Originally Posted by Brilliant Stuff
Spidertracks was still the better solution for tracking because in case of an emergency you don't need to press any buttons, because you might be unable to do so, and the unit due to it's non movement for x minutes deduces there is a problem and sends an emergency message...
Sure, it's a good solution, in particular where global coverage is relevant including the oceans.
However, I don't buy your point of not pressing any buttons. Spidertracks has a "Watch Me" button that you *do* need to press. Yes, once pressed, the Spider headoffice will send an emergency signal, if they (at Spider headoffice) stop receiving movement updates thereafter. It's a clever thought indeed.
This may work, for example, if you lose one engine at 20 000', or a warning light comes on, or if there is a funny electrical smell. OK, you press the button, and then try to ANC. The new emergency drill is WANC (Watchme - Aviate - Navigate - Communicate)
But it won't help with CFIT and many other emergencies where there is no time, or hand (think helicopter), or attention to spare, before the impact. Unfortunately, this doesn't replace a crash-activated G-switch and crash resistant casing, which neither Spider nor SPOT have. That's why those trackers work in
conjunction with ELT's, and are not (yet) a replacement for a proper ELT.
While trackers are ideal for flight following (in particular if somebody sits back in the office and keeps an eye on you), the ELT will take emergency responders to the exact spot where you are.
For example, there are places in dense forest where you wouldn't see a wreck even if you passed just 2 m next to it. And you won't be able to spot it from the air neither.
Remember, aircraft can travel long distances in the few minutes between the last (valid) position fix obtained from a tracker and the crash site. There are a few scenarios where even a satellite-based tracker (like SPOT or Spidertracks) won't send any position fixes from the cash site, such as
- Can't receive position fix from GPS satellites and/or upload message to communication satellite due to view of sky covered by trees or debris;
- Unit damaged on impact;
- Unit damaged by post impact fire before the next reporting interval (that would also be a problem for a ELT, however in particular in fix wing a/c, an installation position for the ELT can be chosen that is less likely to be affected by fire).
That's where the benefits of ELT's come in:
- High transmitter power (because it saves its battery power to only transmit in an emergency);
- External aerial;
- Relatively low frequency penetrating solid objects.
And last but not least the "L" in ELT - the Locator - allows emergency responders to zero in on the ELT device.