Mode 'S' mandatory for gliders.
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Is there a low power transponder for flying >15,000 ft?
In post #79, Spin Buster quotes the CAA as replying to one of Martin Breen’s questions (about whether a low power transponder is available) as follows-
4. There are a number of transponders on the market which produce a peak pulse power of 70W and appear to be suitable for use in many types of glider.
But do they give an adequate signal above 15,000 ft? Gliders can easily exceed that height in wave at a number of UK sites.
The manual for the Funkwerk Avionics (formerly Filser) TRT800 (150W maximum output transponder; 18.5 dBW (71 watts) peak power at the antenna) gives its maximum flight level as ‘15000 ft.’
4. There are a number of transponders on the market which produce a peak pulse power of 70W and appear to be suitable for use in many types of glider.
But do they give an adequate signal above 15,000 ft? Gliders can easily exceed that height in wave at a number of UK sites.
The manual for the Funkwerk Avionics (formerly Filser) TRT800 (150W maximum output transponder; 18.5 dBW (71 watts) peak power at the antenna) gives its maximum flight level as ‘15000 ft.’
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In post #79, Spin Buster quotes the CAA as replying to one of Martin Breen’s questions (about whether a low power transponder is available) as follows-
4. There are a number of transponders on the market which produce a peak pulse power of 70W and appear to be suitable for use in many types of glider.
But do they give an adequate signal above 15,000 ft? Gliders can easily exceed that height in wave at a number of UK sites.
The manual for the Funkwerk Avionics (formerly Filser) TRT800 (150W maximum output transponder; 18.5 dBW (71 watts) peak power at the antenna) gives its maximum flight level as ‘15000 ft.’
4. There are a number of transponders on the market which produce a peak pulse power of 70W and appear to be suitable for use in many types of glider.
But do they give an adequate signal above 15,000 ft? Gliders can easily exceed that height in wave at a number of UK sites.
The manual for the Funkwerk Avionics (formerly Filser) TRT800 (150W maximum output transponder; 18.5 dBW (71 watts) peak power at the antenna) gives its maximum flight level as ‘15000 ft.’
Thread Starter
The Light Aircraft Association's response
This has been posted on gliderpilot.net (which had been out of action for some weeks due to a hacker). It's a very thorough and well reasoned response and well worth reading in full.
www.lightaircraftassociation.co.uk/Consultation/ModeS%20Sub%20Docs/LAA%20Draft%20Mode%20S%20Consultation%20Response.pdf
www.lightaircraftassociation.co.uk/Consultation/ModeS%20Sub%20Docs/LAA%20Draft%20Mode%20S%20Consultation%20Response.pdf
It's a very thorough and well reasoned response and well worth reading in full.
...you discuss the need to operate the UK ground environment in “mixed mode”, that is to say, all radars interrogate in both Mode S and Mode A/C because of safety issues. So all Mode S transponders reply in both modes and we understand this is likely to continue for some years, certainly until 2012 and beyond if equipment programmes are not delivered by then.
Until the day that Mode A/C interrogation is turned off, all Mode S transponders will also respond in Mode A/C. This has not been a problem so far as virtually all aircraft that have fitted Mode S, previously had Mode A/C so the number of units has remained broadly constant.
If all 15,000 aircraft that are now proposed for Mode S fit were to do so by March 2009, they too would respond to Mode A/C interrogation and UK ATC systems would be overwhelmed.
Mixed mode operations are considerably more sophisticated than the author assumes. "All-call" periods, during which Mode A/C interogations are sent, occupy only a small part of the overall cycle. The rest is "roll call", during which the interrogation is selective. Additionally, Mode A/C interrogations sent during that all-call period can be modified (a "short P4") in such a way that a Mode S transponder does not respond.
Thus having 15,000 Mode S transpoder equipped aircraft poses no problem to mixed mode operations -- having 15,000 Mode A/C only transponder equipped aircraft certainly would be more of an issue.
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70W transponder, valid for use above 15,000ft?
In post 84, cats_five suggested that I should ‘Check the manual for the TRT800H’, but did not give its output.
I had referred (in post #83) to the CAA’s suggestion that a number of transponders on the market produced ‘a peak pulse power of 70W and appear to be suitable for use in many types of glider’. I asked if those transponders gave an adequate signal above 15,000 ft.
I had in fact checked the TRT800H before posting. It is indeed good up to 35,000 ft. But its output is 250 W (125 W at antenna), which is a fair bit above 70W. Gliders really need a LPST.
