Its interesting just how much your head can 'rise' through some form of in-flight turbulence. If you think about how (relatively) flexible your neck can be in that axis, and how (relatively) heavy an object your head is, it isn't hard to see the issue :)
I've cracked the canopy on a Libelle some years back while ridge soaring in it. I know I had the canopy straps tight as they'd go - I had sinched them down due to the level of turbulence encountered earlier in the flight, and had even mentioned that on the radio to my colleagues on the ridge as well by way of warning to them as well... and then, seconds later, I ran into a patch of air that felt like hitting a wall. Next thing was the loud sound of rushing air, from what (in my case) had been a 'shoulder to shoulder' crack in the canopy - literally from the frame by my left shoulder, all the way over the top to the same spot on the right. I just curtailed the flight (obviously!) and landed normally (other than it being somewhat louder than normal, and other than my flying at the lower end of the safe speed envelope to avoid further damage if possible). What it has done for me is made me aware that what we might normally consider to be 'sufficient' clearance between the top of the noggin and the canopy 'roof' may in fact not be sufficient clearance after all - in the case of my own physical dimensions and those of a libelle, I basically have trouble squeezing in under there with what I consider 'enough' clearance to be comfortable about the issue - especially after the incident noted above. Also, and perhaps worthy of mention, I believe (its all a long time back, now) that the cap I was wearing at the time was a 'baseball' cap of the sort that has a 'button' at 'top dead center' on the top of the cap. I suspect that button functioned in a manner similar to the sharp end of a chisel, and cracked the canopy rather than distributing the impact load more widely (meaning the canopy might not have broken otherwise). So it might be worth thinking about avoiding the use of that sort of cap if you plan to fly while jammed right in under the perspex without any clearance :) Even worse in some ways is the notion of your head jammed in just under the canopy or cockpit -frame- of a glider, not under the perspex - in a jolt sufficient to stretch your neck and head up through the canopy and break it, think about the belt to the brain you'd get if you hit the frame instead of the (relatively flexible) perspex. Must be a serious potential there to get knocked out by that turn of events, which is all rather less than fun to contemplate. It is a reminder, to us all, of just how much kinetic energy we're working with inside the normal flight speed envelope, and how easily it can be turned into an unexpected outcome by factors external to the aircraft. Regards, Simon -- Simon Hackett, Technical Director, Internode Systems Pty Ltd 31 York St [PO Box 284, Rundle Mall], Adelaide, SA 5000 Australia Email: [EMAIL PROTECTED] Web: http://www.internode.on.net Phone: +61-8-8223-2999 Fax: +61-8-8223-1777 -- * You are subscribed to the aus-soaring mailing list. * To Unsubscribe: send email to [EMAIL PROTECTED] * with "unsubscribe aus-soaring" in the body of the message * or with "help" in the body of the message for more information.
