Freemasm
Well Known Member
If this comes off as a little preachy, sorry. There’s been some threads here where some don’t understand/want to debate:
Torque
Importance of
Proper methods
Application differences
whatever
Here’s a couple of examples:
https://vansairforce.net/community/showthread.php?t=69876
https://vansairforce.net/community/showthread.php?t=187303
Not getting into that again. In oversimplified terms, if you want to be safe and in compliance always follow the hierarchy:
Released engineering, OEM drawings
Released engineering, OEM specs (including service bulletins, etc.)
Industry standards (e.g. FAA Advisory Circulars)
Good Shop practice
Others could be added but are mostly subsets of the above. When in doubt or apparent conflict, inquire. When the aforementioned hierarchy is not followed, bad things can happen.
The following somewhat recent picture is from a Mooney that shed a jug over the UK (picture used with permission). It turned out as well as it could; no injuries and a repairable airframe. Could have been much worse obviously. A certified engine/installation so timing, CR, etc. should not have been contributors. While I haven’t personally inspected the fracture surfaces, it is most certainly a material fatigue issue; no necking near the fracture surface, flat perpendicular fracture surface. One of our very experienced NDEs agrees after viewing the picture.
The relevant OEM has released engineering for torqueing this joint; sequence, values, thread condition, etc. Vegas odds were this was not adhered to. So:
Tension application -> under torque condition -> cyclic load-> metal fatigue -> rupture.
The upside is there’s a good bit of design margin and builder expertise consideration in our builds thanks to the airframe OEM, Vans. That’s not always the case across the wider OEM spectrum. Failure to adhere to specs eats into that margin. Follow the released engineering. Build safe.
Torque
Importance of
Proper methods
Application differences
whatever
Here’s a couple of examples:
https://vansairforce.net/community/showthread.php?t=69876
https://vansairforce.net/community/showthread.php?t=187303
Not getting into that again. In oversimplified terms, if you want to be safe and in compliance always follow the hierarchy:
Released engineering, OEM drawings
Released engineering, OEM specs (including service bulletins, etc.)
Industry standards (e.g. FAA Advisory Circulars)
Good Shop practice
Others could be added but are mostly subsets of the above. When in doubt or apparent conflict, inquire. When the aforementioned hierarchy is not followed, bad things can happen.
The following somewhat recent picture is from a Mooney that shed a jug over the UK (picture used with permission). It turned out as well as it could; no injuries and a repairable airframe. Could have been much worse obviously. A certified engine/installation so timing, CR, etc. should not have been contributors. While I haven’t personally inspected the fracture surfaces, it is most certainly a material fatigue issue; no necking near the fracture surface, flat perpendicular fracture surface. One of our very experienced NDEs agrees after viewing the picture.
The relevant OEM has released engineering for torqueing this joint; sequence, values, thread condition, etc. Vegas odds were this was not adhered to. So:
Tension application -> under torque condition -> cyclic load-> metal fatigue -> rupture.
The upside is there’s a good bit of design margin and builder expertise consideration in our builds thanks to the airframe OEM, Vans. That’s not always the case across the wider OEM spectrum. Failure to adhere to specs eats into that margin. Follow the released engineering. Build safe.