection












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