Someone should invent a transponder that can't be shut off.

[Recursion]

Separate from the rest of the airline circuits, fireproof, etc., with a huge frigging satellite antenna. If any part of its system is tampered with it squawks at max power "I'M BEING TAMPERED WITH AT 93 DEGREES 3 MINUTES WEST LONGITUDE, 43 DEGREES 7 MINUTES NORTH LATITUDE" and keep doing that until someone not in the airplane acknowledges somehow. The response to 9/11 was slowed, among other reasons, because control wasn't sure what primaries it was tracking after the transponders were disabled.

It's 2014. We should be able to fix this.

[pipoman]

1. Anything done will have a way around

It isn't easy to tamper with now...human ingenuity and all that. .

[brooklynite]

2. There's a reason for it to be shut off regularly...

...when the plane is at the airport, the close proximity of all the planes with all their transponder data would make ground radar impossible to read.

[Orrex]

9. What about having the tranponder shut off at altitude < 50 feet?

Or some similar altitude or below a certain speed?

[brooklynite]

11. Denver, CO: 5,130 feet

[Orrex]

12. So I'm 5,136 feet tall in Denver?

One would hope the context makes clear that relative altitude is at issue.

[brooklynite]

13. ...and how do you set the transponder to measure "relative" altitude?

Sometimes simple answers are simple because they don't work.

[Orrex]

14. So there's no way to determine relative altitude?

The pilot shrugs and says "well, we're at 5,130 feet, so we'd better land?"

[former9thward]

15. Planes have been measuring distance to ground almost since they were invented.

It is called an altimeter. The things that are posted here ....

[Orrex]

16. Sometimes simple answers...

[brooklynite]

17. If you have to set the transponder (or altimeter) to the actual altitude of the airport...

...you've introduced a manual setting that goes counter to not tampering with the transponder.

[former9thward]

19. You don't have to set altimeters to airport altitude or anything else.

Altimeters were invented in the 1880s before the invention of the airplane. The first modern altimeters using radio waves were invented in 1938. Modern altimeters know what they are doing -- nobody needs to set anything nor is it even possible in flight. A transponder could easily be tied into the altimeter readings. Right now the transponder is just another switch in the cockpit.

[jmowreader]

20. GPS supplies altitude data. Use that.

[FSogol]

3. They have that already. It is called static.

[mnhtnbb]

4. You might find this opinion piece informative.

The author of this piece said, after 9/11, "At the time, I would have bet my life’s savings that the transponder, which broadcasts an aircraft’s location and identity, would be re-engineered to prevent hijackers from turning such units off. But nothing was done."


And goes on to write:



Why is there a transponder switch in the first place? Until recently, transponders had to be off when a plane was on the ground, to avoid sending signals that disrupted airport radar. The designs for some private aircraft – but not yet the large commercial planes – deal with this by using automated transponders that turn on when the planes become airborne, then turn off when they slow to taxi speed.

Lately, major airports have installed ground-scanning radars that don’t get confused by transponders on taxiways. Large jetliners like the 777 typically operate from such airports, and when they do, they never have a reason to switch the transponder off.

<snip>

The solution is a location-broadcasting system that the flight crew cannot switch off. Over the next few years, much of the world plans to adopt an aviation tracking standard called ADS-B, which should make it harder for a plane to stop reporting its position. Automated transponders should be part of that transition.

Read more here: http://www.newsobserver.com/2014/03/18/3712664/turning-off-airplane-transponders.html#storylink=cpy

[Yo_Mama]

5. I think you are looking at this from the wrong angle

First, as to your suggestion, in practice I can see some problems. Any piece of equipment on the plane is potentially vulnerable to failure, and if it's an electrical circuit, having the ability to turn it off is necessary, if only sometimes to cure a fault.

You can't isolate it from fire - if it's electrical, it can't be fire-proofed.Especially with a big honking antenna. Lightning has done considerable damage to planes in the past.

And if you really want to isolate it from the rest of the aircraft circuits, what are you suggesting? That it should have its own separate power supply? A battery, perhaps? We've had more fire problems with batteries than anything else.

Finally, transponder signals can be reprogrammed. That can be done to flag an emergency, or just to change an assigned flight ID. So even if the transponder were working, it could be spoofed. I don't think you would want to make the transponder unresettable and un-reprogrammable.

If you are talking about a separate bus that can't be easily disconnected, then you are talking about a severe risk to the aircraft if something happens. Finally, there are multiple power sources on the B777 and alternate busses for them. The last line of defense on a B777 is the battery backup, which allows minimal flight time with minimal instrumentation for some time, probably no more than an hour. You would most definitely want the transponder linked in to that power source. So isolating the transponder doesn't seem likely to increase safety, IMO.

I would like to suggest to you that the problem here seems to be that some person or persons got control of the plane for illegal purposes. That's the safety issue that has to be addressed, and fixating on the transponder doesn't make much sense to me. Pilots have destroyed and hijacked their own planes before this, and attackers have seized control of planes before this. Once an attacker has control of the plane, the transponder is the least of the safety concerns.

[Recursion]

7. You sound like my advisor

Yeah, you're right. Maybe that's why I gave up on EE. "Assume it will fail." "What will?" "EVERYTHING." Sigh.

[Yo_Mama]

8. Detected!!!

Yes, that's part of my training. Because everything DOES fail. Usually at the worst possible time under the worst possible circs.

In this case, the human part of the circuit failed. I admit to being deeply depressed over this incident. I feel terribly for the families. Just certainty would be easier for them.

But we shouldn't magnify the future body count because of this.

[Wounded Bear]

10. Fourth Corollary to Murphy's Law..

Murphy was actually an optimist.

[Blue_Tires]

18. this should answer some of your questions

http://www.airliners.net/aviation-forums/tech_ops/read.main/344905/

[Angleae]

21. They can be relocated.

It's impossible to make it fireproof or to separate it from the rest of the aircraft circuits because it still needs 115VAC power to operate. However they Iand their circuit breakers) can be relocated to somewhere people can't get while in flight which is basically the aft cargo bay or somewhere outside the presssurized area of the plane. If the transponders stop operating (keep in mind there are 2 of them) it is automatically assumed that the aircraft is in major trouble.