Because you don't expect to need ACARS to send a position. It is primarily a maintenance system. The AF447 thing was purely fortuitous in context. You already have multiple ways of communicating and it is rather unlikely that they will all fail. Say the pilots are incapacitated, then the transponder would still be active. If the transponder breaks I'm pretty sure airliners have a second one, plus all the radios. Barring foul play (pulling all the breakers), if you're in a situation where absolutely none of that is working, the situation is probably so catastrophic an automated ACARS message won't do anything to save lives.
- Transponder. 2x
- Datalink messaging in some cases.
- Satphone in some cases.
- If you are in visual range, you can signal with aircraft lights and receive from a light gun.
See also below.
|Quoting Enobar (Reply 55):|
Quoting Starlionblue (Reply 36):
There is already a system to determine location: the transponder.
From what i understand from that CNN article the transponder does not send out the aircrafts location per say, rather it only identifies itself when it is on ATC radar systems. So the difference between the transponder and ACARS actively sending GPS coordinates would be that you would still have a location fix on the plane when it is out of range of ATC.
Am I misinterpreting the article? (Or is CNN wrong?). If my understanding is correct, wouldn't it still be useful to have ACARS broadcasting GPS locations with its other information?
CNN article is correct but it only talks about Mode A (code) and Mode C (pressure altitude). A basic transponder like you'd find in a Cessna 172. A bit annoying because it doesn't really help us much with this event.
Airliner transponders do much more than that. In simple terms, with Mode S, transponders can send out position, heading, speed and gobs of other information. Most of the information you see on FlightRadar24 would be blank without Mode S.
|Quoting mandala499 (Reply 60):|
Quoting Starlionblue (Reply 20):
In the case of 777, 320, 330-340 you end up in what is called manual reversion.
Manual reversion is only there in terms of total systems failure ie: the HYD AND ELEC systems are unpowered. The 737 has manual reversion... 777, 320, 330, 340, 767, 747 do not.
Thx for clarifying.
[Edited 2014-03-12 00:29:58]
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