So I’m still looking for a 70W transponder, good for use above 15,000 ft.
I had referred (in post #83) to the CAA’s suggestion that a number of transponders on the market produced ‘a peak pulse power of 70W and appear to be suitable for use in many types of glider’. I asked if those transponders gave an adequate signal above 15,000 ft.
I had in fact checked the TRT800H before posting. It is indeed good up to 35,000 ft. But its output is 250 W (125 W at antenna), which is a fair bit above 70W. Gliders really need a LPST.
So I’m still looking for a 70W transponder, good for use above 15,000 ft.
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Glider pilots need to wake up and smell the coffee.
About 10 years ago, following the Dunblane shooting, Britain's recreational taget shooting community lost the right to own certain categories of gun.
If glider pilots do not adopt a more cooperative attitude, they could find themselves in the same boat and frankly few people in the community at large would shed many tears for them, since most people are more interested in their sun flights than protecting minority rights.
Like it or not that is the reality.
It would be a real shame if this happened.
About 10 years ago, following the Dunblane shooting, Britain's recreational taget shooting community lost the right to own certain categories of gun.
If glider pilots do not adopt a more cooperative attitude, they could find themselves in the same boat and frankly few people in the community at large would shed many tears for them, since most people are more interested in their sun flights than protecting minority rights.
Like it or not that is the reality.
It would be a real shame if this happened.
Last edited by Final 3 Greens; 27th May 2008 at 09:31. Reason: To add that it would be a shame to see gliding decimated
So I’m still looking for a 70W transponder, good for use above 15,000 ft.
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bookworm wrote-
Indeed. I didn’t suggest otherwise.
But the CAA replied to Martin Breen-
So what are these 70W transponders for high-flying gliders? Who makes them?
Are they even technically feasible?
Incidentally, the only study of the potential radiological effects of Mode S transponders cited by the CAA related to ‘an 80 Watt transponder with typical antenna’ (para. 10.3 of the consultation). And it only used a ‘generic computer model’.
So no one really knows what the radiological effects of, say, a 125W transponder in a glider will be.
The power required to meet regulatory requirements is determined by ceiling and max speed. Lower power is permitted only on aircraft not capable of operating above 15,000 ft and with a maximum crusing speed of 175 kt or less. If you exceed either restriction, the transponder doesn't stop working, it just ceases to meet regulatory requirements.
But the CAA replied to Martin Breen-
There are a number of transponders on the market which produce a peak pulse power of 70W and appear to be suitable for use in many types of glider.
Are they even technically feasible?
Incidentally, the only study of the potential radiological effects of Mode S transponders cited by the CAA related to ‘an 80 Watt transponder with typical antenna’ (para. 10.3 of the consultation). And it only used a ‘generic computer model’.
So no one really knows what the radiological effects of, say, a 125W transponder in a glider will be.
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There is a certain arrogance coming across on this discussion that seems to be "put up or shut up!" which is not very helpful. The whole idea of a consultation is to get the views from all parties and to reach a position where most parties are in agreement.
For that to be achieved, the pros and cons need to be considered (not disregarded) and an appropriate response developed.
Enforcing something onto someone who may or may not benefit from it without consideration is worthy of a communist state, not a free country, which I believe the UK is!
For that to be achieved, the pros and cons need to be considered (not disregarded) and an appropriate response developed.
Enforcing something onto someone who may or may not benefit from it without consideration is worthy of a communist state, not a free country, which I believe the UK is!
So what are these 70W transponders for high-flying gliders? Who makes them?
Are they even technically feasible?
Are they even technically feasible?
What you need to argue for is a regulatory change to permit the use of 70W equipment above 15,000 ft by gliders. Good luck.
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Glider pilots need to wake up and smell the coffee.
About 10 years ago, following the Dunblane shooting, Britain's recreational taget shooting community lost the right to own certain categories of gun.
If glider pilots do not adopt a more cooperative attitude, they could find themselves in the same boat and frankly few people in the community at large would shed many tears for them, since most people are more interested in their sun flights than protecting minority rights
About 10 years ago, following the Dunblane shooting, Britain's recreational taget shooting community lost the right to own certain categories of gun.
