November 15, 1999
Web posted at: 4:00 p.m. EDT

(CNN) -- Brendan Murphy, former US Navy Diver, joined the CNN.com chat room on February 01, 2000, to discuss the search and recovery efforts of Alaska Airlines flight 261.

Murphy joined the chat by telephone from CNN's Los Angeles bureau and CNN.com provided a typist. The following is an edited transcript of the chat.

Chat Moderator: Thank you for joining us today Brendan Murphy and welcome to chat.

Brendan Murphy: Hi chatters!

Chat Moderator: Please tell us a little bit about your background.

Brendan Murphy: I was in the navy for 20 years, 18 1/2 as a salvage diver, and the last seven years as a master diver, which is the senior supervisory in management position for diving and salvage operations.

Question from Maia: There have been questions about the control of the airplane and specifically horizontal and vertical stabilizers. With a crash like this into the ocean, how much of the plane will be intact?

Brendan Murphy: I don't know anything about the aircraft controllers. However, I've never been on a salvage operation where any of the aircraft was remotely intact.

Question from Hooyah: What kind of salvage operations have you worked on prior to this

Brendan Murphy: I was one of the master divers for the TWA flight 800 salvage. I was also an advisor to the Canadian govt. for the Swissair 111 salvage. And of course I was a consultant to CNN for the JFK crash and Egypt Air. Besides that I've done numerous military aircraft salvages.

Question from Maia: How long do dives like this stay in your mind?

Brendan Murphy: Oh, well it stays with me all the time. I can remember the details of the dives I made or supervised even today. I don't mean in a negative sense. A lot of professional lessons were learned that I can take into future projects.

Question from Maia: How do you coordinate to find something such as the "black box" with?

Chat Moderator: The equipment and people tracking the "pinging,"… the first thing that will happen is vessels will be used to tell pinger locators. This is a device that is towed behind a vessel and it picks up the pinging from the black box. And is able to give a position of where the ping is coming from. From that point, depending on the depth of the water, and weather conditions, either divers or remotely operated vehicles will be sent to recover the black box.

Chat Moderator: What dangers are their in a recovery such as this?

Brendan Murphy: You have the ever present environmental dangers which include the depth of the water, ocean currents, possibly marine life. Then you have the non-environmental factors such as sharp wreckage, entanglement, and the possibility of some sort of diving related disorder such as the bends.

Question from Hooyah: Were you ever a dive school instructor, and wouldn't this information and experience be a good thing to teach dive school students. When I was in it was mostly ship salvage that was taught

Brendan Murphy: Yes, recently the Navy has been called upon to work or support the NTSB (National Transportation Safety Board) on large commercial national and international aircraft recovery operations. This being the case, it would be beneficial to add a module of training for supervisory level divers dealing with the planning and execution of commercial aircraft salvage operations.

Question from SusieSouth: What is the temperature of the water?

Brendan Murphy: I don't know. The temperature I've heard is 58 degrees on the surface.

Question from LJNoel: How deep is the water where the plane went down?

Brendan Murphy: I've heard 450 feet of depth. I don't know if that is accurate. But I do know from diving off the coast of Southern California that the water is pretty chilly in that specific area. I'd hazard a guess that the bottom water temperature is in the 40s.

Question from Maia: What are the priorities on this type of dive? Survivors and then… what?

Brendan Murphy: The priorities are established by the NTSB. Every job is different and they establish the priorities.

Question from sm: How long does a diver typically stay down for at one time?

Brendan Murphy: The length of time a diver can stay on the bottom is a factor of depth and time. The deeper you are, the less time you can stay on the bottom without incurring significant decompression requirements. For example, TWA flight 800, the average depth was 120 ft and the divers there were able to stay on the bottom for up to 90 minutes. (These are hard hat surface supplied divers, not scuba divers).

In Swissair 111, the average depth was between 180 and 190 ft, and the divers could only stay approximately 40 minutes without a lot of decompression. And in Egypt Air it was determined that the depth of 250+ ft would not enable the divers enough time on the bottom to be efficiently used. Most time they could spend would be probably 25 to 30 minutes

Question from uct1: Were you with a MUSU unit, EOD or UCT?

Brendan Murphy: I was on various salvage ships and also stationed at the mobile diving and salvage unit 2 in Little Creek Va.

Question from sm: When does this become an effort for ROVs instead of divers?

Brendan Murphy: ROV is a remotely operated vehicle. Basically a robot with a long cable running to the surface that controls it. The Navy owns a number of these. They are used predominately in situations where it would be unsafe or inefficient to use divers. In this case, if the water is what I've heard 450 ft deep, ROVs will be used for the entire project. The limit for divers using conventional diving techniques is 300 ft.

Question from LJNoel: Is the water clear?

Brendan Murphy: Visibility is always an issue. When using ROVs however, they have very sensitive sonar systems, which enable them to be used in low visibility situations. I'm not familiar with the clarity of the water where the crash occurred

Question from pinky: How much can you tell about the situation of the crash from the remains?

Brendan Murphy: I'm not an expert on this. However from my own reading and viewing of programs related to aircraft crashes, it seems that the NTSB has been able to determine quite a bit from recovered wreckage. An example is the reconstruction of TWA flight 800 from the recovered wreckage.

Question from MrPumpernickel: I've heard about recent breakthroughs in ROV-technology, with vessels that can weld through 2" of titanium. Any comment on that?

Brendan Murphy: There have been a lot of technological advances. Some include video quality sonar images. Others include extremely accurate positioning devices. And also the tooling available to be used by ROV manipulator arms has become very sophisticated.

Chat Moderator: How long does the recovery process usually last?

Brendan Murphy: That depends on the recovery.

Chat Moderator: What are biggest obstacles in a recovery mission

Brendan Murphy: The first is defining the debris field. That merely means locating the wreckage and determining how much it is spread out. Once that is completed, the recovery process can be hampered by depth of the water, weather, and some of the other variables I previously discussed.

Chat Moderator: What is the likelihood that the submerged plane is still

Brendan Murphy: Zero. The reasons are obvious. An aircraft going at a rapid rate of speed plummeting from 17,000 feet nose first into the ocean completely destroys it. To reiterate, I've never come upon an aircraft that has crashed in the water that even remotely resembles the aircraft prior to hitting the water.

Question from Four17: Why is it that after a few months, these tragedies are soon forgotten as to the possible causes, i.e. Swissair, Egyptian Airlines, etc.?

Brendan Murphy: My opinion, I think people don't like dwelling on tragedies such as this because aircraft flight is such an important and used means of transportation for all of us. Reminders of the small, however inherent dangers of flight are not something to dwell on.

Question from Octavio: Which is the motivation to make a job like this?

Brendan Murphy: It is a job. As a Navy salvage diver, I was initially trained to work on ships and recover vessels. The aircraft recovery, though I have been in the limelight in the past, has only been a small percentage of the diving projects completed by Navy divers.

Chat Moderator: Do you have any final observations you want to share with us?

Brendan Murphy: Only that as we have seen with TWA flight 800, Swissair 111, Egypt Air, the JFK crash, the salvage operations have become progressively more dependent on technology.

Chat Moderator: Thank you for chatting with us today!

Brendan Murphy: It has been a pleasure.