Another midair in the pattern

Tony V wrote:
Bob Whelan wrote:
.....(And even though I'm not an instructor and so can't 'legally'
encourage anyone to practice mentally formulating and making such
calls, I always have...and do! )


In the US, anyway, all that an instructor can 'legally' do is to make
logbook endorsements that the FAA cares about. :-)


What I meant was that *anybody* can instruct but only a CFI can make a
legal logbook endorsement.

Tony

Eric Greenwell wrote:
The silence from people that have a real understanding of radar suggests
it's not an easy answer. Sweeping the beam over 2 mile sphere centered
on the glider is one problem;

For most collision avoidance, I don't think one needs information on the
entire sphere around an airplane. If you have coverage of +/- 30 degrees of
your average flight plane, I believe you would be covered for most
reasonable climb and descent angles that you and other aircraft can muster.

True - someone on a nearly parallel course directly above or below could
collide with you on a climb or descent, so those would be blind spots. I'm
aware of the midairs that happen on final due to one plane landing on top
of another, so I don't dismiss the issue. I think it is a surmountable
issue that hasn't been addressed because the first market is the marine
one.

making the beam small enough to locate
another aircraft with sufficient accuracy is another;

Not sure I follow - what do you think the accuracy is today and why you
think it isn't sufficient? The Lowrance/Simrad/Northstar unit has a
claimed target resolution of 2 to 3 meter at 10 miles. It is interesting to
view their video ads to see what they can and can't do, particularly in
areas with lots of nearby targets:

http://www.youtube.com/watch?v=TEPgcPM6EmY

Two notable examples in the video: when their radar imaged birds on the
water and when it imaged a parasailor (their printed material says they can
image birds out to 500 feet at most, though:

http://www.lowrance.com/Products/Mar...oadband-Radar/ )

and you'd also
have know the glider's attitude, altitude, and position to make sense
of the radar return.

I'm not sure why I would need anything other than range and direction to a
possible collision hazard. More than that would be "too much information."
With a moving map of collision hazards, I think I could mentally project
where things are going well enough to avoid them, even with only "raw"
depiction of radar returns.

On 1/21/2011 4:49 PM, Jim Logajan wrote:
For most collision avoidance, I don't think one needs information on the
entire sphere around an airplane. If you have coverage of +/- 30 degrees of
your average flight plane, I believe you would be covered for most
reasonable climb and descent angles that you and other aircraft can muster.


I was thinking of a previous poster's distinction between "dependent"
(like Flarm) and "independent" collision avoidance technologies (like
airborne radar). If the radar doesn't have full coverage, then it's in
the "dependent" group. With the coverage you mention, it probably does
cover most of what you need. Now I'm trying to imagine where a dome that
size is placed on a glider. It's 11" by 19", 16 pounds, so an image of
an AWACS plane is forming in my mind.

Not sure I follow - what do you think the accuracy is today and why you
think it isn't sufficient? The Lowrance/Simrad/Northstar unit has a
claimed target resolution of 2 to 3 meter at 10 miles.

I saw that statement under the video on YouTube (first link), but not on
the Lowrance site. The claim I saw there was a 5 degree width beam, and
I have no idea how a beam that wide could "resolve" targets 2 or 3
meters across at 10 miles. I can imagine it would _detect_ targets that
small at 10 miles, but it would not be possible to distinguish between
two targets even 20 or 30 meters apart at 10 miles.

It is interesting to
view their video ads to see what they can and can't do, particularly in
areas with lots of nearby targets:

http://www.youtube.com/watch?v=TEPgcPM6EmY

Two notable examples in the video: when their radar imaged birds on the
water and when it imaged a parasailor (their printed material says they can
image birds out to 500 feet at most, though:

http://www.lowrance.com/Products/Mar...oadband-Radar/ )

The modern units are much better than I found last time I looked, and
$2000 doesn't seem too bad. The power consumption is reasonable if you
scale it for the much smaller range the glider would need. The antenna
looks awfully big for a glider, and you need the width to keep that 5
degree beam size. If you aren't concerned about the elevation to the
target, then the vertical antenna dimension can remain small. Possibly,
a higher frequency could be used in a glider, allowing a smaller antenna.

and you'd also
have know the glider's attitude, altitude, and position to make sense
of the radar return.

I'm not sure why I would need anything other than range and direction to a
possible collision hazard. More than that would be "too much information."
With a moving map of collision hazards, I think I could mentally project
where things are going well enough to avoid them, even with only "raw"
depiction of radar returns.


If all you want is knowing something is out there, it really simplifies
things; still, I wonder what the screen image would look like as the
glider banks and pitches. It seems like it would be useless in a thermal
or near a gaggles, the times you would really like to know where people
are, especially vertically.

It'd be fun to explore the possibilities, but I'm not radar-savvy enough
to do it. All I can imagine is a lot of problems that make me think it
would be better to talk other pilots into getting PowerFlarm and MRX units.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl
- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

Eric Greenwell wrote:
It'd be fun to explore the possibilities, but I'm not radar-savvy
enough to do it. All I can imagine is a lot of problems that make me
think it would be better to talk other pilots into getting PowerFlarm
and MRX units.

I think that radar in small aircraft is getting more viable; many of the
problems could be overcome. If ADS-B had not been mandated, I think that in
10 years private radar units could have been available with equivalent
capabilities and cost to ADS-B. Alas, government mandate will cause anyone
interested in radar to pay twice to solve essentially the same problem. A
pity, in my humble opinion.

On 1/25/2011 7:43 PM, Jim Logajan wrote:
Eric wrote:
It'd be fun to explore the possibilities, but I'm not radar-savvy
enough to do it. All I can imagine is a lot of problems that make me
think it would be better to talk other pilots into getting PowerFlarm
and MRX units.

I think that radar in small aircraft is getting more viable; many of the
problems could be overcome. If ADS-B had not been mandated, I think that in
10 years private radar units could have been available with equivalent
capabilities and cost to ADS-B. Alas, government mandate will cause anyone
interested in radar to pay twice to solve essentially the same problem. A
pity, in my humble opinion.

I don't think air-borne radar would solve many of the problems the FAA
is interested in, of which collision avoidance is just one. I also
suspect a few hundred radars operating in a busy airspace might be a
problem, just like mode A/C transponders cause.

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