Uncontained engine failure at YSSY

[Jonny Suave Trousers]

Shivers down spine... Can't find the story anywhere except Facebook.

China Southern MU736 uncontained engine failure after take off from YSSY at 9.30 EST tonight.

No other details except cowling totally breeched.

[peekay4]

http://i.imgur.com/WnRgtSS.jpg

[jaytee54]

That's ahead of the fan! Would blades come off and forward? In all that inward airflow?

[Uplinker]

Isn't there supposed to be a kevlar blanket around the circumference of the fan to contain loose blades ??

[daved123]

And China Southern is spelled on fuselage more like Eastern/Western ?

[Chris2303]

MU is China Eastern

[logansi]

China Eastern, SYDNEY-SHANGHAI, returned immediately https://flightaware.com/live/flight/CES736

https://scontent-syd2-1.xx.fbcdn.net/v/t31.0-8/19095277_1946724588933883_6088268348424768211_o.jpg?oh=6b7a6 ecc86f61a3bb0d85b022e8f80ce&oe=59D7A898


ATC https://mobile.twitter.com/S118869/status/873877703119720449

[Shot Nancy]

Hard to see for sure but those engines use to suffer from acoustic lining cowl failure.

[logansi]

Looks identical to this EGYPTAIR incident less than 1 month ago, both powered by T700, both left hand engine

Incident: Egypt A332 at Cairo on May 15th 2017, rejected takeoff due to engine failure (http://avherald.com/h?article=4a901212)

[lomapaseo]

Possibilities are

primary failure of the inlet cowl and ingestion into the engine

Primary failure of a large part of a blade and parts ejected forward (mechanically)


Closeup evidence would certainly have confirmed which one came first. So no use guessing from casual photos

[Caribbean Boy]

All of MU's A330s are fitted with Rolls-Royce Trent 700s.

[underfire]

I suspect cowl play.

All over the news on tv this morning. Have to love the news with lines line this : A China Eastern flight from Sydney to Shanghai has been forced to turn around after its flight crew noticed a hole in the plane's engine just moments after taking off.


Strange, doesnt look like there is any damage to the blades...

https://au.news.yahoo.com/nsw/a/35898939/china-eastern-airlines-flight-emergency-sydney-landing-after-engine-failure/#page1

[mickjoebill]

Flight Radar shows event took place between the airport and Hornsby Heights.
Presumably it didn't occur within airport boundary or we would be seeing pictures of the debris?
If it occurred outside the boundary, is it likely the debris will be discovered and reported by members of the public?

[esreverlluf]

Event occured just after rotation according to the ATC tapes.

[Overboard111]

Looks identical to this EGYPTAIR incident less than 1 month ago, both powered by T700, both left hand engine

Incident: Egypt A332 at Cairo on May 15th 2017, rejected takeoff due to engine failure (http://avherald.com/h?article=4a901212)

Similar damage to this Emirates incident in 2006 on its right hand engine. See post 26 for pics.

http://www.pprune.org/rumours-news/248980-emirates-a330-fan-blade-dxb-18-oct.html

[PAXboy]

As the failure is on the inboard side - what happened to the portside fuselage?

[jack11111]

Maybe it was harmonic resonance. ;)

[bluesideoops]

Did somebody cry cowl! Looks like separation of the cowl.....

[underfire]

well, they did get a video chat from the engine! What is wrong with the press?!?!? I listened and I heard visual check, not video chat.......

I bet that the inspection and repair requirements of the cowl on that engine has been moved up!

http://services.casa.gov.au/airworth/airwd/ADfiles/over/a330/2011-0173R1.pdf

[barit1]

Extermally, there is some resemblance tp 44 years ago: https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR7502.pdf

[parabellum]

Maybe it was harmonic resonance. http://cdn.pprune.org/images/smilies/wink2.gif

Had that happen to me in 1968 on an AB206A in Indonesia! Compressor looked like a well chewed sweet corn cob and the engine shut down very rapidly! No blades or stators left at all. From the pictures looks as though the cowl failed.

[underfire]

From a different A330 Trent failure..

https://www.flickr.com/photos/98001721@N00/

[A30_737_AEWC]

Ahh, it's a nacelle failure, NOT an engine failure :ugh:

That's ahead of the fan! Would blades come off and forward? In all that inward airflow?

Don't flatter yourself and your engineering knowledge.

Can't you see that a significant part of the first stage low pressure compressor fan appears intact along with the spinner?

