Disabling Aircraft Transponders

[Bazza06]

Following the mystery of the missing Malaysian aircraft I would like to know the following:

1) Why is it possible to disable equipment such as transponders when they provide such vital information in the event of a crash? Is there a genuine technical reason for this to be conducted?

2) Why is no alarm sent to ATC to inform them that the equipment has been disabled either purposefully or accidentally which would then allow emergency procedures to be implemented?

3) Given the possibility to make telephone calls and use the internet in-flight why isn't the position of aircraft and voice cockpit recordings automatically sent and recorded to a land based server for later retrieval if required?

All this to a layman appears basic and common sense but whenever a crash occurs everything seems to rely on finding the black boxes.

[wiggy]

All this covered at length elsewhere...but

1. You get rare occasions where the transponder emits a corrupted/erroneous squawk (the identifying code - sorry about the banter and thanks for the hint George.....), so you might need to perform a reboot, and also it might be a good idea that you can isolate an electrical device from it's supply. Lots of aircraft have been lost due to electrical fires over the years.

2. One for an ATCer but I suspect they don't want an alarm blaring out every time they temporarily lose a squawk( the identifying code) for a matter of seconds.

3. One for the techies - rumours of cost/ bandwidth limitations.

[Georgeablelovehowindia]

Explanation of transponder: Transponder (aviation) - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Transponder_%28aviation%29)

[Bazza06]

Thanks for your reply.

With regard to bandwidth I would imagine that we all use more data on a daily basis then it would take to record the position data.

When you consider we use mobiles for email, text, video etc.

The CVR would take more but it's minimal compared to gigantic servers used for YouTube ec.

I guess it would be annoying if false alarms were continually pinging in the ATC towers but I'm sure this could be managed some other way without the disturbance.

And if it is a rarity that a transponder has to be switched off then the problem wouldn't be that big.

I just feel that there is a better way to keep track of the data they so desperately need when a plane goes down.

[AerocatS2A]

Transponders are generally turned on and off every flight. ATC don't need to see a bunch of aeroplanes sitting on the ground at the terminal, so they are turned off after engine shut down and turned on just after start up. Using the standby switch is not a once in a career event, it happens all of the time. On the other hand, turning the transponder off in order to be undetected by radar is a very rare event. We should design systems to be useful everyday, not design the usefulness out of them just to avoid a one in a billion event.

[chevvron]

None has yet mentioned (to my knowledge) if the Malaysian flight was transmitting an ADS signal. I know not all aircraft have it but surely an aircraft as modern as a 777 is fitted with it.

[DaveReidUK]

None has yet mentioned (to my knowledge) if the Malaysian flight was transmitting an ADS signal.Where do you think FlightRadar24 gets its tracks from? Ans: ADS-B.

Those transmissions stopped at the same time as the transponder signal was lost, of course.

[chevvron]

Sorry I assumed FR24 was a combination of Mode S and ADS-B not ADS-B alone.

[Dont Hang Up]

ADS-B is broadcast using the Mode S SSR transponder. Indeed ADS-B is a Mode S message format, but is transmitted spontaneously (squitter) rather than in response to a radar interrogation.

ADS (sometimes called ADS-C) reports periodically over a satellite link using an established point-to-point connection.

[Bazza06]

It still makes me wonder why a more secure reliable system cannot be introduced.

For example, if the transponders have to be switched off when on the ground to avoid excess noise in ATC then an alert should be produced if they are not switched on following take off.

If they are switched off during flight time an alert should be sent to ATC to alert and to query why.

If no response is received then the respective action can be taken.

Aircraft should, in my opinion, have their movement data compulsorily recorded without the option to switch the system off.

We should not rely on finding the black boxes and we should never be in situation as is the case now where an aircraft and 239 people are missing.

If cost is a factor well how much will this incident end up costing and how much did Air France 447 cost in locating and recovering the black boxes?

Hundreds of millions no doubt.

[Bazza06]

It seems the questions I have raised are being asked elsewhere.

Many are now questioning why we have to wait for the recovery of the black boxes to give us the answers needed.