If glider pilots do not adopt a more cooperative attitude, they could find themselves in the same boat and frankly few people in the community at large would shed many tears for them, since most people are more interested in their sun flights than protecting minority rights
It seem to me as if we have a situation whereby a governing body has already decided how they want to proceed, and have formulated their "options" accordingly. As the light aircraft people have stated, this consultation is badly flawed, does NOT meet government guidelines, is ill conceived and badly thought through with litle or no evidence to support its options and has not given anyone an opportunity to comment on a "do nothing" option.
All the evidence suggests that safety is improving all the time. Proxes are significantly down, I won't re-print the figures - read other posts. The CAA's own figures state that 15% of airspace infrigements involve aircraft without transponders. I would respectfully point out that in reality that means 85% of infringements are by aircraft WITH transponders. So the answer is simple, take out all the transponders and reduce the infringements (I'm kidding of course but I hope you can see the point- the figures just do not make the CAA's case that light aircraft (including gliders) represenrt any kind of threat to other air users,
The only conclusion many of us can come to is that the CAA has recently changed it's name to "Commercial Aviation Authority" and no longer has the best interests of the rest of civil aviation at heart
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The question on feasibility is meaningless. The regulatory requirement makes them unsuitable for aircraft flying above 15,000 ft. The CAA's response is correct in that "many types of glider" do not exceed 15,000 ft.
What you need to argue for is a regulatory change to permit the use of 70W equipment above 15,000 ft by gliders. Good luck.
What you need to argue for is a regulatory change to permit the use of 70W equipment above 15,000 ft by gliders. Good luck.
However, anyone who wants a Diamond height will have to do so and people have been doing Diamond heights for some considerable time, in all sorts of gliders, not just nice white modern GRP ones.
And quite a few flat-landers (who otherwise might well not need Mode S, depending on what the final outcome is) visit Scotland (or other wave sites) in search of that elusive Diamond height. But not, I suspect, if they have to spend some £4k on getting a transponder fitted.
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rocketmandlgc wrote-
The consultation contravenes various provisions of the Government’s Code of Practice on Consultation (September 2005)-
no list of consultees is included (see para. 2.6 of that Code);
there is no glossary, despite the many technical terms (see para. 3.1);
it doesn’t ‘Invite respondents to comment on the extent to which the criteria have been adhered to and to suggest ways of further improving the consultation process’ (see para. 3.9).;
The consultation document should state the … the web address where, the summary of responses will be published (see para. 4.3).
In addition, some parts of the consultation do not satisfy the Principles of Good Regulation (see para. 6.6 of that code), in that they are not proportional or transparent (does any one really know what Option 2 means?).
The code binds UK agencies, such as the CAA, unless Ministers allow departures in exceptional circumstances.
The Code of Practice on Consultation can be found at-
http://www.berr.gov.uk/bre/consultat...page44459.html
the address given at para. 3 in Annex L to the consultation is wrong.
Why does the CAA think that it does not need to bother to comply with the Code?
As the light aircraft people have stated, this consultation is badly flawed, does NOT meet government guidelines,
no list of consultees is included (see para. 2.6 of that Code);
there is no glossary, despite the many technical terms (see para. 3.1);
it doesn’t ‘Invite respondents to comment on the extent to which the criteria have been adhered to and to suggest ways of further improving the consultation process’ (see para. 3.9).;
The consultation document should state the … the web address where, the summary of responses will be published (see para. 4.3).
In addition, some parts of the consultation do not satisfy the Principles of Good Regulation (see para. 6.6 of that code), in that they are not proportional or transparent (does any one really know what Option 2 means?).
The code binds UK agencies, such as the CAA, unless Ministers allow departures in exceptional circumstances.
The Code of Practice on Consultation can be found at-
http://www.berr.gov.uk/bre/consultat...page44459.html
the address given at para. 3 in Annex L to the consultation is wrong.
Why does the CAA think that it does not need to bother to comply with the Code?
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<snip>
All the evidence suggests that safety is improving all the time. Proxes are significantly down, I won't re-print the figures - read other posts. The CAA's own figures state that 15% of airspace infrigements involve aircraft without transponders. I would respectfully point out that in reality that means 85% of infringements are by aircraft WITH transponders.
<snip>
All the evidence suggests that safety is improving all the time. Proxes are significantly down, I won't re-print the figures - read other posts. The CAA's own figures state that 15% of airspace infrigements involve aircraft without transponders. I would respectfully point out that in reality that means 85% of infringements are by aircraft WITH transponders.
