SPOT Versus ELT Analysis (Long)

All,

Some of the recent RAS articles about SPOT got me thinking that this
is a nice device with some important safety features. I decided to do
a quick and dirty analysis of the benefits of the SPOT device versus
the various ELT/PLB devices. Both basically fulfill the same
function, which is to alert someone to come and get you out the jam
you managed to get yourself into.

Below is a comparison of the various attributes of the SPOT device
PLB’s. I’d enjoy any comments that you might have.

Disclaimer: I own an ACR MicroFix PLB.

Background – Many/most (all?) powered aircraft, and some non-powered
aircraft contain ELTs (Emergency Locator Transmitter). The simplest
form of an ELT sends out an emergency signal at a specific frequency
(121.6 Mhz). This emergency signal can be listened for with standard
aviation receivers and then tracked to its source. In the US this
function is often performed by the Civil Air Patrol. Newer ELTs
(operating at 406 Mhz) can transmit GPS location information via
satellites orbiting overhead. A US government agency (NOAA) is then
alerted to the emergency and provides the GPS coordinates to the
appropriate rescue personnel. PLB (Personal Locator Beacons) are
similar in function, using GPS and 406 Mhz, plus being more compact
than ELTs, and typically less expensive. SPOT devices are identical
in function to PLB’s except they are smaller & lighter and transmit
their emergency information via commercial (non-government) satellite
system.

Cost - The SPOT is about $150 while the smallest personal PLB (ACR
MicroFix or ResQFix) is $650. Advantage SPOT it would seem. However,
SPOT requires a $100/year subscription fee (PLB is free). This makes
the cost break even point of 5 years between SPOT and this particular
PLB.

NOTES on Cost: I simplified this analysis by assuming that the cost of
battery replacement and future retail price discounts would not be a
factor. SPOT’s lithium batteries are to be replaced yearly while the
ACR MicroFix’s battery every 5 years). If you want SPOTcasting
(continuous monitoring), there is an extra $50 per year charge (break
even at 3.3 years). PLB’s don’t have a SPOTcast-like monitoring
feature. Important: Spots are being handing out FREE at the 2008 EAA
Airventure (Oshkosh, WI) show from July 23 – Aug 8 (http://
www.airventure.org). However, you must immediately sign up for the
$150/year SPOTcasting plan and also be an EAA member. See
http://www.findmespot.com/eaa.aspx for details. This would equate to
a cost break even point of 4.33 years (ignoring EAA membership
costs). A final aspect of cost, which I have not included, deals with
the potential cost of the first responders (fire, police, rescue,
etc).

Ruggedness – My impression is that the PLB’s (and certainly ELT’s) are
build to a more stringent standard than the SPOT devices. But to be
honest, I haven't researched this too much. Comments?

Monitoring Agency - PLB’s are monitored 24x7 by a government agency
(in the US this is NOAA). SPOT is monitored 24x7 by a private
concern. Which group is more viable in the long term remains to be
seen.

Monitoring Satellites - PLB’s are using government based satellites.
SPOT uses a privately owned satellite system. Which one is built and
maintained better also remains to be seen.

Emergency Response - Does anyone know how fast the “typical” emergency
response would be from first signal activation to first deployment of
the local emergency personnel (obviously the time to final rescue
would differ enormously)? Is SPOT any better or any worse than NOAA
in the US? I do have to wonder if, in an emergency, whether the non-
governmental GEOS team which monitors the SPOT system will be able to
contact a (non-US) government agency as quickly and efficiently as the
government based NOAA organization. Does NOAA carry more weight to
get non-US emergency teams to answer the phone and come to your
rescue? See http://www.magazine.noaa.gov/stories/mag96.htm &
http://www.geosalliance.com/ for some details.

