SH-3A Sea King (San Diego — 210 fsw)

The Tale of the Tail Code

This is a tale of hope, frustration, and persistence during our dives to find and identify a new helicopter wreck off Imperial Beach, California. The final identification was the result of a LOT of research and a somewhat obfuscated tail code that we uncovered on the second dive.

We believe that we are the first (and only) divers to visit the site.

Background

A while ago, Tyler Stalter got a lead on a SH-3 Sea King helicopter in 200+ feet of water off of Imperial Beach, California. The first thing that came to mind was “what if this is the famed Helo 66” that had been responsible for 5 of the Apollo recovery missions.

We had seen ROV footage of the wreck site (but nobody had dove it) and confirmed that it was definitely a Sea King and we knew that Helo 66 had crashed in the same general area. You can imagine our excitement as Helo 66 is probably the most famous helicopter ever flown. It crashed during a training mission back in June 1975 and the accident report listed it as sitting 800 fathoms (4800 feet) of water. However, there have been rumors that divers had located in it 220 feet which is about where our Sea King was.

You can imagine our excitement at possibly finding and identifying the world’s most famous helicopter…not to mention that fact that nobody had ever dived on the wreck site as far as we know….

Helo 66 Crash & Rumors

On the evening of June 4th, 1975 Helo 740 (the newer version of coding changed 66 to 740) left Imperial Beach to perform a nighttime three-hour anti-submarine training exercise. It was piloted by Lieutenant Leo S. Rolek and co-piloted by Lieutenant (Jr Grade) Charles D. Neville and two other crew for a total of four people. They were calling in position and status every thirty minutes. The started conducting their night exercises and lowered the dipping sonar into the water and made all scheduled half-hourly reports until the last report made at 9:25pm.

About 8 minutes later, they started having problems with the dipping sonar at about 100′ deep. The helicopter became unstable and they tried to further lower the sonar which seemed to help temporarily but then it started to get dragged down towards the water rapidly in a rearward flight pattern. The helicopter crashed into the water from a rearward hover at 40 feet and all four crew egressed and were rescued and taken to the Naval Hospital in San Diego. Unfortunately, the pilot died about three weeks later due to critical injuries to his spleen.

According to the location in the report (32 28′ N, 117 26′ W) , the helicopter sank in very deep water and the report includes that it “sank in approximately 800 fathoms (2400 feet) of water. ” The position indicated in the report actually contains a pretty big area since it is only accurate to minutes. The accident report is publicly available but heavily redacted.

If you start searching for “Helo 66” on the Internet, you will quickly discover quite a few rumors and search expeditions that have taken place to find the helicopter. Some key quotes are below:

Several years ago a group of helicopter and space enthusiasts heard rumors that Helo 66 had been found in much shallower water than the Navy had originally reported. Supposedly divers had found the fuselage in relatively good shape and for a brief period of time the enthusiasts sought to form a recovery effort to bring the famous Sea King to the surface and restore her. But the effort foundered when they were eventually told that the reports had to be in error, because the helicopter broke up when it hit the water and could not have been intact.

The last flight of Helo 66 by Dwayne A. Day

During some ASW training off of North Island (San Diego) a few years later, helo “66” developed an inflight instability problem associated with a tail rotor casualty. The pilot tried to effect a safe water landing but just before the sponsons touched down, the Seaking pitched over onto its side and slammed into the water. All the crew escaped, although the co-pilot died two days later from a ruptured spleen suffered in the accident. Helo 66 sank in 220 feet of water a few miles west of the entrance to San Diego Harbor. No efforts have been made to raise her although some divers have reported she is in fairly good shape structurally.

Posting by Richard Jackson based on communication from Bob Fish with the USS Hornet Museum (http://www.collectspace.com/ubb/Forum29/HTML/000205.html)

Anti Submarine Warfare

At this point, it is important to take a quick detour into the mission of the Sea King helicopters assigned to Anti-Submarine Warfare. These helicopters had a “dipping sonar” system that would essentially lower a sonar into the ocean in order to detect submarines in the area. The sonar buoy is connected via a cable to the electronics inside the helicopter.