<snip>
The sort of software on a PDA linked to a GPS that most XC glider pilots use might do more to prevent infringements than a transponder, and it can be implemented for less than £100. (free software, 2nd hand GPS & PDA from Ebay) It's also fairly easy to reload the airspace when that changes - downloads are easy to find on the Internet, and are also easy to check against a chart.
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The sort of software on a PDA linked to a GPS that most XC glider pilots use might do more to prevent infringements than a transponder, and it can be implemented for less than £100. (free software, 2nd hand GPS & PDA from Ebay) It's also fairly easy to reload the airspace when that changes - downloads are easy to find on the Internet, and are also easy to check against a chart.
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Would they have to be switched off - the truth?
Can any of the ATCO’s please advise what is the truth behind suggestions that (a) Mode S would be required to be on at all times and (b) people who say that ATC will tell people to switch them off when the screens become too cluttered and/or TCAS’s trigger too many false alarms.
Two things prompt my enquiry. 1st – a visit to a UK Tower ATC last week – the ATCO said if he saw too many glider responses on the screen, they would suppress the labels because they would garble (I think that is the correct phrase). 2nd: A posting on u.r.a.s. (a UK gliding web site) today includes:
Author : Gavin Short [snip]
I am concerned at ATC overload. My experience is of flying in NE Belgium/Netherlands; Last summer a TMZ was introduced on the southern edge of the Eindhoven CTR which cut off the route east into Germany for clearer airspace and better soaring weather.
The first day of decent soaring weather caused a rush of those gliders who were transponder equiped into the TMZ to head east. Perhaps in excess of 10 gliders which promptly triggered a call from the ATC for 'all gliders in the Eindhoven TMZ to switch of their transponders because ATC could not cope with the multiple contacts' - an interesting legal point - who can authorise aircraft in a TMZ to switch off their transponders?
[snip]
Chris N.
Two things prompt my enquiry. 1st – a visit to a UK Tower ATC last week – the ATCO said if he saw too many glider responses on the screen, they would suppress the labels because they would garble (I think that is the correct phrase). 2nd: A posting on u.r.a.s. (a UK gliding web site) today includes:
Author : Gavin Short [snip]
I am concerned at ATC overload. My experience is of flying in NE Belgium/Netherlands; Last summer a TMZ was introduced on the southern edge of the Eindhoven CTR which cut off the route east into Germany for clearer airspace and better soaring weather.
The first day of decent soaring weather caused a rush of those gliders who were transponder equiped into the TMZ to head east. Perhaps in excess of 10 gliders which promptly triggered a call from the ATC for 'all gliders in the Eindhoven TMZ to switch of their transponders because ATC could not cope with the multiple contacts' - an interesting legal point - who can authorise aircraft in a TMZ to switch off their transponders?
[snip]
Chris N.
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There are two separate issues here
1) Garbling. This happens if multiple transponders respond to the same interrogation, e.g., with same slant range but different ground range, or when transponder replies overlap. This is an increasing issue because of
- more and more interrogators flying (TCAS)
- many ATC radars in Europe with overlapping ranges.
- more data being transmitted in the transponder reply (enhanced Mode S, ADS-B etc.)
S stands for "selective" - a standard Mode A/C transponder will reply to any interrogation for that mode, a Mode S transponder only to one that is directed at that individual transponder, using the 24-bit, which avoids garbling. A Mode S radar does infrequent "all calls" to find out who is around and then interrogates each transponder individually.
Or, put more simply, Mode S is a fix required to accomodate a much larger number of transponding aircraft. That is why universal Mode A/C is not sufficient and the authorities want mode S even for those aircraft that in effect will only ever transmit a 12-bit squawk and pressure altitude, and not only for the heavy/fast guys that transmit a lot more.
2) Screen clutter
That is up to the radar display software, can't comment here.
I am afraid the real debate is whether everyone should squawk or not. If the answer is yes, Mode S is necessary to avoid the ancient A/C technology breaking down in some locations. And while there are better technologies that could do the trick, Mode S is the de-facto incumbent in the airline world.
Maybe the debate is more usefully directed at how to minimise the impact. Do we have to pay silly mod fees for paperwork for safety related equipment?
1) Garbling. This happens if multiple transponders respond to the same interrogation, e.g., with same slant range but different ground range, or when transponder replies overlap. This is an increasing issue because of
- more and more interrogators flying (TCAS)
- many ATC radars in Europe with overlapping ranges.
- more data being transmitted in the transponder reply (enhanced Mode S, ADS-B etc.)