The technology must be there to record the data irrespective of whether the equipment is disabled.

[MCDU2]

The "many" people you refer to fail to understand a simple concept that each life has a value. That value is printed on the back of the ticket or buried deep in the T&CS of an eticket. It is enshrined in international law. Things only get expensive if culpable negligence can be proven once the accident investigation is complete.

Also bear in mind that the many "experts" who grace our tvs espousing the benefits of a certain technology just happen to be stakeholders that will benefit massively from any changes by the regulators.

The reality is that aircraft do not fall out of the sky on a regular basis. In fact the mh370 and af447 hull losses are statistically infinitesimal in the grand scheme of things no matter how sad it is for all involved. It is for these reasons that in the cold light of day and after a few years have passed that very little will change in aviation as a result.

[Dan Winterland]

The technology must be there to record the data irrespective of whether the equipment is disabled.

It is, but not always selected as an option. When AF447 crashed, the initial cause of the problem (probe icing) was self evident as AF maintenance control in Paris were receiving the ACARS messages relating to the faults which triggered the chain of events real time. MAS hadn't opted for an maintenance data-link and weren't receiving such information.

However, Rolls Royce were. MAS pays for ''power by the hour'' which means that the engine parameters are relayed real time to the service provider. I suspect whoever disabled the ACARS didn't realise that the engine data was being transmitted by a separate system through INMARSAT which is why the first clue we had that the aircraft is probably no where near the last point of contact came from RR who were receiving data some four hours after secondary radar contact was lost.



My suspicions are that if the events leading up to this aircraft's disappearance become fully known, then a more comprehensive data-link system will become mandatory. I also suspect some form of auto-release Emergency Position Indicating Radio Beacon (EPIRB) will become mandatory. It's not beyond the scope of technology - my yacht has one!

[rh200]

Cost versus benifit, thats all it comes down to. For all intents and purposes anything is possible if you want to pay for it.

The vast majority of accidents are solved with what we have. So for the cost of implimeting something better what outcome do we get in a cost analysis.

Think of all the aircraft in the air at any one moment, then think about the bandwidth needed for your application, on that 24/7 basis. From simple location via a sattelite, who does it go to and who is the responsable party for it and how long to they need to keep it.

Then theres streaming data from parameters, how many and what update rate, including CVR, who pays and what bandwidth for the thousands of aircraft in the air at any one time.

Then it all has to be certified for use in the air. Its all possible but there has to be a good reason for it. And not just knee jerk reactions.

[teeteringhead]

Cost versus benifit, thats all it comes down to. For all intents and purposes anything is possible if you want to pay for it.

Sadly true and - leaving aside negligence - lives are pretty cheap in the big scheme of things.

Two tales I heard from a chum who used to work for London Transport who ran the 'buses and the Underground (Subway).

The brakes on the 'buses were adjusted to the minimum effectiveness that was legal. The logic was that it's better (read cheaper!) to run over a child than damage 50-odd passengers in an emergency stop.

"Safety Improvements" on the Underground were costed against a theoretical cost of - IIRC - £1M per head. So if a proposed improvement that would save one life a year cost £900K a year to implement - it was done.

If however, it cost £1.1M per year - then guess what?? :eek:

[DaveReidUK]

from RR who were receiving data some four hours after secondary radar contact was lost

They weren't. Rolls-Royce only received data while the VHF ACARS channel was operating.

[Bazza06]

Appreciate the responses my questions have generated.

The arguments for cost, I get that, but look where we are at present. Nearly one month since the aircraft went missing and millions of pounds already spent trying to find it.

And, as I write, all we currently have is satellite images of possible debris from the plane.

How much more will it take to recover the parts, look for the black boxes and establish the cause?

Without doubt this and Air France are exceptions to the rule but when it does happen we witness the devastating consequences.

How much per head per passenger per flight to implement the measures and infrastructure? £1? Would most people object do you think?

Personally I wouldn't and if the likes of Apple, YouTube, Google etc. can produce sufficient storage space for the applications, data and media content they hold I'm a solution for holding CVR and flight data can be sourced.