OpenFLARM project
 

Has anyone any opinions on the OpenFLARM project?

OpenFLARM

It is a £50 GPS and traffic receiver that can also pick up contacts carrying FLARM. It is fully open source and non-commercial and trying to break the closed monopoly we currently have in the light aircraft world and bring the cost of a traffic avoidance system within reach of all pilots.

Be interested to hear if anybody has seen it and/or has an opinion.

http://www.openflarm.co.uk/img/sd-resized.png?s=pprune

This looks interesting and I applaud the fact that it is open source.
However, it looks of very limited value at the moment.
This is because it appears not to pick up transmissions of ADS-B or be visible to FLARM/PowerFLARM users. I am not even sure if it picks up all types of transponders either.
In my experience of using PowerFLARM portable over the last couple of years, the vast majority of light aircraft that I pick up are transponding Mode C/S and the airliners are transmitting ADS-B.
However, perhaps it will develop into the cheap universal electronic detection device that is needed.

PS I prefer a device that warns of imminent collision rather than providing a virtual radar display.

PPS Suggest you have a look at PilotAware- it seems to have been developed along the correct lines!

Looking at the link, it would appear that (at least at this stage of development) the system will do nothing other than detect other 'OpenFLARM' systems. It won't detect ADSB, FLARM, PilotAware or any other transmission. If the other aircraft isn't also carrying OpenFLARM, you simply won't see it.

I would be interested to know two things: does the GPS make use of the WAAS/EGNOS data; does it derive height purely from the GPS or does it also have a barometric sensor. It would appear that the GPS unit they use is GNSS only, so there is no access to other GPS constellations such as GLONASS.

Apart from the laudable open source approach, the strength of OpenFLARM must be the £50 price target, making it likely to be far more widely adopted than the competing systems. If collision warning is added, that would dramatically increase its appeal.

For me, a £50 unit with collision warnings would be worth the punt - until then I'll await developments.

The one idea is the good one - open source low cost. But, I doubt this initiative will be widely used. There are now so many Pi-based (some tinker) solutions out there doing ADS-B (Stratux, Openflightbox, Pilotaware with a similar system ...) jumping on the same and there are now the small Echo devices from uavionix.

My prognosis and a little hope, if politicians finally wake up - after all they will adopt UAT, if they stay that deaf and dump - we get our own European system in 20 years with 10 percent functionality of todays US infrastructure.

It will detect FLARM.

ADSB is mentioned on the web page as not working.

PilotAware claims to be open but in fact does not publish it's protocol, hence leading people down the same terrible path as FLARM did.

I don't know about 'WAAS/EGNOS' but I can tell you (from the link to the GPS datasheet on the page) that the chipset supports GLONASS.

As far as I am aware, SkyDemon and the like calculate their own 'collision warnings' when fed with suitable data, and probably far more accurately given the processing power available to them over and above that in a conventional FLARM.

We need yet another 'standard' for transmitting position like a hole in the head.

Let's think: Mode S. ADSB. Flarm. Pilot Aware. Now this. Too much confusion over standards merely leads to lower overall takeup - there's no point if people are flying around with different systems.

If they want to use something that is 'open' what's wrong with ADSB?

The point about the Flarm anti-collision algorithms (which are the patented bit of the system) is that they are designed for use in gliders, where close proximity is normal - it's only when an actual collision is imminent that there is a warning. It's quite different from, say, TCAS, which has quite a large bubble around it. It's not about processing power, it's about what you do with it.

Paul

I absolutely agree. Taking ADSB and Mode S out of the question for a minute, the problem we as an hobby and private aviation community is that we have had to opt for closed solutions because that was the only choice. I don't blame people for doing that, but their trailblazing is blindly leading the rest of the community down a dead end.

FLARM is completely closed. In fact they take active steps to both encrypt and obfuscate their traffic information in the hope that it will force us to buy their hardware at massively inflated costs. I understand that people have got to make a living, and that we as a community do tend to have reasonable budgets, but the level of cost vs RRP is far too large in my opinon.

PilotAware looked great at the start, a real solution to breaking the FLARM monopoly, but unfortunately their promise of making their protocol open has evaporated. They have never published it, and they ignore requests for information. In conclusion they are using the same predatory tactic as FLARM.

So as I said above, I quite agree that we don't need another protocol but instead an open protocol both in terms of anyone being free to implement it but also anyone being free to comment, expand or suggest changes to without having a manufacturer having ultimate veto. Unfortunately it seems that neither FLARM nor PA wish to take that step.

The OpenFLARM system supports FLARM receive 'out of the box' ie doesn't need an £800 add on to make it work (like PA does). It will be receive only at the outset, purely because there are parts of the FLARM protocol that have not yet been reverse engineered and we do not wish to risk safety by transmitting data without understanding what it does.