Coverage – While I bought my PLB specifically for soaring use, it has
been taken on trips to Borneo and Haiti (as a just-in-case tool). GPS
(based PLBs) have worldwide coverage. SPOT coverage misses some areas
of sub-Saharan Africa, India, Micronesia and the north and south
poles. While these are not exactly prime soaring locations, I bring
this up to make a level comparison. http://www.findmespot.com/ExploreSPOT/Coverage.aspx

Batteries – All these devices rely on batteries. The SPOT FAQ says
that a set of lithium AA batteries will last for one year (non-
SPOTcasting mode). A PLB’s battery is designed to last for ~5 years
between replacements. Because the lithium AA batteries are
approximately 5x the replacement cost of the specialized PLB’s
battery, this ends up being a wash. During emergency use the SPOT is
rated for 7 days (911 mode) while the MicroFix PLB is rated for 40
hours. This time difference is not as critical as it would seem as
long as both GEOS and NOAA get the all important GPS coordinates in
the first few minutes or hours. The critical element is, will the
batteries be fresh when needed? This points to SPOTcasting (battery
life is 14 days) users needing to be rather religious about replacing
their batteries often or risk having a dead unit on their hands when
the chips are down.

Size/Weight - SPOT (4.38 x 2.75 x 1.5 inches) is the same size as the
MicroFix (5.85 x 2.21 x 1.4 inches), 18 cubic inches in both cases.
However the SPOT is 36% lighter, 7.37 oz versus 10 oz, the difference
primarily due to the lithium batteries being used.

Triggering – Unlike ELT’s, both SPOT and PLB devices must be manually
triggered (in emergency use).

Antenna – The antenna on the SPOT is internal while the antenna on the
MicroFix PLB is external. In my experience, external antennas provide
better reception and transmission. However, I don’t know if this
makes a difference with these types of devices.

Conclusion – I think that there are two key points, and two lesser
points, that are important to be considered.

First, the lesser points of size and battery life. Both devices are
basically the same size and small enough to be easily carried. Will
either or both grow smaller as technology advances? Undoubtedly. As
to battery life the SPOT is the clear winner (emergency use only) but
as I stated before, I am unsure if this is truly a critical element in
the analysis.

Next, the primary point of cost and the combination of coverage/
response/monitoring.

Cost - everyone’s primary metric. Obviously, the initial outlay to
obtain a SPOT is much less (4x) than the MicroFix. However, as we all
know from life with cellular phones, service charges can quickly
invert this equation. I fully expect to keep my PLB for more than 5
years and I suspect the SPOT users feel the same about their device.
Crunching the numbers makes this a tie between the two devices.

Finally, let’s look at the trickier coverage/response/monitoring
analysis. I believe that it comes down to the organization behind the
device. At this point in time I am still leaning towards PLB’s as the
item of choice. My reason is that when the chips are down, I would
rather have the reliability, capabilities, contacts and dedication of
a government agency rather than a private enterprise.

My $0.02.

- John “67” DeRosa

Web Links
http://www.findmespot.com
http://www.adventuretrak.com
http://en.wikipedia.org/wiki/Emergen...or_Transmitter
http://www.acrelectronics.com/microfix/microfix.htm
SPOT use video at: http://www.youtube.com/watch?v=-q2um6vGERY

SPOT use video at: http://www.youtube.com/watch?v=-q2um6vGERY
SPOT commercial video at: http://www.findmespot.com/MediaCente...VideoTour.aspx
PLB use video at: http://youtube.com/watch?v=Y8yIXrRZ1DQ
PLB commercial videos at: http://youtube.com/watch?v=C8I5aK_5bZk and
http://youtube.com/watch?v=psel_NhpiUg

John:

Good analysis. I have a few additional thoughts based on limited use
of SPOT at SoaringNV here in Minden:

First, SPOT is a non-emergency tracker. One of our instructors
carries his personal SPOT on long XC flights and we can get his
current position (updated every 10 minutes or so) online. This means
we know if he is making normal progress or is spending a long time
somewhere looking for a thermal. It also lets us know if there's a
good chance he'll make it home without an aeroretrieve, so we can send
the tow pilot home early.

ELTs and PLBs don't offer this kind of capability. It's a
convenience, not an emergency consideration, but it is a
consideration.

