Tez Jet Avro RJ uncontained engine failure - March 2018
The ALF 502 had a history of problems with the turbine bearings (4-5), these involved oil flow - overheat, oil coking, maintenance, filter clogged, ...
More often these issues resulted in a bearing failure, which in isolation was not a major problem - other than engine failure! However, because the 4-5 bearings were a combined package, so that if one or particularly both size it is possible to shear the main shaft due to a differential ‘clamping effect’.
The certification regulations on ‘containment’ require a narrow conical zone of airframe structure and systems which can tolerate debris exiting beyond the engine containment structure.
A major contribution to this safety requirement is that the engine main shaft should not break, not allowing turbine discs to move rearwards or change off axis angle, i.e. anything which can lead to tangental blade shedding or even disc failure outside of the certificated zone.
With continuing problems, the ALF 502 was subject to mandated modification requiring the redesign and change of the 4-5 bearing package. AFAIK all engines were been modified with a new single pack / combined bearing.
The LF 507 used a similar (identical) rear bearing, but I do not know if these engines were required to be modified; it would be surprising if not.
The picture indicates damage which involving multiple turbine blades shedding, typical of a shaft shear - a cut similar to circular saw close to the engine, but further out individual ‘shrapnel’ damage. I don’t recall any situations with a fractured turbine disc, or the disc leaving the engine area.
Dave #8, pedantically the RJ engine is the LF507-1F (FADEC); the -1H (Hydromechanical) was installed in a few late series 146-300.
TR #16, I do not recall any loss of fan blades, nor serious problems with the middle of the engine. A few early gearbox problems were cured, as was the manufacturing / quality issue which resulted in a centrifugal first stage compressor disintegrating.
As for external damage, as above, I can only recall one other adjacent engine failure due to uncontained blades - Aviasca.
More often these issues resulted in a bearing failure, which in isolation was not a major problem - other than engine failure! However, because the 4-5 bearings were a combined package, so that if one or particularly both size it is possible to shear the main shaft due to a differential ‘clamping effect’.
The certification regulations on ‘containment’ require a narrow conical zone of airframe structure and systems which can tolerate debris exiting beyond the engine containment structure.
A major contribution to this safety requirement is that the engine main shaft should not break, not allowing turbine discs to move rearwards or change off axis angle, i.e. anything which can lead to tangental blade shedding or even disc failure outside of the certificated zone.
With continuing problems, the ALF 502 was subject to mandated modification requiring the redesign and change of the 4-5 bearing package. AFAIK all engines were been modified with a new single pack / combined bearing.
The LF 507 used a similar (identical) rear bearing, but I do not know if these engines were required to be modified; it would be surprising if not.
The picture indicates damage which involving multiple turbine blades shedding, typical of a shaft shear - a cut similar to circular saw close to the engine, but further out individual ‘shrapnel’ damage. I don’t recall any situations with a fractured turbine disc, or the disc leaving the engine area.
Dave #8, pedantically the RJ engine is the LF507-1F (FADEC); the -1H (Hydromechanical) was installed in a few late series 146-300.
TR #16, I do not recall any loss of fan blades, nor serious problems with the middle of the engine. A few early gearbox problems were cured, as was the manufacturing / quality issue which resulted in a centrifugal first stage compressor disintegrating.
As for external damage, as above, I can only recall one other adjacent engine failure due to uncontained blades - Aviasca.
Last edited by alf5071h; 9th Mar 2018 at 18:17. Reason: Typo
Certification requirement summaries need to be mindful of words such as
"shall"
"should"
"could"
"must"
Basically there is much wiggle room between a certification rule and its advisory or "how to" comply part that goes with it.
For engines installed in aircraft, it's impractical to design and test for all possible combinations of failure conditions. However in the end it's the degree of threat that should be shown to be minimized by means, that meet the certification requirement.
And even after that is met, anything that happens in-service need be addressed under continued airworthiness, so no one can hide behind a presumption that being originally certified is good enough
"shall"
"should"
"could"
"must"
Basically there is much wiggle room between a certification rule and its advisory or "how to" comply part that goes with it.
For engines installed in aircraft, it's impractical to design and test for all possible combinations of failure conditions. However in the end it's the degree of threat that should be shown to be minimized by means, that meet the certification requirement.
