US Naval Aircraft Designations 1939-45
Or why a Navy AT-6 is really an SNJ
by Randy Wilson
Copyright © 1992 by the Confederate Air Force and Randy Wilson. All rights reserved.
"Say, mister! Is that your yellow AT-6 over there?" "No, but that is my yellow SNJ." "And how come that blue B-25 over there has a sign saying it's a PBJ? What the heck is a PBJ?"
So begins another attempt at explaining the U.S. Navy's World War II system of aircraft designations. When is a C-47 not a C-47? When it says U.S. Navy on its side and is an R4D. What the heck is a PBJ? Just a Navy B-25. Oh!
In 1922, the Navy adapted a new system of aircraft designation, and starting in 1928, all naval planes included their designation in their markings. A major difference between the Army Air Corps and Navy's systems was that the Navy included a manufacturer's code in its scheme. Despite some changes in its first couple of years, this system stayed in effect until 1962. Let's use the AT-6/SNJ Texan as an example to begin explaining the system.
The U.S. Army Air Corps' designation AT-6, stood for Advanced Trainer, sixth design. The U.S. Navy's basic designation of the same aircraft was SNJ, which meant Scout-Trainer built by North American. Hmmm. Maybe this isn't going to be as easy as I thought.
Let's try another one, say the Grumman Wildcat fighter, the F4F, which meant the fourth major fighter design built by Grumman. So, if F stands for Fighter and F stands for Grumman and J stands for North American - say, who figured out this crazy system in the first place?
I suppose we must go back to basics and look at the root of these designations, which is a one or two letter code indicating the type or class of aircraft, followed by a one letter manufacturer's code. After the class and manufacturer's letters, and separated by a dash, is a number indicating the sub-type or difference in configuration from the basic design. Thus, an SBD-1 would be the first version or sub-type Scout Bomber built by Douglas.
But how about those numbers that keep sneaking in between the class and manufacturer's codes, as in F4F, F4U, SB2C and R4D? A number in front of the manufacturer's code indicates that this is not the first design of that type or class for the Navy. Thus, the F4F was the fourth fighter design by Grumman (whose manufacturer's code was F), having been preceded by the F3F, F2F and FF designs. Note that the first design, FF in this example, does not include the number one.
All right, I can understand using F for fighter in the class codes and SB for Scout Bomber, but if an R4D is the fourth Douglas design transport type aircraft, why not T4D? Because the letter T was already in use for Torpedo carrying aircraft, and my best guess is that R is the second letter in transport.
Let's look at some of the different CAF naval aircraft assigned to various units. At the Dallas/Fort Worth Wing's Lancaster hangar [in 1992, Ed.] there is a Douglas R4D, the navy's version of the C-47/DC-3. This specific aircraft was built and is marked as an R4D-6S. Hmmm. Someone snuck the letter S onto the end of our designation. Does that mean that there were 18 sub-sub-types of the R4D-6, lettered A through R? No, suffix letters were used to designate special uses or equipment added, in this case, the S indicates anti-Submarine equipment and use.
Navy suffix letter codes can be very confusing, as the same letter can stand for more than one special use. For instance, the suffix A can mean a minor miscellaneous modification, as in the F4F-3A which had a different dash-number engine from the F4F-3. But an A suffix can also mean armament on a normally unarmed aircraft (J2F-2A), arrester gear fitted to non-carrier aircraft (SOC-3A), amphibious version (PBY-5A) or even Army-built or obtained (SBD-3A)!
Before presenting a bunch of tables to try and list all the possible codes used in the Navy system, why not look at the designations of the other naval aircraft at the DFW Wing hangar?
We've already talked about the R4D-6S, how about the F4U-1D that is really an FG-1D? The CAF's Corsair was actually manufactured by Goodyear, and since it was the first fighter design they built, its proper class and manufacturer's code is FG. The Corsair was originally designed and built by Vought as their fourth fighter type for the Navy, thus Vought-built Corsairs are coded F4U. By the way, the letter V was already in use to indicate heavier-than-air aircraft and squadrons and O was is use for Observation aircraft, so I assume U was the next unused letter in the name Vought. Both the F4U-1D and FG-1D were the first production sub-type, thus the -1, and additionally were a version fitted with underwing pylons for external fuel tanks and/or bombs, thus the suffix D, standing for drop tanks.
