We have to do some pretty deep digging sometimes to get to the bottom of a parts challenge here at AirCorps Library, and our research can highlight some pretty unusual aviation histories and mysteries.
That happened recently when our Technical Research Specialist, Desmond Bolden, was working to find a parts catalog for a United Aircraft Products (UAP) oil cooler (part number: UD840720S40UB) that was used in the P-51B, C, D, and M model Mustangs. Pages 68-69 of the P-51D parts catalog (AN 01-60JE-4 from 15-May-1953) shows an exploded view of what they call the "oil temperature regulator", commonly known as the "oil cooler", and the corresponding parts list for this assembly. Additionally, North American Aviation drawing 102-47006 (seen below) is the offical engineering drawing for the P-51 oil cooler, or as it is listed on the drawing: "radiator assembly - oil complete". However, neither of these sources provided us with all of the information we were looking for - namely overhaul and service information!
When our internal search for resources doesn't turn up any leads, we start scouring the internet and websites like Ebay and secondhand resale shops for help. At this point, we're looking for any references to related part numbers, or manuals that may help us answer our questions. And sometimes these searches take us in unexpeced directions, which was the case for this UAP oil cooler.
When Desmond searched for the UAP parts catalog, he was confused by the fact that half of the search results were blog posts and sales listings on sites like Ebay and Etsy for vintage United Aircraft Products bakeware! Intrigued, Desmond did a bit of research and quickly found that UAP was manufacturing multiple kinds of muffin and popover tins. Listings for these pans on Ebay and Etsy clearly show the UAP logo stamped into the tins (see below).
United AirCraft Products was founded in 1929 and primarily made heat exchangers at their Dayton, Ohio plant. When exactly they got into the baking business remains a mystery. Outside of the bakeware itself and the questions people are asking, there really is no details on when or why the company started to make muffin pans.
Patents filed in the early 1930’s (see image above) show designs by inventor Theodore M. Heister for a metal baking pan with “an annular depression with tapering side and a central projection in the depression.” A design that mirrors the modern muffin pan.
Its unclear whether UAP was manufacturing the muffin pans before, during, or after World War II, when they were providing oil coolers for the P-51. Based on the patent's 1933 approval date it is possible, but there is no detailed history of UAP’s manufacturing available online. However, many manufacturers from the 1930s and 40s had a diverse range of products. Minneapolis-Honeywell, for example, is well known for its heating regulators. In 1927 it was also one of the largest producers of jeweled clocks. Minneapolis-Honeywell would further diversify during the war to manufacture a vast array of parts from aircraft turbosupercharger control units to autopilot system parts. The document pictured below is an example of a Minneapolis-Honeywell clutch arm assembly (T.O. 11-60-5 dated 25-Aug-1943) for the type B-1 and C-1 autopilot system.
Many people, like this Reddit user, suspect UAP diversified its manufacturing after the war when the demand and production of military aircraft fell sharply. The idea being that UAP could most easily produce bakeware based on their existing manufacturing tools and in-house machinery.
The pans produced were stamped with UAP's logo and sold under the "aire ware line" with names like Muffiinaire, Popovaire, or Shellaire.
The Triumph Group acquired UAP in 2003. Today United Aircraft Products is known as Triumph Thermal Systems.
We have more than five dozen United Aircraft Products products documents and manuals on the AirCorps Library website. Here is a sample selection of those documents for you to explore.
- Overhaul Instructions with Parts Breakdown for Oil Cooler Part No. U-520317-2, UA520317-4, UA520317-6 and G.E. 573D264P2, 273D264P3, and 37D400479P101
- NAVWEPS 03-15DA-22, T.O. No. 7J1-50-3, Dated: 1-June-1964
- Overhaul Instructions for Oil Tank Assembly Part No. UA520620-46, UA520620-23, UA520620-32, UA520620-33, UA520620-44, UA520620-45, UA520620-17, UA520620-13
- NAVWEPS 03-15-577, Dated: 1-Apr-1965
- llustrated Parts Breakdown for Oil Tanks Part No. UA520620-13, UA520620-23, UA520620-33, UA520620-45, UA520620-17, UA520620-32, UA520620-44, UA520620-46
- NAVWEPS 03-15-578, Dated: 1-Apr-1965
- Overhaul Instructions with Parts for Air to Oil Cooler Assembly - U-515035-5
- NAVAER 03-15-567, Dated: 15-June-1956
- Overhaul Instructions with Parts Breakdown for Liquid to Liquid Cooler - U-515990-2
- NAVAER 03-15DB-501, Dated: 15-Oct-1955
We are always looking for more documents and manuals from United Aircraft Products and other manufacturers. Click here to learn more about contributing or donating materials to AirCorps Library.