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IO
”Rod1 - how is the empty weight of your homebuilt made up? % due to engine, airframe, avionics, etc. It should be trivial to save 5-10kg by replacing certain non-structural items. I realise you carry a transponder but you gave this example as representing huge numbers of pilots. “ A VLA does not have the problem of a max empty weight. It is the micros, which have the problem. The CT and Eurostar aircraft are within 0.5kg of max empty weight factory built and that is with min allowable kit, no radio and no transponder. My glass panel and standard kit is quite light (the HSI is 300g all in including the solid state gyro). If I had to save weight the navcom is 3.88 lbs and the transponder is about 2 kg excluding wiring and aerial so they would be the obvious choice. I could exchange the CS prop for a fixed pitch, but this is only going to save a few kg as the prop is a state of the art carbon bladed electrical unit. Non of the above will help the CT/Eurostar as they would not have any of it to start with. The empty weight of mine is 253kg, mtow 490kg so she nearly lifts her own weight. I agree that large chunks of GA are below 2000ft, including most spam cans. It was your assumption of a connection between no electrics and flying low that I was disagreeing with. The aerobatic boys do not fly low and a lot of home built and some factory stuff comes with no electrics to save weight and improve performance. I make no comment on this being a good thing, it just is. Ironically, the number of flying machines, which cannot carry transponders, is set to increase massively over the next few years. Literally 100’s of unregulated 115kg max empty weight machines are on order and new designs are coning in to this new CAA approved category. Do not assume these will not fly above 2000ft WR There is a guy at Old Sarum who works in engineering and owns a vintage piper who has exactly the setup you describe. In practice he gets about 1.5 hours out of the battery with the wind generator operating, but that is with the radio and transponder on. It is sufficient to get him into L2K and out again but he only uses the transponder to get into cas. Sorry I cannot remember his name; it has been a long week. Rod1 |
If Richard can only get about 1.5 hours with a wind generator backing up the battery then you would need a very big battery to get 8 hours. I therefore assume that the transponders get interrogated a lot more than the above examples assume. The guy who did the “science” part of the LAA submission to the CAA certainly thought it was a non starter to power an existing transponder with a battery, but I do not have a copy of this assumptions and calculations. Unless you could build an entirely portable box it would be of little use in most aircraft anyway.
Rod1 |
I still think we're approaching the problem with the wrong technology. What's wrong with the gps based FLARM system? see ... http://http://lbs.gpsworld.com/gpslbs/article/articleDetail.jsp?id=308235
It appears very practical, cheap in comparison and light. Power consumption is low and it is self contained. I'm guessing that because the system works aircraft to aircraft and not aircraft to ground, that the CAA ect have nothing to gain. It's the sort of system that could actually work if we all supported it but just like TCAS, will fail if only a few aircraft use it. It does though seem more likely to be practical than transponder based systems, or am I missing something obvious? SS |
A straight calculation based on modern LIPO batteries seems to defy the above logic.