Helicopter lowering a Dipping Sonar

At the time of the Helo 66 crash, the dipping sonar was in the ocean about 100 feet deep and they had lowered it another 30 feet to try to stabilize the helicopter. One other thing to keep in mind: Helo 66 was a type “D” Sea King which had been upgraded to a AN/AQS-13 sonar system vs. the previous “A” version of the Sea King which had a AN/AQS-10 system. File that fact away.

Dive #1 – July 14, 2021 (Brett & Tyler on the Marissa)

We headed down south to see if we could use Lora’s new sonar on the Marissa to locate the wreck. Tyler and Lora had spent a few hours on a previous occasion with the older system; however, they were unable to get a good enough return to make a dive worthwhile. This time, we were able to get a small blip and decided to make the dive to 200+ feet to investigate — hoping we didn’t find just rocks like we have so many times in the past.

Bingo!

We knew the second that we got on the debris that we had found our target. I started taking pictures and Tyler started to investigate the site looking for clues. The wreck is essentially 3-4 different debris fields with different parts of the helicopter. The first is the main rotor, engine and associated areas in the main part of the fuselage. There is also a section of the tail (we’ll get back to that in a bit), the rear rotor, and a landing gear.

Below are some photos of the different sections we found:

Main Rotor

The main rotor is probably the most distinctive section of the wreck and is also next to the sonobuoy. The picture on the right below shows the engine on the port side.

Landing gear / wheel

We only found one of the two main landing gear assemblies.

Tail section

The tail section is interesting. In some versions of the SH-3, the “Danger / Keep Away” with a red arrow is forward of the tail section on the hinge (left photos). In the Helo 66 (right) helicopter, it is clear that it is aft and on the section of the tail that rotates. See the two pictures below for a comparison:

During our dive, we found the very rear part of the tail section and the horizontal stabilizer. Near the end of the dive, I started clearing away debris from the top to see if I could find any identification marks. It is clear that I uncovered the red arrow and you can make out the “A” in Away under the arrow. The rear horizontal stabilizer has collapsed onto the side with the navy star on the underside.

RearTail Rotor

I didn’t get any good photos of the Rear Rotor, but you can clearly tell that some of the blades had been bent and we also identified five rotor blades (some not easy to see in the picture below) which also matches the SH-3:

Tail Rotor with bent blades

Dipping Sonar

This is the sonar system that would be lowered into the water with the spool of cable connecting it back to the electronics in the helicopter. These photos are important to pay close attention to as our story develops….

Dive # 1 – Summary Findings

At this point, we weren’t sure if we had found Helo 66 but we thought we might have. The facts were that it was definitely a SH-3 Sea King that had crashed in the general vicinity and that it was at a depth reported in the rumors.

Given the state of the wreck, it would be unlikely that we will find a Bureau Number or Tail Number or anything that conclusively identifies it as Helo 66 or any other Sea King helicopter.

However, we both had a nagging problem with all of this: the dipping sonar was right next to the main fuselage. If the sonar system had been in the water, there is just no way that it would be right next to the wreck AND with what appeared to be all the cable on the reel.

At this point, it is important to understand the concept of confirmation bias.

Tyler and I said to each other “if you were a sonar operator and you had the system in the water at 100′ and the helo had problems and you lowered it to 130 and they didn’t resolve, what would you do???”

The answer clearly would be “bring the damn thing back up” which would explain why the dipping sonar was by the helicopter and not on a cable far away from the wreck. We still had hope that we had found Helo 66 but we both had doubts.

One thing was for sure: we needed at least one more dive on the site.

Post Dive #1 Research – The Dipping Sonar

We couldn’t shake the fact that the dipping sonar appeared to be right next to the wreck so we started to use that fact to spur our efforts to research other possible Sea King wrecks in that area.

Tyler found a SH-3A that crashed in October 1964 and it was reported as “crashed six miles southwest of Imperial Beach during a routing night mission” and another article put the wreck at “seven miles off Ream Field.” Both match where we found the wreck. The helicopter was also reported as to have sank and the “depth is 185 or more” which closely aligns with the wreck we found.

But, there was another clue here: This was a SH-3A vs Helo 66 which is a SH-3D.

The important part of this is that the -3A had an AN/AQS-10 Dipping Sonar and the -3D had a AN/AQS-13 Dipping Sonar. We started to research the differences between the two sonar systems to see if that could give us further proof for identifying the wreck.

