ColdWarsChild
Recruit
- 1
- Mar 23, 2017
Hello. A few years ago, when I worked for Lockheed Martin, I saw a story the company published bragging on the B-26. It sounded like hype, so, during my lunchbreaks, I'd search the internet about it and read about the controversies. It also made me curious about how the B-26 compared with the B-25, which is what this forum is all about. You have made many good points in your discussions, one of which was that the two aircraft were optimized after their debut for very different roles. In addition to that, the two aircraft came into existence through two very different paths, and that set the stage for how some of the later events turned out. Most of the information on which I am basing the following summary comes from YouTube videos by folks who were there at the time, not professional authors (if any of you want to find those videos, let me know and I'll see if I can find them again). What follows will be more about the development and modification of the aircraft than other considerations. So lets summarize the B-25 first, then the B-26. Summaries tend to be oversimplifications, but they are useful in serving as mental scaffolds on which details can be assembled.
In the 1930s, North American Aviation was serious enough about breaking into the military aircraft business that they built a new plant in Inglewood, California. They just needed to win some business. They entered their NA-39 design as the XB-21 in a competition against the Douglas B-18. A prototype was built and flown in December 1936. The performance of the XB-21 was far superior to the B-18, but the XB-21 cost $122,000 per aircraft and the B-18 cost $64,000 per aircraft. Douglas won. There was another chance with an Army Air Corps spec (circular proposal 39-640) in March 1938 that resulted in the NA-40. A prototype was built and flew in January 1939. Problems were corrected in the NA-40B which flew in March 1939. Competition was the Dougles DB-7 (which won as the A-20 Havoc), Stearman, and Martin, and the customers were Britain and France. There was another chance in an Army Air Corps spec in March 1939 that resulted in the NA-62. There was no time for a prototype, so the NA-62 was ordered off the drawing boards as the B-25. North American's previous prototype experience meant that the initial NA-26 design was close to being operational. Following the first production units, there was a design issue that had to be fixed - the wing dihedral. The word coming back from Britain was that bombers needed defensive armament, so that was another change. But very early into the long production, there was a B-25B that was combat ready. It had low wing loading which gave it a short take off roll. That plus its early maturity caused Jimmy Doolittle to choose it as the aircraft for the Tokyo raid. Going into production, North American put a lot of forethought into modular construction which lowered production costs, made field maintenance easier, and made modifications quicker. Because of the prototypes The B-25 was known for being very adaptable, and the modular construction facilitated this. Later in its combat life, the B-25 was optimized for low level attack using a lot of guns which caused lots of skin fatigue and fixing this became a recurring matinenance task. Some key features to remember: cheap to build and maintain, mature early, adaptable, short takeoff roll, forgiving to fly.
In 1932, Martin produced the B-10 which won the Collier trophy, made all other bombers at the time obsolete, and set standards for bombers which lasted for a decade. The B-10 introduced an all metal monoplane airframe, enclosed cockpits, internal bomb bay, rotating gun turrets, retractable landing gear, and full engine cowlings. It was even faster than the fighters of its day. For Martin, accomplishing this carried a lot of prestige. 121 were built. Now return again to the aforementioned to Army Air Corps spec (circular proposal 39-640) in March 1939. Martin entered Model 179 designed by Peyton Magruder, optimized for speed and range and payload with short, thin wings, high wing loading, high takeoff speed, and a long takeoff roll. Was the design pushing the edge too much to recapture prestige? Were the Army Air Corps and Magruder thinking flying faster than a fighter was achievable? Like the B-25 it was ordered right off the drawing boards - no time for a prototype. But there were no previous prototypes anything like the B-26 - it was very much an unproven concept. The initial production units were sent to the Pacific. They were a challenge to fly and to maintain. Then the same word came to the B-26 as to the B-25 about needing defensive armament. It, as well as torpedo racks, were added, and weight went up 2.5 tons. Pilot training was a Tampa Bay, and there were lots of crashes ("One a Day in Tampa Bay"). The Group Operations Officer investigated. Besides the known mechanical problems with carburetors, distributors, and prop feathering, he determined that inexperienced maintenance crews were causing some of the crashes. He took a B-26 up and simulated at altitude, landing conditions with loss of an engine. Result was an inverted spin that took 4000 feet of altitude to recover. His conclusion was that, as the B-26 was then, a pilot could not successfully takeoff or land on one engine. Problems got corrected. Jimmy Doolittle thought the the B-26 had the makings of a good bomber and got assigned the task of resurrecting its reputation. Eventually the B-26 got sent to England. The first raid was low level and the target was in Holland, and 4 aircraft wre lost. In the second raid, 11 aircraft were launched (one of which aborted). This was also low level and the target was in Holland, but they overflew more land, were attacked by fighters, were attacked by flak, and none of them returned. The B-26 was grounded. The same Group Operations Officer previously mentioned was part of a committee whose charter was to determine what kind of tactics changes were needed for the B-26 to be successful in Europe. The interviewed lots of experienced pilots from the theater and eventually decided, for protection against fighters, on an 18 aircraft box consisting of three sets of two Vs of 3 aircraft each. They flew at 12,000 feet (limited by having no oxygen aboard), and, until the bomb run started, changing direction every 15 seconds to avoid flak. Initially, their targets were the 23 enemy airfields. When operated this way, they had very accurate bombing and found that the B-26 could take a lot of punishment and still get them home. Surprisingly, it ended up with the lowest loss rate in the ETO for all the aircraft types. Some key features to remember: expensive, difficult maturation, narrow envelope but accurate bombing, long takeoff roll, could take a lot of punishment.
