View Single Post
  #9  
Old January 8th 16, 10:18 PM posted to rec.aviation.soaring
Andy Blackburn[_3_]
external usenet poster
 
Posts: 608
Default PowerFlarm and ADS-B solution, can we find one?

On Friday, January 8, 2016 at 5:36:33 AM UTC-8, wrote:
Rarely would this require more than a few hundred feet at most. Modern gliders get up to speed with very little loss of altitude.
What you are describing may be fun but it is not very efficient.
Pull ups obviously can and are more dynamic but even there smoothness pays off. UH


A little math would help - but this seems roughly right.

Any decending air outside a thermal would likely be more gentle than the rising air at the core. I have certainly found I could gain more than 1,000 feet within 15 or 20 seconds with a smooth pull-up into a strong thermal.

We are talking about having adequate closing time (of around 45 seconds) from first being put on the traffic screen until potential collision - and not being . A glider running in say 3 knots of sink at 110 kts will lose around 500 feet in 45 seconds and a glider pulling up into lift might gain 7-800 from the pull-up and another 3-500 from the lift over that time period for a total of 1500-1800 feet net change (assuming the run into the thermal didn't also have some lift). Anything less creates a scenario where you can sneak in outside of the altitude filter for stealth and come into view with less than the requisite 45 seconds. Less than 1200 or so and the surprise can be quite sudden - maybe 8-10 seconds.

Of course getting into lines of lift can yield many different scenarios - running storm shelves is a common tactic, but so is convergence and occasionally wave - all have pairings of strong lift and some level of sink and pairings of gliders maneuvering. The fact that sink tends to generate push-overs and lift tends to generate pull-ups means that the effects are amplified, rather than canceling, so you need to look at both together.

9B