One of the key differences between the two systems: The AN/AQS-13 has 500 feet of cable per the military spec:

Mil Spec for AN/AQS-13 Cable Assembly

The AN/AQS-10 had 250 feet of cable according to one website we found:

Radar details from http://jproc.ca/rrp/rrp3/seaking_equipment_details.html

If you look at the photos of the dipping sonar, there is one that has the bolt snap from the front of Tyler’s scooter in the picture. That bolt snap is 3″ long so I made an initial estimate of the cable length based on that length, the number of turns of cable, and the number of rows and came up with 200+ feet. However, that was just based on a guess and analyzing the photo.

CONCLUSION : Clearly, we had to return.

Dive # 2 – August 9, 2021 (Brett & Ben on the Marissa)

I had my trip to dive the amazing wooden ships from the 1800s in Lake Huron already scheduled and Tyler had a vacation planned so we had move a few things around and it took nearly a month to get back to schedule the follow-up dive.

Ben Lair and I conducted a second dive on the site to gather further data and for Ben to see the wreck. I had some specific objectives and brought along a scrub brush (of course, attached via a bolt snap and cave line) to do some work.

The primary goals of the mission were to measure the cable spool dimensions and scrub the tail further to see if I could find any additional information to positively identify the wreck. I also had some secondary objectives to get some better pictures of the rotor and possibly build a photogrammetry model of the main part of the wreck.

Sonar Measurements

One key piece of data I wanted to obtain was an approximation of the length of the cable to double-confirm that it is indeed an AN/AQS-10. During the dive, Ben and I made four measurements of the cable spool: inside diameter, outside diameter, number of rows, number of turns. The measurements and guesses on turns aren’t exact, but we came up with the following: 15″ inside diameter, 22″ outside diameter, 5 deep, 12 across.

Ben had left his video camera going with the lights on. It isn’t in focus, but you can see the shenanigans as we make the measurements in the video here: https://vimeo.com/587492363.

Because there are 12 rows, the calculations become pretty simple when you convert from inches to feet. My crude calculations look like this for each row: Diameter x Pi x 12 rows / 12in/ft = Diameter x Pi

Each of the five rows going from 15″ to 22″ must be: 15″, 16.75″, 18.5″, 10.25″, 22″. That results in 92.5 x Pi = 290 feet. That is a little more than 250 but also note that the outermost row of the cable is only about 1/2 way across the spool. If I take that into account, I end up with almost exactly 250 feet.

I also took some additional photos of the cable spool and dipping sonar system.

CONCLUSION: The sonar type is an AN/AQS-10 which rules out Helo 66 because it was BuNo 152711 which is after the switch to AN/AQS-13 at BuNo152104 AND Helo 66 is listed as a SH-3D which also indicates the newer type of radar.

Tail Section

After taking some pictures for a potential photogrammetry model, I went over and started scrubbing the tail section to see what I could find. Below are a few updated pictures.

The first thing to note is that it is definitely the “Keep Away” sign from the tail of the SH-3. You can see where the tail section rotates in the toy model pictured below — which also unfortunately is just aft of where the all-important Bureau Number is painted on.

More importantly, I uncovered some other parts of the tail section behind the “Keep Away” sign that had part of the Navy “Tail Code” that would identify the Carrier Air Group that the crashed helicopter belonged to at the time of the accident.

Tail Code

The first letter is definitely an “N.” The second letter isn’t really clear due to damage to the tail. At the time of the crash, Helo66 was badged with “NE 740.”

At first, we thought it could be a “U” which aligns with the tail code from the Luczak crash in 1964 so we started going down that path further. In fact, we went very far down that path and even consulted with a few other people to get their opinions. I had some doubts about the letter being a “U” since it seemed to have a blank white space above the bottom of the letter when it should have been continuous black (see red circle below which is a screen capture from video that Ben took).

2nd Tail Code Letter

But, again, confirmation bias starts to kick in and we thought maybe the paint just got eroded or scraped off.

I then reached out to Tommy Thomason who has written multiple books and articles on military aircraft, including Helo 66.

