On Monday, December 16, 2013 12:17:44 PM UTC-6, Papa3 wrote:
Not quite the direct answer you're looking for, but you do know that DG seems to think that venting cockpit air matters, right?



http://www.dg-flugzeugbau.de/index.p...dl-absaugung-e



On the theory that the Nixon Air Extractor had a better chance of working than the Plastic Jesus, I installed one two winters ago. Obvious improvement in cockpit airflow and decrease in canopy noise at high speed suggest it's doing "something". I built a little foam block with a string attached and plan to do some testing on cockpit pressure at speed with/without the exit orifice available. Expect to be able to show increased cockpit pressure with my handy-dandy NK Kestrel Wx meter and also see if there is measurable outflow by locating the Kestrel in the exit area. All that proves is a first-order measurement (i.e. something is happening due to the vent). In terms of performance measurement, maybe faith (along with the Plastic Jesus) is justification enough?



P3



On Sunday, December 15, 2013 6:51:45 PM UTC-5, wrote:

On Sunday, December 15, 2013 1:01:20 PM UTC-5, wrote:



Noticing all the openings behind the cockpits of mainly Schleicher gliders such as -27 and 29's I'm asking myself if this is a real drag reducer or a placebo. For those unfamiliar: people have been cutting 4x2 openings into the fuselage about 8" behind the canopy cutout and put air vents - some with funnel-like contraptions on the inside of the turtle deck into their gliders. The funnel seems to suggest to the air molecules "this way out", some pilots may put arrow stickers on the inside so the air knows which way to flow. The whole thing is meant to avoid pressurizing the cockpit from the front air vent. Air leaking from the canopy seal would trip outside air flow to become turbulent. Are there any serious comparison flights that were done following a scientific protocol to show the effect of such devices? Is this really better than putting a Tibetan prayer flag on the tail or a plastic Jesus on the glare shield? The latter can serve double purpose since I know where I would stick my transponder or PFlarm antenna... Seriously, I'd be interested if anyone has found this thing useful beyond the statement that it must be good since all these hotshot pilots (insert call signs here) have one. I'm waiting with jigsaw in hand for your responses, the LS8 rests uneasily in the basement! Herb, J7







Ask Erik Mann his opinion. He has one in his LS-8.



UH

Eric,

I'm quite aware of the DG publications on their air extractor (Mandl Absaugung or Mandl Sucker)and now read with interest that you have Nixon Extractor in your LS8. DG is claiming an incredible 2 glide point increase in performance on the LS10 with the extractor. I'm wondering if you had to adjust the polar in your glide computer to account for the better performance? My interest in this modification was raised after seeing nearly all '27 and '29s at New Castle this year with Nixon Extractors.
For those questioning why Schleicher seems slow in putting these into new gliders: re-certifying even such a small change with the Luftfahrtbundesamt and the EASA takes a lot of time. Looks like DG puts these into all of the few LS gliders they are building these days - but not into the DG 808.
Maybe I should get the Nixon Extractor AND the Plastic Jesus!

Herb