Talking Proud: Service & Sacrifice
Electric Goons of Naked Fanny
“The mere thought of flying a tail dragger is intimidating
to outright terrifying to pilots who haven’t flown them.”
A Goonie Pilot
Aircraft Types
There were three types of EC-47s used in the Indochina War: the EC-47N, EC-47P, and EC-47Q. In addition, there were three types of ARDF systems employed: the AN/ALR-34, AN/ALR-35, and AN/ALR-38.
EC-47N
The EC-47N was the most basic of the three models, coming from the C-47A family of aircraft, the latter of which were first ordered in 1940. By the end of WWII, the Army Air Force and Navy had bought over 10,000 of them. The C-47A was produced in Tulsa, Oklahoma, and Long Beach, California, and had a 24-volt DC electrical system. Those familiar with the C47A say her greatest defense was her turning ability, but you had to be careful not to over-stress the airframe.
The EC-47N sported two Pratt & Whitney R-1830-92 “Twin Wasp” engines. The R-1830 used 14 cylinders in two rows of seven, mounted to a forged aluminum crankcase. It was made mainly of magnesium to reduce its weight. It was an air-cooled radial design, a piston engine.
This was an efficient and reliable engine. It had 1,200 hp (895 kW). Some 178,000 of these engines were produced. The initial variants of this engine could only produce 800 horses. The EC-47N needed much more power than that, and all 1,200 horses obtained during the upgrades were needed.
All EC-47Ns employed the basic ARDF system, the AN/ALR-34. One set of vertical whip antennas was installed on the top and bottom of each wing, on top of the cockpit, and on the belly below the cockpit. There were also long-wire antennas strung from above the cockpit to the top of the vertical stabilizer.
There were three positions inside the cargo area, marked X, Y, and Nav. You also see a notation called the periscope. That was actually a single optical drift meter used in pre-Doppler aircraft. Positions X and Y were manned by the 6994th SS enlisted operators, while the navigator was a TEWS officer. The navigator used the drift meter to locate the aircraft’s position relative to known spots on the ground. With this, the navigator could look directly under the aircraft to refine its position.
Positions X and Y were COMINT intercept positions. The X position also employed the ARDF system. The ALR-34 was a high-frequency (HF) ARDF aircraft, meaning it could intercept and direction-find transmitters operating in the HF frequency range. The enemy preferred HF because that frequency allowed long-haul transmissions and transmissions that could work their way around terrain. The enemy operated in Indochina with a long logistics tail, so this was important to him. But most ARDF targets employed lower power HF transmitters, just enough power to get by the terrain to the neighboring units. Flying near the target was the best way to intercept and locate it.
The X position could fix targets within the frequency range of 2-16 MHz, while the Y position operated in the frequency range 0.5-30 MHz. The targets were enemy manual Morse transmissions.
This photo is of the interior cargo area of an EC-47N with the AN/ALR-34 ARDF system.
The door at the front was for the cockpit, pilot, and co-pilot. There was also a place up there for the flight engineer, in a small compartment just behind the left seat pilot. To the rear, you see the navigator sitting with his back to you, and his navigator’s table, where he plotted the lines of bearing (LOBs) manually. The X position was in front of him, and the Y position to the right.
EC-47P
Like the EC-47N, the EC-47P sported the Pratt & Whitney R-1830 engines.
There were two significant differences.
The first was that the aircraft carried an updated ARDF system known as the ALR-35. The ALR-35, among other things, automated the navigator’s position to some extent. Fundamentally, when the X ARDF position locked onto his target and shot a LOB, that data flowed automatically to the navigator’s position and spit a paper-tape printed read-out to the navigator. The navigator would then use that hard data to plot the LOB manually. In addition, Doppler navigation was provided to the navigator through this more automated system.
This is a look at the navigator’s new automated system on the ALR-35. You can see the drift meter just off his right shoulder.
The second big difference was that the EC-47P could carry two more COMINT intercept positions, one positioned in front of Y and the other to the rear of Y. These were known as Z1 and Z2, though I see they have also been referred to as Q1 and Q2. These were straightforward intercept positions, though they too could tip off X to targets they had for ARDF. The ALR-35, like the ALR-34, was an HF DF system.
The Z1 position offered something new and valuable, the capacity to operate in the HF and VHF ranges, the latter usually carrying enemy voice traffic. Position Z1 enabled the operator to hear voice targets in the 0.2-300 MHz range, while Position Z2 was configured much like the Y, in the range 0.2-30 MHz.
One problem for the EC-47P carrying the ALR-35 plus two extra positions and two more operators was that the R-1830 engines were put to the max to push this load down the runway, into the air, and up to altitude.
EC-47Q
Finally, the EC-47Q. She had three significant differences from the “N” and “P” models.
First, she was powered by two Pratt & Whitney R-2000 Twin Wasp engines. This engine was more powerful than the R-1830, kicking out 1,450 hp instead of 1,200. This engine was more fuel-efficient as well. These two factors were huge in Indochina. First, with four positions (X, Y, Z1, and Z2), plus the navigator, two pilots, a flight engineer, and a mission analyst, the aircraft was heavier and needed more power. Second, especially during the summer, the aircraft could not carry as much fuel because of the fuel expansion due to intense heat, so the power and the fuel efficiency were beneficial.
Most missions lasted eight hours, and most crews did not want to stop off at another base on their way home to refuel. One take-off and landing was enough, no call for two if not required. In the earlier days, with the smaller engines, missions might last only 5-7 hours.
