syscom3
Pacific Historian
Lets collect some info on what constitutes production model terminology and what was decided on to be a block change of WW2 era aircraft. Such as "P38L-5-LO". What did it mean? What were the major changes? And how did different countries assign model and block numbers.
PRODUCTION BLOCKS vs FIELD CHANGES
Robert A. Mann
What is a production block – besides a part of the model number? Irving B. Holley Jr., in Buying Aircraft: Materiel Procurement for the Army Air Forces, defines it as:
"The block system was nothing more than an arbitrary pattern of model identification. Thus a B-24J, after being equipped with a different type of life raft and improved sights on the waist guns, might be designated the B-24J-15 to distinguish it from the B-17J-10, the last production block without those additions"
"The series letter "J" would be changed only when there were modifications affecting major alterations in structure of the primary armament of the aircraft."
To illustrate the need for what Holley called ".. the closest kind of production control.", in the case of the B-29, there were 1,174 engineering changes introduced even before the first plane was accepted by the USAAF.
Some 900 of these were last minute modifications growing out of flight testing and training aircraft flights
The five digit jump in block numbers, assigned at the factory, was built into the system to accommodate field modifications not 'large' enough to merit a new block number for changes to all planes not incorporated at the factory . Thus a field relocation of antenna attachment points and the installation of a new antenna location is certainly a change of form, fit or function to the –15 production block described above, and so would be described as block –16. The author has seen photographs of B-29's at an overseas base with the model painted in the Technical Data Block as B-29-16-BW, thus indicating some change(s) had been made to the plane beyond the –15 level.
But let us consider the situation with the early B-29's sent to the CBI. Two situations for which the author has never seen an explanation are evident: (1) to what block number were the modifications done in the "Battle of Kansas" assigned; and (b) how, and to what block number(s), were the field modifications done in the CBI assigned.?
An aspect not given not widely considered is the relationship of individual aircraft model designation, and in particular the block number, to the activities of the Logistics Command in regards of the delivery of replacement parts.
Let's examine a hypothetical situation within the fifty airplanes of the B-29-5-BW production block. Field modifications are done to the cowl flaps for improved cooling by the installation of locally manufactured shortened cowl flaps. Ditto the field installation of relocated antenna mounts. Thirdly there was the installation of new locally designed doors for the camera hatch.
Were drawings made of fabrication and installation of these modifications? Were new block numbers assigned? By who? Were drawings entered into the Logistics pipeline? Again, hypothetically, depending on the timing of the changes, these could be block numbers –6, -7 and –8. What happens if two more dash numbers to the –5 block were developed. That would be –9 and ?????
With time to incorporate changes in the production line, said changes can be incorporated in "five digit " block numbers. There is no upper limit. The B-24J's produced at the San Diego Convair plant go up to B - 24J - 210 – CO. But a high number of field modifications with the 'interior' block numbers
PRODUCTION BLOCKS vs FIELD CHANGES
Robert A. Mann
What is a production block – besides a part of the model number? Irving B. Holley Jr., in Buying Aircraft: Materiel Procurement for the Army Air Forces, defines it as:
"The block system was nothing more than an arbitrary pattern of model identification. Thus a B-24J, after being equipped with a different type of life raft and improved sights on the waist guns, might be designated the B-24J-15 to distinguish it from the B-17J-10, the last production block without those additions"
"The series letter "J" would be changed only when there were modifications affecting major alterations in structure of the primary armament of the aircraft."
To illustrate the need for what Holley called ".. the closest kind of production control.", in the case of the B-29, there were 1,174 engineering changes introduced even before the first plane was accepted by the USAAF.
Some 900 of these were last minute modifications growing out of flight testing and training aircraft flights
The five digit jump in block numbers, assigned at the factory, was built into the system to accommodate field modifications not 'large' enough to merit a new block number for changes to all planes not incorporated at the factory . Thus a field relocation of antenna attachment points and the installation of a new antenna location is certainly a change of form, fit or function to the –15 production block described above, and so would be described as block –16. The author has seen photographs of B-29's at an overseas base with the model painted in the Technical Data Block as B-29-16-BW, thus indicating some change(s) had been made to the plane beyond the –15 level.
But let us consider the situation with the early B-29's sent to the CBI. Two situations for which the author has never seen an explanation are evident: (1) to what block number were the modifications done in the "Battle of Kansas" assigned; and (b) how, and to what block number(s), were the field modifications done in the CBI assigned.?
An aspect not given not widely considered is the relationship of individual aircraft model designation, and in particular the block number, to the activities of the Logistics Command in regards of the delivery of replacement parts.
Let's examine a hypothetical situation within the fifty airplanes of the B-29-5-BW production block. Field modifications are done to the cowl flaps for improved cooling by the installation of locally manufactured shortened cowl flaps. Ditto the field installation of relocated antenna mounts. Thirdly there was the installation of new locally designed doors for the camera hatch.
Were drawings made of fabrication and installation of these modifications? Were new block numbers assigned? By who? Were drawings entered into the Logistics pipeline? Again, hypothetically, depending on the timing of the changes, these could be block numbers –6, -7 and –8. What happens if two more dash numbers to the –5 block were developed. That would be –9 and ?????
With time to incorporate changes in the production line, said changes can be incorporated in "five digit " block numbers. There is no upper limit. The B-24J's produced at the San Diego Convair plant go up to B - 24J - 210 – CO. But a high number of field modifications with the 'interior' block numbers
