EPIRB - Real-world testing - Soundings Online

EPIRB - Real-world testing

Author:
Publish date:

Some McMurdo units didn’t acquire a GPS fix in independent tests

Some McMurdo units didn’t acquire a GPS fix in independent tests

McMurdo Ltd. is offering upgrades of some of its EPIRB and PLB emergency signaling devices after field trials by an independent testing organization showed the McMurdo beacons routinely failed to acquire a GPS fix under “real-world” conditions.

McMurdo of Plymouth, England, says it will offer free factory software upgrades of both the GPS and processor firmware in its Precision 406 MHz GPS EPIRBs and Fastfind Plus 406 MHz personal location beacon. This should enable the beacons to operate more efficiently and acquire a GPS location fix more quickly, says McMurdo marketing director Kevin Robertson.

He says McMurdo planned to contact consumers directly by mail in late May and early June to offer the upgrades.

The offer is to owners of the SOS Precision 406 GPS EPIRB (Cat II), SOS Precision 406 GPS EPIRB (Cat I), G4 406 GPS EPIRB (Cat II), G4 406 GPS EPIRB (Cat I), Sailor 406 MHz Satellite GPS EPIRB, and Fastfind Plus personal location beacon with built-in GPS. Robertson says affected units number in the thousands. McMurdo owners with questions can call (800) 783-0889.

In recent trials the Equipped To Survive Foundation, a Chandler, Ariz., testing group, questioned whether the McMurdo devices reliably acquire a GPS location fix under real-world conditions so rescuers know right away where the distress signal is coming from.

Robertson says McMurdo still stands by the beacons, their compliance with international standards, and their ability to send a 406 MHz distress alert within three minutes to geostationary satellites, which

retransmit the distress signal to rescue authorities.

McMurdo’s Precision and Fastfind Plus products use integral GPS technology to fix the location of the user when the EPIRB or PLB is activated, and send that location with the distress signal. If the device’s GPS fails to fix a location, it goes ahead and sends the distress alert anyway, minus that information. Rescuers still can find the device using Doppler effect measurements from two polar-orbiting satellites, but that can take 45 to 90 minutes longer, and the location is accurate to 2 to 5 kilometers compared to 100 meters with a GPS fix.

Doug Ritter, executive director of ETS, says that is unacceptable for a device that is supposed to provide a GPS location in the initial distress signal.

“[Our] tests revealed that purchasers of these GPS-equipped 406 MHz beacons — who paid a premium for the added GPS technology in the hopes of potentially shortening rescue response with faster location information and increased location precision — are apparently not getting what they paid for and are operating under false expectations,” Ritter says in a summary of his findings, available at www.

equipped.org. The tests were funded by the BoatU.S. Foundation for Boating Safety and Clean Water and retail giant West Marine, along with ETS, which acted as an independent testing agency. As a result of the study, West Marine has offered a full refund or exchange on the McMurdo devices.

Responding to the report, McMurdo — which with ACR is one of the top two manufacturers of GPS EPIRBs and PLBs for U.S. boaters — said it would commission independent tests of the devices to verify or refute Ritter’s findings. The company also says it hoped to analyze the beacons tested by ETS. “We don’t understand the results,” says McMurdo’s Robertson. “They don’t measure up against the results we’ve had anyplace else by anyone else. We just don’t understand what’s happened.”

Meanwhile, before upgrading any beacons now in customers’ hands, McMurdo plans to test units with the new software, with expert Peter Forey as an independent witness, Robertson says. That software will carry updated information on satellite locations and new logarithms.

“We are very confident these enhancements will bring benefits to the end user,” Robertson says.

ETS’s Ritter says he “feels obligated” to conduct his own tests of the upgraded McMurdo beacons. Ritter says his test findings shouldn’t be interpreted as an “indictment” of the COSPAS-SARSAT satellite distress system or 406 MHz distress beacons in general. “This system has proven to be an extremely reliable and effective means of distress alerting that has saved thousands of lives worldwide since its inception, ” he says. The tests raise concerns only about the GPS position fixing capabilities of some models.

