On 2/10/2016 5:07 PM, Martin Gregorie wrote:
On Wed, 10 Feb 2016 16:27:09 -0700, BobW wrote:

Dave, wow - what timing!

On 2/10/2016 3:32 PM, Dave Nadler wrote:
Snip...

Anyway, someone mentioned to me years ago that it is a bad idea to
mount things on the canopy or canopy rails (PDA, Camera, etc) as it
could prevent full ejection of the canopy and leave it tethered to the
fuselage by a power or control cable. This could make a bad situation
worse (take that statement for what it is worth). Truth or myth?

Truth, implicated in at least one fatality (PDA mount prevented canopy
jettison).

Having just spent most of the day extracting info related to every
2000-2015 glider-based fatality from the NTSB database (and, yeah, I'm
pretty familiar with how much crunch-related info can manage to never
make it into their reports and conclusions), I'm curious as to year and
country of the above fatality. It doesn't seem to ring a mental bell
from my day's work.

There was a mid-air in the UK (Yorkshire) in 2006. One pilot got out, the
other didn't. http://news.bbc.co.uk/1/hi/england/6158561.stm

The AAIB report said that latter had electronics mounted on his glare
shield and canopy frame, cables secured with cable ties. The ASW-19B, hit
the ground with part of the canopy still attached. The front jettison
lock had been released, rear locking pins still locked.


Ah, so - that would appear to qualify in my book. Thanks, Martin. If : 1) the
Beeb is accurate, and 2) I've understood them correctly, it would appear the
(rear-raising via strut under normal conditions?) canopy had its
front/emergency release pulled, but not the rear, *and* the front end was
restrained to "some extent" by cabling? (That's not to wonder if the pilot
simply ran out of time - for whatever reason - to operate the aft latch[es?].)
I got the bit about the AAIB speculation, though what, precisely, I should
infer is unclear. Would it have been 100% necessary to "go through the canopy"
due to the degree of front-end restraint, or would the degree "only" have
hindered the amount the front end could raise before coming up against the
wiring, thus (possibly) resulting in a partially-raised canopy, if the strut
could overcome airloading?

In any event, any degree of hard-cabling between airframe/instruments and
ejection-desired-canopy certainly seems a bad idea to me!

As always, the devil is in the details...

Bob W.