Taking the "Search" Out of "Search-and-Rescue"

The new generation of 406 MHz Personal Locator Beacons

After years of bureaucratic delay, the FCC has finally approved the use of 406 MHz PLBs in the United States starting July 1, 2003. For less than $600, you can now carry technology in your flight bag or survival kit that will alert Search-and-Rescue agencies of your identity and exact location within five minutes. These new PLBs provide protection not just for flying, but also all sorts of other outdoor activities.

by Brent Blue, MD (brent.blue@aeromedix.com)

COSPAS-SARSAT 406 MHz PLB Search and Rescue System
The digital distress signal from a 406 MHz PLB is received by one of ten COSPAS-SARSAT satellites, and then relayed via a local ground station (LUT) to the Mission Control Center (MCC) and then to the nearest Rescue Coordination Center (RCC).



You can carry a PLB in your flight case or survival kit while flying, then take it with you for protection during all sorts of other outdoor activities.


Since I wrote this article, I did have an accident in my Flaglor.  We aborted a take off from a grass strip in the middle of Jackson Hole.  We hit a fence at the end of the strip and flipped over it into a three foot deep stream.  My passenger and I were upside down underwater.  Fortunately we were able to extricate ourselves and not hurt.  We were stuck holding on to the aircraft in the strong current and were lucky there was another plane behind us because even though we were near civilization, no one was near by to haul our freezing butts out of the water.  The cell phones we had were toast due to the water.

As I held on to that plane, I remember that I took off from that same field the year before without anyone else around.  If it had happened last year and I had been hurt, the only help I would have had was my 406 beacon. 

Think again if you think it can’t happen to you.

I was ferrying my antique open-cockpit biplane -- a rare Flaglor High Tow -- from my home base in Driggs, Idaho (just west of Jackson Hole) to the maintenance shop at Idaho Falls. That's about 45 nautical miles, which doesn't sound like much unless you're flying an open-cockpit airplane for a half-hour in sub-freezing 6 a.m. temperatures.

I started to think about what I'd do if the engine quit.

The terrain below was rugged and sparse. There's not much civilization between Driggs and Idaho Falls, and the cellular coverage is spotty at best. If I had to make a forced landing, how long would it take before someone found me?
I silently chastised myself for being in too much of a hurry to file a VFR flight plan. It sure would be reassuring, I thought, if I had one of the new 406-MHz Personal Locator Beacons (PLBs) with me.

Now I'm not a pessimist by nature, but I have had five engine failures over past 14 years with one leading to a short-of-the-runway landing in Green Bay, Wisconsin. Even though Green Bay is a large airport, the tower was closed and nobody realized I'd gone down. It was a good thing that the crash site was in an area of good cellular telephone coverage, because I had to notify local authorities via cell phone that our current location was 30 feet short of the runway threshold. By the time all the telephone calls were made by the local "authorities," it was a half hour before the first rescue vehicle arrived.

That's why I was first in line to carry one of the new GPS-augmented PLBs as soon as they are approved or land-based use in the United States on July 1, 2003. In fact, I've already got one on order. Once it arrives, I don't plan to leave home without it. The new 406-MHz PLBs are small, economical, and amazing. One prominent expert on search and rescue remarked recently that they "take the search out of search and rescue."

Not your father's ELT
For decades, our aircraft have been required by government mandate to carry an Emergency Locator Transmitter (ELT) that transmits on the civilian 121.5 MHz and military 243.0 MHz emergency frequencies. Pilots and rescuers have both become pretty soured on these ELTs because they have been the source of thousands of false alarms and precious few actual "saves" to their credit, not to mention being a source of mounds of paperwork and maintenance cost. Most aircraft owners would pitch them in a flash -- and will be permitted do just that in 2006 when the satellite system that monitors those two frequencies is scheduled to be phased out.
While ELTs are known for their uselessness, 406 MHz PLBs offer a huge technological advance. I predict their small size, economical prices and advanced functionality will make them a must-have item for most pilots to carry in their flight bag or survival kit, as well as when camping, snowmobiling, cross-country skiing, and the like.

One of the primary differences between ELTs and these new PLBs is that the 406 MHz units are digital. They don't just send out the familiar anonymous "whoop whoop whoop" signal, but transmit a digital data stream that includes the unique unit identifier of your particular PLB. If your PLB is equipped with optional GPS capability, your precise GPS position is also transmitted digitally. This information is received by an orbiting satellite and digitally downlinked to a ground receiving station called a Local User Terminal (LUT). If the LUT is not in range of the satellite when it receives the PLB transmission, it can store the information and forward it to the LUT as soon as it does come into range.

This is significantly different than the analog 121.5/243.0 MHz ELTs. For those, the receiving satellite must simultaneously have the ELT beacon and ground relaying station in range, because the satellite cannot store any analog information.
When the digital information from a 406 MHz PLB reaches the Mission Control Center (MCC), the unique identifier is looked up in a master database and the name, address and contact information for the PLB's owner pops up on a computer screen in the MCC. The MCC will then call the registered emergency contact to find out where the owner is, what he/she is doing, and whether the signal is due to a genuine emergency or a false alarm. The instant ability to identify the PLB owner provides a dramatic improvement to the staggering false-alarm problem that exists with analog ELTs. It is estimated that there are 1,000 false ELTs alarms for each genuine emergency activation. So far, experience with the new 406 MHz beacons averages just eight false alarms for each true emergency.
Another dramatic difference is the accuracy of location. Satellite location of 121.5/243.0 ELTs is accurate only within a radius of approximately 12 nautical miles, identifying a search area of 452 square miles, and on average it takes six hours for search-and-rescue centers to be notified of the beacon coordinates. Compare this to the new 406 MHz PLBs that can be located to within a radius of two nautical miles, identifying a search area of just 12.5 square miles, and an S&R notification time of one hour. Add the optional GPS capability to the PLB and the location radius becomes 0.05 nautical miles, a search area of 0.008 square miles, and five-minute notification time!

