EgyptAir 804 disappears from radar Paris-Cairo

[FE Hoppy]

Originally Posted by Lonewolf_50

@grizzled: for the edification of the casual reader/lurker/ we could point them to the Tech Log forum,
where there's a thread with a discussion of ELT's with at least one good post. Summary from that (PPruNer avspook)

1. ELTs transmit on 121.5/243/406 MHz. (406 MHz contacts a satellite monitoring system. It uplinks the serial No of the Box which the Satellite authority uses to look up the Regulatory authority, who keep a list of serial no's versus tail nos)
2. Some ELT's are tied into the Navigation system to uplink last position.
3. Many rely on the Satellite system to direction find the signal
4. An ELT (due to the frequencies involved) is not able to contact the satellite from underwater. It is also not a waterproofed box.
5. The aircraft hull mounted ELTs are typically set up to transmit when a G-load of a particular magnitude is detected (crash)

Sample product sheet (Honeywell; Thales and some other vendors also make products in this class).
FAA Spec TSO-C126A (not sure if an international spec is also in print) DO-204A, DO-160F are cited on some product sheets.

For the love of god! don't show them the way to tech log it's the last bit bit of sanctuary I have on here.....