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.

What I meant was "In order to detect gliders I have to carry a completely separate bit of kit...", not that such a thing would be mandated. The point was that there would be a proliferation of incompatible standards.

I've obviously wound you up which was not my intention, sorry: it's evident from your past contributions that you take a balanced and logical approach. Nevertheless, I would maintain that

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.

What does one do when this occurs?

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.

Just out of curiosity, why would you reduce load here? As far as I can see, that would simply increase the current available to go into the battery, making the problem worse.

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.

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.