C-123B and C-123K Provider's Avionics

[yahya]

Could someone share the pages from the original flight manuals that list and elaborate the C-123B and K avionics suite please?

 

[MIflyer]

Unfortunately I do not have a C-123 flight manual in my collection. But I worked with someone who was a crew chief on NC-123B aircraft that were used for special operations missions. Those aircraft had a weather radar in a radome installed above the cockpit, a doppler radar installed in the tail, and extensive radar jamming equipment. They also had Collins 618T HF radios for communications relating to the special operations. Other equipment would have included an ARC-27 or ARC-34 UHF communications transceiver (pretty much standard on USAF aircraft of that era) and in all probability an ARN-6 ADF receiver.

That's all I have.

 

[yahya]

Thank you for the reply. While I do not have any source material on the NC-123B avionics suite, I presume that this could have been related to the ROCAF C-123B of that vintage, which were also used for special ops in SEA. The main difference was the primary nav system, since the ROCAF Providers were equipped with Omega instead of Doppler.

The photos of the C-123B/Ks available online suggest that the Providers were indeed equipped with the ARN-6 ADF, but perhaps also with VOR or TACAN DME. That's why I still count on someone's flight manuals library.

 

[MIflyer]

Oh, I would expect that they would have VOR and TACAN, but I do not know which equipment. I would suspect they would have VHF Comm as well as UHF but I don't know which gear. I did a short write-up on what my friend told me and if I can find that again I will post it here.

The 618T was used for comm with the HQ and not the ground units they were supporting. It seems that all comm with the ground units was via the HQ. I would think they would have gear that could talk with backpack gear like the PRC-25, such as an ARC-114, but my friend did not indicate that.

 

[yahya]

Some hints from the scanned manual pages available online.

On the captain's station, the ID-250 RMI was slaved to the ARN-6 on the C-123B/K. The pointer #1 showed the ADF indication. The pointer #2 was slaved to the ID-251 VOR indicator or the ID-307 TACAN bearing indicator depending on the avionics suite.

On the co-pilot's station, the ID-250 RMI was slaved to the ARN-6 ADF #1 and #2. So, two such sets were used on some a/c.

However, there were also the C-123 examples that used a single ARN-6 ADF.

It also seems that the ARA-25 UHF DF was also used on certain military Providers. It was slaved to the ID-250 RMI.

I presume that the ARC-114 solid state COM was too modern to see use on the C-123s in Nam. I would rather think that old tube radios from the 1950s were installed on the cargo Providers.

 

[MIflyer]

I would rather think that old tube radios from the 1950s were installed on the cargo Providers.

I would think so, too, but the NC-123 special ops birds had quite extensive avionics mods, so they could have had almost anything installed that was available at the time. It's funny! The ARC-116 UHF comm is basically the same size and weight as just the ARC-27 control box! I have an ARC-116 and built a 28 VDC power supply with mike pre-amp for it. But my ARC-27 requires so much power that I'll never be able to fire it up.

 

[yahya]

I still tried to obtain documents on the avionics setup used in the C-123s.

The variant that you mentioned above, the NC-123B, appears to be unique unless it belonged to the two-aircraft series known as the AC-123K and NC-123K after the addition of jet engines.

Wikipedia described the NC-123B as a radio relay aircraft operating over the Ho Chi Minh trail, with equipment to read the signals from various sensors on the ground designed to pick up enemy truck activity.

Which one did you mean? I am especially puzzled by the weather radar in a radome installed above the cockpit which you described and which was rather characteristic to the ROCAF special duty C-123B and K. A photo of such a ROCAF aircraft is below:


View: https://www.flickr.com/photos/mambo1935/5405123137/

ROCAF special duty Providers used the AN/ARN-131 Omega Navigation System rather than Doppler nav.

 

[MIflyer]

No, to my knowledge the C-123's I was talking about were used for insertion and extraction of special ops teams. They had both the WX radar dome over the cockpit and a Doppler radar antenna under the tail as well as jammers capable of "taking out the electronics on a whole base" if activated on the ground. There were C-123 flareships used for dropping illumination over the Ho Chi Minh Trail and in support of ground troops in places such as Laos, but I don;t think their avionics fits were anything special.

 

[yahya]

I see. So, if I'm not mistaken, the NC-123B variant that you mean was pictured in the Squadron-Signal book titled "C-123 Provider In Action" on p. 18. From the outside, it resembles the ROCAF special duty Provider. The description suggests the plane was used to detect VC trucks and then to direct strikes on them by fighter-bombers. The photo is, however, not sharp enough to identify the avionics suite except the radome above the cockpit and a Doppler box antenna under the tail. Perhaps it also had an RWR, which protected the rear hemisphere. Doubtful this particular a/c was fitted with FLIR, etc.

The more capable Project Black Spot NC-123K was fitted with pretty decent avionics of that time, though, as evidenced by the vid pasted below.


View: https://www.youtube.com/watch?v=biTslRKmTMA

 

[MIflyer]

The description suggests the plane was used to detect VC trucks and then to direct strikes on them by fighter-bombers.

Well, they had C-130's doing that job, with night vision TV.