In the 1930s, North American Aviation was serious enough about breaking into the military aircraft business that they built a new plant in Inglewood, California. They just needed to win some business. They entered their NA-39 design as the XB-21 in a competition against the Douglas B-18. A prototype was built and flown in December 1936. The performance of the XB-21 was far superior to the B-18, but the XB-21 cost $122,000 per aircraft and the B-18 cost $64,000 per aircraft. Douglas won. There was another chance with an Army Air Corps spec (circular proposal 39-640) in March 1938 that resulted in the NA-40. A prototype was built and flew in January 1939. Problems were corrected in the NA-40B which flew in March 1939. Competition was the Dougles DB-7 (which won as the A-20 Havoc), Stearman, and Martin, and the customers were Britain and France. There was another chance in an Army Air Corps spec in March 1939 that resulted in the NA-62. There was no time for a prototype, so the NA-62 was ordered off the drawing boards as the B-25. North American's previous prototype experience meant that the initial NA-26 design was close to being operational. Following the first production units, there was a design issue that had to be fixed - the wing dihedral. The word coming back from Britain was that bombers needed defensive armament, so that was another change. But very early into the long production, there was a B-25B that was combat ready. It had low wing loading which gave it a short take off roll. That plus its early maturity caused Jimmy Doolittle to choose it as the aircraft for the Tokyo raid. Going into production, North American put a lot of forethought into modular construction which lowered production costs, made field maintenance easier, and made modifications quicker. Because of the prototypes The B-25 was known for being very adaptable, and the modular construction facilitated this. Later in its combat life, the B-25 was optimized for low level attack using a lot of guns which caused lots of skin fatigue and fixing this became a recurring matinenance task. Some key features to remember: cheap to build and maintain, mature early, adaptable, short takeoff roll, forgiving to fly.
In 1932, Martin produced the B-10 which won the Collier trophy, made all other bombers at the time obsolete, and set standards for bombers which lasted for a decade. The B-10 introduced an all metal monoplane airframe, enclosed cockpits, internal bomb bay, rotating gun turrets, retractable landing gear, and full engine cowlings. It was even faster than the fighters of its day. For Martin, accomplishing this carried a lot of prestige. 121 were built. Now return again to the aforementioned to Army Air Corps spec (circular proposal 39-640) in March 1939. Martin entered Model 179 designed by Peyton Magruder, optimized for speed and range and payload with short, thin wings, high wing loading, high takeoff speed, and a long takeoff roll. Was the design pushing the edge too much to recapture prestige? Were the Army Air Corps and Magruder thinking flying faster than a fighter was achievable? Like the B-25 it was ordered right off the drawing boards - no time for a prototype. But there were no previous prototypes anything like the B-26 - it was very much an unproven concept. The initial production units were sent to the Pacific. They were a challenge to fly and to maintain. Then the same word came to the B-26 as to the B-25 about needing defensive armament. It, as well as torpedo racks, were added, and weight went up 2.5 tons. Pilot training was a Tampa Bay, and there were lots of crashes ("One a Day in Tampa Bay"). The Group Operations Officer investigated. Besides the known mechanical problems with carburetors, distributors, and prop feathering, he determined that inexperienced maintenance crews were causing some of the crashes. He took a B-26 up and simulated at altitude, landing conditions with loss of an engine. Result was an inverted spin that took 4000 feet of altitude to recover. His conclusion was that, as the B-26 was then, a pilot could not successfully takeoff or land on one engine. Problems got corrected. Jimmy Doolittle thought the the B-26 had the makings of a good bomber and got assigned the task of resurrecting its reputation. Eventually the B-26 got sent to England. The first raid was low level and the target was in Holland, and 4 aircraft wre lost. In the second raid, 11 aircraft were launched (one of which aborted). This was also low level and the target was in Holland, but they overflew more land, were attacked by fighters, were attacked by flak, and none of them returned. The B-26 was grounded. The same Group Operations Officer previously mentioned was part of a committee whose charter was to determine what kind of tactics changes were needed for the B-26 to be successful in Europe. The interviewed lots of experienced pilots from the theater and eventually decided, for protection against fighters, on an 18 aircraft box consisting of three sets of two Vs of 3 aircraft each. They flew at 12,000 feet (limited by having no oxygen aboard), and, until the bomb run started, changing direction every 15 seconds to avoid flak. Initially, their targets were the 23 enemy airfields. When operated this way, they had very accurate bombing and found that the B-26 could take a lot of punishment and still get them home. Surprisingly, it ended up with the lowest loss rate in the ETO for all the aircraft types. Some key features to remember: expensive, difficult maturation, narrow envelope but accurate bombing, long takeoff roll, could take a lot of punishment.