The second significant difference was that the ALR-38 was an HF-VHF intercept and ARDF system. The ALR-38 ARDF system was the most complicated of the three from an electronics and automation standpoint. Very High Frequencies (VHF) are typically used for short-haul transmissions, usually demanding line-of-sight. Intercepting them almost always required an aircraft. You had to get within line-of-sight of the enemy transmitter to intercept and locate him.
The third significant difference was that the EC-47Q received blade antennas instead of whip antennas. You can see them on this EC-47Q in flight. Note the blade antenna sticking out of the fuselage just aft of the cargo door and the blades on the belly.
ARDF Process
The X position worked closely with the pilots and the navigator and was tied into the antennas that provided the direction-finding data to X. The Y position across the aisle was a COMINT position that searched for targets to exploit for intelligence and to hand off to the X position for ARDF location. The Y position usually had a typewriter to note down what the operator was hearing.
A typical scenario might be for Y to acquire a target and start typing. If the signal strength were good and the target were of interest, he would pass the target to X. Often, the X operator would latch onto the same target almost at the same time the Y operator got it. These guys were good.
X had a special set of ARDF equipment. He would acquire the signal and then go through a series of steps to lock onto the signal. Once done, X frequently would ask the navigator to make frequent turns and to obtain the best signal quality to lock on. Quite often, the navigator would ask the pilot to hold the aircraft “straight and steady.” The pilots were always keenly aware of where the threat circles were, and things could get a little tense when the navigator kept asking for “straight and steady” or “turn right or turn left,” and the pilots felt they were getting too close to or even inside a potential kill zone.
The navigator and X, of course, were looking for a nice spread between the LOB shots, so the process could take a few minutes. The navigator wanted at least three good LOBs to get what was referred to as a “fix.” Only two good LOBs would give him a less accurate “cut.”
The fix would come with an estimated Circular Error of Probability (CEP), which was usually an elliptical area on a map, inside of which there was a high probability that the target was there. The lower the CEP, the better the location. The crew considered they had a good fix if they had a CEP of 1000 meters or less. If they got that, the crew usually called the target into the ABCCC, which in turn would launch a FAC to take a look; it was before my time, but I understand that in the early days, they might even call the target down to a friendly ground station in Laos for action from there. However, a navigator has told me a 1000 meter CEP was not so good, that in his day, the best they could get was 250 meters.
When the AMS (who almost always manned the X position) turned the target over to the navigator, the navigator would see the target’s relative direction on his N1 compass. The navigator would direct the pilot to turn the aircraft so that the target is 45 degrees off the nose. He then printed out an LOB. As the aircraft progressed, the target’s relative position was off the wing, and another LOB was printed. Then, a bit later, another LOB was printed when the target was 135 degrees off the nose. The navigator then directed the pilot to a Doppler set point, resolved the LOBs to a target position, and updated the aircraft position to assure the ‘fix'.
All the navigator really needed was three good LOBs to get his fix. One navigator told me that any more would be like the law of diminishing returns. Better to go on to the next target.
The EC-47 navigator used the drift meter to update the aircraft’s position so that the LOBs could be accurately plotted. The navigator, using Doppler, had a good idea of aircraft location and would check the map for a good reference point near this assumed location, like a road intersection or a sharp bend in a river. He would then direct the pilot to take up a heading toward that reference point, or Doppler set point.
The navigator then looked down through the drift-meter and found that point of reference somewhere up ahead. Looking into the drift-meter, he continued to direct the pilot to fly over that point. When that point was reached, the time was noted, and the position was marked on the map. The Doppler position was also noted, and the two were compared (drift-meter fix and Doppler). A good Doppler would be close but could be as much as a half-mile off, depending on the time since the last Doppler set. The Doppler was then corrected, and the LOPs were drawn on the map using the updated position. The intersection of the LOPs would make a point or a small triangle, marking the position of the target. This would be written on a log sheet.
The Threats
During much of the war, the main threat to the EC-47 was the enemy’s single-barreled and twin-barreled 37mm towed anti-aircraft artillery (AAA) gun. The twin-barrel version is shown here. This Chinese-manufactured gun could attack an airborne target to a distance of 8,500 meters (roughly 4-5 miles) or a slant range of 3,500 meters (roughly two miles). She could fire 160-180 high-explosive rounds/min.
The most significant benefit to the EC-47 was that the 37mm was optically sighted and manually operated, which left room for lots of error by the enemy firing crews. That said, the 37mm remained a significant threat in part because there were so many of them located in so many places in Laos, the RVN, and Cambodia. An EC-47 flying at 100-120 knots and 10,000 ft. was very vulnerable to this gun, especially if the enemy firing crew was good.
Later in the war, the EC-47s began to experience the wrath of the enemy 57mm towed AAA gun. This gun was developed especially for low-speed airborne targets at short-to-medium range. The initial guns were optically sighted. Multiple guns could be fired simultaneously by a single remote control, enabling very intensive fire. Later variants employed the dreaded target radar, which improved its accuracy enormously and substantially increased its threat to the EC-47. Initially, these guns were saved to defend very high-priority enemy targets. As time went by and the Ho Chi Minh Trail became more and more important, the 57mm guns showed up in more and more places along the trail and elsewhere. This was a formidable threat to the EC-47.
This is an EC-47 the skipper and crew brought back to NKP after being hit by a 37mm gun.
There were losses.
“Tide-86” on March 9, 1967, flown out of Nha Trang, all seven souls lost.
“Cap 72” on February 5, 1969, flown out of Pleiku AB, all ten souls lost.
“Cap 53” on April 22, 1970, flown out of Pleiku AB, two souls lost, others rescued.
“Baron 52” on February 5, 1973, flown out of Ubon RTAFB, all eight souls lost.
