On Friday, July 20, 2018 at 10:19:01 PM UTC-5, Steve Koerner wrote:
On Friday, July 20, 2018 at 6:15:40 PM UTC-7, WB wrote:
On Friday, July 20, 2018 at 6:30:07 PM UTC-5, Jock Proudfoot wrote:
National Transportation Safety Board
Aviation Accident Preliminary Report

The glider was equipped with a FLARM electronic flight collision
alerting device, which records flight track, altitude, and airspeed.
About 11 seconds prior to impact with the ground, the glider entered a
left hand descending spiral at an airspeed of 48 knots, which continued
to ground impact.

https://app.ntsb.gov/pdfgenerator/Re...atorFile.ashx?
EventID=20180710X25659&AKey=1&RType=HTML&IType=FA
.

Doesn't really sound like a stall/spin from low altitude. Sounds more like the behavior of a glider trimmed for an off-field landing with no one at the controls.

WB: In what way does it not sound like stall/spin? Secondly, what do you mean about trimmed for an off-field landing? I've never heard about trimming differently for an on-field landing vs an off-field landing?
Separate remark: Flarm does not record airspeed as stated in the report.. It could be that airspeed was inferred from the spiral descent dynamics; but that seems more complicated than suggested by the brevity of this preliminary report.

11 seconds just seems like a very long time to be in a spin or spiral dive. 11 seconds suggests adequate altitude and enough time for an unimpaired pilot to recognize the problem and perform a recovery. I am under the impression that most stall/spins to impact start below 200 feet and usually the glider only makes a partial rotation before impact. Just guessing, but wouldn't a spiral dive of 11 seconds duration involve shedding parts before impact?

Regarding trimming for an off field landing: If one is landing in a smaller than usual space, one might trim the glider to fly at the minimum safe approach speed. In my 301 Libelle, I trim for the pattern speed that I want, usually about +-60 knots depending on wind, and slow up on final. If I am landing in a tight field, I might trim down around +-50 knots if it's calm. In my 20, the trim is left to float and the glider trims out based on flap setting (until one gets to the "jeezus!" notch). I've never flown a Ventus of any flavor, and don't know if the Ventus drivers typically even bother to set trim or let it float. As someone else pointed out, 48 knots is also a plausible thermalling speed.

Answering the "separate remark" question: My first thought was that the NTSB report was sloppily written when it stated "airspeed" since the PFlarm wouldn't know airspeed. However, I read that PFlarm will record airspeed if it is being fed that information from another instrument like a modern complex vario. So maybe the NTSB did get airspeed.

It is just terribly frustrating that we keep losing skilled and experienced people to these puzzling crashes. Scares the crap out of me to be honest.

Please fly safely.