FREE e-Newsletter
Important News - Hot Topics
Get them Now!
Brian Cain

Brian Cain

Brian Cain is a sergeant with the Holly Springs (Ga.) Police Department, and is known as the "Millennial cop" on Twitter. He has been in law enforcement since 2000. He hosts and produces a podcast for Millennials in law enforcement.



Michael Bostic

Michael Bostic

Mike Bostic, of Raytheon Corp.'s Civil Communication Solutions group, specializes in open architecture, systems integration of communications and data programs. Mike spent 34 years with the LAPD. He managed IT and facility development, as well as the SWAT Board of Inquiry, which developed new command-and-control systems.
Technology

Side-Scan Sonar Identifies N.Y. Crash Evidence

A multi-agency task force generates visual images from sound-pulse data to recover evidence.

September 01, 2009  |  by - Also by this author


The New Jersey State Police dive team recorded and reviewed hours of side-scan sonar data to provide divers with a potential location of the fuselage (middle right) on the river bottom. Photo via FBI.

A multi-agency task force used side-scan sonor to recover critical debris from the fatal mid-air collision of a small plane and a helicopter over the Hudson River earlier this month.

The area of the Hudson where the plane's fuselage entered the water on Aug. 8 represented the most dangerous elements that an evidence recovery diver could face — deep water, shifting currents, zero visibility, and entanglement hazards.

Earlier in the year, they had recovered a lost engine from US Airways' Flight 1549 after its emergency landing in the river after striking a flock of geese.

Side-scan sonar is known as a "towfish" — it's a torpedo-like device towed behind a boat. The towfish converts acoustic sound pulses into a video image of the river bottom. To a trained operator, the resulting image offers a photographic view of the bottom that can be used to identify items interest, according to an FBI release.

Side-scan systems can cover large swaths of water in fairly short periods, typically a square mile per day. They can also provide clarity in zero-visibility conditions when the murkiness of the water makes it impossible for divers to see with their eyes.

Watch a clip of the sonor video, released by the FBI.

The state police team reviewed many hours of side-scan data they gathered after the crash and provided FBI divers with a general location of what looked like the fuselage of a small plane. On Aug. 9, the agency deployed a sector-scan system to verify the target and to identify its location.

Sector-scan sonar also uses sound pulses to create a visual image. The difference between the two systems is that sector-scan sonar is housed in a six-foot-high tripod that is lowered to the river bottom. Once it is stationary, a transducer rotates in a 360-degree path to paint a real-time picture of the immediate surroundings. Since the location of the tripod is known, precise GPS points can be plotted from the surface.

This sonar can also show the position of a diver, who can then be directed to a specific target through underwater communications systems. In this case, the FBI sonar operator located the same object that was scanned by the state police sonar operator and was able to direct a diver — despite a strong current and zero visibility — to the wreckage.

Once the plane was identified, the team turned its efforts to marking the wreckage for recovery. To accomplish this without risking a diver in high current, the sector scan was utilized again. After a dozen or more attempts, we deployed the tripod successfully, and state police divers were able to drag a large weight alongside the plane. They were then able to provide a direct line from the plane to the surface. An Army Corps of Engineers' crane was used to lift the wreckage from the water.

In the end, the multi-agency effort that included the New Jersey State Police and New York Police Department, led to the safe and successful recovery of the wreckage and of the remains of the victims of this tragedy.

Tags: Dive Teams, Sonor, FBI, Crash Sites, Agency Cooperation, Recovery Operations, New Jersey State Police


Be the first to comment on this story





POLICE Magazine does not tolerate comments that include profanity, personal attacks or antisocial behavior (such as "spamming" or "trolling"). This and other inappropriate content or material will be removed. We reserve the right to block any user who violates this, including removing all content posted by that user.

Other Recent Blog Posts

What Went Wrong in Jersey City?
How did there become such a huge rift between the Jersey City police and the people that...
Warrior Tech's SafeCycle Chamber Verification Device
Warrior Tech, LLC took the chamber flag concept and improved upon it greatly. The...

Get Your FREE Trial Issue and Win a Gift! Subscribe Today!
Yes! Please rush me my FREE TRIAL ISSUE of POLICE magazine and FREE Officer Survival Guide with tips and tactics to help me safely get out of 10 different situations.

Just fill in the form to the right and click the button to receive your FREE Trial Issue.

If POLICE does not satisfy you, just write "cancel" on the invoice and send it back. You'll pay nothing, and the FREE issue is yours to keep. If you enjoy POLICE, pay only $25 for a full one-year subscription (12 issues in all). Enjoy a savings of nearly 60% off the cover price!

Offer valid in US only. Outside U.S., click here.
It's easy! Just fill in the form below and click the red button to receive your FREE Trial Issue.
First Name:
Last Name:
Rank:
Agency:
Address:
City:
State:
  
Zip Code:
 
Country:
We respect your privacy. Please let us know if the address provided is your home, as your RANK / AGENCY will not be included on the mailing label.
E-mail Address:

Police Magazine