I asked to get his opinion on the tail code after I sent him a couple pictures. Initially, I only told him that we didn’t think it was Helo 66 but we were trying to get a positive ID. During the email discussion I mentioned that we thought it was probably Luczak’s helicopter that crashed in 1964. He was quick to point out that the tail in the photos was white and that the Navy switched from the all grey paint scheme to white & grey after it was approved in 1967 so there is just no way that we had the right ID.

Back to the drawing board, but we now have three facts:

  1. The sonar is the older version (AQS-10) but…
  2. The paint job was the newer white version which started phasing in during mid-to-late 1967 and …
  3. We know the tail code started with “N.”

Given the pattern of the second letter, Tommy believed it was a “S” which was disestablished in 1973 which gives us a 6-ish year period during which it could have crashed (white paint in ’67/’68 until ’73). I also thought it could be a “J” which was disestablished in July 1970 which means there is essentially a two year period in which this aircraft could have crashed.

CONCLUSION: The tail cannot belong to Helo 66 because the second letter is not an “E” and we have yet another data point that rules out that specific helicopter (much to our disappointment).

At this point, Tyler started talking about needing to see a therapist…

The research continues

Tyler and I were plotting dates for a third dive to find more clues and then he found an article in the newspaper about a SH-3A that had crashed on September 3, 1968 and we found a couple other newspaper references:

However, we had to answer the all-important question: did it have the right tail code to align with our wreck?

To answer that question, you need to follow the bread crumbs. That helicopter with Bureau Number 152114 was written off on the date of the crash (3 Sept 1968) and belonged Helicopter Squadron 6 (HS-6) at that time. The Tail Code NS corresponded to the Antisubmarine Carrier Group CVSG-53 which was active from 1960-1973. On the date of the crash (Sept 1968), CVSG-53 was in between deployments and included the HS-6 squadron — which means that it would have had a NS tail code when it crashed.

Tyler also confirmed that the pilot, Lt. Donald R. Sanborn, was in the USS Kearsarge cruise log book from 1968 as the HS-6 representative.

To summarize, we have the following facts:

  1. The wreck site is a SH-3 Sea King which matches the wreck in Sept 1968
  2. The location of the wreck matches what is indicated in the newspaper articles
  3. The sonar type found in the wreck (AN/AQS-10) matches the date range and type of sonar from that version of the helicopter (SH-3A)
  4. The date of the crash matches the right color paint scheme for the tail
  5. The tail code matches the deployment on CVSG-53

About the only data we don’t have is the specific Bureau Number from the wreck site and I don’t think that we will ever have that. We are 95+% confident that we have located, dived, and identified the wreck of SH-3A Bureau Number 152114 in 210 feet of water off the coast of Imperial Beach, California.

Next Steps

We have filed a Freedom of Information Act request to get a copy of the accident report to see if there are any additional clues that would help confirm the identity.

At some point, we will probably return to the dive site but we do not have a concrete date.

I would like to get a few more photos to build a better photogrammetry model. I missed a few photos in key places to stitch together the main part of the wreck. A screenshot of a portion of the wreck site is shown below:

“Draft” Photogrammetry Model

Thanks

As usual, on any project like this, it takes a team of people and help from a lot of different areas. I would like to specifically thank:

  • Lora, Chris, Captain, and Scout from the Marissa for making the long journey south the dive the wreck (twice)
  • Tommy Thomason for helping with the tail code identification and paint color
  • Ben Lair for diving it the second time and helping with measurements (well, admittedly, that wasn’t really a hardship on Ben!)
  • Tyler Stalter for being a good dive and research partner. We push and challenge each other in good ways.
  • My wife for putting up with all my stories and rants about “the helicopter”

10 thoughts on “SH-3A Sea King (San Diego — 210 fsw)

  1. Brett-this was an absolutely “great read” and hearing about all the details and twists/turns in the dives. Very, very cool …love it!!!

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  2. Wow. That has to be the best example I’ve seen of researching and identifying a wreck. Excellent job!

    BTW, I like the use of “confirmation bias.” I have gone down that road before too.

    Steve

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    1. Thanks for the kind words, Steve. It was definitely a twisting journey to get to the final ID (as you know)! Confirmation bias is definitely real and alive and well. The good thing about Tyler and I is that we question each other, we challenge our assumptions, and (hopefully) arrive at the right conclusion.

