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Extreme Search

by Col. William J. Moran, Jr., USAF (Ret.), Daedalian Member #9091


Civil Air Patrol C-182T NAV III

The Call

Under the National Search and Rescue (SAR) Plan, the United States Air Force provides resources for over-land SAR.  Those resources are Civil Air Patrol (CAP) personnel and 550 high wing Cessna aircraft stationed across the country flown by CAP volunteers. 

Air Force Rescue Coordination Center (AFRCC) called me at 2100 hours local on Sunday, 15 February 2015 because New Hampshire Fish and Game (F&G) was requesting New Hampshire CAP search and rescue assets under the Memorandum of Understanding between AFRCC and NH F&G.  A 32-year-old female hiker was missing in the Presidential Range of the White Mountains.


Search Area, Presidential Range, New Hampshire

As the on-call incident commander (IC), I agreed we could provide air assets but not ground assets. As I looked out my window toward snow- covered Mt. Washington forty miles north of my house, I already knew we did not have ground assets qualified to enter such weather. A Nor’easter had barreled through, and Sunday was one of those hundred-plus days a year when the winds would exceed hurricane strength at the top of the White Mountains. 

I called my contact at NH F&G, with whom I had built a good relationship when I was New Hampshire CAP wing commander. He said to call at 0900 hours Monday morning, and he would then make the decision to fly. NH F&G’s first call is always to the New Hampshire Army National Guard UH-60 helicopters out of Concord, NH. For pickup, they are the best – but very expensive – asset. However, they do not have emergency locator beacon directional finder equipment. As such, for search purposes CAP is the most economical, at less than $150/hour.

My CAP unit was the closest airport to the search area. I arranged for another IC to take over while I lined up a crew for Monday morning. At takeoff time we had one set of coordinates somewhere in the vicinity of Star Lake – really a small pond – in the saddle between Mt. Madison (5,367ft) and Mt. Adams (5,774ft), approximately four miles north of Mt. Washington.

At an elevation of 6,288 feet, Mt. Washington is the highest mountain in the northeast, situated in the Presidential Range and White Mountain National Forest. Roughly 75% of the storms that trek through the United States pass over the Presidential Range. The Mt. Washington Observatory, located atop the mountain, has been recording weather observations since 1870 and the highest wind ever recorded in the Northern Hemisphere, two hundred thirty-one miles per hour, was observed in 1934. The Mount Washington Observatory routinely publishes an Aviation Meteorological Aerodrome Report (METAR) using KMWN as the identifier. In the northeast, most local aviators look at this report before flying.

Background

Search and Rescue (SAR) instruments are flown on low earth polar orbiting (LEO), medium earth orbiting (MEO) and geostationary earth orbiting (GEO) satellites provided by the U.S., Russian Federation, India and the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT). These instruments are capable of detecting signals coming from the Earth’s surface transmitted by emergency beacons.

More than 695,000 406 MHz emergency distress beacons are registered with National Oceanic and Atmospheric Administration (NOAA). The different types of distress beacons are the Emergency Locator Transmitters (ELT) for aircraft, Personal Locator Beacons (PLB) for personal use, and Emergency Position Indicating Radio Beacon (EPIRB) for boats. Of these registered beacons, 293,000 are PLBs including 20,000 registered in 2020 alone.  I call the new PLBs aviation technology in the hiker’s backpack.

406MHz emergency distress beacons send a data burst to the SAR satellites (SARSAT) which includes the owner’s registration data.  If equipped, some beacons transmit a 406 MHz data burst signal that includes encoded GPS coordinates. Some environmental factors such as orientation, cover and physical obstructions can prevent beacons from receiving a GPS satellite fix.  A five-watt 406 data burst can be detected and processed by geostationary satellites (GEOS), by low earth orbit satellite (LEOS) using a Doppler-shift locating technique, and medium earth orbit satellites (MEOS, using a method similar to triangulation).  Although all 406 MHz beacons must be registered with the NOAA every two years, many are not registered.

An activated beacon’s data/coordinates are received through NOAA’s Search and Rescue Satellite Aided Tracking (SARSAT) and automatically forwarded to AFRCC. The United States Air Force is responsible for coordinating inland SAR in the United States. USAF defers to local state agencies but provides CAP resources for ground and air search.  Most CAP aircraft have emergency beacon directional finding equipment.

