On Friday, January 31, 2014 7:52:24 AM UTC-8, JJ Sinclair wrote:
On Friday, January 31, 2014 6:57:01 AM UTC-8, wrote:

Additional compounding illusion that most of us know from theory and instruction but may forget when flying instinctively under stress:

Above a certain altitude when you make a coordinated turn with a given bank angle the inside wingtip traces a circle in the opposite direction vs the ground. In a low turn to final the wingtip goes the same way around versus the ground leaving a subtle sensation that the turn lacks enough rudder.

So you are too slow from a high horizon and pulling the nose up to the back side of the polar in a misguided effort to stretch your glide, while at the same time you have a tendency to under-bank to keep the wing away from the ground and over-rudder due to the wingtip motion illusion.

All these illusions nudge you in the wrong direction at the wrong time.

On a related topic - I installed a new flight computer/vario last year (an LX 9000). Like a lot of current generation instruments it has accelerometers built into it. I believe the primary purpose for these is to add some additional capability to separate horizontal gusts from vertical lift (that surge in the seat of your pants that we all know and love). They seem to still be working out exactly how to do this in the software.

The other think they appear to be doing is using some combination of airspeed, g-load and pilot input wing loading to estimate angle of attack and provide a stall warning. I've only done a little testing with it but it appears to be pretty reliable.

Given that stall/spin has been the cause of 39% of all fatal glider accidents and 36% of fatalities over the past 20 years a decent warning system might help. Has anyone done any serious testing of the accuracy of these systems under the kind of scenarios in this thread?

9B