Production Block Discrepancy
Update: This is now solved, see bottom of page for resolution.
In performing a lookup request for a new friend of mine I came across a very large discrepancy that, as of the time of this writing, I cannot reconcile.
Dr. Joseph Baugher is a noted Aviation Historian. He runs a massive website with all of the USAF Serial Numbers listed, and it includes things like which production blocks the planes belong to.
Scott Thompson is also a noted Aviation Historian who has written many books, including a fantastic book on the A-26.
While no historian is perfect, both of these individuals are what I consider as reputable secondary sources when looking up information. Both of them have published information about the Production Blocks, and importantly, the information published by both historians agree with each other. A small sample of their list is outlined below. (I'll keep it to just the Production B models for clarity sake). (Note that the B-15 block range also includes some of the C-model serials- the main point of this page is to illustrate the point of the problem, not to accurately list all of the serial number, which are found elsewhere on the site).
| Production Block | USAF S/N Start | USAF S/N End |
|---|---|---|
| B-1 | 41-39100 | 41-39104 |
| B-5 | 41-39105 | 41-49119 |
| B-10 | 41-39120 | 41-39139 |
| B-15* | 41-39140 | 41-39198 |
| B-20 | 41-39201 | 41-39299 |
| B-25 | 41-39300 | 41-39349 |
| B-30 | 41-39350 | 41-39434 |
| B-35 | 41-39426 | 41-39499 |
I'll take a moment here and quickly explain why this information is important. As aircraft go through their life cycles small changes are made to the specifications which result in new revised standards, which become a new production block. Some examples include: Block 1 & block 5 planes were built with a 75mm cannon in the nose, but by block 10 the noses were changed to the swappable 6-gun general purpose nose. Other changes include: cockpit changes, armament changes, avionic equipment changes, etc.
So what's the problem?
The USAF maintains inventory records for all of the planes, during WWII and Korea these records were called "Individual Aircraft Record Cards". Among the data on these cards in the Production Block. These cards, being official records of the USAF are considered Primary Sources. The problem is that they don't align with the Baugher/Thompson list.
Production Block 5 is 41-39105 and 41-39106
Production Block 1, with the exception of the two planes listed above, runs from 41-39100 through 31-39207.
There is no Block 10 listed in the record cards.
Production Block 15 begins at 41-39208.
As you can clearly see, these numbers do not coincide. I do not have an explanation for this at this time. I did reach out to Baugher and Thompson, hopefully they can clarify.
Update: Dr. Baugher informed me that his information came from the book: "McDonnell Douglas Aircraft since 1920: Volume 1" by Rene Francillon (a famed Aviation Historian).
It has occurred to me that there are other ways of verifying which set of data is accurate. I know what changes occurred during each of the production blocks. I also have over 9,700 photos in my archive. I can go plane by plane through my archive and visually compare the details and see what they line up with. I had been meaning to do this anyway, this just further necessitates that project.
Update
Since this writing I have come across another USAF document entitled "Report of Serial Numbers Assigned to Aircraft on Active Air Force Contracts, Part I, Section II" dated 24 Feb 1956. In that report, for Contract AC-21393, dated 31 Oct 1941, it provides the serial numbers as stated by Dr. Baugher and Scott Thompson. Thus, the conclusion is that the clerk(s) in charge of the IARC documents made errors in documenting the production blocks on the cards.