We are quite happy to support PA's PI3 protocol if they wish to start talking to us. We are also quite happy to give them our information so that they can integrate with our system.

And just for the record, any OpenFLARM system can transmit and receive data from any other OpenFLARM, be that aircraft or ground station relay.

Yes, I also agree, having every aircraft running Mode S/ADSB would be a great solution. However as of today how many hobby and private pilots - the sort of people who would buy a FLARM or PA - actually carry the equipment to transmit it? In my experience, virtually none. The approval process to actually having transmit capability, ie to be seen yourself, is prohibitively expensive and those that can afford it are likely to be 'up high' and out of the way.

My conclusion therefore is that it is of limited use in the real (hobby and private) world at the moment, and that is the root of the problem. Any system needs critical mass, you end up playing 'chicken and egg', and when the cost of entry is so high it prevents that cycle being broken.

OpenFLARM on the other hand is a £50 punt, less than most of us pay for 0.5 hours I would expect, and just plugs in an goes. An external GPS receiver for your tablet costs more than that, so even without the collision avoidance it is a useful device.

Back on ADSB, the time I can actually see it being useful is in the vicinity of a large airfield where light aircraft are mixing it with bigger stuff. There is a solution for that built in to the OpenFLARM protocol where a ground station at the airfield can retransmit ADSB or Mode S data for this exact purpose and that data can be shared between devices in flight in order to increase range.

Also please take a look at the video on ADS-B linked from the OpenFLARM site. It is a of a presentation given at the DEFCON hacker convention which points out some massive security weaknesses in ADS-B. Quite scary stuff when you start thinking about it. I am actually split on my opinion on this. Part of me says hopefully the aviation community as a whole will wake up and fix these issues, either by extending the standard or replacing it altogether. The other part of me says that if that does happen it is likely to make the approval process even more difficult and put the technology even further out of reach.

That may be true in the UK but it certainly isn't everywhere. In Germany, for one example, even many ultralights are carrying a mode S transponder. Myself will soon be installing a Trig transponder too, and mainly to be more visible to other pilots.

I might however be interested to add "something", preferrably open source, perhaps running on a RasPI or so, to display nearby ADSB transmitting planes. Flarm I will not touch even with a barge-pole - it is not under any formal norm or control, bases upon the cheapest consumer electronics, and is partially non-open.

Your bit about security holes in ADS-B is a bit disconcerting, though, I will have to look into that before proceeding any further. If substantial modifications to ADS-B are found to be in order, my transponder investment might loose a lot of its value, perhaps even all.

Make up your mind Jan, are you going with 'cheapest consumer electronics' or not? (Not that Flarm is, actually, that).

But more importantly, in the UK at least, probably 75% of gliders flying cross country carry Flarm. If you want to see them, that's what you need. You might wish they carried something different, but they don't.

Paul

A fair remark, Paul, still I'll stand my ground: for announcing where I am, I will use something decent. This is after all both towards ground stations (my main concern) and towards other pilots (a side benefit). On the receiving side, I might be less demanding, as I consider electronics only a help in detecting other traffic. Not wanting to redo the discussion on the Mk1 eyeball, though, that has been done to death.

As for gliders using Flarm: it must be quite general yes, on the continent too. Still we should not follow them in this abhorrence. At my homefield, the better equipped gliders carry both Flarm and ADS-B transmitters - if that isn't a waste of payload and of electric power!

I think this whole thing is a tough problem, though I don't think anyone is suggesting that everyone should adopt Flarm. I can think of lots of cases where multiple technologies existed for a while before some sort of shake out. In this case though, there's a 'natural monopoly' in that having anti-collision systems which can't see each other kind of defeats the point.

A few thoughts:

• There probably isn't a one size fits all solution. The requirements of functionality, reliability, size, cost and power consumption are different for different use cases (airliners in controlled airspace different from a glider outside etc).
  
• Ability to encrypt / not spoof might be illusory. You can make it more difficult to break, but probably not more than that. See the huge amount of work that went into making DVDs and Blu Rays secure, and how far that got them. And Flarm's attempts at encryption.
  
• I don't think the market can afford too many non-co-operative products. It means that none of them actually achieve their aim.
  
• Regulation is probably actually getting in the way. In the UK there are some trials of ADSB with low cost GPSs, but they are moving awfully slowly.

So what to do? Personally I wish that the powers that be actually get on with a low cost ADSB and make it happen. Get some products out, remove the regulatory barriers. Gliders will probably continue with Flarm in the short to medium term, not least because of the anti-collision algorithms, but everybody gets to receive both.

[I carry a Flarm and a mode-S in my glider. The first helps me with gliders, the second keeps big things with a traffic service away from me. Neither helps me much with GA]

Paul

First off, thank you to the mods for reconsidering their decision to remove this thread. Glad we can continue to have a reasonable discussion on this matter.