The CT and Eurostar aircraft are within 0.5kg of max empty weight factory built and that is with min allowable kit, no radio and no transponder - you cannot fly to NORDO airfields (loads of them) - you cannot fly in transponder airspace (plenty of that too esp. abroad) Looking at 253kg, saving 5-10kg on that should be easy. There are loads of parts which are not significantly stressed and these could be made of magnesium instead of ally. I machine Mg routinely at home; it's perfectly safe. Finally, I agree aerobatic planes fly potentially anywhere vertically but they are not a statistically significant bit of the big picture. If they were, they would be introducing a new hazard, but aerobatic pilots generally choose places to do it where there isn't much traffic. |
Finally, I agree aerobatic planes fly potentially anywhere vertically but they are not a statistically significant bit of the big picture. If they were, they would be introducing a new hazard, but aerobatic pilots generally choose places to do it where there isn't much traffic. We do indeed tend to fly in places that see little through traffic though, try to get the best ATC service available (well, at least I do) and squawk either the assigned discrete code or 7004. There is an implicit expectation that ATC, where possible, will issue traffic warnings about aerobatics pilots when they know about them, regardless of "limited service due to controller workload" or the exact service that someone obtained, as keeping a lookout while doing an aerobatics sequence is a tad harder. Fortunately we do change direction, altitude and speed a lot, making us a little more conspicuously than traffic that flies straight and level. Remember it's the traffic that doesn't move with respect to your windscreen that kills you. |
“I know I keep coming back to this, but do the dealers who sell these clearly state that”
I have no idea and it is not really relevant to the debate. If you allowed us to junk the current rules and start from scratch we could knock up a better regulatory set of rules in a few days. When we started all this the CAA said that there would be a mobile phone size transponder, when it did not materialise we pointed out some basic ideas. Number one was allow micros with a transponder to increase the max empty weight by 5kg. The CAA group who were peddling the “transponders for all” went away and asked their opposite number in a different department, who said no way. This was one of the nails in the transponders for all coffin. It would still be good if we could win the concession, but I am unaware of any progress on this in the last 9 months. You now start to see what we are up against… If you think it is possible to save 10kg on my aircraft basic structure give Cristoph Robin a call at Dyn Aero, he will probably reward you greatly. Just remember it is mostly carbon fibre and is much lighter than any of the opposition, which is why it performs so well. “FLARM system” This was pushed hard by the BGA. The formal CAA response to the 1st consultation spends some time dismissing it as unsuitable. I think you will find the document on the LAA site, but it must be on the CAA site too. Can I suggest that if some of you would like to get involved at the sharp end of all this I know of several organizations who are desperate for help. Be prepared for a big shock, as any allusions you had that there is a big plan and somebody has thought it all through will rapidly disappear. The considerable number of people who worked on this on your behalf may not have won every battle, but we did iron out a huge number of kinks in the plan. There is a meeting on the 15th March at LAA headquarters open to all. The CAA will be presenting the case for the second consultation and will be available to answer questions. I will be there and it would be nice to think you would all come along... Rod1 |
Thanks Rod..will try to make it.:ok:
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There is a mode a/c on afors
Rod1 |
Battery powered transponders
I've installed battery-only powered transponders in non-electric aircraft.
A couple of light-weight/low power examples: Filser TRT800. Weight 570g. Consumption typical 200A. Becker ATC6401. Weight 800g. Consumption 370mA. A typical battery used in Tigermoths and many gliders is the Yuasa 6.5A/Hr sealed lead-acid. When operating both a VHF (Becker AR4201) and a transponder, battery life is normally around 5 hours. A new aviation approved Lithium battery is about to be available which doubles the capacity to 13A/hr in the same size case - it's being targeted directly at the glider community. If you needed to swap the transponders between different aircraft, both of the above units store the aircraft data in non-volatile memory, either in the aircraft mating connector (TRT800), or in a 'dongle' (ATC6401) which plugs into the transponders (same method as many 406 ELT's use), so you don't need to re-programme or risk sending the incorrect Mode S address when you swap units around. |
And all this is approved, as far as approvals are necessary? Sounds very interesting.
Is this mode A, C or S? If C or S, do you get static pressure from the cockpit or does it tie in with existing static plumbing? Are the units accessible in-flight to change a squawk? How about the antenna. Is it permanently wired into the aircraft or portable in some way? Oh, and I assume the Filser uses 200mA instead of 200A...?:} |
Backpacker
Whoops! Yes, 200mA.
