Question for the FLARM users out there

[Simon Waddell]

Hello all

Schempp-Hirth provide a FLARM antenna in the fin where it is not shielded by carbon fibre.

I have heard that its efficiency is (may be) limited by the long run of cable from the instrument panel to the fin because the cable is not suited to the high frequencies used by FLARM  (over 800 MHz) and so both the sent and received signals are attenuated.

Since we use a PowerFLARM Core with twin antennas - the one in the fin and one underneath the fuselage behind the wheel well - it is difficult to be sure about our own performance (I suppose we could run a test by unplugging the lower one...)

The fix would be simple - install a traditional FLARM antenna on the top of the rear instrument panel.  Before doing that, I would really like to hear the feedback of this group.

Pip pip

Simon

Arcus M s/n 76

[Mark B]

I have an LX 9000 F (Flarm inside the LX, single aerial only). I have the aerial on the top of the rear instrument panel. I find the reception very disappointing. Any suggestions for improvement welcome!

[Simon Waddell]

Hello Mark

Interesting - or worrying.... Have you seen on the FLARM website that they have a tool to evaluate overall antenna performance?  It requires collecting a lot of flight data, which you may already have available.  I plan to make use of it next year.

Meanwhile, I'm guessing that with the antenna mounted on the binnacle the fuselage will create a significant radio shadow in the glider's 4 to 8 o'clock.

I see that LXNav, and others, offer an antenna for external mounting, which could be mounted on top of the fuselage behind the cockpit.  This should give best electrical performance but I don't know about the impact on gliding performance.  It looks a bit like the kind of whip antenna you find on walkie-talkies.

Our external antenna under the fuselage is just a bit of copper wire about 10 cm long (from memory).  I imagine the same could be used on top of the fuselage; that should have no impact on gliding performance but would it be effective electrically?

KR

Simon

Arcus M s/n 76 

On Thursday, 4 December 2014 09:54:07 UTC+1, Mark B wrote:

[Simon Waddell]

Hi Mark

Supplementary question: is FLARM widely used in the UK?  I thought it was regarded with deep suspicion by the BGA pundits....?

KR

S

On Thursday, 4 December 2014 09:54:07 UTC+1, Mark B wrote:

[Mark B]

I have used the tool for evaluating Flarm performance (for the LX you use an LX specific one). I think it is flawed, in that it reports where Flarm contacts have been spotted. It cannot tell where Flarm contacts have failed to be spotted, and unfortunately I cannot rely on always getting contacts reported from the ranges reported by this tool.

Although my aerial is in the conventional position on the top of the rear instrument panel, I presume that it gives a good signal downwards, because my glider gets good reception from the ground monitoring stations which now cover most of the area where I fly (in competitions it is possible to follow the progress of most gliders).

On the question of the UK attitude to Flarm generally, in my club the great majority of cross country pilots have Flarm (very few Powerflarms), and I think that would apply to the majority of active cross country pilots in the UK.

This is more a topic for RAS or URAS. You are right that the BGA do not give whole-hearted support to Flarm. I think this, from 2009, is still the stated position:

“Effective lookout is vitally important at all times. The BGA considers that the widespread adoption of mutually compatible and low cost proximity/collision awareness technology in support of effective lookout can be beneficial to the gliding community. Owners who choose to equip with such technology should consider, among other installation and operational issues, compatibility with existing systems. These currently include FLARM, used primarily within air sport, and devices capable of detecting transponders employed elsewhere in aviation.”

Note - BGA accident statistics demonstrate that there is a higher risk of a midair collision in the circuit, in thermals and when hill/mountain soaring than in any other phases of flight. Effective lookout is vital at all times.

Mark Burton

Arcus M s/no 24, Dunstable, UK

My club has not installed Flarm in club gliders which are mostly flown locally and often by less experienced pilots. We don't have it in the tugs either There is a thought that on our busy local hill and in the circuit, where good lookout is essential and a vital part of training, Flarm warnings may do more harm than good by causing distraction. The club would probably fit Flarm if there was a clear recommendation to do so from the BGA, and particularly if there was a syllabus for training the use of Flarm.

[Simon Waddell]

Hello Mark

The attached FLARM range analysis was the result of a single long flight from St Auban by my friend Heini in his Arcus M equipped with a Power FLARM Core and dual antennas: the short rod antenna below the fuselage and that standard S-H antenna in the fin.

I'm not a specialist but it looks pretty good to me with a consistent, long range in all directions.  I suppose it would be nice to know on how many contacts it is based.

KR

Simon

Arcus M s/n 79

[Errante]

Hello Simon

We must be careful with the analysis of Flarm record made by LxNav, is generally more optimistic ...
I enclose analysis of the same igc record made by LxNav and Flarm,
Anyway, a flarm range of more than 22 Kph is really outstanding, indeed. Try it with:

http://www.flarm.com/support/analyze/index_en.html

Best regards and good flights,

Errante
Arcus M s/no 49 Santiago, CL

[cernauta]

Since a few years I have never been able to get more Flarm range than
3km (frequently just 1km) from original "swiss" flarm units, of which I
tried at least a dozen units.

The PowerFlarm allows consistent long range detection. It has a
secondary antenna input as an option (recommended). I'm not sure wether
both inputs have the same high sensitivty receiver.
The "main" antenna connector allows both tx/rx functions.
The secondary input is rx only. I connected it to a home made 1/2
wavelength dipole installed on the canopy frame and I regularly get more
than 18km which is satisfactory.
So, if you have the fin antenna, it's great. If you don't, it's not that
bad.

An Italian guy builds an external antenna amplifier for swiss flarms. It
brings receiver sensitivity up to Powerflarm level, and can be
configured to increase tx output power also. Most owners are happy.
Unfortunately, it's only a little less expensive than a "PF core pure",
so I wouldn't highly recommend it.

Aldo Cernezzi
Arcus M, s/n 37
www.voloavela.it