[dingaling]

> Point is a $100 spot device could be added (powered by Li AA's) as a backup system

Li AAs... without a means of isolating them from the circuitry?

How many aircraft are you prepared to lose through in-flight fires for this 'benefit'? Reference: Ethiopian Airlines 787 fire at Heathrow originating from lithium cells in the ELT.

Who is going to check the battery status at regular intervals?

Who is going to certify and sign-off those checks?

Who is going to be qualified to change those cells?

What interfaces will there be with the aircraft avionics to relay data such as call sign and flight code? How do we protect those connections from overload? There's a reason every single electrical circuit on an airliner can be isolated.

$100 is, frankly, a laughable estimate.

[001sky]

Laugh all you want, but the tech is pretty simple. You need to look at what it is doing. Replacing a transponder with something that is much simpler than an epirb. The example I gave is a $100 dollar current piece of tech that weigs 150 grams including power-source, and if it was available to LOS througha window could track the plane for 4-7 hours off a single set of batteries. If you want to raise the budget for an order of magnitude or two, for 10k dollars you could surely create a redundant system for the transponder.

The larger point is that any "real situation" that would need the transponder turned off (power/fire/corruption) would have almost no bearing on the operability of such a simple system.

FYI the imarsat pings are not all that different, are they? Its just a simple ping with some data that including headers is going to be very minimal payload...like SMS text type level of data.