If you remember anything about convergent flow in ducts, you will remember that the static pressure in an accelerating stream of fluid/air flow drops compared to that of the freestream (external/adjacent to the cowl opening). There is a net suction inside the lip of the nacelle/cowl opening.

It's highly likely that the material that separated from the forward cowl/shroud initially was sucked inward in relatively large pieces, making it less likely that pieces of any significant size were ingested into the engine core. Some smaller pieces of debris may in fact have passed through the bypass (cold air) section of the engine.

Isn't there supposed to be a kevlar blanket around the circumference of the fan to contain loose blades ??

Ah, not where there are not turning/burning engine components. This is an area of cowl/shroud AHEAD of any spinning parts (low pressure compressor). And there's no evidence that any blades of any sort were liberated.

As the failure is on the inboard side - what happened to the portside fuselage?

You are assuming that high speed rotating objects were liberated from the engine/cowl.

That may not be the case, especially if the relatively light structure which 'disappeared' was sucked in towards the centre of the cowl/shroud.

That's ahead of the fan! Would blades come off and forward? In all that inward airflow?

Do you even understand what you are looking at ? :ugh:

well, they did get a video chat from the engine! What is wrong with the press?!?!? I listened and I heard visual check, not video chat.......

I bet that the inspection and repair requirements of the cowl on that engine has been moved up!

http://services.casa.gov.au/airworth/airwd/ADfiles/over/a330/2011-0173R1.pdf

From the EASA AD identified by the link above, it seems that modifications were required to be incorporated to a number of A330 aircraft. Later build aircraft appear to have been delivered with modified cowls. Seems to me like a design/analysis screw up. Possibly the need to beef up the acoustic treatment/damping of the inner surfaces was identified at some point without properly assessing whether additional beefups were required at panel perimeters where attached to more substantial structure.

This AD goes back to 2011 with a revision in 2014.

An Airbus SB afford inspection and subsequent modification action.

One wonders if the airline has evidence of compliance with the ADs/SBs?

[A30_737_AEWC]

A piece from the Guardian on the matter:

https://www.theguardian.com/world/2017/jun/12/plane-makes-emergency-landing-in-sydney-with-huge-hole-in-engine-casing

Some better images here:

https://au.news.yahoo.com/nsw/a/35898939/china-eastern-airlines-flight-emergency-sydney-landing-after-engine-failure/#page1

[msbbarratt]

One wonders if the airline has evidence of compliance with the ADs/SBs?

I was wondering if they have RR's TotalCare package, and whether or not that covers things like the cowl. Anyone know?

Presumably if they did, and it did cover the cowl too then it'd be down to RR to demonstrate compliance. Yes, I know it's part of the airframe, not part of the engine itself, I just don't know how much of the airframe is covered by RR's package.

[bekolblockage]

Is the hole near the wing root a normal air intake/landing light mounting position? Or has it been made by damage from the cowling disintegration? Hard to tell at the resolution in Post # 1.
I couldn't see it on a few other A330's parked here.

Disregard. Found another photo showing it being a normal opening.

[underfire]

From a different A330 Trent failure..

Ahh, it's a nacelle failure, NOT an engine failure


I have been stating the acoustic cowling failure issue with Trents.

It appears that the EgytpAir failure is virtually the same failure...

failure is failure.

[mommus]

Assuming this is a failure of the cowl, and not the fan, who's responsibility is it?

RR don't build the nacelle - or do they?

[Landflap]

Train for this over and over again. Fellas did a well rehearsed and competent job.

[Arkroyal]

That's ahead of the fan! Would blades come off and forward? In all that inward airflow?
Since it's the fan pulling the aircraft forward, of course the fan blades go forward and outwards if released.

[TURIN]

Don't flatter yourself and your engineering knowledge.

Can't you see that a significant part of the first stage low pressure compressor fan appears intact along with the spinner?

If you remember anything about convergent flow in ducts, you will remember that the static pressure in an accelerating stream of fluid/air flow drops compared to that of the freestream (external/adjacent to the cowl opening). There is a net suction inside the lip of the nacelle/cowl opening.

It's highly likely that the material that separated from the forward cowl/shroud initially was sucked inward in relatively large pieces, making it less likely that pieces of any significant size were ingested into the engine core. Some smaller pieces of debris may in fact have passed through the bypass (cold air) section of the engine.

Back to school lad.

The intake is a divergent duct. Convert ram effect to higher pressure and slower airflow.

