PowerFLARM leeching comments

On Thursday, November 1, 2012 5:45:02 AM UTC-7, Don Johnstone wrote:
At 02:05 01 November 2012, Ramy wrote:

Don, can you back up your claim that Flarm was designed mainly for wave

flying by providing some reference?

Also,can you share with us your actual experience flying with Flarm?



Ramy



The original FLARM was conceived to assist pilots in detecting difficult to

see gliders, particulary in wave where the relative movement is small, the

closure rate is slow and the track of another glider cannot easily be

detected by observing the way it is pointing.

I fly a Discus fitted with FLARM and an LX8000. The LX8000 linked to the

FLARM provides a "radar" display on the moving map. I have found the system

to be useful when flying in wave, I have found it to be less useful, if not

distracting in thermals. On a short 3 mile ridge with 20 or 30 gliders it

is positively lethal.

I do not use the LX8000 display at all when flying a ridge or in thermals..

I have used it when flying in wave, however I still feel the time spent

looking at the LX display and trying to make sense of it would be better

spent looking out.

The most scary thing, even using just the clock lights on the basic system,

is that it is misleading when flying a ridge in higher wind speeds. The

light bears no relation to the direction of the threat so I hear the bleep

and look all round. I have to say that there have been very few occasions

when the alert has sounded and I have not seen the glider causing it before

the alert sounded, lucky maybe?

Lucky, yes.

In a dozen flights I probably picked up 10-15 conflicts that I had not already determined to be a threat visually. Examples include: an LS-8 doing a zoomie from down below my nose after overtaking me from behind/below, a Discus 2 that decided to leave a thermal by cutting through the middle of the circle and across my path from above/behind, a glider a half mile abeam of me that changed to a converging course line. On top of that there were multiple cases of traffic encountered on course and gliders adjusting their circles in thermals, I found most of them immediately useful and a couple were downright sobering.

I never use the radar display in a thermal - it's not good for that and not intended for that, but it is useful in making you aware when a glider you might not have seen is now in your general vicinity. Mis-using the radar display by going heads-down in close quarters is not grounds for a sweeping criticism of the device. You could make the same criticism of an airspeed indicator - staring at it until you fly into an obstacle would be dangerous and dumb, but isn't a reason to remove the instrument from your panel.

I recall the same as UH - that Flarm was developed for Alpine flying, but not especially for wave - (which is a small portion of overall flight time). I always understood Flarm was targeted at a general set of glider collision threat scenarios - all of which would be exacerbated by the traffic funneling that mountain flying of every form tends to generate. I expect Urs could clarify.

9B

On Wednesday, October 31, 2012 10:05:38 PM UTC-4, Ramy wrote:
Don, can you back up your claim that Flarm was designed mainly for wave flying by providing some reference? Also,can you share with us your actual experience flying with Flarm? Ramy

I recall hearing that Flarm was developed to attempt to address the issue of mid air collisions and collisions with obstacles in the Alps. There is a big issue with coming around the corner of a rock and there is another glider. They also have a huge number of wires and such that you can't see.
Maybe the Flarm folks can clarify this bit of history. I'm sure we all would like to know.
UH

On Thu, 01 Nov 2012 05:50:48 -0700, unclhank wrote:

I recall hearing that Flarm was developed to attempt to address the
issue of mid air collisions and collisions with obstacles in the Alps.
There is a big issue with coming around the corner of a rock and there
is another glider. They also have a huge number of wires and such that
you can't see.

I heard that too - especially the point about flying round a corner in a
mountain face and meeting traffic coming the other way. I think that also
explains the built-in obstacle database.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

I recall hearing that Flarm was developed to attempt to address the issue of mid air collisions and collisions with obstacles in the Alps. There is a big issue with coming around the corner of a rock and there is another glider. They also have a huge number of wires and such that you can't see.

Maybe the Flarm folks can clarify this bit of history. I'm sure we all would like to know.

FLARM has been designed and deployed since the beginning for gliders and light aviation.
It has *not* been designed specifically for wave flight, but rather to cover a wide range
of situations where the human eye can fail. (Wave flight accounts only for a very
small percentage of flight time at least here in the Alps, so the benefit would've been minimal).

The FLARM algorithm is general enough to support any type of aircraft and maneuvers,
with the exception perhaps of aerobatics.

Initially, most installations were in gliders, but tow planes and other GA aircraft
soon followed.

The collision algorithm does work in wave, however with the caveat that the relative
bearing may be off because of the wind influence. This is covered in the manual.
(BTW, the relative bearing will also be off if you fly inverted!

I hope this clarifies a few questions!

Best
--Gerhard

On 10/31/2012 6:46 AM, Don Johnstone wrote:
Of course FLARM can help, IF it is used as intended
and the human bit understands what he is bing told. It still relies on good
old fashioned lookout.

If Flarm alerts you, it's probably because your "good old fashioned
lookout" has not alerted you. Flarm does depend on you finding the other
glider that caused the alert, but finding a threat after it's position
is given to you is not part of "good old fashioned lookout".

The pilot should continue to use his "[not really so] good old fashioned
lookout" after he has installed a Flarm unit, because there are still
aircraft that don't have Flarm or a transponder, and because Flarm isn't
perfect.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)