On Oct 12, 6:25*pm, Darryl Ramm wrote:
On Oct 12, 2:08*am, John Smith wrote:





Darryl Ramm wrote:


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Moving topic somewhat but I want to make the point that we've lost
several airliners full of passengers in fatal-midair collisions with
light-aircraft and the response to that was largely transponders and
TCAS/ACAS. And gliders operating near high density airline and fast
jet traffic without transponders are effectively bypassing that
evolution. I worry that human nature and perception of risks can allow
apparent reduction of risks in situation because we don't perceive
those rare but critical accidents happening frequently enough to
register as practical risks even if they have catastrophic outcomes. I
start my talks on collision avoidance with the following (USA centric
information). There are similar fatal mid-air collisions outside the
USA.

Allegheny 853
MD DC-9 vs. Piper Cherokee
Fairield, Indiana 1969 -- 83 killed

Pacific Southwest 182
Boeing 727 vs. Cessna 172
San Diego, California 1978 -- 144 killed

Aeroméxico 498 (the mid-air that lead to Mode C transponder and TCAS
carriage requirements in the USA)
MD DC-9 vs. Piper Cherokee
Cerritos, California 1986 -- 82 killed, 8 injured

NetJets N879QS
Hawker 800XP vs. Schleicher ASG-29
Reno, Nevada 2006 -- 3 minor injuries (we were very lucky)

Darryl

Yes terrible accidents such as those cited motivated the regulators
and industry to require the carriage of transponders. The FAA Near
Midair Collision Avoidance database suggests that annual reports of
reported near midair collisions in the US have decreased in number
since the 1980s.

http://www.asias.faa.gov/portal/pls/...sion id=30289

Still, only 45 of 6624 records (0.6% of the total) in the NMAC
database contain the term "glider". Only nine records contain the
terms "glider" and "US air carrier".

The other 6579 reports (99.4%) do not involve gliders. Many of these
other reported near midair collisions presumably happened between
transponder-equipped powered aircraft.

In conclusion, experience shows that the possibility of a mid-air
collision between a glider and an air carrier is real enough (and
warrants prudent action) but let's put it into perspective. Gliders
form a very small part of the total collision risk that commercial
passengers are exposed to.

Ian Grant IN