Let me take a step back for a minute; as I understand it (and I don't claim to be an expert) the two main issues with ADS-B that were revealed in the DEFCON talks were essentially the following:

1. There is no mechanism to verify that a position report transmitted on ADS-B actually originated from the aircraft it claims to be from.

2. There is no geographical protection to the receiver system; in other words a message could be received in the UK giving a position report in the US and the ADS-B network would propagate even though it is clearly not possible (if the plane was really in the US a UK receiver would not pick it up)

The latter could easily be fixed in software; in fact it probably already has been (I would certainly hope so!) but the former is a lot more complicated.

Certainly encryption is not the answer for the fundamental reason that in order to read the data every device must have they key to decrypt and once that key gets into the open suddenly your encryption is broken. This is what happened with DVD - someone managed to extract a decryption key and made it public. There are other reasons to encrypt of course, for example to make your traffic difficult or obscure (as FLARM does) but ultimately if you sell a device containing a decryption key (which any receiver would need to have) it will be a possible to recover that key and break the encryption.

What ADS-B needs is a way of signing a clear text message with a cryptographic system that proves that the message was sent from the aircraft it claims to be from. Something like an RSA signature or a PGP signature on an email. Such systems are based on a public and private key.

Adding this signature to the ADS-B message is not a huge issue but the problem comes when you realise that in order to implement this a receiver would need to maintain a database of the public keys of all aircraft it is likely to come across. This is not a huge problem for modern electronic systems* but certainly beyond the scope of transponders as we know them. Maybe someone will come up with an add-on box that authenticates ADS-B transmissions - in fact I suspect that is quite likely - but really the powers that be in the aviation industry should be taking the opportunity to come up with a better solution that takes into account all users (ie not just the 'big boys') and solves the inherent issues with ADS-B.

However, like any technology this comes down to critical mass, and ADS-B certainly has that in the commercial aviation sector. As such we are unlikely to see changes any time soon, and given that fact an interim solution of allowing non-approved GPS units to be connected to ADS-B is probably a sensible step, if it ever happens of course.

Back on to FLARM and OpenFLARM, the question really is 'Why is everyone not carrying a FLARM?'. Personally I think the answer is that it is too expensive for what it actually achieves, and part of that lack of functionality is down to critical mass. If all light aircraft carried one (as well as all the gliders that already do) it would be a far more useful device.

The whole aim of the OpenFLARM project is to put the technology within the 'why wouldn't you?' price bracket therefore stimulating the market to achieve this critical mass.

Chris

*A quick Google brought up this article which suggests a figure of 150,000 planes ever being produced. It's not clear whether that figure includes light aircraft, but it is sufficient for an order of magnitude. So let's say each aircraft needed a 64bit public key, that's 8 bytes x 150,000 keys = 1.1 megabytes. Even if we allowed for 100x that number it would still be a tiny amount of data in today's world.

bcw wrote:
"We are quite happy to support PA's PI3 protocol if they wish to start talking to us. We are also quite happy to give them our information so that they can integrate with our system."

This strongly suggests that bcw is closely associated with the OpenFLARM project. If so, I am very disappointed that bcw did not declare an interest in OpenFLARM in the initial post. Perhaps that is why the moderators initially removed it.

Having said that, a very useful discussion has developed on a subject that has interested me for several years because Mark 1 eyeball is simply not good enough!

I came to the conclusion a couple of years ago that a low cost electronic anti-collision warning system would eventually be developed for GA, probably based on ADS-B.
However, I also came to the conclusion that it was several years away. In the meantime, imho PowerFLARM offered valuable safety benefits immediately.

That is why I bought PowerFLARM portable despite the cost. In any event it was/is a fraction of the cost of TCAS. Since then, I have found it very capable and useful but of course it is not perfect. The Mark 1 eyeball is still important because a lot of traffic still has no electronic signature. And amazingly, I have found that in a lot of Mode C equipped aircraft, the pilot does not even switch it on.

So you can wait for perfection or use what is already available and useful. I have done the latter. You pays your money and you takes your choice.

PS I have no commercial connection whatever with PowerFLARM or FLARM.

For the record, I am a volunteer developer on the project.

(I did write this in the thread which was removed, apologies if this was not clear)

£50? Is that "all in"? Can it be run in conjunction with a Stratux or PilotAware? Can it be seen on the Open Glider Network receivers?

Yes, I'm interested but I would like the capability to see both ADS-B and those that have now got PilotAware.

iRaven

Yes, 'all in' in terms of it will be a box with an aerial on the back and a GPS puck. You pop it on the coaming, connect your iPad to the wifi network it transmits, and you are off.

The intention is that you use this device as an alternative to either of those or a FLARM

Probably not as things stand. I was in regular contact with Paweł from the OGN and even went to visit him at the University of Oxford. He has however stopped responding to my emails recently. I do hope however that he will change his mind and support the OpenFLARM protocol.