Another aspect of ELT use (which does not, I don't think, apply to PLB
use) is that they are frequently triggered inadvertantly. I fly with
the local Civil Air Patrol, and I think more than half the alerts they
are called out on turn out to be to search for an ELT alarm that they
subsequently learn is in an aircraft sitting on an airport somewhere.
And this high incidence of false alarms brings to light how slow the
response actually is to a signal on 121.5. By the time the Sheriff or
CAP locates the triggered alarm it has often been alerting for a
number of hours. My understanding is that the NOAA satellite that
responds to 121.5 needs to get two signals from the same location
before it alerts, and this requires two passes of the satellite. This
might not be the case any longer, but I'm pretty sure it was when the
service was first put in place.

Finally, SPOT and PLBs both offer active alert capability, while ELTs
offer passive alert. I suppose this could be a consideration if you
are incapacitated upon reacing the ground -- maybe you couldn't push
the "help" button -- so you need to think about what you want to be
prepared for: letting people know you're ok, or letting the NOK know
where to find the remains. (Sorry for the gruesome touch.)

Fred

Hi Gang
Having used a Spot for some time now I agree that it is almost an
essential safety item for XC either in a glider or power plane. All
modern power planes require not only the use of an ELT but also that
the ELT can be operated from a control on the instrument panel or
equivalent so that if you are going to have an emergency landing you
can actuate the ELT before the landing and not rely on the G forces to
trigger it. I have this on my Jabiru J250 LSA. I also take and operate
my Spot on all flights whether in the LSA or in a glider. I set the
Spot to the tracking mode so that it sends out messages every 10
minutes. My wife and a couple of close friends have my Spot user name
and password so that they can either track a flight in real time or
bring up a flight later if they so wish.
I have not found any significant problems with the Spot system. It
works! If Steve Fossett had used a Spot he would have been found
(assuming he wanted to be found) and for its low cost, simplicity and
ruggedness I consider to be an
essential piece of safety equipment. I won't fly without it. Don't
procrastinate you pilots just go and buy one. Could be one of the best
investments you might ever make?
Dave

Has anyone heard of any prospect of an improved SPOT coming out.

My biggest hang up is I don't like replacing batteries and I would
want to use it in tracking mode. It would be Ideal if it had an
external Power option. I am sure I could jury rig something but it
would be nicer to have the external power for normal operation and
still have the batteries for emergency operation.

An external antenna option might be nice as well.

A display of your current postion might be of use as well but of
lesser concern to me.

Brian

On Jul 5, 5:49*pm, Brian wrote:
Has anyone heard of any prospect of an improved SPOT coming out.

My biggest hang up is I don't like replacing batteries and I would
want to use it in tracking mode.

I tested battery life earlier this year by leaving on in tracking mode
on the dash of my car, and restarting it every 18-24 hours to ensure
it was operating 24/7. Sometime around day 12, the power LED turned
RED, and the SPOT continued to operate just fine for several more
days. So this means at least 300 hours of CONTINUOUS live tracking.
That's pretty much a typical season for a fairly active pilot.

The local grocery store sells a 4 pack of the batteries for $12 or
so. I'm sure they can be found elsewhere for even less.

Why on earth would you want to complicate things and add an external
power cord??? ;-)

The only improvement that could come from SPOT is if the unit
transmitted a NEW position every minute instead of what it does
currently, which is the same position every 10 minutes.

Think about it, if a new position were transmitted every minute, and
if 90% were lost, that would still provide a position every 10
minutes.

The compelling reason to fly with SPOT is that it provides a
RELATIVELY failsafe crash location. If I'm incapacitated in a crash,
then the PLB is useless. If there's major damage to the airframe,
then the ELT is useless. The SPOT will give rescuers a 10 minute
search radius and a flight vector. Yes, I understand that sometimes
SPOT leaves holes of 2, 3 or even more intervals, and it's possible I
chose to reverse course immediately after the SPOT sends a position
report. But this still provides an excellent starting point for S&R.

-Tom

And I do have an ELT as well. And am installing a transponder
tomorrow. ATC radar history is yet another passive way to find a
downed aircraft, especially if used in conjunction with SPOT to
isolate the VFR target.

