If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#161
|
|||
|
|||
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? |
#162
|
|||
|
|||
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
|
|||
|
|||
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. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Parowan Fatal Crash | ContestID67[_2_] | Soaring | 30 | July 3rd 09 03:43 AM |
Rare fatal CH-801 crash | Jim Logajan | Home Built | 8 | June 22nd 09 03:24 AM |
Fatal crash in NW Washington | Rich S.[_1_] | Home Built | 1 | February 17th 08 02:38 AM |
Fatal Crash | Monty | General Aviation | 1 | December 12th 07 09:06 PM |
Fatal Crash in Fittstown, OK | GeorgeC | Piloting | 3 | March 7th 06 05:03 AM |