And even after that is met, anything that happens in-service need be addressed under continued airworthiness, so no one can hide behind a presumption that being originally certified is good enough
The ALF 502 had a history of problems with the turbine bearings (4-5), these involved oil flow - overheat, oil coking, maintenance, filter clogged, ...
More often these issues resulted in a bearing failure, which in isolation was not a major problem - other than engine failure! However, because the 4-5 bearings were a combined package, so that if one or particularly both size it is possible to shear the main shaft due to a differential ‘clamping effect’.
The certification regulations on ‘containment’ require a narrow conical zone of airframe structure and systems which can tolerate debris exiting beyond the engine containment structure.
A major contribution to this safety requirement is that the engine main shaft should not break, not allowing turbine discs to move rearwards or change off axis angle, i.e. anything which can lead to tangental blade shedding or even disc failure outside of the certificated zone.
With continuing problems, the AFL 502 was subject to mandated modification requiring the redesign and change of the 4-5 bearing package. AFAIK all engines were been modified with a new single pack / combined bearing.
The LF 507 used a similar (identical) rear bearing, but I do not know if these engines were required to be modified; it would be surprising if not.
More often these issues resulted in a bearing failure, which in isolation was not a major problem - other than engine failure! However, because the 4-5 bearings were a combined package, so that if one or particularly both size it is possible to shear the main shaft due to a differential ‘clamping effect’.
The certification regulations on ‘containment’ require a narrow conical zone of airframe structure and systems which can tolerate debris exiting beyond the engine containment structure.
A major contribution to this safety requirement is that the engine main shaft should not break, not allowing turbine discs to move rearwards or change off axis angle, i.e. anything which can lead to tangental blade shedding or even disc failure outside of the certificated zone.
With continuing problems, the AFL 502 was subject to mandated modification requiring the redesign and change of the 4-5 bearing package. AFAIK all engines were been modified with a new single pack / combined bearing.
The LF 507 used a similar (identical) rear bearing, but I do not know if these engines were required to be modified; it would be surprising if not.
As for external damage, as above, I can only recall one other adjacent engine failure due to uncontained blades - Aviasca.
It does make a difference what parts are ejected through the engine case structure (turbine disk pieces or small blade fragments) the latter are broken into smaller bits just by penetrating through a structure and as a result lose a good deal of their velocity as well. Thus many of the blade pieces will only partially pierce the skin of other aircraft structures (adjacent engine nacelles plus case walls).
What is more likely to happen is that a fog of small debris makes it into another engine's inlet and results in FOD . The latter is cause for concern to the crew (abnormal indications) but only rarely completely causes failure of another engine (albeit the crew may shut it down)
interpret the historical reports carefully.
What is more likely to happen is that a fog of small debris makes it into another engine's inlet and results in FOD . The latter is cause for concern to the crew (abnormal indications) but only rarely completely causes failure of another engine (albeit the crew may shut it down)
interpret the historical reports carefully.
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@BRE. 99 passengers within the bound of possibility.
From elsewhere on the web:
"RJ85 - Max seating in passenger cabin for 112 at six abreast and 74cm (29in) pitch."
From elsewhere on the web:
"RJ85 - Max seating in passenger cabin for 112 at six abreast and 74cm (29in) pitch."
What is more likely to happen is that a fog of small debris makes it into another engine's inlet and results in FOD . The latter is cause for concern to the crew (abnormal indications) but only rarely completely causes failure of another engine (albeit the crew may shut it down)
It's an unlikely scenario for the 146/RJ where the engines are much closer together.
interpret the historical reports carefully.
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Engine Certification Requirements are quite clear. All failures must be contained. Blades, vanes and so on.
Discs and possibly shafts are the only components where non contained failures are considered possible. So we make sure that failures do not happen, and we mitigate as far as possible against the effects of such failures.
Major engine rotating parts are the only components on the whole of the aircraft to be considered non fail safe.
Discs and possibly shafts are the only components where non contained failures are considered possible. So we make sure that failures do not happen, and we mitigate as far as possible against the effects of such failures.
Major engine rotating parts are the only components on the whole of the aircraft to be considered non fail safe.
Major engine rotating parts are the only components on the whole of the aircraft to be considered non fail safe.