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  3. First of all I love the info and am intrigued with it because I too was station at NASIB 73-76, with HS-2 and flew as an aircrew man on the SH-3D. I was curious about the photo with the tail rotor blades and I noticed the rope wrapped around the tail rotor hub and shaft. However you didn’t mention anything about that in the story. It appears that maybe someone earlier dove on the wreck and may have tried to bring up the unit??? Also I’m sure you’ve looked for data plates on the equipment, black boxes etc. Sometimes you can trace where that box might have been assigned to a certain aircraft. The landing gear might hold that info for ya. Thanks, Mike Pater

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    1. Hi Mike,

      Thanks for reading and for the feedback.

      I’ve seen ROV footage from a couple years ago that didn’t have that rope (and the wreck was is basically in the same condition — i.e., it really wouldn’t make sense to try to raise it). I’ve seen it many times before where there are just random pieces of rope caught on wrecks. The rope basically just drifts along the ocean floor until it gets caught on something.

      We haven’t yet looked for data plates on the equipment. We’ve conducted two dives on the site and they were focussed on trying to find identifying characteristics and markings on the external parts of the site and making measurements of the sonar system cable reel. It is 210′ deep and so you get a limited amount of time on the site before your deco obligation starts to accelerate.

      For example, on the second dive, it took me 5 minutes to get down and I had 18 minutes on the wreck. At that point, my deco obligation was 45 minutes. However, another 5 minutes on the wreck would have cost me at least another 15 minutes in decompression.

      Looking for info on the landing gear is a good idea. I’m sure we’ll go back at some point and I’ll put that on the task list.

      Regards,

      – brett

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  4. Sir, Read your website with great interest as I flew the SH-3A in HS-10 in late ’71 as an RP and in HS-6 in ’72-’74. We had AQS-13 sonars in all of them. I received no training regarding the AQS-10 except as an historical footnote. I compared all the bureau numbers in my logbook and found a few older than 152014, which you note as the Buno which began the transition to the AQS-13. That Buno is not assigned to Sikorsky SH-3 (it is an A-4, but a run of 34 began with 152104, which I would think would be the appropriate time to transition to the AQS-13. Did you perhaps transpose 014 and 104 at some point? I don’t think it changes anything in your sleuthing. I am pretty sure all the AQS-10s were upgraded to AQS-13 but have not found when such a transition happened. I may be misremembering, but I think the receiving staves of the AQS-10 may not have been visible like they definitely were for the AQS-13 and as shown in your photos.

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    1. Hi Tom,

      Thanks for reading the post and for your comments. You are 100% correct, I had transposed the digits. According to my records, the retrofit started with BuNo 152104 (and not 152014 as I had posted) in the 1970 timeframe which was after 152114 crashed. I’ve corrected the post. Thanks for the sharp eyes!

      I was a bit confused on one aspect of your comment. Are you saying that you think the photos depict an AN/AQS-13 or an AN/AQS-10? Our measurements indicate a cable length matching the -10 mdel which would make sense since it crashed in ’68 and the retrofits started in ’70.

      Thanks,

      – brett

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  5. Excellent article Brett! I am a junkie for this kind of stuff and you and Tyler really wrung this wreck out. I have a friend from church who recently retired flying Sea Kings and wonder if he would be of help? Enjoyed this very much. I also did a bunch of ASW work years ago with simulation CO’s for the Lockheed P3 Orion aircraft.

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    1. Very cool — thanks for the comments, Jamie!

      I’m sure your friend would enjoy the article and if he has an insights, feedback, or comments we’d love to hear them. I can also send him specific photos if there is something he wants more detail on.

      Also, thanks for the information on the P3 Orion. I’ve never really researched that bird and it is fascinating. I’d love to dive one, but my guess is that if any of them have crashed in dive-able depths then they have been salvaged due to the secrecy of the electronics on board.

      The P-3 Orion replaced the Neptune and I know of at least one of those that crashed right here off Dana Point but it has never been found and I’m guessing it is in deep water. I know a guy who spent a lot of time side scanning the area and he was never able to locate it.

      https://www.baaa-acro.com/crash/crash-lockheed-p2v-5f-neptune-dana-point-4-killed

      Regards,

      – brett

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