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Boeing XB-39 (Spirit of Lincoln)


Heavy Strategic Bomber Prototype Aircraft


United States | 1944



"Intended to test the feasibility of an alternative powerplant, the Allison-powered Boeing XB-39 Superfortress ended its days as a single prototype."

Power & Performance
Those special qualities that separate one aircraft design from another. Performance specifications presented assume optimal operating conditions for the Boeing XB-39 Heavy Strategic Bomber Prototype Aircraft.
4 x Allison V-3420-11 W24 liquid-cooled engines developing 2,100 horsepower each.
Propulsion
404 mph
650 kph | 351 kts
Max Speed
36,089 ft
11,000 m | 7 miles
Service Ceiling
6,251 miles
10,060 km | 5,432 nm
Operational Range
1,000 ft/min
305 m/min
Rate-of-Climb
Structure
The nose-to-tail, wingtip-to-wingtip physical qualities of the Boeing XB-39 Heavy Strategic Bomber Prototype Aircraft.
10
(MANNED)
Crew
99.0 ft
30.18 m
O/A Length
141.2 ft
(43.05 m)
O/A Width
27.7 ft
(8.45 m)
O/A Height
74,516 lb
(33,800 kg)
Empty Weight
133,512 lb
(60,560 kg)
MTOW
Armament
Available supported armament and special-mission equipment featured in the design of the Boeing XB-39 (Spirit of Lincoln) Heavy Strategic Bomber Prototype Aircraft .
STANDARD:
10 x 0.50 cal Browning M2 heavy machine guns in four remote-controlled turrets.
2 x 0.50 cal Browning M2 heavy machine guns and 1 x 20mm M2 cannon in tail unit.

OPTIONAL:
Up to 20,000lb of conventional drop stores held internally.
Variants
Notable series variants as part of the Boeing XB-39 (Spirit of Lincoln) family line.
XB-39 - Base Project Designation; single, flyable prototype completed.
Authored By: Staff Writer | Last Edited: 07/29/2020 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site; No A.I. was used in the generation of this content.

Such was the importance of the Boeing B-29 Superfortress to the United States Army Air Forces during the latter stages of World War 2 (1939-1945) that the program was given several fail safes to keep it a viable heavy bomber product moving forwards. This led to a YB-29 developmental machine being set aside by the USAAF for alternative powerplant implementation - assuming that the required stock of problematic Wright R-3350 radial engines would not be available for one reason or another. A modification process was undertaken by Fisher Body (General Motors) in 1944 on the YB-29 aircraft and this went on to produce the XB-39 "Spirit of Lincoln" bomber prototype.

Its basic form and function remained faithful to the original Boeing design but the powerplants in play were now focused on 4 x Allison V-3420-17 series liquid-cooled engine (the original B-29 relied on the aforementioned Wright air-cooled units). Fisher was also using these engines in its (ultimately failed) P-75 "Eagle" long-range escort fighter. Delays in the intended turbosuperchargers dogged the XB-39 project so the first-flight on December 9th, 1944 was had without these installed - though the aircraft provided a successful demonstration nonetheless.

Despite the promising nature of the large aircraft, the Wright air-cooled radials, warts and all, remained the primary focus of the B-29 production campaign, leaving the XB-39 without a battlefield role or notable buyer. Additionally, Fisher was pushed to commit more and more of its resources to the XP-75 fighter prototype which held higher priority for the USAAF at this point in the war. Decisions led to the ultimately abandonment of the XB-39 project with the single prototype being completed and flown (if only for a short time).

As built, the XB-39 held 4 x Allison V-3420-11 liquid-cooled engines of 2,100 horsepower each able to propel the aircraft to speeds of 405 miles per hour out to ranges reaching 6,300 miles and a service ceiling of 35,000 feet. Its crew numbered ten and the armament suite was similar to that of the original B-29 (including remote-controlled turrets and tail cannon). 20,000lb of drop stores could be carried internally.

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Operators
Global customers who have evaluated and/or operated the Boeing XB-39 (Spirit of Lincoln). Nations are displayed by flag, each linked to their respective national aircraft listing.

Total Production: 1 Units

Contractor(s): Boeing Company / Fisher (General Motors)
National flag of the United States

[ United States (cancelled) ]
1 / 2
Image of the Boeing XB-39 (Spirit of Lincoln)
Image from the Public Domain.
2 / 2
Image of the Boeing XB-39 (Spirit of Lincoln)
Image from the Public Domain.

Going Further...
The Boeing XB-39 (Spirit of Lincoln) Heavy Strategic Bomber Prototype Aircraft appears in the following collections:
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