On Saturday, January 9, 2016 at 12:14:07 PM UTC-5, Dan Marotta wrote:
Hi Kirk,



Yes, I've towed you during at least one contest at Moriarty and I've
admired your LS-6.



Please understand that I don't "poo-poo" Flarm in my comments, I
only respond to the comments of some, which I believe are
unreasonable or downright wrong.* I always welcome logical proofs
like the math-based analysis of the pull-up (in a previous thread).



And yes, I think Flarm is a great tool for situational awareness but
I don't think that knowing a blip's ID is a requirement for safety.*
And I'm neither for nor against "stealth" mode - I don't care either
way.* The idea of coordinating an escape plan with another aircraft
5 miles away by radio is simply ludicrous.* Remember when contests
were fully manned and there was no Flarm or GPS?* I'm not against
either, as a lot of the folks here think, but I think a lot of the
fun has gone and that's the main reason I don't fly contests any
more.



So why do I keep posting?* It's out of a genuine concern that false
perceptions, unchallenged, will eventually become policy, and I
don't want any more policies.


Thank you Dan for your posts. Your opinion is important, too. I especially agree with this last paragraph.

I'll give you one example that needs to be challenged stated just a little while back. One post says"the requisite 45 seconds" and goes into some simple calculations based on 45 seconds on the display. I would like to see some actual physics calculated, but aside from that there is no basis for the 45 seconds. This is the kind of overstatement I keep talking about. It is not a lie but people are trying so hard to make their case for the outcome they desire they sometimes overstate the facts.

Pull out your iPhone and run the timer for 45seconds and you'll see it is a lot of time. There are other alternatives that may help. When a new target appears on the screen there can be simple audio alert letting you know of the new bogie. I would suggest that in this case 25 seconds of warning is plenty if collision avoidance is what you are really after. Don't take my word for it though, use some real science to come up with a real number.

The TCAS operators guide that I am looking at allows 5 secs as the outside reaction time to initiate corrective action (pitch change in the case of TCAS) resolution advisory. This is similar to the FLARM warning when a collision path is detected. I don't have complete TCAS specs readily available but perhaps other time values from TCAS could be used since their research is probably more thorough.

It makes a big difference in the final numbers if you use 45 seconds or 25 seconds. Let's make sure these numbers are based on some evidence.

XC