In New Hampshire, NH F&G is responsible, by law, for missing persons. Through the AFRCC and NH F&G Memorandum of Understanding, New Hampshire Fish and Game can request CAP air assets that are specifically equipped to track and find all emergency locator beacons.

406 MHz beacons also transmit a low-power 121.5 MHz signal intended for close-range locating/homing.  Current CAP directional finder equipment, RT600, can receive all 18 406 MHz frequencies/channels as well as the low-power 121.5 MHz signal.

These direction-finding signals should not be confused with satellite messaging systems such as the Delorme in Reach, SPOT and SPIDER, which drop GPS bread-crumb trails through two-way satellite text messaging. These commercial products are not tied into the SARSAT system, nor do they transmit direction finding signals.

PLB Function

When a PLB unit is activated, the GPS receiver turns on, searches to find satellites to develop coordinates, and incorporates the coordinates into the 406 MHz signal data burst transmission. As soon as the GPS receiver acquires valid positioning data, the red flashing light is replaced by a green flashing light once every three seconds. The same GPS data is sent with each 406 MHz signal for the next thirty minutes.

After thirty minutes the internal GPS starts up again and repeats the process of finding the coordinates to incorporate into the next data burst. If the internal GPS cannot update coordinates, it will use the previous position for the next four hours. The green LED stops blinking and the red LED flashes every three seconds until new GPS data is obtained.

Signal Accuracy vs. Reliability

Reliability of the PLB signal depends upon the proper deployment of the beacon and its location, such as terrain and obstructions, in reference to the satellite. Beacon location and orientation may cause signal propagation and degrade both reliability and accuracy. The GEOS in this area is located over the equator at seventy-five degrees longitude, and likely cannot see a beacon on the north side of a ridge.

The 406 MHz beacon system considers the Doppler-shift signal – a change in frequency due to the Doppler effect – received by LEOS to be more reliable and the primary signal, mostly because many PLBs are not equipped with GPS and do not transmit an encoded data-burst.

When a GPS beacon is properly deployed, with a good line of sight to both the GPS and GEOS/LEOS satellites, the position is considered to be highly accurate.

Mt. Madison Weather

The winds Sunday night at the observatory gusted over one hundred forty MPH and the temperature with wind chill was minus eighty-eight degrees (F). At 0500 hours on Monday our NH F&G contact called and requested NH CAP assistance as part of the search.  When my crew arrived at the Laconia Municipal Airport (KLCI) hangar Monday morning, the temperature with wind chill was still well below zero at the airfield elevation of five hundred forty-five feet mean sea level. After shoveling out the snow drift in front of the hangar doors, a hair dryer was needed to thaw a fuel sump. The winds were gusting out of the west. Luckily, the runway is orientated to the west. As we taxied to the runway, the airfield looked like a frozen tundra with blowing snow. We already knew the KMWN METAR was reporting winds out of the northwest at one hundred MPH, gusting to one hundred ten.

To determine how high we would climb I added half the elevation of Mt. Washington (three thousand feet) to the Mount Madison elevation (five thousand three hundred sixty-seven ft) and then I added another one thousand feet for a risk buffer (or for “good luck”).

The best altitude for a directional finder search is one thousand feet above the ground. There is no way to fly this at six thousand four hundred feet, with a six thousand three-hundred-foot mountain to the south and a five thousand seven-hundred-foot mountain directly west, and winds over hurricane strength.  We would conduct our search at ten thousand five hundred feet.

Missing Person

The thirty-two-year-old female hiker started her journey Sunday morning. She intended to traverse several mountain peaks along the Appalachian Trail: Mt. Madison, Mt. Adams, Mt. Jefferson and Mt. Washington, and then descend down the Mt. Washington Cog Railroad. Post Nor’easter winds were already gusting near hurricane strength when she set off.

At approximately 1500 hours on Sunday the hiker activated the 406 MHz Personal Locator Beacon (PLB) she carried in her pack.  Her husband said if she activated her PLB, she was in real trouble.  At that time the Observatory temperature was -17F with a sustained eighty-four MPH wind.

The Search

Once airborne, we loaded the initial coordinates into the GPS and followed them north some forty miles. We then picked up the 406 MHz signal on our directional finder which was in agreement with our northerly heading. Shortly thereafter, we picked up a very strong 121.5 MHz homing signal on our secondary very high frequency radio. We put that homing signal frequency into the directional finder and tracked it to near Mt. Madison.

