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Fatal crash Arizona



 
 
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  #26  
Old September 13th 16, 11:24 PM posted to rec.aviation.soaring
Don Johnstone[_4_]
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Posts: 398
Default Fatal crash Arizona

At 17:28 13 September 2016, BobW wrote:
On 9/13/2016 9:26 AM, Dave Nadler wrote:
On Tuesday, September 13, 2016 at 10:34:20 AM UTC-4, BobW

wrote:
As for the report's claimed missing pawl spring...I must be

getting
dense
in my old age, since I'm still puzzled by the intended function

and line
of force of that implicated piece of (missing?) hardware. Back

to the
hook design - what am I missing? Thanks!

Bob W.


If I understand correctly, the missing spring pushes the pawl in

the
direction opposite of pulling the release knob. Otherwise, the

pawl is
not
secured in the "latched" position, except by a bit of friction with

the
hook plate (from the spring that is present and any rope

tension).

Do I understand correctly??


Quite possibly. I suppose such a spring fairly might be considered

the
"suspenders" to the hook-retract-spring's "belt." It's not obvious

from the

photos (Figure 1 shows it best), but installed-geometry, plus

gravity, in
the
pawl's as-installed position/angle work "against" the pawl

remaining
detent-seated...i.e. the pawl pivoting by itself (no other physical
contacts)
would tend to flop its "business end" *away* from the detent due

to the
longer
cable-attach arm's length compared to the detent-engagement

arm's length
(unequal length teeter-totter).

Nonetheless, whether the absence of a compression spring

between the pawl
and
receptacle/pawl-spring-housing was a crucial element in this

accident is
debatable; it would take very little force on the rope to rotate the

cable
hook from the barely-engaged position (Figures 9) to the fully

engaged
position (Figure 8). Once there, further testing definitely required

to
determine whether the design would be more or less prone to

back-releasing
in
the absence of the pawl spring, in the presence of a rope bow...

That said - and since a number of these hooks have been installed

into the
noses of German-built ships originally entering the USA with only

a CG hook
-
owners of ships with these hooks SHOULD (and easily can) VERIFY

the
presence/absence of such a compression spring by checking to

see if the
pawl
is positively forced against the rotating piece of the cable hook
throughout
its rotation range. Positive engagement = spring-present. (Note

that the
spring itself is hidden in the hook's assembled state...and might

easily
escape unnoticed in the event of the hook being disassembled for

any
reason.)

Bob W.


I am now confused by the "installed in German" part. Is the release
you are talking about a TOST release?

 




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