As above, PA is an issue because they will not publish their protocol even though they originally said that they would. As with OGN, hopefully they will change their mind and either let us implement their protocol or, better, implement our protocol which will be fully open and published in full for anyone else to use in the future.

Direct ADS-B reception will not be possible on the version 1 units however you will be able to connect a unit on the ground to an ADS-B receiver (or Internet feed) and have it relay ADS-B contacts to aircraft in the vicinity. The idea here is that airfields with a mix of traffic can have one of these units to provide ADS-B coverage near to their field.

Chris

So this OpenFlarm device cannot see ADSB, Mode C, Mode S, Flarm.
It can see other OpenFlarm.
Please can someone tell me the advantages over Pilot Aware which can see all of the above except Flarm.
And why is it called "OpenFlarm" which implies it can "open the encrypted Flarm signal" ?

At the risk of repeating myself...

It can see FLARM users, FLARM cannot see it. FLARM appears to be the incumbent standard for small aircraft ie the number of units deployed in the kind of aircraft that private and hobby are likely to come during normal operation. What I mean by this is that of the small aircraft that carry collision avoidance technology the largest proportion of these are using FLARM and it is therefore the one you are most likely to come across in normal operations.

It cannot see ADSB (and the related technologies you mention) directly but can via a ground station, the intention being that these can be deployed in areas where small aircraft are likely to be mixing it with larger ones carrying ADSB transmission equipment. The reason for not including this functionality is that only a tiny minority of small aircraft carry ADS-B transmit capability (Pilot Aware only receives) and it is therefore of limited use to small aircraft pilots at this time.

It can see other OpenFLARM units.

We hope it will be able to see other PA units in the future but this is subject to their cooperation.

It is significantly cheaper than a FLARM setup of the same functionality (ie that can link to a tablet via wifi)

It is cheaper and far less complicated than a Pilot Aware and does not require any DIY. If you factor the cost of adding FLARM capability to Pilot Aware the cost is also significantly less.

The advantage to the community as a whole is that it promotes a collision avoidance technology that is both open (as in ADS-B) and does not require expensive (due to heavy certification requirements) equipment. None of the standards current available tick both of these boxes.

It is 'Open' as in 'Open Source' That means that the protocol, software and hardware are going to be released to the public (the latter already has).

As such, any manufacturer can build they own device either based on our hardware and software design or their own. Market pressures will decide whether Pilot Aware and/or FLARM make their units compatible with this protocol. As a community it should be obvious that it would be a good thing to promote an open standard instead of the closed shop we have now and we as individuals and potential customers should therefore be pushing the manufacturers down this road. Up to now though there has been no viable alternative and therefore no way to develop the critical mass to force the manufacturers to wake up. The sole driver behind coming up with a device that is priced at such a level that it becomes a must-have item and achieves this critical mass.

Ok my mistake, it can detect Flarm.
But it can't detect a transponder nor Open Glider network nor Pilot aware.
It uses a wifi connection to the iPad.
How many separate wifi connections can an iPad handle at one time?
I'm not very computer literate so that may be irrelevant.
Can SkyDemons and their various other flavours use multiple GPS signals from Pilot Aware and Open Flarm?
I don't want to knock it but it seems there are still a number of different systems out there that are each limited to being able to see "some" other systems but not all of them.
Could this device be used in conjunction with Pilot Aware instead of the Flarm mouse at £££ ?
Flarm may be extremely numerous but I'm under the impression that it is a short range device, designed to keep gliders separated.
How many of the numerous Flarm units are used by GA?
How many GA aircraft have a transponder?
How many gliders have a transponder?
If gliders fitted with expensive Flarm units also fit a Pilot aware in order to see/be seen by GA, gradually the take up of Flarm alone will diminish.
The cost difference between Pilot Aware and Open Flarm of times four is not really significant if the coverage is considered.
The cost of Flarm would put it out of consideration now that other systems are available.

A device can only support one connection per antenna.
They can indeed.
The multitude of systems is indeed the problem, hence why I suggest things like Stratux that use the industry standard (ADS-B and Mode S)
There would be no advantage to doing that
That is exactly what FLARM was designed for
Most now. How many have Mode S and ADS-B is less clear...
Few
Yes, particularly as FLARM have not published their protocol
Indeed.

The other *massive* advantage of PilotAware that has not been mentioned as far as I can see, is that with a Mode S transponder it can be configured to make ADS-B broadcasts - along the open standard, that all the controllers and commercial traffic use. Surely this is better than FLARM etc? It is certainly cheaper than the £2.5k needed for the "official" unit and before people ask, yes it is allowed and has been "approved" by the CAA.

Disclaimer: I'm a software engineer but not affiliated with any of these projects.