Aircraft Naming and Designations
For the second post in this series let’s take a look at the designating and naming systems used by the United States. I know this sounds dry, but I find it fascinating and I hope you readers aren’t completely bored by this!
Like Japan, The Army Air Force and Navy (and Marine Corps) used completely different systems.
The Army (Air Force) system is fairly simple to understand, and similar to what is used to this day. A letter was used indicating general type, followed by a number indicating the type’s design order. So the B-17 was simply the 17th bomber design ordered by the Army Air Force. This may not be an earth shaking revelation, and apart from sequence it only gives relative information about the age of the design (the B-29 is a later design than the B-24). Usually, when a new aircraft was needed, several competing designs were ordered at once. Typically only a single type would end up seeing production; but on occasion (B-25/B-26 or P-39/P-40) multiple aircraft from the same order might see production.
Most of the letters designating the type are pretty obvious; “B” for bomber, “C” for cargo, “T” for trainer. A few oddities exist. Fighters had been called “Pursuits” through the 1930s. In 1942 all Pursuit Groups were re-designated as Fighter Groups (apparently to align with common word usage), but the aircraft type designator would not be changed until after the war. So fighters remained “P” for Pursuit through the war. Of course that meant the “P” had already been taken for photo-recon types; so they were designated “F” for foto. Because that’s not at all confusing…
There are some oddities for the numbers too. When the Air Force realized it would be several years before the P-61 night fighter was ready, they ordered Douglass to modify their fast attack bomber (A-20) into a radar equiped night fighter as the P-70; which would serve only until it could be replaced by the P-61. When the Mustang was ordered into production with the Merlin engine, the Air Force initially gave it the new number of P-78, before reverting to a P-51, “B” model. When a single seat fighter version of the AT-6 Texan was order by Siam (modern Thailand), the delivery was embargoed because of Siamese involvement with Japan, so the Air Force took possession of the type and designated it a “P-64”. All of these odd numbers are actually in sequence when you look at all such designations and their order or acceptance date.
There are a couple out of any sequence. There were two types the British bought, then refused delivery of; the Lightning and Airacobra. They weren’t just being rude (!); the British were under some pressure to let the US military take some “extras” off their hands early in the war, so the British released two types that were disappointing to them. But in both cases, the British aircraft were a bit different from any US models. So the repossessed Airacobras became P-400 and the Lightnings became P-322 (Lockheed called the type “Model 322” which is presumably the source of the Lightning’s number. I don’t know the source of “P-400”). The US Army Air Force actually agreed these types were pretty deficient, and they were supposed to be used exclusively with training units. But such was the early war desperation that a number of P-400 Airacobras saw combat with groups already using P-39 Airacobras. There may be other such out of sequence designations I haven’t encountered.
Which all leads to the sub types. This is seemingly pretty straight forward; the first example of a type gets no letter, then a modification to the type becomes an “A” type, the next mod is the “B” type and so on (I think in modern usage the sub-types start at “A”). Many changes were paper projects only and never saw production. The funny thing is, it wasn’t always clearly defined what constituted a significant change. There was a tendency in the early war years to burn through letters fast, then in later years to allow more incremental changes with no changes in designation. One example could be the P-51B and P-51C, which were identical, except the “B” was made in Burbank while the “C” was made in Dallas. When it came to the “D”, the Air Force decided the distinction was silly and both plants would get the same letter. Until… due to supply problems with Hamilton Standard propellers, the Dallas plant took delivery of an Aero-Products propeller. The Air Force decided this was a significant change, so these Mustangs would be “K” models. Funny thing then, the Aero-Products propeller was found to be troublesome. So most “K” Mustangs were lend-leased to the British. Many of the “K”s that the Air Force took had the propellers swapped out for Hamilton Standard units at forward depots. So now is it a “K” or a “D”? The data block would still say “K”.
There also could be “block numbers” to indicate sub-types within a sub-type, or suffix indicating different manufacturers or plants. So a late model Flying Fortress might be a B-17G-115-BO. Most of the later parts of information are pretty trivial, I’ll typically only mention them if they seem interesting for some reason. Like the P-39Q-21 was unique among Airacobras with a four bladed propeller; a good example of how early in the war such a variation likely would have earned the type its own letter. If anyone is still reading this say “Hi Dave” in comments.
