“Full Stall Landing” — TBF-1C Avenger (Point Loma — 150 fsw)

Background

We believe that we have located, dived and identified a new WW II TBF-1C Avenger (Bureau Number 24272) airplane wreck in Southern California off of Point Loma.

A couple months ago, Tyler had a “breakthrough” on how to combine and overlay a few different disparate data sources in order to locate potential new targets. It was pure genius but we weren’t sure how accurate it would be.

Given our conflicting schedules and the really variable ocean conditions here locally, it took some time for us to find a date that worked for everybody to go do some sonar work. We were just itching to go and finally booked a date with Chris and Lora at Marissa Charters.

The conditions weren’t great on our dive date but we didn’t want to wait any longer so we headed out. The were some large, rogue swells at the entrance of Mission Harbor and the water was an ugly brown-ish / green-ish color.

Our first target was in 200′ and we got a decent return and definitely saw some fish, but we weren’t really sure so we moved on to test target number 2. It can be challenging to get a consistent sonar image when the swells are larger, wind is blowing, the ship is being moved around, etc. but we finally got a good scan and it looked very promising (side scan image on the left, sonar image on the right).

The Dive

I suited up as they were getting the downline setup and was anxious to see if Tyler’s new data was going to pan out. The sonar and sidescan images certainly looked good. As I mentioned, the ocean was not very “friendly” looking and was, as Tyler describes it, like “chocolate milk.”

I started my descent and the visibility was probably 5 feet on the surface. I was hoping it would clear up as I got deeper. It got a little better but was probably 10 feet at most when I got deep. I saw a very large rockfish and knew that we had something nearby but didn’t know what.

This is where having a really good captain and divemaster pay off.

In that kind of visibility, if the downline is slightly off of the target, it can be impossible to find. Luckily, Chris & Lora are VERY good at what they do. I got to the bottom of the downline and saw the outline of a wing no more than 5 feet away and knew that I was on an airplane.

We had a late start that day due to some business commitments I had and so I didn’t want to rack up a lot of deco. Also, the conditions weren’t very favorable to doing a long deco schedule so I limited my bottom time to about 20-25 minutes and then had about 15 minutes of deco.

The Wreck

When I first got on the wreck, I did a quick survey and thought that maybe it was a Hellcat similar to the plane I dove a few months ago off Laguna Beach. The front of the airplane looked very similar. The Hellcat is on the left and the target is on the right. I noted the “beefy roll bar cage” at the front.

Also, the target I was diving had two rows of radial pistons, similar to the Hellcat.

I took a lot more pictures and we started to analyze them after I got back home from the dive. Given the bad visibility, it was hard to get any good photos but I got enough to do a preliminary analysis.

Identifying a new wreck is usually a two step process. The first step is to identify the type of aircraft and then the second step is to try to identify the specific airplane.

Airplane Type

Identifying the type of aircraft can be tricky business — especially one that was involved in a crash and has been sitting on the bottom of the ocean for 70-80 years. One of the best clues is usually the type of engine.

Engine and Propeller

Below are some pictures of the engine and propeller. The first thing to notice is that the propeller is three blades and that it isn’t bent which means that it was probably not spinning when it crashed. This will be important when we are identifying the specific airplane.

The second key is identifying the number of cylinders and configuration of the engine.

In this case, it obviously is a radial engine with two rows of pistons. If you start counting pistons, it looks like three pistons in any given radii take up a little less than 180 degrees which leads us to deduce that it is 2 rows of 7 pistons — or a 14 cylinder engine.

Given that it is a 14 cylinder radial engine, we can start to narrow it down. It also rules out the airplane as a Hellcat. Other than some initial prototypes, the production Hellcat had an 18 cylinder radial engine.

The engine is likely a Pratt & Whitney R-2600 Twin Cyclone. That engine was used in a number of different aircraft during the 1930s and 1940s. Some of the single engine aircraft that had that engine are:

• Brewster SB2A Buccaneer – Wrong landing gear (more on this later)
• Curtiss SB2C Helldiver – These airplanes had 4 blades on the propeller so we can rule it out
• Grumman F6F Hellcat – This was our first suspicion. The early prototype aircraft had the 14-cylinder engine but it was changed for the more powerful 18-cylinder R-2800 Double Wasp for production.
• Grumman TBF Avenger – We believe this is the airplane type in the wreck we located

There are a few other single engine aircraft that used the R-2600, but not anything that would be considered given the location.

There was another possible aircraft that used a 14 cylinder engine. That was the Douglas TBD Devestator which also happened to have a three bladed propeller. We were excited by this possibility since it is a very, very rare airplane to find with only 129 production models ever built. However, we ruled it out based upon the armament (discussed further below). The Devestator had a single forward facing machine gun that was mounted next to the engine which didn’t match our wreck.

The propeller is also an interesting. While researching information on the oil cooler on the TBF/M (more on that later in the post), I ran across a post about the propellers of the different versions of the Avenger. Below is a screenshot of that post:

If you look at the pictures of the propeller on the wreck, it is definitely an “Elliptical” Propeller belonging to a TBF-1 and NOT a “Paddle-blade” Propeller from a TBM-3.

You are probably asking yourself two questions: (1) What is the difference between the TBM and TBF anyway and a “-1” and a “-3” version? and (2) Why does it matter?

Both are very valid questions.