Basic engineering knowledge. But you knew that.

[Overboard111]

Since it's the fan pulling the aircraft forward, of course the fan blades go forward and outwards if released.

You'd think that but I've seen the damage done to the front luggage compartment of a Beech King Air that had a prop let go on take off and the holes were almost exactly in line with the prop hub exhibiting almost no forward movement at all. I expect a fan would perform similarly.

[.Scott]

In most photos you can see that at the top of the hole the remaining cowling is bent well outward - suggesting that most of the separated cowling passed over the top of the engine. Almost all of the other tearing seen also suggests this upward motion.

A look at the inside bottom of the hole also shows metal bent up - in that case, toward the engine. This is best seen 0:33 seconds into this video:

https://au.news.yahoo.com/nsw/a/35898939/china-eastern-airlines-flight-emergency-sydney-landing-after-engine-failure/#page1

This suggest that the bottom of the separated cowling passed directly over the intake. It's hard to imagine (but possible) that none of it was ingested.

[barit1]

Back to school lad.

The intake is a divergent duct. Convert ram effect to higher pressure and slower airflow.

Basic engineering knowledge. But you knew that.

Basic engineering knowledge. Without a LOT of airspeed, and certainly around Vr, there ain't much ram effect. We used to call it ram recovery speed; works well for you later in climb & cruise.

[Caribbean Boy]

Assuming this is a failure of the cowl, and not the fan, who's responsibility is it?

RR don't build the nacelle - or do they?

It doesn't matter who built any part of the engine, RR is the supplier and is responsible for any design or production defect.

Of course, the problem could have been caused by a maintenance error, so the Australian Transport Safety Bureau will be checking this out.

[TURIN]

Basic engineering knowledge. Without a LOT of airspeed, and certainly around Vr, there ain't much ram effect. We used to call it ram recovery speed; works well for you later in climb & cruise.

Ram recovery typically will occur at about 160kts.

What's the take off speed of a typical A330?

[lomapaseo]

Since it's the fan pulling the aircraft forward, of course the fan blades go forward and outwards if released

Not so fast. Give a thought to the lift forces vs time on the airfoil. The amount they move forward is miniscule before the airfoil effect is lost.

Kind of like an airplane glider wing that breaks off a toy

The forces driving the blade forward are friction like a skier on snow and only act at the tip surface

[Jonny Suave Trousers]

I think we can agree now no fan blades left the engine and it was a failure of the cowling. Was this perhaps a panel not properly tightened?

A 'big bang' was heard by multiple different people on the ground over a Sydney suburb. (It's widely reported on social media), so we can assume the cowling went into the engine causeing failure?

Me thinks this is a mantaince screw up. It would be interesting to see who last had hands on the cowling.

[ITman]

A seemingly similiar incident also involving a Trent 772 engine happened about 4 weeks ago, see Incident: Egypt A332 at Cairo on May 15th 2017, rejected takeoff due to engine failure.

Possibly related there may be two Airworthiness Directives released by EASA, see 2011-0173R1 of Aug 21st 2014 and 2016-0086R1 of May 13th 2016.

AD 2011-0173R1 reasons: "Two operators of A330 aeroplanes fitted with Rolls-Royce Trent 700 engines reported finding extensive damage to engine air intake cowls as a result of acoustic panel collapse, most probably caused by panel disbonding. This condition, if not detected and corrected, could lead to the detachment of the engine air intake cowl from the engine, possibly resulting in ingestion of parts by, and consequence damage to, the engine, or injury to persons on the ground."

AD 2016-0086R1 reasons: "During shop visit, cracks were found in several primary structural parts of Rolls Royce (RR) Trent 700 engine air intake cowls, specifically in the forward bulkhead web, web stiffeners and outer boundary angles (OBA). In addition, several attachment links were found severely worn, and some became detached. In two cases, the thermal anti- ice (TAI) piccolo tube was found fractured. Investigation results show that the cracks are most likely due to acoustic excitation and vibration. A broken piccolo tube, if not detected and corrected, in conjunction with forward air intake cowl bulkhead damage, could lead to in-flight detachment of the outer barrel, possibly resulting in damage to the engine or reduced control of the aeroplane."

[TURIN]

Me thinks this is a mantaince screw up. It would be interesting to see who last had hands on the cowling.

As there are no removable panels on the intake, I doubt it.