Both units have EASA ETSO approval, so installation is good in any European state. These units are approved for aircraft below 175kts/15000 feet, but both manufacturers make similar units for higher speed/altitude. The Filser unit has a built-in altitude encoder - you connect the aircraft static directly to the back of the unit. The Becker needs an external encoder (they were promising an encoder module to plug on the back, but I haven't seen one yet). An external antenna is required (Comant CI01 for about $90), and this needs a ground plane - this can be foil or copper mesh on a plastic aircraft - it needs to be about 15cm diameter. You can even mount the antenna internally on fibreglass or fabric aircraft (not with carbon-fibre, as it shields the signal) If you want to do the installation in an EASA certified aircraft, you will need some form of design approval, either from an EASA Part 21J design organisation, or via a direct minor modification application to EASA. If it's an annex 2 aircraft, you apply directly to the National Authority for the minor change (In the UK, most Part 21J companies also have a UK national design approval as well for annex 2 aircraft). Hope this helps. |
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So what about FLARM? Anyone have any experience of know anything about the system first hand?
SS |
These units are approved for aircraft below 175kts/15000 feet, but both manufacturers make similar units for higher speed/altitude. I would like to know what is the real meaning of an "aviation approved" lithium battery. It's a bit like a barbeque approved for use inside a petrol refinery. Wigglyamp - should there be a problem with a transponder which is fixed to the (non-electric) aircraft's panel, and the battery being on a flying lead with a connector? That makes the battery portable, and portable stuff does not need approval (except for transmitting equipment where the CAA has the responsibility for approving e.g. Icom handheld transceivers). It also means that if the battery starts smoking, you can unplug it and chuck it out of the window (if you have a window at all). |
IO-540
You can't have an approved transponder installation with a PORTABLE battery - it's not certifyable. To certify the installation means showing that all component parts will remain in place to specified G loads - bits in the cockpit which can injure the occupants in an accident must be secure to 18G forwards. Hidden bits need to meet 9G (all details are in EASA CS23.561)
The Lithium battery problems with catching fire have long been recognised - hence they've not seen widespread use so far, other than memory back-ups in GPS systems and deployment batteries for ADELTS (helicopter deployable ELT's used on North Sea). The new development in Li batteries is meant to address these issues and provide the opportunity for smaller, higher capacity batteries so you can run essential equipment e.g. transponders in non-electric aircraft. I've heard it mentioned from a battery manufacturer that the EU will ban production of Lead-Acid batteries from 2012 - will we go to Ni-Cad, with similar overheat problems, or to the new high-capacity Li. I think it'll be the latter, as we'll end up with more glass cockpits needing more power for continued operation when the generator fails. On the different transponder units for height/speed ranges, certainly the Filser unit required a different altitude sensor to get the required 35000 feet, and it's got to maintain it's accuracy, so it's got to be pretty good, considering it's tiny space in the existing transponder case. Also, for both Filser and Becker, the output power is higher for the greater range requirements. As aviation product runs are much smaller that commercial electronics, I guess the manufacturers see this as a way to claw back some of the additional development and certification costs. |
ChrisN has lots of experience of FLARM, but the CAA are quite clear that currently it is illegal to use it in the UK - apparently it upsets people who have radio-controlled garage doors, or something!!!
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>>>>>>>>>>Can I suggest that if some of you would like to get involved at the sharp end of all this I know of several organizations who are desperate for help. Be prepared for a big shock, as any allusions you had that there is a big plan and somebody has thought it all through will rapidly disappear. The considerable number of people who worked on this on your behalf may not have won every battle, but we did iron out a huge number of kinks in the plan.
