Boeing XB-39 Superfortress
prototype bomber aircraft by Boeing
The Boeing XB-39 Superfortress was a United States prototype bomber aircraft, a single example of the B-29 Superfortress converted to fly with alternative powerplants. It was intended to demonstrate that the B-29 could still be put into service even if the first choice of engine, the air-cooled Wright R-3350 radial engine, ran into development or production difficulties.
Design and development
Starting life as the first YB-29 delivered to the United States Army Air Forces, it was sent in November 1943 to the Fisher Body Aircraft Development Section of General Motors to be converted to use Allison V-3420-17 liquid-cooled W24 (twin-V12, common crankcase) inline engines. Fisher was chosen for the modification as it was familiar with the engine, as it was to power the P-75 Eagle that they were then developing. Testing on it began in early 1944.
Further development of the engine and the aircraft was delayed by a series of changes in the planned turbosuperchargers, as the originally specified GE Type CM-2 two-stage turbosupercharger became unavailable due to demands on GE's production of its other turbosuperchargers. Other turbosuperchargers were considered, but the result was that the first flights of the XB-39 had to be made without any turbosuperchargers at all.
Operational history
Fisher finally focused again on the B-39. The first flight of the B-39 was made on 9 December 1944 at Cleveland, Ohio. The initial flight tests of the B-39, without turbosuperchargers installed, were impressive.
“Boeing XB-39 Superfortress” enters the record as prototype bomber aircraft by Boeing. Crown Archives preserves that source wording while asking what Boeing, XB-39 and Superfortress can confirm, complicate or overturn.
Why this record matters
“Boeing XB-39 Superfortress” is worth following because a concise public description often conceals a longer documentary argument. Here, Boeing, XB-39 and Superfortress provides the most credible route into that argument.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Dec 8, 2024. The linked authority identifier is Q580897. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1943 and 1944.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Boeing XB-39 Superfortress”, its source revision and the description used here.
- Expand the search: follow Boeing XB-39 Superfortress primary sources, Boeing XB-39 Superfortress archive and Boeing research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Boeing XB-39 Superfortress”?
- Which institution is responsible for the underlying evidence?
- What terminology or title could unlock a more precise catalogue search?
Search terms from this dossier
This entry incorporates text from “Boeing XB-39 Superfortress” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.