Some have suggested the cowl anti-ice PRV failed. I'm not so sure. :ok:

[megan]

Since it's the fan pulling the aircraft forward, of course the fan blades go forward and outwards if releasedIn all the cases of blade release from the fan, in the reports I've seen, the blades were released centrifugally, no forward motion. Reports on two DC-10's refer, N60NA and N1819U as examples.

[Turbine D]

Perhaps this information will help the discussion:

AD 2011-0173R1 reasons: "Two operators of A330 aeroplanes fitted with Rolls-Royce Trent 700 engines reported finding extensive damage to engine air intake cowls as a result of acoustic panel collapse, most probably caused by panel disbonding. This condition, if not detected and corrected, could lead to the detachment of the engine air intake cowl from the engine, possibly resulting in ingestion of parts by, and consequence damage to, the engine, or injury to persons on the ground."

AD 2016-0086R1 reasons: "During shop visit, cracks were found in several primary structural parts of Rolls Royce (RR) Trent 700 engine air intake cowls, specifically in the forward bulkhead web, web stiffeners and outer boundary angles (OBA). In addition, several attachment links were found severely worn, and some became detached. In two cases, the thermal anti- ice (TAI) piccolo tube was found fractured. Investigation results show that the cracks are most likely due to acoustic excitation and vibration. A broken piccolo tube, if not detected and corrected, in conjunction with forward air intake cowl bulkhead damage, could lead to in-flight detachment of the outer barrel, possibly resulting in damage to the engine or reduced control of the aeroplane."

[EEngr]

From the Trent failure photos posted by underfire (#22) it looks like the nacelle inner lining failure began at a seam or panel edge judging by the clean edge of the hole. The lining would probably be peeled off in the direction of the fan rotation, CW looking into the inlet. And the trailing edge of the tear (near the top) looks ragged.

[Turbine D]

In all the cases of blade release from the fan, in the reports I've seen, the blades were released centrifugally, no forward motion.
Except for the DC-10 over New Mexico where a CF6 fan blade was liberated and exited forward, walked up the fuselage, broke a window and the passenger was sucked out with his remains never to be found.

Also, there was at least one incident where the shaft to the fan on an RB211 engine sheared releasing the entire fan which spun out forward and away from the aircraft.

[Almostfamous]

Lots of discussion about which way and what way things go when they go out. This incident came to mind, which involved an MD-88. Perhaps it might dispel or confirm certain lines or reasoning expressed. Oh, and never sit in the back of the MD/DC jets...

https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR9801.pdf

[underfire]

I believe that Safran manufactures the nacelles for the A330...

[lomapaseo]

Don't mix up fan disk failures (DC10 /MD88) with fan blade failures alone.

It's the tip portion of the blade that slides forward not the inner parts.

Meanwhile back to this incident. Any distortion of the fan airfoil from the breakup of the cowl inner barrel, at high power, is sure to cause the engine to go bang with or without debris ingestion.

[GrahamO]

It doesn't matter who built any part of the engine, RR is the supplier and is responsible for any design or production defect.

Except its not part of the engine, not designed by RR and nor supplied by RR.

But apart from those errors, your comment is 100% correct.

:=

[megan]

Except for the DC-10 over New Mexico where a CF6 fan blade was liberated and exited forward, walked up the fuselage, broke a window and the passenger was sucked out with his remains never to be foundThe unfortunate passenger was sitting at the sixth window forward of the S3 door (row 17, seat H) when the #3 engine let go, just behind the wing root leading edge, and in line with the plane of rotation. #1 engine damaged by shrapnel also, along with fuselage below the window and wing leading edge between root and engine #3. No damage forward of the plane of rotation.

[Caribbean Boy]

Except its not part of the engine, not designed by RR and nor supplied by RR.

But apart from those errors, your comment is 100% correct.

:=

Are you seriously telling me that any engine supplier delivers engines without a cowling?

[TURIN]

Yes.

When changing an engine one often has to swap the cowl from the u/s engine to the new one. :E

[Caribbean Boy]

Yes, I know about what happens when a swap takes place, but the cowling came from RR in the first place, so RR is liable if they supplied a faulty product.

[swh]

I think the part numbers are SJ30020,SJ30361,SJ30810 and they are made by Bombardier. The cowl and EBU do not form part of the engine TCDS, so technically they are not part of the engine.

[MATELO]

being where the logo is.. you could understand the confusion...

[GrahamO]

..but the cowling came from RR in the first place, so RR is liable if they supplied a faulty product.

