SDF UPS down

I'm not sure reaching a conclusion based on failure modes of a ground-based turbine is valid. Fuel controls in jet engines have largely rigorous standards for failure modes and mitigation, and a catastrophic full-flow runaway based on a single wire failure, or *any* single=point failure, is highly unlikely.

That being said, there are also standards for uncontained rotor failures, yet there have been a few, so the standards (or the validation) clearly don't prevent everything. I just think it's a little early to be guessing at specific failures that are far out of the ordinary.

geezer said:
For the record, there were 2 men and 1 woman on that aircrew, she was one of the full Captains. Sympathy for all their families, and coworkers.
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Dana is also a male name, and in this case a male's name, if that's whom you're referring to.

Nauga,
and a game of telephone
 
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geezer said:
If the GE turbines on this MD 11 had a similar fail safe system and lost the low power reference signal,
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To add to the above, you'll find most aircraft turbine engines have overspeed protection systems or topping limiters built into the fuel control systems. And most of those are automatically actuated with no input required from the cockpit. Matter of fact, I've seen more instances of overspeed system failures which would auto-decel the engine at an inopportune time. But I must agree, there are very limited similarities between industrial and aircraft turbines built on the same core design having worked on both versions from Allison and P&W.
 
JimLAFB said:
Nauga is cleared to put his MD-11 back in service, having inspected it and finding it needed no corrective action.
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And not knowing what the root cause(s) of the incident was (were), he did not know what he did not know, and inspected all he knew and thinking that he was doing the right thing, put it back in service.
 
455 Bravo Uniform said:
And not knowing what the root cause(s) of the incident was (were), he did not know what he did not know, and inspected all he knew and thinking that he was doing the right thing, put it back in service.
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Yeah, there's the rub. Fortunately emergency AD's rarely leave it to the operator to wing it (NPI) when it comes to compliance, and the AMOC process in the subject AD is unclear on the process but very clear on what that lack of clarity means.

Nauga,
collecting dust
 
Just to add, all inspections for the AD must be approved by the AIR branch as noted below. And given there are no specific inspection tasks listed in the AD usually points to the need for flexibility in those checks depending on the results, aircraft total time, etc. Plus it keeps things under control until they can narrow down the failure sequence.

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I don't believe that the return-to-service inspection has been established yet. They need to know exactly what failed before they can design an inspection to look for a similar failure.
 
Larry in TN said:
They need to know exactly what failed before they can design an inspection to look for a similar failure.
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Not necessarily. A number of EADs I’ve seen are used as part of the investigation and inspections into the failure(s). So it wouldn’t be unusual if some 11s are permitted fly while the interim EAD is valid. The direction I would look in is if Boeing and/or GE issue any bulletins listing specific inspections pertaining to this accident. For example, cracks were noted on the rotorshaft of a specific model helicopter which triggered a global EAD. Several days later the OEM got a fleet wide AMOC approved to continue flight with a 10-hour repetitive check after removal of the blade bolt nuts. About 3 weeks later the AMOC was revised to allow pilots to perform the 10 hour check without nut removal and about 6 months later the final terminating action AD was released. Now how important it is to get those 11s flying again will usually dictate the speed at which this process moves.
 
Bell206 said:
Not necessarily. A number of EADs I’ve seen are used as part of the investigation and inspections into the failure(s). So it wouldn’t be unusual if some 11s are permitted fly while the interim EAD is valid. The direction I would look in is if Boeing and/or GE issue any bulletins listing specific inspections pertaining to this accident. For example, cracks were noted on the rotorshaft
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I'm not sure where we disagree. In your example, cracks were found. That is the type of evidence they need to develop a test procedure.
 
Bell206 said:
Not necessarily. A number of EADs I’ve seen are used as part of the investigation and inspections into the failure(s). So it wouldn’t be unusual if some 11s are permitted fly while the interim EAD is valid. The direction I would look in is if Boeing and/or GE issue any bulletins listing specific inspections pertaining to this accident. For example, cracks were noted on the rotorshaft of a specific model helicopter which triggered a global EAD. Several days later the OEM got a fleet wide AMOC approved to continue flight with a 10-hour repetitive check after removal of the blade bolt nuts. About 3 weeks later the AMOC was revised to allow pilots to perform the 10 hour check without nut removal and about 6 months later the final terminating action AD was released. Now how important it is to get those 11s flying again will usually dictate the speed at which this process moves.
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I’m wondering how many, if any, other planes have the same engine. It is looking like the engine is what started this. I’d think an AD should be out on the engine.
 
luvflyin said:
I’m wondering how many, if any, other planes have the same engine. It is looking like the engine is what started this. I’d think an AD should be out on the engine.
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Curious…What have you seen that indicates Engine vs Pylon vs Water Buffalo on runway?
 
kyleb said:
Curious…What have you seen that indicates Engine vs Pylon vs Water Buffalo on runway?
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“…There were a lot of sheared off fan blades from the Number 1 engine found on the parallel runway…”

That maybe could have happened after it separated from the plane, I dunno. It’s been said there was a fire warning alarm in the cockpit. How can that happen after it separates? And it’s just the logic check to me. I just don’t see the engine not being the first thing in the sequence of events. The first hole in the cheese so to speak.
 