Next issue would be the name. You know, those colorful labels that give personality to the machine. Before World War II, the US Army Air Force did not use names. Many manufacturers did, which I think leads to some confusion on the subject. Boeing’s P-26 never had an “official” name, although it was nicknamed “Peashooter”, and the manufacturer embraced this name, but the Air Force never did. Curtiss named all their fighters “Hawks”. So Curtiss called the P-36 the “Hawk 75”. When they put a new engine on it (Alison V-1710) they called it a “Hawk 81”, the Air Force called it a P-40. When they put a newer, better V-1710 on it, Curtiss called it a “Hawk 87”; the Air Force said its still a P-40.
[Now I’m going to be fuzzy here on dates. I have this information in an archaic storage format known as “books”. And sadly the search engine for “books” is pretty inefficient. So I may footnote this if I later track down exact dates, but for now I’ll have to wing it.]
Shortly before World War II, the Army Air Force decided that actual names would work much better for PR purposes. This may have had to do with dramatic stories coming from Europe about the great deeds of Hurricanes and Spitfires. So they started assigning names to existing and new types. The British had already been buying many US types for their war, and the British used names as the official, primary identification for all types. So in many cases, the Air Force simply took the names the British had already assigned (Mustang, Lightning and others started with the British). Sometimes they took manufacturer’s names (Flying Fortress and Airacobra started with their builders). The P-40 was a humorous problem; because the British had called Hawk 81s “Tomahawks” and Hawk 87s “Kittyhawks”. So the Air Force called them all “Warhawks”. Also, the British liked naming bombers for cities; which the Air Force didn’t find cool enough, so most bombers got original names.
The US Navy system is both more complex and provides more information. It is very similar to the short system used by Japan, probably because the Japanese had copied theirs from the US Navy. The main block consists of three pieces of information, a type code, a sequence number, and a manufacturer code. So one famous type was coded F4F; which can be read as “the fourth fighter type built by Grumman”. Some of the letter choices seem odd, they usually have to do with letters already in use (North American was “J”, because “N” already belonged to The Naval Aircraft Factory. I don’t really know the story for how Grumman came to be “F”, but I have a guess. During the war “G” belonged to Goodyear; since the same designation system applied to blimps, which Goodyear supplied, it is possible Goodyear was coded before Grumman). Unlike the Japanese version of this system, the first aircraft of each type received no number; so the first Torpedo Bomber by Douglass was a TBD (while in Japan the first floatplane by Mitsubishi was an F1M).
Sub-types received a sequential dash number. So the two main types of Hellcat would be the F6F-3 and the F6F-5. Missing numbers sometimes flew as experimental types, sometimes never made it off the drawing board.
The fun thing with this system, is that identical aircraft could have different numbers based on builder. The last version of the Wildcat mass produced by Grumman was the F4F-4; after which, General Motors took over production with the nearly identical FM-1. When a new hot rod Wildcat was desired, Grumman stepped up with the much improved XF4F-8 (the “X” prefix for experimental). That the Navy then ordered produced by General Motors as the FM-2.
There are many irregularities in the system; some I find amusing. Like the main Cruiser floatplane used during the war was the SOC Seagull, for “Scout-Observation by Curtiss”. Later, a new type was ordered, but the Navy felt “Observation” wasn’t really a job function any more, so the new type was the SC Seahawk (for “Scout by Curtiss”). Oh and of course, “Observation-Scout” generates a different sequence of numbers than “Scout-Observation”…. Sorry. This is just my government employee bureaucratic sense of humor at play again!
The Navy also started adding official names about the same time as the Army Air Force. The only real difference being the Navy seemed to really dislike the British name choices, there are few examples of borrowing from that source. In fact, later in the war, the Royal Navy renamed all American types in service to match the US Navy names. Perhaps the names were part of lend-lease…
Post War (1962), a unified system was started that used a new sequence of numbers (starting at F-1, B-1, C-1 etc) for all US Military services.
Up Next: Gloster Gladiator Mk I