I did the FAA BFR today. Coming back to Shoreham, I usually stay high because it helps to avoid conflicting traffic. This time the airport was busy so I got an orbit instruction on a (sort of) left base, at some distance. No problem… still at 3000ft. Then when halfway around the orbit I got cleared to descend into the circuit and do left base for 20.
Then I noticed a target on TCAS, 400-500ft below me i.e. at ~2500ft. As I continued the orbit, he was following me around the orbit. I reported it, saying I cannot really descend at present. ATC was not aware of any traffic there so they cleared me to the overhead at 3000ft. As I made my way there, the “follower” got left behind and gradually departed in the opposite direction.
They thought it was probably a glider.
There was certainly a lot of updraughts, with SCT bases of 5400ft and tops about 5800ft, so plenty of turbulence anywhere below the 5500ft base of CAS. It was hard to fly straight – reminded me of the FAA IR in Arizona which was 2 weeks of getting chucked around in a PA28-161.
I commend whoever it was for being responsible to the flying community and carrying a Mode C (or C/S) transponder, but I wonder how many gliders carry them?
The £12k system certainly repays its cost very regularly. Obviously one cannot say how many collisions it has avoided; statistically it is close to zero, but you need only the one…
Off-topic, but
they cleared me to the overhead at 3000ft
Shoreham shoudn’t clear you like that, as it is totally uncontrolled airspace, and even well outside their ATZ.
In the circumstances, perfectly fine IMHO.
They also have IAPs there, and can stack people up to the base of CAS, from 2200ft in 1000ft increments to 5200ft.
The whole business of a “clearance” in Class G is a big debate but both parties know what it means. You can legally fly overhead, non-radio, at 2000ft AAL, right through “normal overhead” traffic. Really stupid, happens all the time, 100% legal.
Your TAS might get you one out of ten gliders, whereas a Flarm would get you 9 out of 10 gliders…
Mode C is not widespread among gliders as it needs a lot of power and means extra weight. It depends on the airspaces the gliders typically frequent.
I agree with Achim. Mode C is very expensive compared to FLARM. Most glider pilots I know, say that there is no need for a transponder as they have FLARM and every plane should have FLARM installed.
Most glider pilots I know, say that there is no need for a transponder as they have FLARM and every plane should have FLARM installed.
Where do you then get the target position readout?
Where do you then get the target position readout?
¿¿ On the FLARM device, I should think ??
every plane should have FLARM installed
It is bad enough that they want to trust to a non-standardised non-certified toy building on consumer grade electronics – no way they are going to impose it on me!
Our gliders that are to fly in controlled airspace have transponders. Not all of them have, controlled airspace start at 13500 ft at ENOP, so you would also need oxygen, lots of clothes etc. Other glider places also have similar alt around 10k before controlled airspace. But, when going longer distances, controlled airspace could come down to 2-3k, so you would enter controlled airspace all too easily, and a transponder would be handy. But then again, those low alt airspaces are mostly along the cost into the North Sea where there are little of anything of thermals or waves (could be waves there though). Better suited for albatross-style dynamic soaring, but so far only the albatross manages to do that 
The glider itself have zero need for a transponder, it’s purely an ATC requirement, and today they enforce it rather strict. After all, why should a glider that is almost impossible to see be allowed to fly without it, while all others must have it? I have never used a transponder in a glider myself, but I’m only a novice glider vise, I usually just pull them off the ground. Battery is not an issue, lots of power in a slightly modern glider. FLARM is the collision avoidance system for gliders, and it works perfectly.
The problem is that there is little gain in installing a xpdr in a glider: On the flarm you see other traffic, with a xpdr you need another box for that. With a flarm you get collision probabilities based on typic movement prediction of the type of aircraft (the tow machine has an other key than the parajumper plane, the glider or the rescue helicopter). Flarm is used as a tool for team flying and as a igc certified logger.
On a symposium, around the time when flarm was introduced, i have heard they wanted to build the system on the 1090ES, that was discussed back then, for compatibility reasons with xpdr / other ga. But EASA back then didn’t have safety in mind and thus did not open their minds for the possibilities in traffic avoidance If i recall correctly there were issues with minimum power output and certification requirements for the proposed system. Since the developers didn’t want to give up, they had to use a free accessible frequency and thus flarm was born.
