The U.S. Navy says one big difference is that in 1989 the USS Houston was at periscope depth, running parallel to the surface when its antenna snagged the tow line of the tug boat Barcona and pulled the tug boat underwater. The NTSB said it will at least look at the Houston probe because it is part of the board's standard operating procedure to review previous investigations and recommendations that might have some relevance to the current accident they are investigating. So board members said they would go back and look at the recommendations in the Houston incident and look at the Navy's response to the suggested guidelines. One recommendation was submarines should use active instead of passive sonar during non-combat situations, but the Navy did not believe that was necessary.
Passive sonar listens for sounds of other ships or activity in the water.
Active sonar sends signals in different directions to try to gauge what is out in the water. Submariners will tell you that active sonar is something they prefer not to use because it makes it very easy for they themselves to be detected. And the Greeneville incident may help us examine that question, especially when they have civilians on board on a public relations cruise in peaceful waters and while conducting such a noisy exercise. Pages will open in a new browser window External sites are not endorsed by CNN Interactive. An AOL Time Warner Company.