Call for stricter testing

McMurdo says all its beacons are tested for GPS lock before they leave the factory, and they comply fully with international standards. Under U.S. law a Coast Guard-certified test lab has certified that the units meet those standards. Ritter is calling for immediate tightening of standards and for a testing protocol that subjects the beacons to conditions more nearly like those encountered in a distress situation.

“I would like to see somebody — some government organization or the industry — develop some kind of practical test standards to give consumers a way to decide how well they perform,” Ritter told reporters in a conference call in April, when the report was released.

McMurdo — and Ritter, too — stresses that the beacons that fail to acquire a GPS fix still work and still provide a location to rescuers, just not as fast or as accurately as with the GPS fix. Rescuers receive the location of an EPIRB or PLB in either of two ways. If the beacon acquires a GPS fix using a low-orbiting geostationary satellite, rescuers can have in hand a vessel’s location accurate to 100 meters in under three minutes. If it doesn’t get a GPS fix, the beacon still can transmit a distress signal to the geostationary satellite in under three minutes without a position. It then transmits a signal to low-orbiting satellites that compute the location using Doppler effect and triangulation, but this can take up to 90 minutes while the satellites pass overhead. The location is accurate to 3 kilometers.

All 406 MHz distress beacons also emit a 121.5 MHz homing signal that guides rescuers to the device’s exact location.

“The report did find that all of the tested beacons successfully allowed a Doppler location to be derived — a minimal acceptable level of distress alerting,” according to a summary of findings from BoatU.S.

CG discovered problems

Ritter decided to test the distress beacons with the GPS feature after the Coast Guard undertook tests in March 2003 off Key West, Fla., to find out why 66 percent of all actual alerts from GPS-enabled beacons (mostly EPIRBs) didn’t include the GPS-derived location coordinates. Lt. Cmdr. Jay Dell, the Coast Guard’s liaison for SARSAT — the U.S.-operated part of the worldwide COSPAS-SARSAT satellite-based rescue system — says that in those tests a “significant percentage” of beacons failed to send a valid GPS-derived position when activated. He says one manufacturer’s beacon (McMurdo) had significantly greater problems than the others.

McMurdo’s Robertson says the company didn’t find the Coast Guard findings alarming. “We succeeded in 70 percent of the tests that were carried out,” he says. “The ones we couldn’t get a lock-in were explainable.” The unit either was trapped under a life raft, or was transmitting from under dense foliage or from under the canopy of the raft. “We were perfectly satisfied with the results attained,” he says.

Dell says bad weather or rough seas clearly affect the beacons’ ability to fix a GPS location. “In terms of the ability to get a GPS position or fix with a satellite, any beacon in rough sea conditions that is moving around quite a bit is going to have a very difficult time getting an initial GPS position or lock,” he says. However, he says the 8-foot swells that seemed to stymie the McMurdo beacons in Ritter’s tests hardly qualify as “rough.” He says those seas are normal in the Pacific.

Beacon changes possible

Dell said COSPAS-SARSAT, the organization that governs satellite rescue programs worldwide, likely will take notice of Ritter’s findings. “I think what we’re going to see over the next several months is that all the parties will be taking a close look at these test results and the [beacon] standards,” he says. “There may be some higher standards we could be setting for sale and use of these beacons worldwide.”

Dell says consumers should expect that if they buy a GPS-based EPIRB the GPS feature will work more consistently in adverse conditions.

In defense of McMurdo, a longtime player in the distress beacon business, Dell says all Coast Guard personnel carry McMurdo PLBs on their life jackets, though without the GPS feature. “Every one of the manufacturers that works in this program has worked very hard to build products that can be used,” Dell says. All beacons on the market today are approved to international performance standards and are tested in a controlled environment. Dell says the standards may have to be tightened to be sure the beacons work in tougher conditions.