One problem with a transmit every minute, rather than 10 minutes, would be
that it would shorten battery life considerably. I am guessing it would
approximate 10% of the present battery life. The 300 hours of transmit
quoted would be reduced to 30 hours.

Also, with transmissions every minute, the processing through the satellite
might be overloaded with present equipment, which would require more money
to correct - hence higher user fees.

The external antenna would reduce reliability considerably, and may not gain
much. The exposure to a satellite from a sailplane would be very high, so
the most reliable and simplest antenna should work well.

Colin Lamb

On Jul 5, 9:21*pm, "COLIN LAMB" wrote:
One problem with a transmit every minute, rather than 10 minutes, would be
that it would shorten battery life considerably. *I am guessing it would
approximate 10% of the present battery life. *The 300 hours of transmit
quoted would be reduced to 30 hours.

Also, with transmissions every minute, the processing through the satellite
might be overloaded with present equipment, which would require more money
to correct - hence higher user fees.

The external antenna would reduce reliability considerably, and may not gain
much. *The exposure to a satellite from a sailplane would be very high, so
the most reliable and simplest antenna should work well.

Colin Lamb

If they respin the packaging in future it would be pretty easy to fit
4 x Lithium AA cells inside the current packaging volume that only
holds 2 x Lithium AA cells.

I suspect the largest reasons things are as they are are likely not
techncial - it seems like marketing decisions targeted at an intended
user base of hikers etc.

A large issue with external power is maintaining a well sealed
packaging and SPOT wanted to claim good specs/complaince for water
resistance/sealing and how many hikers carry around 12 volt power?

I also suspect no external power and also the need to reset tracking
every 24 hours was in part, or in large, to prevent cannibalization of
exiting parts of the asset tracking market that Globalstar (who own
SPOT) services.

... but folks don't put of buying a SPOT now if you want one, just
becasue something better might be coming some time in the future.

Darryl

On Jul 5, 10:21*pm, "COLIN LAMB" wrote:
One problem with a transmit every minute, rather than 10 minutes, would be
that it would shorten battery life considerably. *I am guessing it would
approximate 10% of the present battery life. *The 300 hours of transmit
quoted would be reduced to 30 hours.

See other SPOT threads, but as I understand it, the SPOT does transmit
once a minute already. It is a "blind" transmission, so there's no
acknowledgment from the satellite. So in live tracking, it transmits
the same message 10 times, then updates the coordinates, and repeats.

An OK is also transmitted repeatedly, that's why both LEDs will flash
for 15-20 minutes after pressing OK.

Again, this is all part of the design, which is targeted at the hiking
market. An aviation unit might also include an altitude.

-Tom

snip

I tested battery life earlier this year by leaving on in tracking mode
on the dash of my car, and restarting it every 18-24 hours to ensure
it was operating 24/7. Sometime around day 12, the power LED turned
RED, and the SPOT continued to operate just fine for several more
days. So this means at least 300 hours of CONTINUOUS live tracking.
That's pretty much a typical season for a fairly active pilot.

The local grocery store sells a 4 pack of the batteries for $12 or
so. I'm sure they can be found elsewhere for even less.

Why on earth would you want to complicate things and add an external
power cord??? ;-)
snip

I didn't realize the battery life was this good. Replacing the battery
once per year would be ok.
Does it auto power off after a period of time? Especially if it can't
get a GPS fix like when the glider is in the trailer.. I can certainly
see me leaving it on and having dead batteries when I go to fly. Or
course I do always have spare batteries.

If it did have an external power supply it would be nice if it could
automatically power up to track mode when power is applied, One less
thing to remember to turn on.
It could possibly even be programmed to send a position when power is
turned off. LIke an external OK or Help button.

I like things that stay in the glider and I don't have to mess with
them until I need them.

More batteries I don't need. I already have a 9V in my B40 and 9V in
my EW FR 4 AA in my GPS, a watch battery and lithium battery in my
PDA. All are connected to my aircraft power supply.

Thanks for the info,

Brian