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Fatal crash Arizona



 
 
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  #161  
Old September 13th 16, 11:24 PM posted to rec.aviation.soaring
Don Johnstone[_4_]
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Posts: 387
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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  #162  
Old September 14th 16, 02:25 AM posted to rec.aviation.soaring
BobW
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Posts: 481
Default Fatal crash Arizona

On 9/13/2016 4:24 PM, Don Johnstone wrote:
At 17:28 13 September 2016, BobW wrote:

Snip...
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.

Bob W.


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


Sorry for any confusion. A number of "Applebay releases" have been
subsequently installed in (on the fuselage bottom surface, near the front of
the nose of) non-USA-built gliders imported into the USA with only a single,
CG-mounted, release back by the wheel. This second cable attachment point
provided "a nose-hooked aero-towing option." Many - not all - such modified
ships were of German origin.

FWIW, I've been privately informed by a fellow Zuni owner (of S/N 28) that his
ship's release uses a(n easily visible) *tension* spring (not compression, as
on S/N 2) to positively seat the pawl against the rotating/indented cable hook
part...which is what my fallible memory kinda-sorta remembered from my own
(not recently looked at) Zuni (S/N 3).

In either case, any owner of a ship with an "Applebay nose release" can/should
easily confirm the presence of such a spring by verifying the business end of
the pawl is "somehow or other" positively forced against the rotating cable
hook as it operates throughout its range of motion. The truly curious can
disconnect it before operating their releases to get a better feel for what I
sought to describe in an earlier post. Please do reconnect it...or YMMV!

Bob W.
  #163  
Old September 14th 16, 09:18 AM posted to rec.aviation.soaring
Don Johnstone[_4_]
external usenet poster
 
Posts: 387
Default Fatal crash Arizona

At 01:25 14 September 2016, BobW wrote:
On 9/13/2016 4:24 PM, Don Johnstone wrote:
At 17:28 13 September 2016, BobW wrote:


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.

Bob W.


I am now confused by the "installed in German" part. Is the

release you
are
talking about a TOST release?


Sorry for any confusion. A number of "Applebay releases" have

been
subsequently installed in (on the fuselage bottom surface, near

the front
of
the nose of) non-USA-built gliders imported into the USA with only

a
single,
CG-mounted, release back by the wheel. This second cable

attachment point
provided "a nose-hooked aero-towing option." Many - not all -

such modified

ships were of German origin.

FWIW, I've been privately informed by a fellow Zuni owner (of S/N

28) that
his
ship's release uses a(n easily visible) *tension* spring (not

compression,
as
on S/N 2) to positively seat the pawl against the rotating/indented

cable
hook
part...which is what my fallible memory kinda-sorta remembered

from my own
(not recently looked at) Zuni (S/N 3).

In either case, any owner of a ship with an "Applebay nose

release"
can/should
easily confirm the presence of such a spring by verifying the

business end
of
the pawl is "somehow or other" positively forced against the

rotating cable

hook as it operates throughout its range of motion. The truly

curious can
disconnect it before operating their releases to get a better feel for

what
I
sought to describe in an earlier post. Please do reconnect it...or

YMMV!

Bob W.


Thanks for that. My ASW17 was fitted with a TOST winch hook near
the nose for aerotow. There was a wooden block installed behind
the back release ring to prevent it's operation as a back release
function on an aerotow hook is undesirable. Back in the 60's we
would tape up winch launch hooks to prevent the back release from
operating when aerowtowing.

 




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