Aero Vintage Books

Interesting piece of research - every B-17 book lists 42-97173 as the first B-17G-45-BO.... the aircraft cards tell a different story - according to the cards, the last B-17G-40-BO was 42-97227 (and of course the first B-17G-45-BO being 42-97228)

Interesting. I wonder if the source for the published information is from the Army contracts.

I was wondering why all the published data, the block 40-BO only came to 115 aircraft built, this additional 35 brings this block to a even 150 and the block 45-BO down to 200 ships.

Need to try and find a readable datablock for one of these 35 see what it reads. Not sure which way to go with these in the book at this time - conventional or break with the flow and as printed on the cards

Food for thought... What was the installed equipment changes from a Block 40 to a Block 45 aircraft? Could there have been enough of a parts shortage for critical equipment at that time, that the contracting officers issued a contract modification to equip those 35 aircraft as Block 40's, even though they were slated to be -45's?

I know that configuration control of aircraft production is started well before the first metal is cut and there are times that part number rolls and equipment substitutions along with necessary engineering changes happen all the way up to DD-250 signature. Could there have been either a shortage or delivery delay of sufficient depth or duration, that those aircraft were completed out, using production spares and repaired equipment that had not been delivered at that point? At that time, even a couple week delay in delivery of critical equipment could have far reaching impact on production.

Block Changes

B-17G-40-BO

c/n 7531 / 7645
(115 aircraft)

1. External life-raft release.
2. Model RC-43B marker beacon (replaces Type RC-183 marker beacon)


42-97173 / 42-97407

B-17G-45-BO

c/n 7646 / 7880
(235 aircraft)

1. Electrical bomb control system
2. Model A-8 signal container (replaces Type A-7)
3. Modifications to SCR-281 radio (addition of TU-5B Tuning unit

Did a little cruising thru some of the top level drawings. Based on the data presented on them, it appears that the Block number roll was probably altered due to significant parts shortages and design changes. From just a couple of drawings, the s/n's in question had over 100 design variances that applied to that drawing alone. There were also notations that there were installation changes based on parts availability at the time. On one drawing, I found something like 90 variances for a single installation, covering almost 250 airplanes. On another, I found an effectivity list of more than 229 sets of s/n's. Did you know that there were 4 variations of the Navigator's Table installation? I think someone that had the time and enough of the top level drawings and the IPB's, could probably come up with what drove the differences on the block roll.

If you have never done it, chasing a configuration through drawing applicability can give you a real headache...

Apologies for being late to the discussion.

Below I've uploaded the pages for the B-17G-40 covering the Boeing, Douglas, and Vega aircraft showing the serial number range and contract number from the June 1, 1945 "Monthly Chart: Armament and Bomb Installations." I've cropped them to show just the left column.

The board's size restricts the jpgs to 256kb. Will email higher resolution copies should they not be viewable.

Thought this might be helpful to the discussion.
Nick

cvairwerks wrote:Did a little cruising thru some of the top level drawings. Based on the data presented on them, it appears that the Block number roll was probably altered due to significant parts shortages and design changes. From just a couple of drawings, the s/n's in question had over 100 design variances that applied to that drawing alone. There were also notations that there were installation changes based on parts availability at the time. On one drawing, I found something like 90 variances for a single installation, covering almost 250 airplanes. On another, I found an effectivity list of more than 229 sets of s/n's. Did you know that there were 4 variations of the Navigator's Table installation? I think someone that had the time and enough of the top level drawings and the IPB's, could probably come up with what drove the differences on the block roll.

If you have never done it, chasing a configuration through drawing applicability can give you a real headache...

The next step to chase this down through the IPC

I took a quick look at how the IPB's are done at Boeing and they are a bit different than everyone else. Boeing configured their catalog at that time, with a Usage Table, with letter coding for a block of serial numbers, that carries through the entire volume. You will need to run the table and pull the codes for each s/n block that covers the particular a/c. A quick glance shows that a large number of the codes between A and SI will apply.

If I were going to chase thru the IPB, I'd make a separate list of the codes for the two a/c in question, and build an assembly variance table and not bother at this point with a parts difference listing. That would allow you to discard changes that were applicable to both a/c.
This could be an exercise in frustration, depending on your temperament for chasing details. If you do it, I'll be curious as to what you discover.

finally found a readable data block for one of these aircraft - 42-97182.

Clearly shows it as a B-17G-45-BO.

So the books are right. Still wondering what made the early break in the block