Originally Posted by
Check Essential
OK, I will admit my ignorance and probably embarrass myself for a lack of aircraft systems knowledge but I have to ask this question:
The search for the Malaysian jet is now going on in the middle of the Indian Ocean. The news media says that is based on "satellite data" and they keep showing some huge "arcs" that are supposedly based on satellites and they talk about the 7 hours of data that kept coming in after the ACARS and transponder were turned off or quit transmitting, etc. etc.
What system are they talking about? What emitter is there on a 777 besides ACARS, transponder and the radios? They seem to be implying that engine data continues to be transmitted and I know the new generation Boeings all sing like a bird the entire flight, but I always thought that data was transmitted through ACARS? I know ACARS can send via VHF, HF or SATCOM but its all still ACARS, which was supposedly turned off. Is there another system that I'm not aware of?
It's been an interesting case to follow, because virtually all the information has been filtered through non-aviation media that have been wrong more than they've been right even while quoting aviation sources. Basically, what I've picked up is that the ACARS VHF transmissions shut down (supposedly manually) before the MH370 even went feet wet around Kota Bharu. However, the engines' maintenance computer is designed to keep pinging info back to Rolls Royce via satcom once out of range of VHF -
if the carrier is signed up for the service. MH was
not signed up, but the satcom system still checks in with the Inmarsat satellite once an hour. It last did this at 8:11am MST (GMT+8), roughly 7.5 hours after takeoff. Likely the pilot, or whoever was in control at that point, had no idea the Satcom system would keep doing this. Based on the ping response time from the geostationary Inmarsat satellite, they've established a number of arcs - one an hour - along which the airplane had to be each time it sent a ping. Based on the expected cruising speed of a 777 and the range given the FOB at takeoff, they've established two possible routes and rough final positions for it to run out of fuel (shortly after the final 8:11 ping). One is in Kazakhstan after a route through western China, and one is southwest of Australia in the southern Indian Ocean. The former is unlikely due to the number of military radar systems it would have had to circumvent (India, Pakistan, China), and the latter is unlikely for any theoretical reason other than suicide with the intention of hiding the evidence - which unfortunately every other piece of evidence supports. In any case, they don't seem to have any theory for which they've been able to find a motive on any theoretical perpetrators' part.
Pilots are pretty straight arrows near as they've been able to tell. CA is a bit weird with a homebuilt flight sim in his house...and strongly supported the least nutty, least corrupt opposition politician in MY politics. FO was somewhat religious, but let a South African hottie ride in the flight deck last year while he & the Captain lit up a few ciggies. Dunno.