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nimbusaviation(at)YAHOO.C
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 Posted: Mon Apr 08, 2013 4:12 am Post subject: Self-disassembly of outrigger OR12 spring fitting? |
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This is strange.
Hopefully attached to this posting is a picture of the starboard outrigger mechanism as we found it on preflight yesterday; ops were cancelled due wx, and also due to uncertainties about this discovery.
The stiffnut normally securing the rearward part of OR12 spring is only partially threaded onto its bolt, and finger loose. The AN960-10L washer is missing, and OR12 hangs from one end.
An engineer in our group also inspected the locknut and found it satisfactory on a new bolt. The original bolt awaits closer examination, however a new fresh nut was secure when attached to it.
These parts would potentially be missing in any accident investigation search.
I cannot understand how a stiffnut can come undone in this installation. This assembly was fine when inspected one week earlier prior to a test flight, during which the gear needed cycling once to achieve an outrigger- retracted green light indication. It was not examined post flight then, but the aircraft was subsequently unattended.
If we hypothesize that perhaps the washer was missing from the original assembly, methinks unlikely, then could the thing manage to self-disassemble in the course of one short flight with two gear cycles?
I can think of one _possible explanation for this which is a worrying one, but perhaps other folks have ideas? No maintenance was needed or carried out on this part of the airframe in recent time.
Glenn Rainey / Martin Burns
G-OJHL
Classic monowheel
Scotland
* my second attempt to post, perhaps the image is a problem. Can anyone help with image posting / hosting?
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Fred Klein
Joined: 26 Mar 2012
Posts: 503
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| Posted: Mon Apr 08, 2013 10:02 am Post subject: Self-disassembly of outrigger OR12 spring fitting? |
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Glenn...as someone still in the throes of building, I feel it would presumptuous to offer an opinion on how this situation evolved other than to note that the AN960-10L washer serves a critical purpose between the sleeve and the stiffnut, and that the profile of the stiffnut may suggest at first glance that a washer is in place when in fact it is not.
On a previous post-flight inspection, unrelated to our Europas, I was utterly astonished to learn how quickly a bolt (once unconstrained) can back out from its threaded receptacle just from the subtle vibrations of a VERY short flight...
Fred
A194
On Apr 8, 2013, at 5:04 AM, Glenn Rainey wrote:
| Quote: | This is strange.
Hopefully attached to this posting is a picture of the starboard outrigger mechanism as we found it on preflight yesterday; ops were cancelled due wx, and also due to uncertainties about this discovery.
The stiffnut normally securing the rearward part of OR12 spring is only partially threaded onto its bolt, and finger loose. The AN960-10L washer is missing, and OR12 hangs from one end.
An engineer in our group also inspected the locknut and found it satisfactory on a new bolt. The original bolt awaits closer examination, however a new fresh nut was secure when attached to it.
These parts would potentially be missing in any accident investigation search.
I cannot understand how a stiffnut can come undone in this installation. This assembly was fine when inspected one week earlier prior to a test flight, during which the gear needed cycling once to achieve an outrigger- retracted green light indication. It was not examined post flight then, but the aircraft was subsequently unattended.
If we hypothesize that perhaps the washer was missing from the original assembly, methinks unlikely, then could the thing manage to self-disassemble in the course of one short flight with two gear cycles?
I can think of one _possible explanation for this which is a worrying one, but perhaps other folks have ideas? No maintenance was needed or carried out on this part of the airframe in recent time.
Glenn Rainey / Martin Burns
G-OJHL
Classic monowheel
Scotland
* my second attempt to post, perhaps the image is a problem. Can anyone help with image posting / hosting?<Image1.jpg>
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