Think about the significance of those numbers if you are the one being rescued and the outside temperature is below freezing!

In addition to the 406 MHz digital signal, all PLB units also transmit on 121.5 MHz so that rescuers can use their current equipment to home in on a beacon on the ground.

Eyes in the sky
All locating beacons utilize the National Oceanic and Atmospheric Administration (NOAA) satellites that carry payloads supplied by Canada and France called Search and Rescue Satellite Aided Tracking (SARSAT) systems. Russia operates similar satellites known as COSPAS. A few years ago, all the countries involved established a cooperative rescue effort known as COSPAS-SARSAT. The low-earth-orbit COSPAS-SARSAT satellites have recently been joined in the rescue monitoring by high-orbit geosynchronous GEOSAR satellites and its global network of ground receiving stations.

The SARSAT satellites circle the earth every 102 minutes while the Russian COSPAS satellites circle every 105 minutes. They view a circular area of the earth of about 2,500 miles at any one time each. Because they pass the poles on every orbit, coverage is most frequent at the poles and least frequent at the equator but coverage is global. Average time for a 406 MHz transmission location in the mid latitudes is 30-45 minutes (without GPS input). Now that's technology.

The GEOSAR satellites are geostationary and can receive the 406 beacon and recognize its identity, but cannot help with actual location because they have no relative motion to earth which is required for the Doppler shift technology used for position location. The ground station can try and locate the registered owner of the PLB and activate S&R groups while the orbiting satellites establish a position fix. If the PLB has GPS capability, however, the GEOSAR can relay the GPS supplied position immediately.
You can bet I'll be carrying a GPS-enhanced PLB just as soon as the July 1 release date arrives!

What was the delay?
This 406 MHz digital technology has been in use for quite some time in marine applications, but terrestrial use of this technology has been forbidden until 2003.

Why? Bureaucratic bungling.

To quote survival guru Doug Ritter of Equipped to Survive®  (www.equipped.org), "it's been an uphill battle against bureaucracies that haven't given a damn about the lives lost by their inaction…the U.S. Air Force and the FCC deserve credit for the dubious distinction of holding up PLB approval…" Apparently, the U.S. Air Force had fears of too many false alarms (apparently not understanding that the new technology offers a dramatic reduction in false activations) and didn't feel saving civilian lives was part of the USAF mission. Who knows what splinter the FCC had up their butt.

Although there are several manufacturers of 406 MHz marine Emergency Position Indication Radio Beacons (called EPIRBs just to confuse you), only two of them have gone to 406 MHz PLBs: ACR Electronics and McMurdo. Other manufacturers expected to enter the PLB market later on include NAT, Kannad, and Microwave Monolithics.

(The primary difference between a marine EPIRB and a terrestrial PLB is battery size: The larger marine unit is required to operate at -40º C for 48 hours while the pocket-sized PLB only has to function for 24 hours at -40º C. These times are extended considerably at warmer temperatures.)

PLBs from ACR and McMurdo
ACR MicroFix PLBI have evaluated five PLB models, three from ACR Electronics and two from McMurdo. Two from ACR and one from McMurdo have internal GPS while each company has one without internal GPS. (I am not sure why anyone would not want the GPS version given it is only about $100 more.  If you need help, why not tell people where you are to the tree stump you are sitting on instead of a three mile circle?)

My hands-down favorite is the "Microfix" from ACR (pictured at right), because it's the the smallest with a built in GPS.  This is one I carry when I mountain bike, backcountry ski, and other non aviation activities.

In the aircraft, I carry a McMurdo “FastFind”mainly because this was the first unit out with an internal GPS.  It is larger so I relegated it to aircraft only when the Microfix came out.
Both units have tested well and fully self contained.  Both operate with simple off on switches and are rugged and waterproof.  Both have simple to deploy antenna and self test features.

Although these prices are more than 121.5 MHz ELTs, keep in mind that a 406 MHz PLB is very likely to get you rescued in time to do some good, whereas the same can't be said for a 121.5 MHz ELT. (Remember that a PLB does not replace an ELT.  The PLB does not automatically activate with a G switch nor is an FAA approved replacement.  It just gets you rescued while an ELT helps find your body.)  A 406 MHz PLB is also portable and self-contained, so you can carry on your person -- not only when flying, but also during any remote area activity such as snowmobiling, backcountry skiing and hiking, canoeing, and climbing.  This also means if you have to move from the crash site, the rescuers will know where you have gone.

Some outdoors enthusiasts now carry satellite phones, but they are quite expensive, comparatively fragile, and do not have a shock-resistant or waterproof case like a PLB. Unlike a satellite phone, carrying a PLB involves no cost for registration or monthly subscription fees.

Now, I leave one at the airport to use in the aircraft and one I keep in my backpack for the car and the backcountry.  And I hope I never need to use one!