FAIL SAFE PARTS
Joined: May 2000
Posts: 340
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From: Worldwide
aviatorpk….
A fail safe structural item would be designed to have redundant (backup) load paths, this can be achieved via a variety of methods.
Items are designed to be fail safe to prevent minor defects from interfering with the dispatch of the aircraft, or from the aircraft failing with a major defect occurrence.
If a fail safe item were to break surrounding structural members take the loads of the broken item.
The design engineers would be responsible for determining the inspection period for a fail safe item so that any defect can be picked up by maintenance at the specified interval.
Most aircraft are flying around with a number of structural defects in them, inspecting the parts at the required service intervals identifies the defects and replacements made so the can be corrected.
Fail safe design allows aircraft to continue in service until the next service for minor defects (eg delamination of composite control surfaces due the expansion of absorbed water when at flight levels), or to enable the aircraft to land in the safest method available for a major defect (eg explosive decompression due to a pressure vessel failure)
If a defect in a failsafe item is not detected at a prescribed service interval, and a subsequently a major failure occurs it’s a maintenance issue.
If a fail safe item repeatedly fails (over multiple part sets) it’s a design or manufacturing issue and would get rectified by an airworthiness directive by the regulator and/or a manufacturers service bulletin either changing the specified service interval, or recalling the parts.
Z
PS If someone loads a corrosive substance into the cargo hold and it leaks it’s an insurance issue
A fail safe structural item would be designed to have redundant (backup) load paths, this can be achieved via a variety of methods.
Items are designed to be fail safe to prevent minor defects from interfering with the dispatch of the aircraft, or from the aircraft failing with a major defect occurrence.
If a fail safe item were to break surrounding structural members take the loads of the broken item.
The design engineers would be responsible for determining the inspection period for a fail safe item so that any defect can be picked up by maintenance at the specified interval.
Most aircraft are flying around with a number of structural defects in them, inspecting the parts at the required service intervals identifies the defects and replacements made so the can be corrected.
Fail safe design allows aircraft to continue in service until the next service for minor defects (eg delamination of composite control surfaces due the expansion of absorbed water when at flight levels), or to enable the aircraft to land in the safest method available for a major defect (eg explosive decompression due to a pressure vessel failure)
If a defect in a failsafe item is not detected at a prescribed service interval, and a subsequently a major failure occurs it’s a maintenance issue.
If a fail safe item repeatedly fails (over multiple part sets) it’s a design or manufacturing issue and would get rectified by an airworthiness directive by the regulator and/or a manufacturers service bulletin either changing the specified service interval, or recalling the parts.
Z
PS If someone loads a corrosive substance into the cargo hold and it leaks it’s an insurance issue
Joined: Aug 1998
Aviation Qualifications: ATPL
Posts: 6,623
Likes: 847
From: Ex-pat Aussie in the UK
"Failsafe" doesn't mean that the part in question is guaranteed never to fail. it only mean that when (or if) it fails, it will fail in the safest condition.
For example: Usually, if an engine anti-ice valve fails, it will fail OPEN - minimal performance loss (unless you fly a 146 ) but you still have engine anti-ice.
If a wing or tail anti-ice valve fails, it usually fails in the position selected at the time of failure - i.e. if you need it, you still have it, if you dont' then you don't have to wear the significant (especially in a 146 ) performance loss.
Who is to blame? - usually no-one.
For example: Usually, if an engine anti-ice valve fails, it will fail OPEN - minimal performance loss (unless you fly a 146
) but you still have engine anti-ice.If a wing or tail anti-ice valve fails, it usually fails in the position selected at the time of failure - i.e. if you need it, you still have it, if you dont' then you don't have to wear the significant (especially in a 146
) performance loss.Who is to blame? - usually no-one.
