EC-47 Model Designations

From time to time we get questions concerning the various designations applied to the EC-47 ARDF aircraft. Over the years, a bit of legend and some misinformation has crept into the knowledge base so, although we thought we had it covered in the EC-47 Serial Numbers and Data article, maybe the subject deserves more in-depth treatment. 

Let’s begin at the beginning. Despite what you may have heard somewhere, all the airplanes that were eventually converted to EC-47s were delivered to the U.S. Army Air Force between April, 1943, and November, 1945, as either C-47A or C-47B models. (Yep, those babies were old, but that pre-Pearl Harbor data plate you remember really wasn't there.) We’ll get into model designations shortly, but first let’s deal with serial numbers. We’re fortunate to have several photos of C-47 43-15979 showing the airplane at various stages of her career. In fact, we probably know more about this airplane than any other in the EC-47 fleet—so much so that we’ve devoted a whole article to this fine old bird. Since the photos of her illustrate the evolution of the USAF “tail number” system so well, we decided to expand that article to include an explanation of the USAF aircraft serial numbering scheme and how that translated into those numbers painted on the tail.1 Click here to view a history of 43-15979 and see how those tail numbers looked “back when.”

EC-47N, P, or Q?

Leaving the EC-47Q aside for the moment, let's look at how the EC-47Ns and Ps came to be so designated. The serial number list linked in the opening paragraph was derived mainly from a 1968 USAF Tech Order. The S/N not listed there were gleaned from other USAF documents. The 1968 T.O. shows the “EC” model designation (i.e., N, P, or Q) along with the original aircraft serial number. By comparing those original serial numbers with the EC model number, it will be seen that all the EC-47Ns came out of the Douglas factory as C-47A models; all the EC-47P aircraft began as C-47Bs.2 That’s it, end of story. 

How do we know that? First, there's a straightforward Systems Command memo on the subject. The USAF stationery formatting is virtually illegible, but the content is quite clear. (Remember, the ARDF C-47s were initially designated RC-47, and the TEWS started as Reconnaissance Squadrons. The reasons for the change from recon to electronic warfare were likely more political than technical, but we don't know the details behind the switch.) The biggest piece of the puzzle is provided by a USAFSS document which lists by aircraft serial number the back end configuration of the EC-47 fleet as of August, 1969. By correlating this equipment list with the 1968 S/N list, any particularly equipped aircraft can then be further identified as an EC-47N, P, or Q. 

The table below is a graphical representation of the linked document. The top numbers in the equipment column represent the type of AN/ALR ARDF system installed: AN/ALR-34, -35 or -38. "38*" indicates the ALR-38 "Mini-mod", while "38" indicates the full-up ALR-38 system. All aircraft had the Y position; certain others added Z or Q consoles as indicated. Configuration counts, particularly with regard to the Z consoles, likely changed as more sets became available.3 In at least one case, the "X" equipment may have been replaced or upgraded, but precise details are lacking. Regardless, it's clear that the EC-47 model letter designation had nothing to do with the back end configuration.


The "unknown" category includes five additional Q models, which in late 1969 had not yet been fielded, as well as the six aircraft already written off due to accident or enemy action. The configuration of the lost aircraft was three X,Y, one X,Y, Z, and two X2, Y, Z but these cannot be tied to a particular S/N. Presuming the five "new" Q models to have been equipped with -38 systems, the EC-47Q equipment totals would be: 5 x -35, 3 x -38 "mini-mod", and 7 x -38 systems. One unequipped EC-47Q crashed in Alaska on the way to Vietnam. We believe the -38 system intended for this aircraft may have replaced the -35 in another aircraft. We're looking for confirmation.
 

The EC-47Q 

The purpose here is not to provide a detailed description of the several EC-47Q modifications, the most obvious of which was R-2000 engines in place of the R-1830s in the N and P models. The more powerful R-2000s enabled longer mission duration while toting the extra weight of the two Z consoles and their operators. Both C-47A and B/D airframes were converted to EC-47Q models. Visually, the most obvious difference in the Q was the extended position of the propellers. We are informed by a knowledgeable mechanic that what appears to be a longer prop shaft on the R-2000 is in fact a difference in the propeller attachment mechanism. The shaft itself is the same length as that on the R-1830. Stay tuned for more on that. Finally, there’s the matter of the ARDF equipment and the associated antenna arrays. This is covered in detail elsewhere on the site. As shown in the table above, not all EC-47Qs were equipped with the VHF-capable AN/ALR-38 system. Those fitted with the -35 system retained the dipole antennas found on the N and P models.

The “Jammer” Aircraft 

Five EC-47N aircraft were equipped with the QRC-346 communcations jamming (COMJAM) electronic countermeasures suite.4 These aircraft could be visually distinguished by the “banjo” array of six long wire antennas, as opposed to the standard two on all other ECs. These long wires were a hold-over from the original WWII C-47 configuration and still served the same purpose—receiving and transmitting HF radio signals. The jammers were fitted with a retractable trailing wire antenna which, if it could be seen at all in the retracted position, might’ve been given away by the “fishing sinker” weight attached to the end.5

The added weight of the “Q” gear quickly proved detrimental to the already marginal performance of the heavily loaded EC-47. When it became evident that the COMJAM system was not going to be used for its intended purpose some of the ECM gear was removed to lighten the load, although the Q consoles were retained in order to provide a reduced collection capability version of the “Z” birds, which were still in short supply. Even this option proved unsatisfactory and in October, 1969, the Q consoles were removed. The jammers served out their time as standard ALR-34/Y position ARDF aircraft.6 All five were eventually passed to the VNAF, still in this configuration, 

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Footnotes.

1. For more on this and U.S. military aircraft serials in general, see Joe Baugher's website.

2. Most B models later had the supercharger removed from the R-1830-90C engines, after which they were redesignated C-47D. The most extensive source on the DC-3 family of aircraft is the three-volume set published by Air Britain, The Douglas DC-1 / DC-2 / DC-3 The First Seventy Years. (Volume 3 extends to the first 75 years.) This tome, totaling over 1,000 pages, contains a thumbnail sketch, by constructor's number and military serial number where applicable, of virtually every Gooney Bird ever built. The C-47 entries are based on the USAF "history cards" for each individual aircraft. 

3. One caveat concerning the Z positions: The USAFSS document notes that the aircraft so indicated were wired to accept the Z consoles, which were removable and therefore interchangeable. At any given moment the aircraft may or may not have actually carried the consoles, although we believe that by 1970 all properly wired aircraft were Z equipped.

4. 42-100984, 42-100513, 43-15603, 43-16055, and 43-16123. The USAFSS document has a couple of typos (or errors) for these S/N. See the document as linked above.

5. Tom Nurre, who served as training NCO at NKP, 1970-71, remembers that the "sinker" could be seen "nicely tucked inside the cone-shaped cable receiver unit." 

6. History of the 6994th Security Squadron, 1 July - 31 December, 1969, pp. 28-30; 48-49.

Article by Joe Martin
31 December 2017