The main collision danger in gliding is the close proximity to other gliders while flying at or around the speed of minimum sink, which is pretty close to the stall speed, turning in dynamically changing turn rates and bank angles; as well as flying high speed along lift lines either in mountainous areas or beneath cloud streets. So the development of an independent system makes sense to a certain degree and is much better than having no such system.
And you have to keep in mind, that the installation of a fully (certified) TCAS system (the only alternative during the development stages of flarm) is neither financially sensible, nor is it even possible in a glider as a retrofit for the aged existing fleet. Even today, when you want to build the system based on a XPDR and 1090ES, you need much more financial funds than with the portable flarm.
The occasions where flarm doesn’t work are quite rare and frankly, if it is okay to base navigation information delivery on consumer products even in commercial aviation (i.e. the iPad or an android tablet to display charts and maps), I see no reason for banishing traffic awareness on “consumer-grade avionics”.
After a bit of research, I agree with Achim now, that if the regulations for the use of 1090ES is loosened, it is a great possibility for aviation traffic information and if these units can be offered at consumer electronic prices, then they might have a chance to supersede flarm, provided the functionality (i.e. igc flight logging and compatibility with gliding computers and software) remains at least the same.
For the original question: In Germany many cross country gliders now use transponders, as those have become smaller and draw less current. However, the installation is only due to the fact that a transponder opens some airspace for gliders in Germany. Many pilots only use the transponder for flying in airspace that necessitates a transponder and turn it off otherwise. It is not linked to traffic awareness and draws currents. Especially in old club class or older standard class gliders, where the possibilities for the installation of more batteries is not that easy, even when using LiFePo4 battery packs. This has sometimes reasons in the mass and especially in the position of the CoG of the glider, not only for performance, but for maximum pilot mass. More modern gliders often have several batteries (sometimes in the vertical stabilizer) and could run a transponder a day through. The installation of solar panels is not always possible, because they affect the aircraft structure, it’s heating through solar radiation and aerodynamics, a very important factor in gliding.
Cheers,
..::EDIT::..
Better suited for albatross-style dynamic soaring, but so far only the albatross manages to do that
It is off topic, but there has been documented dynamic soaring by Ingo Renner on his H301 Libelle and later with a PIK20 back in the mid 70s. There were some interesting articles on that in the German aviation magazine Aerokurier at that time. This is manned dynamic soaring. Many model aircraft pilots use dynamic soaring for quite a while now and it is investigated for drones to use wind sheer as alternative energy (with varying success).
The obvious comment I would make on the weight issue is that a transponder+battery weighs much less than the possible difference between one person and another person, and that would be true even if the battery was out of a 40 ton container truck The person’s weight could be 45kg (a “UK size 8” girl) or 120kg+ (a male who eats a lot). A TXP+battery+antenna is c. 3-4kg.
From my point of view, I can’t connect any FLARM product (or any ADS-B product for that matter, but despite the hype almost nobody in light GA is radiating ADS-B anyway ) to my Avidyne TAS/TCAS system, so the display would be on yet another box which needs to go somewhere. Where? That is a big barrier to adoption.
I realise most glider pilots could not possibly install such a system (money, size, power, etc) and why should they? For glider-on-glider awareness it’s not as precise as FLARM, because it doesn’t use GPS data for the target’s 3D position. But the fact is that a significant % of modern powered GA aircraft do have such systems today, straight from the factory usually (if you are paying half a million $ for a Cirrus you want all the latest gear otherwise its resale value is affected… who would buy a car without the aircon option) but often retrofitted. It may have cost me £12k to get mine but it is far from a rarity, and if you don’t want to collide with some 150-180kt piece of metal, carrying a Mode C box (pretty cheap on Ebay – fill your boots) would seem a good idea. If I had a glider I would definitely have one. And screw certification.
Many pilots only use the transponder for flying in airspace that necessitates a transponder and turn it off otherwise.
A lot of powered pilots do that too 
Another discussion, on morality!
It is not linked to traffic awareness and draws currents.
It is definitely linked to traffic awareness, even if not the glider pilot’s traffic awareness It is pretty closely linked to the traffic awareness of the pilot of the 150-180kt lump which might hit the glider.
