Not really a secret weapon, but what we'd have used if the war had gone on longer.
The XB-24N was the prototype aircraft for the production version of the XB-24K. The -K was a production B-24D with a B-23 tail 'spliced' on replacing the normal empennage. The B-24N design was based on the B-24J and used data from the XB-24K tests to faciltate the extensive design changes necessary for a single tail. The B-24N was also had improved tail and nose turrets to increase defensive capabilities. Aerodynamic and weight reduction improvements gave the B-24N very good estimated performance. The Army Air Force ordered more than 5,000 -N models built and the prototype began its test program in late 1944. However, World War II ended before full-scale production began and only a single XB-24N and seven pre-production YB-24Ns were completed before the entire order was canceled.
Basically, it was produced because of the poor flying characteristics of the Twin Tailed B-24s vs the single tailed B-17s; and included various cleanups, like a nose ball turret with significantly increased field of fire and less drag compared to the normal nose turret; and the single tail allowed a much better field of fire for the tail guns.
4 x PW R-1830-75s 1,350 hp @ 30,000 ft
110' wingspan
67'2" length
26'9" height
1,048 Sq ft wing area
38,300 lb empty
56,000 lb gross
65,000 lb max
2,814 to 3,614 gallons of fuel
Top Speed: 294 MPH @ 30,000 ft
Cruising: 213 MPH
Landing: 95 MPH
Service Ceiling: 28,000 ft
Climb: 20,000 ft in 29 minutes
2,000 mile range with 5,000 lbs of bombs, 3,500 mile maximum range
Tail Turret Type Adopted
B-24N taking off.
B-24N Nose Ball Turret
Top down view of nose area.
From "Warbird Tech: B-24 Liberator":
And the new Emerson Model 128 spherical nose turret, tested earlier in a twin-tail B-24G was said to improve the Liberator's speed and handling because of its improved streamlining, over other nose turrets like the Emerson A-15 and Motor Products/Consolidated designs.
Servo tabs on the control surfaces of the "N" made control forces lighter than on previous Liberators—another feature welcomed by pilots.
The revamped B-24N promised to rectify problems that had grown like parasites on B-24s through the crush of wartime expedients that saw the traditional Liberator's design burdened with weight and drag concessions.
The desirability of a single tail for B-24s was stated succinctly in an Army Air Forces Proving Ground report in April 1944 that evaluated the first AAF single-tail Liberator,
the XB-24K. In part, the report concluded: "The handling characteristics of the B-24K model are excellent. The rudder and elevator controls are a great deal more sensitive than in the conventional model and should alleviate pilot fatigue." The report continued: "The performance of the 'K' model with two engines out on one side is decidedly superior to that of the standard 8-24 airplane. Comparatively little change in rudder trim is necessary for straight and level flight."
Additionally, the XB-24K afforded large increases in the fields of fire for the ball turret, waist guns, top turret, and tail turret, the report noted.The report, signed by Col. C.B. Overacker, chief of the proof department at the Eglin Field AAF Proving Ground Command facility, recommended a single tail similar to that oftheXB-24K "be incorporated in all future production B-24 aircraft,"
Another Eglin test report from August 1944 highlighted benefits derived from the installation of the spherical Emerson Model 128 turret in the modified nose of a B-24G. The resulting nose contours on the adapted G-model closely resembled the lines of the Ford XB-24N. The report concluded:"The all-around performance, especially during formation flying, of the B-24G with the subject nose turret, is greatly superior to that of any B-24 of the G, H, or J series which has been tested at this station.... The superior performance of this airplane can be attributed largely to the Emerson 128 ball turret installation in the nose." Visibility for the bombardier and navigator were found to be better with the Emerson 128 installation than with standard B-24s. Side windows afforded bombardiers the ability to look aft, watching bomb impacts, and the side view was said to be adequate for even short approaches from 90-degree angles to the target run. Pilot visibility was enhanced by the smoother contours of the modified nose in this test airplane. (In a standard nose-turreted B-24, the turret protruded above the normal nose contour, obstructing the pilots' view forward.) Testers did comment on the excessive number of canopy frames in the otherwise-unchanged B-24G cockpit—a hindrance that would be corrected on the B-24N.
B-24 pilots sometimes spoke about the Liberator's "step," meaning a particular cruise attitude that was desirable to attain, and was achieved, they said, by climbing
above desired cruise altitude and diving slightly to gain speed, and set the aircraft "on the step." According to the test report of the modified B-24G with the Emerson 128 nose turret, a standard B-24J used for comparison "was extremely sluggish and hard to maintain 'on the step'at air speeds of 158 to 160 MPH. The B-24G handled very well and was much easier to keep "on the step" at that speed.... Operating with a full military load, the B-24J type aircraft becomes unmanageable in close formation at air speeds of 155 MPH or less. Although the handling characteristics of the (modified) B-24G left much to be desired at similar speeds, they were a decided improvement over those of the B-24J."
In these two 1944 Liberator tests, validation was found for two major design innovations built into the Ford B-24N: A single tail and the Emerson 128 spherical nose turret. In addition to better handling and working arrangements for the crew, all the changes poured into the XB-24N, including the use of R-1830-75 engines, were said to give this variant 300 miles more range than any other nose-turreted B-24, when all were flown at maximum cruise power with a 5,000-lb. pay-load.
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In January and February 1945, ongoing message traffic between HQ USAAF, Eighth AF, and 15th AF documented a search for a late-model B-24 configuration that would satisfy the needs of both Eighth and 15th Air Forces. A February 12,1945, message from General Arnold anticipated the production of B-24Ns for combat as it spoke about configuring B-24Ls for Europe: "The B-24N will soon replace the B-24L in production and such changes that cannot be readily incorporated in the B-24L will probably be incorporated in the B-24N aircraft."On February 17, 1945, General Spaatz asked General Arnold to dispatch a B-24N to the European Theater of Operations and Mediterranean Theater of Operations as soon as possible to allow Eighth and 15th Air Force representatives to come to an agreement on how to configure N-mod-els jointly. The actual end of fighting in Europe was less than three months away, and still the need for B-24Ns was apparent to U5AAF planners in February 1945, who could not afford crystal-ball hunches about when their war would end.
