R44 Missing North of Montreal

[Hot and Hi]

Originally Posted by [email protected]

Whilst the coverage from the Iridium satellites is impressive, your tracker still needs to have a clear view of the sky to see them so not infallible.

The difference is that the tracker shows the track to the accident site even if - for one or the other reason - it stopped working after the crash. So it still served its purpose even if it died in the crash.

Whereby the ELT is silent until the crash happens, and then only works - for one or the other reason - in 1/3 of the cases.

[[email protected]]

Won't argue with that - as a rescuer you want as many ways as possible of finding your missing person/aircraft.

[[email protected]]

What I'd like to clarify when we are talking about the efficacy of the sat trackers is - are we talking about one installed on the aircraft with an external aerial or are we talking about a personal one stuffed into a pocket?

I should imagine the signal is somewhat different and therefore the tracking resolution varies.

[aa777888]

Originally Posted by [email protected]

What I'd like to clarify when we are talking about the efficacy of the sat trackers is - are we talking about one installed on the aircraft with an external aerial or are we talking about a personal one stuffed into a pocket?

I've been talking about the pocket-size variety, but have briefly mentioned more complex equipment, the most typical example perhaps being the Spidertracks brand.

Let me also preface my response by I am assuming that a pocket size unit is not buried in some ridiculous place, but perhaps in a shirt or sleeve pocket.

I should imagine the signal is somewhat different and therefore the tracking resolution varies.

This is a complex question that divides itself into three parts.

Part 1: GNSS positioning accuracy (I write GNSS because some of these units utilize more than just the GPS constellation. For instance many of the more expensive Garmin units use both GPS and Galileo).

GNSS positioning accuracy is affected by many factors. However, in this case we are only concerned with how many satellites the unit can see simultaneously. More is better because a) it can make more measurements, and b) it can choose more measurements with more favorable geometries. To use a very loose analogy that may be familiar to you, think more LOBs, and LOBs that have better spacing.

Certainly an external antenna will be able to have a direct view of more satellites than one in cabin. Nevertheless, because there are now so very many GNSS satellites in orbit, it makes very little difference in practice. We are talking maybe a 10 or 20M difference, at most, if even that much. Once on the ground, experience has shown that externally mounted antennas fare poorly in crashes, so there's another difference to consider.

Part 2: Iridium link resilience

Again, it's a similar answer to Part 1, but in this case it's a question of if any updates are delayed or missed. There are normally only 1 to 3 Iridium satellites in view at any given time. In addition, in the cases where there is only a single Iridium satellite in view it tends to be at a high angle in the sky. This definitely favors an external antenna. However, if the pocket sized device is in, say, the chest pocket of the pilot, and the helicopter is of a typical civilian nature with a large forward bubble windscreen, it's not that big of a difference.

Part 3: position update rate

With an inReach or similar product they only offer a 2 min. update rate, and that's an average because of "Part 2" effects. This is primarily driven by battery life, but also because more messages cost more. With something like Spidertracks, you can pay (quite a bit) extra for 30 second update rates. Again, that's an average because Iridium short message service completion times vary.

Of the three parts of the problem, this last part would make the biggest difference, of course. But this matters only if there is no active beacon or tracker signal emanating from the accident site.

Interestingly, I would be willing to bet a beer or two that most Spidertracks installations do not use an external antenna. These units tend to get installed with internal antennas in the area of the chin bubble or instrument panel in order to avoid the paperwork and expense of external aircraft modifications. We've got a transient 206 in the hangar like that right now. However, I could not tell you what sort of update rates most Spidertracks (or similar service) users typically pay for.

[[email protected]]

Good info, thanks aa777888

[Hot and Hi]

I agree with a78 that the tracking interval is the single most critical parameter. I use 1-min position updates on the inReach.

Wasn’t aware that Garmin (as a service provider) didn’t offer that. I buy my Iridium sat subscription from a 3rd party VAS provider (Global Safetrack Systems) who also do server-based flight following, exception reporting (“deadman alerts”) and escalation management.

[[email protected]]

Hot and HI - presumably yours is a commercial operation rather than a private one like this crash.

[Hot and Hi]

The underlying satellite communication technology is the same for most products (spider, inReach, etc): it’s the Iridium sat network.

inReach is most suited for the pilot who owns the devise (both commercial pilots and private operators, like the mishap pilot in this case). As it can be carried between aircraft, and the owner’s tracking and messaging activities determine the data cost.

My VAS provider offers different contracts, some where you can activate the service only when you need it (which again makes it affordable for private operators who don’t fly every day).

Spidertrack lends itself to fleet operators and has great fleet management functions. As the fleet operator pays the (sat data) bills, they had to artificially limit the texting feature to “base”. (They found that bored fix wing pilots would text all night with their girl friends - via satellite on company expense...)

[[email protected]]

From the Garmin site, it looks like it costs less than many people spend on their mobile phone every month and the handsets are much cheaper than an i-phone

[aa777888]

And you can charge then with all the same stuff you have for your mobile phone, solar chargers, whatever, so no need to double up on that stuff. They are truly a cut above PLBs. But...if you forget to charge it all bets are off. On the other hand, people find them as addicting as cell phones, so they are highly motivated to keep them "fed and watered". Super popular in the US among backcountry adventurers of all types. You know they are popular when Garmin buys the original manufacturer, which was Delorme, and then proceeds to add more inReach-enabled devices to its line up every year.

H&H thanks for that clue as to your service provider. A quick review of their offerings has me intrigued by their inReach equivalent device, the "A*LIVE". I'm particularly keen on their use of the uBlox chipset that processes three out of the four major GNSS systems and how it also integrates a cellular radio. These are noteworthy improvements. Lots more plan options than through Garmin as well