What about the Wildcat, which is painted as an F4F-3 but is really an FM-2? We have already seen that the F4F-3 decodes to the fourth fighter built by Grumman (don't ask me where the F is in Grumman, please), third sub-type. Even thought it was the third numbered sub-type, the F4F-3 was actually the first production version of the Wildcat.
In late 1942, General Motors Eastern Aircraft Division started manufacturing the Grumman F4F-4 design, but since it was being built by Eastern, the Navy gave it the new designation FM-1, with M being the code for General Motors Eastern Aircraft Division. The next sub-type was the FM-2, which was only produced by Eastern.
Why all this emphasis on giving each manufacturer's model a different designation? At least part of the answer comes from a study of the parts and maintenance manuals for these aircraft, as it seems that each manufacturer made some minor or not-so-minor modification to the original designs, and sometimes a part or sub-assembly for a Vought Corsair was not the same as a Goodyear or Brewster built model.
Marine aircraft also shared the Navy's designations, and if you look closely at the DFW Wing assigned Stinson L-5 Sentinel, you will see that it is painted and marked as a Marine OY-1. The O stands for Observation and the Y indicates manufacture by Consolidated, because Stinson became a division of Vultee in 1942, which then merged with Consolidated.
Just rejoining the CAF Ghost Squadron after a lengthy restoration by the West Houston Squadron is the Naval Aircraft Factory N3N, better known to naval aviation cadets as the Yellow Peril. This biplane primary trainer is often confused with the Army's Stearman PT-13 and PT-17 series of biplane trainers, and the Stearman design also saw service with the Navy with the designation N2S.
In a few cases, the Navy used a prefix letter to indicate a special class or use. The most common was the X prefix for an experimental design, such as XF4F-2, but also used were H for helicopter and L for glider. These last two were combined with more common type codes to produce designations such as HNS for Helicopter Training built by Sikorsky and LNS for Glider Training built by Schweizer.
There is not enough space to list every naval aircraft in the Ghost Squadron in this article, and a future installment will tackle the Japanese naval aircraft designation systems, to explain the CAF A6M2 Model 21 Type 0 Carrier Fighter.
Here now, in detail, is a recap of the U.S. Navy's system, showing how all six parts of the designation were assigned and used, along with tables of the various letter codes.
Author's Note: Special thanks to George Coombes, a former World War II naval aviator, for helping to proof this article and for pointing out a couple of omissions in the tables. He also noted that in 1945, some fighters that were used in reserve training and for proficiency had an N added to their designation, an example being the NF6F-5 Hellcat. He also questioned some of the odder types or classes, such as BT and TS, both of which were used only on prototypes like the Curtiss BTC and BT2C or Grumman TSF.
The Basic Components of the Navy's Designation System
Let's look at three examples of navy aircraft, the XF4F-2, SNJ-6B and HO2S-1, and see how each letter or number is used to form the plane's designation:
Special Status or Class Prefix
These codes were added in front of the usual class codes, for example HO2S-1, LNS-1 or XF4F-2.
Aircraft Types or Classes
Classes marked with an asterisk (*) were rare or uncommon during World War II. One experimental design, the Hall XPTBH-2 of 1937, bore a three letter class code for Patrol Torpedo-Bomber but was never produced.
Codes mared with an asterisk (*) were rare or limited to gliders and drones in World War II.
Manufacturer's Type Sequence
If this was the first design of a type, i.e. Fighter, Scout, etc. that a company had produced, no number was included, otherwise, a number, 2 or greater, was inserted between the type and manufacturer code.
Sub-type or Configuration
A number, beginning with one, preceeded by a dash to indicate minor to moderate changes in the design. In some cases, numbers were skipped, indicating sub-types not put into production.
Special Use or Equipment Suffix
Suffix codes marked with an asterisk (*) may also stand for Navy equivalent of an Army model or sub-type, i.e. PBJ-1D = B-25D.
Sources and Further Reading
Two major sources were used to compile this article. First, James C. Fahey's The Ships and Aircraft of the United States Fleet, published in four editions, the 1939 edition, Two-Ocean Fleet edition (1941), War Edition (1942) and Victory Edition (1945). The set of four has been republished, and is an excellent concise contemporary guide to both ships and aircraft of the US Navy.
A second source is Gordon Swanborough and Peter M. Bowers' United States Navy Aircraft Since 1911, published by Putnam and others. About fifteen pages of the introduction are devoted to explaining the navy's designation system, to the current day.
I've added a list of USN Squadron designations that were not included in the original article. Randy
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