There is a meeting on the 15th March at LAA headquarters open to all. The CAA will be presenting the case for the second consultation and will be available to answer questions. I will be there and it would be nice to think you would all come along... Rod1<<<<< Rod Well said. The whole issue is one that needs constant monitoring in our 'copious spare time'. I have been to many such meetings and have spoken to the CAA staffers. I have usually come away somewhat mollified, then, weeks later, found that others in the department have reneged on everything that was said previously. Whilst I have great respect for one or two in the Mode S CAA team, I can see that they have decided to use 'salami tactics'. That is to come to the original conclusion slice by slice. Where in this new consultation is the commitment to the 'mobile phone sized, sub 700 euro LAST/LPST? They do state that in Phase 2 gliders will lose exemption, but, again, make no comment as to how this can happen. The radiological study is lacking the 'Ladybird Guide' for scientific innocents like me, despite a strongly worded request from the LAA. No, as many of us as possible need to highlight the outstanding stupidies and impracticalities in the CAA document and a good start is to attend one of the roadshows. I'll be at Turweston, as well, if only to scrag a CAA rep |
Re Flarm, and batteries for gliders
robin wrote:
"ChrisN has lots of experience of FLARM, but the CAA are quite clear that currently it is illegal to use it in the UK - apparently it upsets people who have radio-controlled garage doors, or something!!!" ------------------------ Sorry, not quite accurate. I have a Flarm, but have not yet used it in the air – a job for this season, assuming CAA approves it. I have, however, read lots about it, including results of trials in 2007 at Portmoak and elsewhere. My impression is still that it does more good than harm, but only of course between Flarm-equipped aerial conveyances, which is likely in the UK only to be some gliders, some tugs, and maybe some of various other categories at the light GA end. Nothing would prevent other GA from getting them too, especially those who complain that they hate gliders/can’t see us/it’s our fault we can’t fit transponders (even for those gliders where it is not our fault, of which there are many) etc. – but I’m not holding my breath. Although Flarm uses radio-controlled garage door frequency, I have been told it is too low powered to cause a problem. No doubt that is part of what CAA were/are looking at. CAA were saying it had no approval YET for UK use, but the BGA told me, in effect, watch this space; it was likely to get either approval or at least not actively disapproved early this year. - - - - I shall be interested to see if the Li battery mentioned by somebody comes about with aviation “approval”. I’d like the extra juice, but don’t think I would dare use them unless the “approval”/formal certification is real. (Would chancing it without such approval endanger insurance cover in the event of a fire or other incident/accident? Don’t bother answering here – the only answer I would believe would be from my insurer and only then if in writing.) Chris N |
Nothing would prevent other GA from getting them too, especially those who complain that they hate gliders/can’t see us/it’s our fault we can’t fit transponders (even for those gliders where it is not our fault, of which there are many) etc. – but I’m not holding my breath. There's a perfectly good standard out there for this which is an ICAO standard. It's ADS-B over 1090ES which most large aircraft and an increasing number of light aircraft already have the equipment to use. The issue is surely only about the power required vs the range of the equipment -- I can't see anything about FLARM that improves the range to power over 1090ES. All the cost is in the certification and it's as easy to certify a light and low-power 1090ES transponder (or at least, ADS-B-out box) as it is to certify FLARM. |
I've heard it mentioned from a battery manufacturer that the EU will ban production of Lead-Acid batteries from 2012 - will we go to Ni-Cad, with similar overheat problems, or to the new high-capacity Li I've designed countless charging circuits for battery powered appliances over the years. NICD or NIMH needs a constant current charger with a voltage and/or temperature-rise based cutoff. I wonder how they charge the ones used in jets? |
bookworm
I think the point about FLARM is that it is very popular in parts of Europe so it has an installed base. However the CAA have rejected it and given a full explanation as to why. I have never seen this refuted, and as far as I know FLARM is off the table. wigglyamp I do not think CS23.561 would apply to most of the aircraft with no electrics. Most would come under CS-VLA or Section S which I think uses lighter loads. In LAA land you could certainly get approval for a mounting box which would allow a battery to be clipped in and removed. Approval might involve full stress calculations etc though and this only overcomes one of the many problems such as weight, space etc. Rod1 |
The clever bit, if it worked, Rod1, is that a removable battery might not feature in the empty weight ;)
Mind you, even a "huge" laptop LIPO battery weighs only a fraction of 1kg. |
IO540,
It would defiantly not count in the empty weight if it was powering “optional equipment”. If the aircraft had to carry a serviceable transponder and it needed the batt to work then it would count. Rod1 |
Re FLARM, Mode S and ADS-B
Bookworm on 26.2.08 quoted me: “Quote: Nothing would prevent other GA from getting them [Flarm] too . . . “ and wrote “ . . . So I have to carry a completely separate bit of kit, displaying on a separate screen, to detect gliders... And then next year, the microlight community will decide they want to use a different technology with different standards and I have to go and buy/fit another piece of kit...”
