Another transponder question

Why would the transponders in a commercial aircraft have a way to turn them off. Under what situation would having an “on” transponder be detrimental?

If the transponder is malfunctioning, or reporting an incorrect altitude, or otherwise being a spaz, , it will annoy the air traffic controllers who will ask you to turn it off.

It also needs to be turned off when you’re on the ground to avoid cluttering up the scope.

And it may need to be turned off if there’s an electrical problem on the plane.

There’s another thread started yesterday with the exact same question. The answer is electrical problems, confusion in congested airspaces, on the ground. For example, in the huge fly-in at Osh Gosh they ask that planes turn them off 20 miles before landing.

Would a different transponder for emergency tracking be a good idea? That is, a system that squawks on relatively low power in a band that is not normally monitored by ATC or FAA, so crowding and ground clutter are not an issue? A system that for safety and security cannot be turned off, carries its own backup power system so craft power could be cut if necessary (or it could continue operating if the craft lost power for any reason). A redundant system beyond the reach of even catastrophic failures, terrorists and mistakes? Maybe squawking a fixed airframe ID rather than a flight or carrier ID?

Thanks for the information. I suspected there might be a similar thread, and for once even searched for it “Transponder” but did not turn that up.

Almost like an Emergency Locator Transmitter? Sounds like a good idea to me.

I know there are a variety of transponders and tracking devices. What happened to the ones on the Malaysian flight?

A transponder costs about $2,500 to at least $7,500. I have no idea how much one for a ‘heavy’ would cost with volume discounts and such, nor how much a purpose-designed-and-built ‘secure’ transponder would cost, but let’s say the average is $5,000. That’s a lot of dough when you’re equipping the whole fleet.

Next, how are you going to find the aircraft? It’s been mentioned above why transponders are turned off in flight: too much clutter on the radar. The VFR transponder code is 1400. ATC can filter those so that they do not appear on the radar. How would they filter the ‘secure’ (and redundant) transmissions? Who would monitor them? And if they weren’t displayed, what good are they?

And if it uses power, there’s the potential for a fire. There would have to be some way of turning it off in case of a malfunction. If you have a transponder that can’t be turned off, that needs a way to turn it off, then you’re better off using the one on the panel.

If your ELT goes off, it is hunted for. It was an faulty? A bad bouncy landing? A goofy friend who hit the plane with his fist in just the right way? Magic?

They are usually or used to set at 121.5 so every aircraft could listen for them.

If they were all on all the time, they would be useless. So we need an accident or a switch to turn them on on purpose. That is what an ELT does & has.

They can & do fail because of faulty or inadequate maintenance.

What if the people in the cockpit for some reason do not want to alert anyone that they are doing or going someplace they shouldn’t.

Cost / Benefit seems to say that it is cheaper for the insurance to pay off than to implement these schemes.

So no, lives do not get saved at any cost, even in the first world countries. We just don’t like to think about it. People will put in their time & resources, even governments will, up to a point to try to save other people. But their are limits and the whole peoples pretty much determine that in different parts of the world.

If any cost was workable, we all would be driving with helmets on. They help save lives even in today’s miracle cars.

People who fly now are unhappy at the cost. Make it cost more for very small increase in safety. They will hunt you don’t and be very mean for starting this program that fails the cost / benefit test.

Of course I could be wrong about all of this. I’m pretty sure someone will be along to say I’m wrong. maybe they will underwrite the cost… Ya think?

This device costs around $200 to buy and $3/hr to operate, sending a fix (time, latitude, longitude, altitude) every minute. It communicates via the Iridium satellite constellation, which covers the entire globe (much superior to transponder coverage).

It seems a bit lame that all airliners (at least) do not carry one, or the equivalent. The cost of equipping every airliner in the world with one is probably less than what the search for Flight 370 is likely to cost.

I am speaking a little vaguely and in ignorance, but I didn’t mean regular flight transponders or the existing ELTs, but a bit more like what Xema mentions. Something NOT routinely monitored, so clutter/confusion does not apply, but something that does not depend on activation or specific circumstances, can’t be cut by terrorists or accident and would be immune to even catastrophic systems failure.

You know, like flight 370 could have used.