Revisiting the TBM Avenger: A Deep-Wreck Photogrammetry Project

Intro / Background

A TBM Avenger lies at a depth of approximately 250 feet near the Point Loma Outfall pipe. The wreck was discovered years ago and has gradually deteriorated over time. Before the fuselage collapsed, Tyler cleared away dirt and debris and identified the Bureau Number as 53439.

This wreck has been particularly challenging for me. My first attempt was aborted because of strong surface currents. A few weeks later, Justin and I reached the wreck and I captured several useful images, but not the systematic photo set needed for a strong photogrammetry model. I returned a couple of years later to work on the site with Lauren, but adverse current again prevented meaningful progress.

Because I had long wanted to produce a strong photogrammetry model of the wreck, I returned recently with the specific goal of collecting a better image set. The site may ultimately be featured in the book, so improving the visual documentation was a priority.

The Dive

I completed the dive alone. Finding a partner for a deep dive on short notice during the workweek can be difficult. Even so, this wreck continues to carry a distinct atmosphere, and this dive was no exception.

The wreck sits in an area of extremely fine silt and sand, so careful finning is essential to avoid creating a significant silt-out.

Conditions were favorable, with almost no current at the surface or on the wreck. I spent approximately 18 minutes on the bottom, completed about 80 minutes of decompression, and finished with a total runtime of 1 hour 43 minutes. Visibility was good, and the dive itself was uneventful.

For those interested in the dive profile, I used a 10/52 diluent. A slightly higher helium fraction may have been preferable, but the mix was adequate for the dive. Bottom temperature was 51°F, while the shallower decompression stops ranged from 65°F to 67°F.

One notable observation was the absence of the large white metridiums that I usually see around the cockpit area. On this dive, none were present. I am not sure whether that difference was seasonal, temperature-related, or caused by another environmental facto

Photogrammetry Model

I captured approximately 860 photographs, of which about 820 were incorporated into the model. Several images takennear the end of the dive, out in the sand near the wingtip, did not align successfully. One particularly interesting detail is the presence of what appears to be lettering or numbering near the point where the starboard wing disappears beneath the silt and sand.

Below are screen captures of the model, along with a link to the online version.

The model is at the link below:

Model Evolution

As a useful comparison, I wanted to show the different versions of the model to illustrate how time and experience can improve the final result.

Next Steps

I do not plan to spend much more time refining the model itself, but two follow-up tasks remain.

First, I would like to return with a scrub brush to uncover more of the lettering or numbers on the starboard wing; this is a lower priority, but it could still be worthwhile. 

More importantly, we believe we know the location of the engine and additional debris fields, and I would like to return for exploratory dives to confirm that assessment.