BW, there is a great difference between “ nothing would prevent” and “ have to”, as I’m sure you must be aware. I have better things to do than spend time on a fruitless dialogue. If, however, anyone seriously wishes to discuss the issues based on facts as far as they can be determined, logic rather than emotion, and realistic possibilities of outcomes, I might be prepared to spend some further time on the subject. For what it’s worth, the present position that I have reached is that mode S. has its place, but mandating it across all aircraft in the UK is not on. FLARM and ADS-B also have their place at present in some parts of the world, and I believe that could include the UK today as far as FLARM is concerned. It may be that at some future point FLARM could be replaced by ADS-B, but that would require further development of ADS-B, taking on board the utility that FLARM already has, and a price, package, and weight combination that makes it feasible. I suspect that even then, there would be issues that it simply is not practical to fitted into certain aerial conveyances. Mandating any universal requirement for additional instruments would either result in grounding some aircraft, or there would have to be exemptions if they were able to continue flying. That is a matter of hard, practical fact. I am not totally opposed to mode S; I have already taken some steps to be able to fit one into my glider, and if there is a reasonable technical solution I might well obtain one because of the particular areas in which I fly, and the particular things which I wish to do myself. I do not regard the technical and price package available at the moment as acceptable or justifiable, but if and when that changes, I would probably go for it. I don’t mind explaining the reasons for my present position, if anybody is interested and wants to have a sensible dialogue. Chris N. |
BW, there is a great difference between “ nothing would prevent” and “ have to”, as I’m sure you must be aware. I have better things to do than spend time on a fruitless dialogue. a) in collision avoidance systems, interoperability is crucial, hence common standards are paramount b) there is no technical reason why a 1090ES certified system would be more expensive or more power hungry than a certified FLARM system of equivalent range -- the reason FLARM is cheap and light is that it is uncertified and shorter range. c) 1090ES is the established ICAO standard Therefore the sensible way forward for all airspace users is to rally around a light and affordable 1090ES-based system that is proportionate in its cost and power consumption to the class of aircraft in which it is to be used. |
BW wrote 27.2.08: “
a) in collision avoidance systems, interoperability is crucial, hence common standards are paramount b) there is no technical reason why a 1090ES certified system would be more expensive or more power hungry than a certified FLARM system of equivalent range -- the reason FLARM is cheap and light is that it is uncertified and shorter range. c) 1090ES is the established ICAO standard Therefore the sensible way forward for all airspace users is to rally around a light and affordable 1090ES-based system that is proportionate in its cost and power consumption to the class of aircraft in which it is to be used. ----------------------------------- My reactions: a) in collision avoidance systems, interoperability is crucial, hence common standards are paramount In an ideal world, and other things being equal, I would agree. But other things are far from equal today, and I see no sign that they will be in the foreseeable future. b) there is no technical reason why a 1090ES certified system would be more expensive or more power hungry than a certified FLARM system of equivalent range -- the reason FLARM is cheap and light is that it is uncertified and shorter range. Even the difference between certified and uncertified is likely to add so much cost that it will preclude wide use, except where it is virtually or actually mandatory, such as glider flying in the Alps. EASA replacing the hitherto BGA airworthiness and modification system in the UK at the very least adds cost, and in practice may make widespread or universal adoption virtually unattainable. I suspect that, for many gliders, even uncertified FLARM, in a portable rather than installed form, is at the very least difficult to put into universal operation. Anything bigger, certified, requiring more battery, and if developed for other users and not delivering the algorithm-based outputs for which glider pilots designed it, it’s going to be less welcome and/or less practical. c) 1090ES is the established ICAO standard Fine, but new developments based on it will have