Larry in TN said:
I'm not sure where we disagree. In your example, cracks were found. That is the type of evidence they need to develop a test procedure.
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I was mostly replying to your comment: "the return-to-service inspection has been established yet." That would imply final action. My example was to merely show a lot can happen before a RTS or final action. In both cases, a cracked rotorshaft and a structurally failed pylon were the initiating events, but the cause was/is unknown. Unfortunately, there is an economic effect that must be dealt with by the FAA in these situations which tends to influence the process. So whether the intent of the EAD is to find the terminating or "return to service" action, or simply a method to get the 11s flying again is yet to be seen. Regardless, my guess is there is a lot being discussed on both issues.

luvflyin said:
’m wondering how many, if any, other planes have the same engine. It is looking like the engine is what started this. I’d think an AD should be out on the engine.
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I don't know the specific engine dash number on this 11, but the CF-6 is used on a number of other Boeing/Airbus models. While its always possible an AD maybe issued against the engine, its my take the focus is on the failed pylon which should not have failed in that location no matter what engine type was installed.

luvflyin said:
It’s been said there was a fire warning alarm in the cockpit. How can that happen after it separates? And it’s just the logic check to me. I just don’t see the engine not being the first thing in the sequence of events.
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There are usually different types of fire detection on large aircraft with one being a "fire loop" type that is usually installed on the interior of the cowling areas and is basically a continuous loop of specialized material. In general, when the loop senses excessive heat or when the loop continuity is compromised, it triggers an alarm or light in the cockpit. So in one scenario, the aircraft was well into its takeoff roll and if the engine pylon failed first, as the functioning engine dropped off it would sever the fire loop connections causing an alarm without an any engine issue. And since they supposedly have video of the pylon failure during the roll out, my guess they have determined at what point the fire alarm activated.
 
Bell206 said:
I was mostly replying to your comment: "the return-to-service inspection has been established yet." That would imply final action. My example was to merely show a lot can happen before a RTS or final action. In both cases, a cracked rotorshaft and a structurally failed pylon were the initiating events, but the cause was/is unknown. Unfortunately, there is an economic effect that must be dealt with by the FAA in these situations which tends to influence the process. So whether the intent of the EAD is to find the terminating or "return to service" action, or simply a method to get the 11s flying again is yet to be seen. Regardless, my guess is there is a lot being discussed on both issues.


I don't know the specific engine dash number on this 11, but the CF-6 is used on a number of other Boeing/Airbus models. While its always possible an AD maybe issued against the engine, its my take the focus is on the failed pylon which should not have failed in that location no matter what engine type was installed.


There are usually different types of fire detection on large aircraft with one being a "fire loop" type that is usually installed on the interior of the cowling areas and is basically a continuous loop of specialized material. In general, when the loop senses excessive heat or when the loop continuity is compromised, it triggers an alarm or light in the cockpit. So in one scenario, the aircraft was well into its takeoff roll and if the engine pylon failed first, as the functioning engine dropped off it would sever the fire loop connections causing an alarm without an any engine issue. And since they supposedly have video of the pylon failure during the roll out, my guess they have determined at what point the fire alarm activated.
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Ok, that makes sense. I hadn’t read there was video of the pylon separating. And the ‘loop’ being broken setting of the alarm makes sense.
 
luvflyin said:
I’m wondering how many, if any, other planes have the same engine. It is looking like the engine is what started this. I’d think an AD should be out on the engine.
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Many of those engines are in service, and there aren't huge numbers of whatever occurred occurring. So what would you check?
 
luvflyin said:
“…There were a lot of sheared off fan blades from the Number 1 engine found on the parallel runway…”

That maybe could have happened after it separated from the plane, I dunno. It’s been said there was a fire warning alarm in the cockpit. How can that happen after it separates? And it’s just the logic check to me. I just don’t see the engine not being the first thing in the sequence of events. The first hole in the cheese so to speak.
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Fair enough and reasonable. I figure it is about 50/50 pylon vs engine, but I guess we're gonna have to wait for more info from the NTSB to satisfy our curiosity...
 
kyleb said:
Fair enough and reasonable. I figure it is about 50/50 pylon vs engine, but I guess we're gonna have to wait for more info from the NTSB to satisfy our curiosity...
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Certainly some of the highest normal-operation stresses on the pylon occur at rotation.
 
AvNavCom said:
I swear, I read this thread title as 'SDF Upside-down' every time.
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Can't worry about being "upside down" in 2025 . . ..

P.S.: (from Typogylcemia @ U Chicago) "Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe."
 
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Taylor Not Swift said:
Can't worry about being "upside down" in 2025 . . ..

P.S.: (from Typogylcemia @ U Chicago) "Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe."
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I wonder if the Orbis MD-10 is grounded, or if it was even airworthy when this all went down.
 
avbrief.com

FAA Grounds DC-10s, Too - AvBrief.com

AD now includes special purpose conversions.
avbrief.com avbrief.com

The FAA has expanded its Emergency AD on MD-11 aircraft to include the entire roster of DC-10 models and their derivatives. The agency issued an AD on Nov. 8 covering MD-11 and MD-11F models but then determined that the engine nacelle and pylon structure that was the focus of the original AD is pretty much the same in all the aircraft.
 
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