It didnt.

Sorry to burst your preconception. Its supplied by the airframe manufacturer.

[Caribbean Boy]

Airbus and RR would both be liable if the cowling is faulty. Action would be taken against MU and/or Airbus who in turn may take action against RR.

[Turbine D]

Yes, I know about what happens when a swap takes place, but the cowling came from RR in the first place, so RR is liable if they supplied a faulty product.
I very much doubt that is the case. In general terms, the engine nacelle is designed by the airframe manufacturer, in this instance, Airbus. Airbus determines the shape of the exterior, and the engine manufacturer (Rolls Royce) has significant input into the interior aerodynamic flowpath design starting with the entrance lip and perhaps input into the thrust reverser requirements. Once the nacelle design is firmed up, it is turned over to a nacelle manufacturer. It is Safran for the Rolls Royce Trent engine. The nacelles are supplied to Airbus who is the customer.
Airbus and RR would both be liable if the cowling is faulty.
Not true, if anything, responsibility would be between Airbus and Safran depending on the fault, design or manufacturing.

[underfire]

In reality, this issue has been an issue, and directives on corrective actions are in place.

It is evident from the Airbus directive, (not a RR directive), who is responsible.

It appears that either the directive is not sufficient ( there are many if/thens) or was not followed.

[Airmotive]

Airbus and RR would both be liable if the cowling is faulty. Action would be taken against MU and/or Airbus who in turn may take action against RR.

Stop.
Please just stop. You don't know what you're talking about.
The cowl is designed and supplied by Airbus, and built by Bombardier. There are no RR part numbers on the inlet cowl.

[keith williams]

Go away.

Now Now. This is supposed to be fun!

If you cannot play nicely then don't play at all

[PEI_3721]

Oh the desire for humans to seek blame / responsibility.
Why not consider what might be learnt; does this event involve design, manufacture, maintenance, operation, etc. As yet not known. Are safety activities in progress?
My interest is in operations with intake flow distortion with acoustic panels. Does this aircraft / engine have restrictions on acceleration in crosswinds, speeds, or recommended handling. And I am not seeking to blame the human, just understanding, and particularly how close to any safety margin modern operations might be.

[Airmotive]

Now Now. This is supposed to be fun!

If you cannot play nicely then don't play at all

Adjusted appropriately. :-)
The demanding for legal action turned a screw.

[lomapaseo]

My interest is in operations with intake flow distortion with acoustic panels. Does this aircraft / engine have restrictions on acceleration in crosswinds, speeds, or recommended handling. And I am not seeking to blame the human, just understanding, and particularly how close to any safety margin modern operations might be

Doesn't appear to be anything more than an inflight shutdown at the lowest level of "unsafe operation" of a powerplant system.

Costly? yes

[barit1]

Except for the DC-10 over New Mexico where a CF6 fan blade was liberated and exited forward, walked up the fuselage, broke a window and the passenger was sucked out with his remains never to be found. . .

Well, not quite.

The original CF6 fan assembly was secured together by the spinner, which physically retained the blades in their dovetail slots.

In the above case (a colleague was an investigator on the case) the #3 engine fan case got into a standing wave vibration (like a rung church bell) that scrubbed the fan blade tips a couple times each revolution; this overcame the centrifugal force holding blades in the fan disc. Each time the blade tip scrubbed, aero load on each blade pushed the blade forward a fraction of a millimeter, breaking the spinner loose, and eventually each blade traveled completely free of the disc. #3 fan blades flying every which direction.

One traveled completely under the fuselage to strike the #1 engine accy gearbox. It's fuel pump disabled, that engine flamed out.

Another blade was swallowed by the #2 engine, which coughed and grumbled, but kept running.

Yet another blade hit the RH cabin window at row 10, which depressurized the cabin. The unlucky pax exited via the window.

The aircraft (N60NA, "Barbara") landed at nearby ABQ without further damage.

All of which has virtually nothing to do with the present A330/Trent case.

[Vzlet]

I can't decide if that's a lucky or unlucky plane:
8 months later (https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR7409.pdf)

[lomapaseo]

You left out the guy who fell to his death from the wheel well and the guy who killed himself in the loo all in N69NA as it transited through its owners,

I last saw it at the gate in Pan Am livery at JFK. I called it the devil ship.