That way a really bad engine day is quite rare compared to a myriad of other causes. The larger risks are where the aircraft is on the ground (debris re-bounds, fuel pool fires, etc.)
Most rotating components on an engine have some sort of life limit (often expressed in cycles rather than hours - sometimes both) and are designed to never fail within that life limit.
However sometimes $hit happens and one lets go due to a manufacturing defect or improper maintenance.
While the regulations basically say you need to design the aircraft in such a way to minimize the hazard, the associated regulatory guidance generally points to a "1 in 20" analysis. Basically, the airframer analyzes all the potential disc burst scenarios, and makes sure that 5% (or less) will have a catastrophic outcome. I've had secondary involvement in 1-20 analysis, but the prime 1-20 task is almost black magic. For small, lightweight debris such as compressor/turbine blades, you can take credit for shielding - for large pieces of disc shielding is deemed to be impractical (Where does a third of a fan disc go? Anywhere it wants to...) so location of flight critical components becomes critical.
Uncontained engine failures are considered to be a 10-8/hr. event - so if 1 in 20 is catastrophic the probability of a catastrophic uncontained engine failure is less than 10-9/hr. which in the regulatory arena means 'it'll never happen' (yea, I know, but you have to draw the line someplace and it was agreed that 1/billion was good enough).
However sometimes $hit happens and one lets go due to a manufacturing defect or improper maintenance.
While the regulations basically say you need to design the aircraft in such a way to minimize the hazard, the associated regulatory guidance generally points to a "1 in 20" analysis. Basically, the airframer analyzes all the potential disc burst scenarios, and makes sure that 5% (or less) will have a catastrophic outcome. I've had secondary involvement in 1-20 analysis, but the prime 1-20 task is almost black magic. For small, lightweight debris such as compressor/turbine blades, you can take credit for shielding - for large pieces of disc shielding is deemed to be impractical (Where does a third of a fan disc go? Anywhere it wants to...) so location of flight critical components becomes critical.
Uncontained engine failures are considered to be a 10-8/hr. event - so if 1 in 20 is catastrophic the probability of a catastrophic uncontained engine failure is less than 10-9/hr. which in the regulatory arena means 'it'll never happen' (yea, I know, but you have to draw the line someplace and it was agreed that 1/billion was good enough).
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[QUOTE=lomapaseo;10078600]Well they are like aircraft components such as keel beams and wing spars sized and life limited to not fail and if the(engine) do fail the aircraft design need to provide mitigation against the loss of the aircraft from such uncontained consequences
I do not believe that is the case. Aircraft structure is designed to fail safe principles with dual load paths and so on and safe lives in the rotating part sense are not used. The integrity philosophy of engine rotating parts is in no way similar to aircraft structural disciplines. A good thing, too.
And don't get me started on rotorcraft.
I do not believe that is the case. Aircraft structure is designed to fail safe principles with dual load paths and so on and safe lives in the rotating part sense are not used. The integrity philosophy of engine rotating parts is in no way similar to aircraft structural disciplines. A good thing, too.
And don't get me started on rotorcraft.
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Have heard from a buddy that a ME operator a few months ago had all 4 engines overtemp due fistfuls of throtles by the flight crew. Anyone know anymore of this? NB 4 engine overtemp must be a first for any operator...
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Somebody asked about a similar incident to the Citylink RJ whereby debris from one engine caused the failure of the adjacent unit.
I believe there was a Lufthansa RJ that had departed LCY that had a similar set of circumstances. I recall seeing the photos which were not for the faint of heart.
Perhaps somebody with some time on their hands can find the incident.
From memory it would have been 2008 ish
I believe there was a Lufthansa RJ that had departed LCY that had a similar set of circumstances. I recall seeing the photos which were not for the faint of heart.
Perhaps somebody with some time on their hands can find the incident.
From memory it would have been 2008 ish
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never heard that story....the QRH does call for "thrust levers fully forward" in the event of a wind shear encounter, that action would probably produce some interesting EGT indications..but never had to do that thank goodness
the QRH does call for "thrust levers fully forward" in the event of a wind shear encounter, that action would probably produce some interesting EGT indications..but never had to do that thank goodness
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Should not even notice on new engines that being said, the auto throttles will take the EGT to 649c if the wind shear system is activated with the automatics engaged...which is well above any take-off, or max continuous EGT limit
