Editing North American B-25 Mitchell (section)

==Design and development==

In March 1939, the [[United States Army Air Corps|US Army Air Corps]] issued a specification for a medium bomber that was capable of carrying a payload of {{convert|2400|lb|abbr=on}} over {{convert|1200|miles|abbr=on}} at {{convert|300|mph|abbr=on}}.<ref>Baugher, Joe. [http://www.joebaugher.com/usaf_bombers/b25_2.html "North American B-25 Mitchell."] ''American Military Aircraft: US Bomber Aircraft'', 6 March 2000. Retrieved: 24 May 2015.</ref> [[North American Aviation]] (NAA) used its [[North American NA-40|NA-40B]] design to develop the NA-62, which competed for the medium bomber contract. No YB-25 was available for prototype service tests. In September 1939, the Air Corps ordered the NA-62 into production as the B-25, along with the other new Air Corps medium bomber, the [[Martin B-26 Marauder]] "off the drawing board".

[[File:Alfred T. Palmer - Assembling the North American B-25 Mitchell at Kansas City, Kansas (USA).jpg|thumb|North American B-25 Mitchell production in Kansas City in 1942|alt=Interior of huge aircraft factory where rows of bombers are being assembled]]

Early into B-25 production, NAA incorporated a significant redesign to the wing [[Dihedral (aeronautics)|dihedral]]. The first nine aircraft had a constant-dihedral, meaning the wing had a consistent, upward angle from the fuselage to the wingtip. This design caused stability problems. "Flattening" the outer wing panels just outboard of the engine nacelles nullified the problem and gave the B-25 its [[gull wing]] configuration.<ref name="chor aero p74">Chorlton ''Aeroplane'' May 2013, p. 74.</ref> Less noticeable changes during this period included an increase in the size of the tail fins and a decrease in their inward tilt at their tops.

NAA continued design and development in 1940 and 1941. Both the B-25A and B-25B series entered USAAF service. The B-25B was operational in 1942. Combat requirements led to further developments. Before the year was over, NAA was producing the B-25C and B-25D series at different plants. Also in 1942, the manufacturer began design work on the cannon-armed B-25G series. The NA-100 of 1943 and 1944 was an interim armament development at the Kansas City complex known as the B-25D2. Similar armament upgrades by U.S-based commercial modification centers involved about half of the B-25G series. Further development led to the B-25H, B-25J, and B-25J2. The gunship design concept dates to late 1942 and NAA sent a field technical representative to the SWPA. The factory-produced B-25G entered production during the NA-96 order followed by the redesigned B-25H gunship. The B-25J reverted to the bomber role, but it, too, could be outfitted as a strafer.

[[File:B25-1 300.jpg|thumb|Late war development B-25J2 Mitchell strafer bomber|alt=Black and white photo of an early bomber parked perpendicular to the camera, facing left, rearward of the wing is a star in front of horizontal stripes.]]

NAA manufactured the greatest number of aircraft in World War II, the first time a company had produced trainers, bombers, and fighters simultaneously (the [[North American T-6 Texan|AT-6/SNJ Texan/Harvard]], B-25 Mitchell, and the [[North American P-51 Mustang|P-51 Mustang]]).<ref>{{Cite web|title=T-6/SNJ/HVD Information (Ray) – NATA|url=https://flynata.org/content.aspx?page_id=22&club_id=812035&module_id=241058|access-date=2020-07-13|website=flynata.org}}</ref> It produced B-25s at both its Inglewood main plant and an additional 6,608 aircraft at its [[Kansas City, Kansas]], plant at [[Fairfax Airport]].<ref name="ReferenceA">Parker 2013, pp. 77–79, 83, 88, 92.</ref><ref name="autogenerated70">Borth 1945, pp. 70, 92, 244.</ref><ref>Herman 2012, pp. 11, 88, 115, 140–143, 263, 297.</ref>

After the war, the USAF placed a contract for the TB-25L trainer in 1952. This was a modification program by Hayes of [[Birmingham, Alabama]]. Its primary role was [[reciprocating engine]] pilot training.<ref>{{Cite book|last=Johnson|first=E. R.|title=American Military Training Aircraft: Fixed and Rotary-Wing Trainers Since 1916|publisher=McFarland|year=2015|isbn=9780786470945|pages=162}}</ref>

A development of the B-25 was the [[North American XB-28 Dragon]], designed as a high-altitude bomber. Two prototypes were built with the second prototype, the XB-28A, evaluated as a photo-reconnaissance platform, but the aircraft did not enter production.<ref>Norton 2012, p. 68.</ref>

=== Flight characteristics ===
The B-25 was a safe and forgiving aircraft to fly.<ref>Tallman 1973, pp. 216, 228.</ref> With one engine out, 60° banking turns into the dead engine were possible, and control could be easily maintained down to 145&nbsp;mph (230&nbsp;km/h). The pilot had to remember to maintain engine-out directional control at low speeds after takeoff with rudder; if this maneuver were attempted with ailerons, the aircraft could snap out of control. The tricycle landing gear made for excellent visibility while taxiing. The only significant complaint about the B-25 was its extremely noisy engines; as a result, many pilots eventually suffered from some degree of [[hearing loss]].<ref name="dbvxho">Higham 1975, 8; Higham 1978, 59.</ref>

The high noise level was due to design and space restrictions in the engine cowlings, which resulted in the exhaust "stacks" protruding directly from the cowling ring and partly covered by a small triangular fairing. This arrangement directed exhaust and noise directly at the pilot and crew compartments.{{Citation needed|date=April 2018}}

=== Durability ===
[[File:B-25 bomber is assembled.jpg|alt= B-25 Engine Assembly|thumb|The B-25 engine cowling assembly]]

The Mitchell was exceptionally sturdy and could withstand tremendous punishment. One B-25C of the [[321st Bombardment Group|321st Bomb Group]] was nicknamed "Patches" because its crew chief painted all the aircraft's [[flak]] hole patches with bright yellow [[zinc chromate]] [[Primer (paint)|primer]]. By the end of the war, this aircraft had completed over 300 missions, had been [[Belly landing|belly-landed]] six times, and had over 400 patched holes. The airframe of "Patches" was so distorted from battle damage that straight-and-level flight required 8° of left [[aileron]] trim and 6° of right rudder, causing the aircraft to "crab" sideways across the sky.<ref>[http://www.usaf.com/pastplanes/b-25.htm "A Brief history of the B-25."] {{Webarchive|url=https://web.archive.org/web/20150303172949/http://www.usaf.com/pastplanes/b-25.htm|date=3 March 2015}} USAF.com. Accessed: 25 May 2015.</ref>