XB-39 Superfortress
- Section source: see Baugher and National Museum
The XB-39 Superfortress was a single YB-29 modified to use water-cooled Allison V-3420-17 inline engines. Since the Army Air Force was concerned that problems might develop with their first choice of engine, the Wright R-3350, they contracted General Motors to do testing on a modified aircraft to show that it could still be used even if the R-3350 failed. Since the R-3350 did not have significant enough problems to prevent its use, no XB-39s were ordered.
Read more about this topic: Boeing B-29 Superfortress Variants