Air intake disbonded attrition liner
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Air intake disbonded attrition liner
I am interested in finding examples of incidents involving disbonded V2500 air intake attrition liner, either in anectotal form or, better yet, as links to documentation or reports.
Reason being a discussion as to what can be the consequence of lacking timely maintenance action.
Other engine makes with similar problems would be interesting to hear about too of course!
Reason being a discussion as to what can be the consequence of lacking timely maintenance action.
Other engine makes with similar problems would be interesting to hear about too of course!
Usual disclaimers apply!
Join Date: Nov 1999
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RB211 suffers a lot from disbonded attrition linings! I have no idea of the make-up of the v2500 but the 211 panels are in segments and were originally bonded in with 'Hysol' a very brittle adhesive that over time separated from the case in part due to flex. Also, holes in the septum layer cause corrosion of the honeycombe due to water ingress. We now use a 'thiokol' type material that is flexible to a degree and so at least the flexing factor is removed.
Disbond: Not a problem in itself (RB211) as long as there is no lifting. Depending on the amount of disbond and where on the panel it can be allowed to fly on for upto about 900hrs with regular inspections.
Panel loss: Usually causes a fan stall/surge due to the disturbed airflow and if unlucky will bend a couple of blades!
Disbond: Not a problem in itself (RB211) as long as there is no lifting. Depending on the amount of disbond and where on the panel it can be allowed to fly on for upto about 900hrs with regular inspections.
Panel loss: Usually causes a fan stall/surge due to the disturbed airflow and if unlucky will bend a couple of blades!
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Occassionally the fan blade attrition liner starts to crack and disbond. The limits are far more restrictive than on the RB211 or 535 and requires a hangar input almost immediately for fan blades out and a new liner bonded in. Once a crack starts it usually gets worse very quickly (probably from all the vibration these engines seem to manufacture for themselves)
What seems to be a bigger problem is the acoustic lining in the c ducts. Once this debonds somewhere on the inner or outer barrels it normally comes off in big strips requiring a c duct change (hopefully after a ferry flight to the hangar). I have seen a few c ducts with just a perforated aluminum skin (aka 535 and other RB211's) which seems a definate improvement on the metallic fabric type.. presumably a mod on later aircraft?
The CFM drinks a lot more fuel and is a lot noisier but apart from the odd fan blade blend out and HMU change never really seems to go wrong.
What seems to be a bigger problem is the acoustic lining in the c ducts. Once this debonds somewhere on the inner or outer barrels it normally comes off in big strips requiring a c duct change (hopefully after a ferry flight to the hangar). I have seen a few c ducts with just a perforated aluminum skin (aka 535 and other RB211's) which seems a definate improvement on the metallic fabric type.. presumably a mod on later aircraft?
The CFM drinks a lot more fuel and is a lot noisier but apart from the odd fan blade blend out and HMU change never really seems to go wrong.
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A solution to attrition liner disbonds
I am aware of disbonding attrition liners on one type of military fast jet that was occurring over ten years ago. The problem was fixed not by changing adhesives, but by using a more effective surface preparation process. Adhesive bonds function by chemical bonds at the interface, and depending on the type of surface preparation performed at the time of bonding, those chemical bonds may be susceptible to dissociation, usually by hydration of oxides on the metal, and that results in disbonding. The trick is to use a process that provides resistance to hydration. We were able to reduce the repeat-repair rate (for all bonded repairs not just attrition liners) from 43% in 1992 to almost zero by using a more reliable surface preparation process.