S stands for "selective" - a standard Mode A/C transponder will reply to any interrogation for that mode, a Mode S transponder only to one that is directed at that individual transponder, using the 24-bit, which avoids garbling. A Mode S radar does infrequent "all calls" to find out who is around and then interrogates each transponder individually.
Or, put more simply, Mode S is a fix required to accomodate a much larger number of transponding aircraft. That is why universal Mode A/C is not sufficient and the authorities want mode S even for those aircraft that in effect will only ever transmit a 12-bit squawk and pressure altitude, and not only for the heavy/fast guys that transmit a lot more.
2) Screen clutter
That is up to the radar display software, can't comment here.
I am afraid the real debate is whether everyone should squawk or not. If the answer is yes, Mode S is necessary to avoid the ancient A/C technology breaking down in some locations. And while there are better technologies that could do the trick, Mode S is the de-facto incumbent in the airline world.
Maybe the debate is more usefully directed at how to minimise the impact. Do we have to pay silly mod fees for paperwork for safety related equipment?
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Cobalt, I was pointing also to what seems to me at least a third issue – that if all the things (not only gliders) below, say, a TMA, have transponders, then descending CAT gets TCAS triggers all the time – because TCAS does not know that the CAT will level out before reaching the below-TMA level – so lots of false alerts. So ATC tell the below-TMA people to switch off.
Presumable the same could happen as a result of ATC’s collision alert system.
So would ATC tell people to switch off – as they reportedly are doing in Holland – or not?
-----------------
And another post on u.r.a.s. said:
“With Mode S, an ATC unit can instruct any S-transponder not to respond to signals from that unit.
“It will still respond to TCAS. However TCAS does not, at present, cope with multiple threats, so guess how much use your mode S will be if you fly in gaggles. FLARM would be a better bet!
[snip]
Chris N.
Presumable the same could happen as a result of ATC’s collision alert system.
So would ATC tell people to switch off – as they reportedly are doing in Holland – or not?
-----------------
And another post on u.r.a.s. said:
“With Mode S, an ATC unit can instruct any S-transponder not to respond to signals from that unit.
“It will still respond to TCAS. However TCAS does not, at present, cope with multiple threats, so guess how much use your mode S will be if you fly in gaggles. FLARM would be a better bet!
[snip]
Chris N.
Last edited by chrisN; 28th May 2008 at 12:52. Reason: addition of another quote
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"who can authorise aircraft in a TMZ to switch off their transponders? "...and how ? Would this mean that everybody would need to have a radio tuned in to a designated frequency ? Cue frenzied feedback about "my glider/parascender doesn't have a radio/no space/already at max weight, etc etc". Suppose it'd resolve the issue of garbling when you have 20+ gliders all circling within a 50 metre radius of each other and all using Mode-S.
Does beg an interesting question though....if you're TCAS equipped, operating in a TMZ, and all the GA in the sector has been told to switch their transmitters off....Who tells the TCAS enabled pilots that they'd better start watching out ?
Seperate point made earlier provides an interesting scenario too whereby you have intensive Mode-S transponding GA below controlled airspace but climbing, at the same time as you have controlled, TCAS equipped aircraftdescending towards the bottom of their operating zone. Would this mean that TMZ buffer zones would be needed around the TMZ's ? That'd then constrict much of GA into an even smaller area. There's likely to be a few nasty crunches under that scenario.
Does beg an interesting question though....if you're TCAS equipped, operating in a TMZ, and all the GA in the sector has been told to switch their transmitters off....Who tells the TCAS enabled pilots that they'd better start watching out ?
Seperate point made earlier provides an interesting scenario too whereby you have intensive Mode-S transponding GA below controlled airspace but climbing, at the same time as you have controlled, TCAS equipped aircraftdescending towards the bottom of their operating zone. Would this mean that TMZ buffer zones would be needed around the TMZ's ? That'd then constrict much of GA into an even smaller area. There's likely to be a few nasty crunches under that scenario.
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Closing date is 31st May
Whatever your standpoint on the Mode S proposals, the closing date for sending your response to the CAA looms.
The consultation closes on the 31st May, which is this coming Saturday. It's not clear to me if snail mail replies have to arrive by then (I'm sure they don't work on a Saturday!) or be postmarked 31st May or earlier.
The consultation closes on the 31st May, which is this coming Saturday. It's not clear to me if snail mail replies have to arrive by then (I'm sure they don't work on a Saturday!) or be postmarked 31st May or earlier.