For the first question, as with most aircraft, there are different versions (or variants). In the case of the Avenger the difference between the “TBF” and the “TBM” is that the “F” was built by Grumman and the “M” was manufactured by General Motors. Both of the dash-1 versions had the 14 cylinder engine. The dash-3 version had the more powerful 18-cylinder R-2600 engine but was only made in production by General Motors so there is only a TBM-3, Therefore, if this is an Avenger, it must be a “-1” version.

As to the second question, that will lead us to the oil coolers.

Oil Cooler

Most airplanes I have seen have one oil cooler. One of the interesting aspects of this wreck site is that I saw two distinct oil coolers. One was on the port side and one was on the starboard.

This raised the obvious question: did the TBF/M-1 have two oil coolers? Did we have a match?

Once again, referring to the post on Tailhook, we learn that the TBF-1 actually had two oil coolers with ducts on either side of the airplane:

Now we have match for the engine, the propeller, and the fact that TBF-1 versions had two oil coolers. You can clearly seem them at the bottom of the diagram on the left below and the starboard side oil cooler (part #150) on the diagram on the right.

Pilot Seat

When I was reviewing the photos from the dive, I noticed an interesting object that was strapped into the bottom back of the pilot’s seat. When checking the cutaway diagrams for the Avenger, it also seems as though there is a match. See the diagram below with part number 94 and the picture I took from the site.

They are from opposite sides of the plane but there is definitely a match with the item in the diagram and the picture.

Armament

One of the first things I noticed on the wreck was the armament on the starboard side wing. It looks like a 50 caliber machine gun.

One of the standard configurations for the Avenger was two wing-mounted 50 caliber M2 Browning machine guns so that would match.

Wing

The port side wing has a big “break” in the wing as soon below. Note that the Avenger was a carrier-based aircraft and had folding wings to reduce the deck space required. This break in the wing is likely where the wing “folded” as seen in the picture on the right.

Also note that the wreck has the control surfaces broken off so you only see the leading edge of the wing. Below is a screenshot of a photogrammetry model from the starboard side wing. You can see the “crease” where the wing folded right by the 50 caliber gun sticking out the back of the wing.

Wheel

I noticed this relatively late in the dive. I swam around the port wing and notice this “bump” below the wing and took a closer look and realized that it was the wheel. You can see where the wheel well is. This also helped rule out the wreck as a Hellcat since that airplane had a very different landing gear design. The photo on the left is looking forward from the back of the wing and the two photos on the right were looking from the front of the wing.

According to Steve Lawson, the tire pattern was changed to a diamond tread design in 1943 and so this would match with our belief that it is an earlier model TBF-1 or TBM-1.

Engine Mount

It was pointed out to me in the post to the forum that the engine mount is also a match between the photos and the cutaway for an Avenger. The picture below was posted to the WW2 Aircraft Forum by “FlyboyJ” and shows the engine mount along with a photo I took during the dive.

Current Aircraft Type Conclusions

Given the following clues, we are relatively sure that the wreck is a “dash-1” version of the TBF/M Avenger:

• 14 Cylinder engine matches
• Dual oil coolers
• Propeller type
• Wheel location on the wing
• Armament
• Pilot seat details

Follow-up dive

Tyler and I went back for a follow-up dive about a week later. Tyler was looking forward to seeing the wreck and we had a few other targets we wanted to look at.

The conditions were about the same as the previous week — 5-10 foot of visibility with a lot of particulate matter in the water. We did some closer inspection for clues and I took a bunch of photos in hopes of building a photogrammetry model but knowing that it would be hard given the conditions.

We were still pretty sure that we had found a TBM/F-1 Avenger but I thought I would check in to get some opinions from some WW II airplane enthusiasts so I posted some photos and questions to the WW2 airplane forum and a lively discussion ensued with the general consensus that it was indeed an Avenger.

https://ww2aircraft.net/forum/threads/identifying-new-ww2-wreck-off-pt-loma-san-diego.58291/

Photogrammetry Model

This was a tough one given the conditions on the dives. I was able to cobble together a few different models but couldn’t get all of the to align. However, they lend a valuable perspective on the wing shape which allowed us to help confirm the airplane type. Below are links to the two different models on Sketchfab.

Airplane Identification

This is the fourth step in any project after finding, diving and identifying the type of airplane. It can also be the hardest given the lack of records from crashes back in that era.

Tyler and I did a lot of research and had 3-4 possible candidates. One them was a mystery wreck mentioned in Pat Macha’s book on San Diego airplane crashes.

Tyler ordered accident reports for a few that seemed likely and then got one that was the proverbial “fits just right” match. Without a tail code or Bureau ID or some specific mark, we can never be 100% sure, but we are very confident we have identified this wreck.

The accident report mentions that it is 4 miles south of Pt Loma which matches the location of the wreck perfectly.

More importantly, it says that it was a “complete loss of power” and the pilot “made a full stall landing.” Remember that the prop wasn’t bent which would indicate it was not turning when it hit the water. Bingo.

Below is a copy of the accident report and some newspaper articles that Tyler found that also describe the accident.

Luckily both crew survived the crash and were rescued shortly thereafter.

Thanks

These projects always involve more that one person. Thanks to Chris and Lora at Marissa Charters. It is always a pleasure to dive with them and they are deadly accurate with down lines and they make deep technical diving safer.

As always, thanks to my partner in exploration, Tyler Stalter. We make an unstoppable team.

References

Wikipedia R-1830 Twin Wasp

Wikipedia R-2600 Twin Cyclone Engine

Tailhook Topics TBF-1 vs TBM-3

Historynet