I had the earliest Aurora (sp?) model with the identical decals as N69NA but the decal was missing a window on the right hand side ahead of the wing ... go figure

[Oro-o]

Except for the DC-10 over New Mexico where a CF6 fan blade was liberated and exited forward, walked up the fuselage, broke a window and the passenger was sucked out with his remains never to be found.

Also, there was at least one incident where the shaft to the fan on an RB211 engine sheared releasing the entire fan which spun out forward and away from the aircraft.

There were a few things here that surprised me, namely the forward ejection of blades, "walking" along the fuselage of said debris, and the lack of retrieval of the victim after all this time. So I looked into them. They are not as stated.

N60NA/National 27 lost a passenger on that flight. His seat, 17H (from the FAA report), based on both contemporary 2-class domestic DC-10 configuration AND photographs of the airframe after landing, show the broken window and his location is completely orthoganal to the fan blades. There are score marks a few feet forward of the window and six to eight feet below, but more logically explicable by deflection of additonal blade ejecta from the inboard wing, which shows significant damage. None of the physcial evidence I could find supports forward ejection of the blades or "walking" along the fuselage.

The remains were recovered two years later (Winter 1975/76) during construction of the VLA radioastronomy facility. They were not "never to be found."

What is really interesting is if the flight crews' unsanctioned flight tests at the time of the incendent contributed to it. The FAA report is an interesting read and surprisingly circumspect on that. Hopefully a DC-10 FE could shed light on that.

[lomapaseo]

orthoganal

a very big word that doesn't apply to a rotating body at the instant of release.

After release there are many conditional elements to consider, namely whether the fan case is present and whether other adjacent blades are still present. All of this varied in the N60NA incident.

and don't ignore windage if the release has to exit through any kind of shielding that slows it down.

[barit1]

My edits:


. . .
Another blade was swallowed by the #2 engine, which coughed and grumbled, but kept running.


As others have pointed out, the blades at high energy went orthogonal (or radially outward if you prefer). As such they would not intersect the #2 inlet; it must have been low-energy debris i.e. cowl pieces.

Besides, I'm sure that had the #2 fan had swallowed an extra blade, the result would be a dead-stick landing.


Yet another blade hit the RH cabin window at row 10, which depressurized the cabin. The unlucky pax exited via the window.


Row 17 per the report, not row 10.

[megan]

It's fuel pump disabled, that engine flamed outAnother correction barit, the engine did not flame out. Its oil tank was punctured and continued to lose oil for the remainder of the flight, as did its hydraulic system, but the engine operated throughout. Additionally, the wiring for the fuel flow transmitter and generator were severed.it must have been low-energy debris i.e. cowl piecesA small piece of fan blade was found embedded in the forward section of the #2 engine inlet cowl, and two of the fan blades had leading edge damage. Boroscope inspection found three compressor blades had small nicks.

[ThreeThreeMike]

Regarding N60NA, two of the three hydraulic systems were comprised and the reservoirs emptied when the wing leading edge was damaged.

While this was mentioned in the NTSB document, there was no significance at all attached to the implications. As we all know, it would take some years before another uncontained failure on a DC-10 resulted in the loss of all three.

[parabellum]

Just a bit of add-on. Hull insurance does not include mechanical breakdown of the engine, there is specialist engine only cover available in the insurance market, the engine cowls are considered a part of the airframe. Hull insurance does, I think, cover FOD in an engine and in this case the engine cowl would, I think, be classified as FOD. Anyone in the current insurance market will know for sure. Any legal activity, possibly between underwriters, will take place behind the scenes and you are unlikely to ever hear of it.

[ThreeThreeMike]

That's interesting. I didn't know there were underwriters for FOD damage.

[lomapaseo]

Big operators self insure up to certain levels

Small operators farm out some maintenance and/or insure at lower levels.

Most crossover points have to do with source of damage as well.
Some FOD is argued as engine generated and versa-visa.

Inlet cowls have often been covered as above the self insurred level. for some operators.

Even the biggest operators often insure for reverser and/or pylon involvement in engine damage incidents.

the fine print rules and subjective judgments are sought

[SeenItAll]

Not that it is directly relevant to this incident, but the NTSB report on the National Airlines DC-10 N60NA accident over New Mexico is incredibly frightening in terms of the malfeasance it suggests occurred by the airline's management, its maintenance staff, its flight crew and (somewhat) its cabin crew. I certainly hope that now 40+ years on, procedures and professionalism have improved substantially. That National Airlines is now dead does not seem saddening. See: https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR7502.pdf