incremental development costs which have to be recovered, and will take time which means it is not an immediately available solution. “Therefore the sensible way forward for all airspace users is to rally around a light and affordable 1090ES-based system that is proportionate in its cost and power consumption to the class of aircraft in which it is to be used.” AFAIK, it is not accepted by any of the major players, stakeholder organisations, or the majority of their constituencies, that it is the sensible way forward. For such a plan to get off the ground, I think it would need selling to them. They would need to see how it addresses their concerns, and how it is going to benefit them. Everyone with a financial turn of mind would want to see that their personal costs and the overall investment in any such scheme are a sensible and proportionate use of money, in relation to the risks and/or costs of not adopting universal and interoperable systems. I am certainly not so persuaded myself, at present. Again, AFAIK, mode S, ADS-B, and Flarm were all developed in different “communities” and even different countries, to address different needs. They each obtained sufficient support and take up among their respective communities to justify their respective development. Their continued expansion by those who want them shows that this process is continuing. The strength of objection to spreading any of the three, potentially to take over some part or all of one or both of the other two functions, is indicative of the difficulty in convincing people that there is a widely acceptable universal solution to collision avoidance. I realise that these arguments are largely glider oriented, but that of course is where I come from, although I do take a wider view too. Chris N. |
Batteries and design rules
IO-540
Many aircraft, particularly gas-turbine heliciopers and small turbo-props, have Ni-Cad batteries charged directly from the constant voltage bus - Bell 206 JetRanger amongst others. They do have overtemp warning fitted. The new generation Ni-MH batteries currently under development have a patented charging system to allow use in environments such as aircraft, and the designer is confident we'll have them in certified aircraft in the not to distant future, and certainly in gliders in the UK very shortly. They are already in service with the UK and foreign military forces for specific roles (not yet primary aircraft power as far as I'm aware) Rod 1. I mentioned CS23.561 with my Part 21J hat on - in EASA land, I'm required to show compliance in design with the latest standard (21A.101) unless I can show good reason for staying with an older cert basis. I accept that many LAA type aircraft don't come under this rule, but if I was to certify a design in an Annex 2 aircraft (Tigermoth etc) under my BCAR design approval, I'd still have to meet the same design criteria, as the BCAR approval is piggy-backed on the EASA Part 21J approval and has to use the same design rules and procedures. |
They do have overtemp warning fitted One can indeed charge a NICD or NIMH from constant voltage but the battery draws an awful lot of current when it is charging from a low state, and the charging (constant) voltage needs to not only be quite accurate but needs to be temperature compensated to achieve full battery capacity. I wonder how this is addressed in jets? |
Battery temps
It quite usual when a small turbine is started, to see a huge charge current when the genny is switched on. With a 200A starter/generator, it can easily be well over 100A initially.
On large aircraft such as the L1011, the battery system had a pulsed charger with separate control, rather than the battery being charged directly from the regulated bus. For the smaller aircraft with a HOT BATTERY arning, it's just that - a warning. The pilot is meant to follow the Emergency procedues section of the AFM to reduce loads and land ASAP. |
For the smaller aircraft with a HOT BATTERY arning, it's just that - a warning. The pilot is meant to follow the Emergency procedues section of the AFM to reduce loads and land ASAP. |
Some aircraft have an automatic system to disconnect an overheating battery. In others, the cockpit drill is for the pilot to switch it off manually.
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Okay, I get it. So the assumption is that you either have multiple batteries, or have an alternator that doesn't require a connected battery to work(*). In any case, you can safely disconnect the battery without losing vital avionics.
(*) If you know what I mean. The whole "alternator field" thing that needs to be powered by the battery is still a mystery to me. |
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