Our groundspeed varied from thirty to two hundred thirty knots as we performed airborne direction finding (DF) on the 121.5 homing signal. We lost one thousand five hundred feet in downdrafts and climbed three thousand feet in the updrafts as we tracked the beacon from different headings. Altitude above the ground and winds made homing in on the beacon very difficult. A one-thousand-foot horizontal error in our estimate of the hiker’s location could have meant a two-thousand-foot vertical difference.

As it turned out, our estimate of the hiker’s location was south of where she was located. Her PLB was inside her backpack and due to antenna orientation, this caused signal propagation errors. We started the record mode of our iPad ForeFlight aviation app and recorded all our tracks.

We overflew her location four times but because of limited ground visibility we could not see her location. Below us, a major ground blizzard was raging. An NH F&G conservation officer – who is also a CAP pilot – heard us from the ground but could not see us. After noon on Monday, a SAR team found the hiker.  She died from exposure and hypothermia, near the trail.

Snow-covered Presidential Range on The Day of the Search

Understanding Data

Over the twenty-one hours of the search and rescue mission, AFRCC received thirty-five coordinate fixes. Eight GPS fixes were in one location and four more were three hundred feet away from that location. Fifteen Doppler-shift fixes were scattered over the Presidential Mountain range. The average error of the GPS fixes was one thousand four hundred feet, and eleven thousand six hundred feet for the Doppler fixes, while the composite – coordinates combined – fix error averaged five thousand seven hundred feet.

A lack of reliable information and data caused much consternation for NH F&G. They had previously completed a summer search very quickly with one single coordinate from a commercial satellite messaging service, Spotify Technology SA.  For this search there were many coordinates across a rugged mountain range. Brutal weather in the mountains only served to complicate matters.

During a search like this, NH F&G operates their own deployed command center, usually in a nearby fire station and CAP is not a partner in this arrangement. Neither CAP nor NH F&G understood the coordinate labeling that came with the Keyhole Markup Language Zipped (KMZ) files provided by AFRCC. AFRCC uses KMZ files output from Google Earth to transfer NOAA search and rescue information to incident command staff. You must have Google Earth on your computer to open KMZ files.

The KMZ files contained distress beacon coordinates, indicated by place markers on Google Earth. GPS coordinates are preceded by an “E” (indicating an Encoded GPS embedded in signal) and received by GEO-geo-stationary satellites (GEOS) and LEOS. GPS coordinates do not list a probability as they are thought to be one hundred percent correct; this is not always the case. Because they sit in a geostationary location over the earth’s surface, the GEOS are NOT capable of determining a beacon location without an encoded GPS coordinate.

406 MHz signal coordinates derived by LEOS are preceded by an “A” or “B” label, indicating that the coordinates were derived from Doppler frequency shift analysis with 1-3 NM accuracy.  Because LEOS equipped to receive beacon signals are in a non-stationary orbit, initial detection time is around 45 minutes but may take up to 2 hours. Doppler shift coordinates are broken down by “A” or “B” labels indicating which side of the satellite’s path was used in the measurement.  The “A” position is not necessarily more accurate, and a second LEOS pass is required to resolve ambiguity.

A and B coordinates should include a stated probability based upon many factors. Doppler-shift derived coordinates are also called Satellite Solution.  A “C” preceding a fix number indicates the coordinates are a composite of “A “or “B” or multiple fixes, but not necessarily more accurate. Signals and therefore reported positions are subject to errors such as satellite azimuth, terrain reflection, signal propagation, obstacles and operator error (no clear view of sky). NIL labels indicate data is invalid. Medium Earth Orbit satellites (MEOS) coordinates will be labeled with a “D”.  ALL satellites can record, and report GPS encoded coordinates.

Conclusion

This search was conducted under extreme conditions but not so unusual for a New Hampshire winter day post-Nor’easter.  Also, not so unusual was the response from both ground and air SAR responders.  The book, Where You’ll Find Me, Risk, Decisions, and the last Climb of Kate Matrosova by Ty Gagne, goes into great detail about the hiker’s preparations, decisions and path till she succumbed to the horrific weather.  He also goes into great detail about the SAR responders’ efforts to climb the mountain and search under the most dreadful winter conditions.  It is a testament to the dedication of those who lay their lives on the line so that others might live.

Bill Moran is a retired USAF colonel and former New Hampshire CAP wing commander. During his USAF career, he was an aircraft commander in the B-52G, F/FB-111, and B-1A/B.

Lt Bruce Determann and Capt Bruce Neff were crewmembers on this mission and provided excellent aircrew coordination.