Qantas Emergency Return KSFO, Explosion in Engine?
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An visual engine inspection following disassembly of the engine showed that all turbine blades had separated from the IP (intermediate pressure) turbine disk. The blades of the three LP (low pressure) turbine stages were fractured through the airfoil section of had separated from the disk. The LP stage nozzle guide vanes were destroyed, the remaining LP nozzles were substantially damaged. The LP turbine bearing and adjacent phonic wheel and speed probe were destroyed. The IP shaft was severed towards the aft end.
Incident: Qantas B744 near San Francisco on Aug 31st 2010, uncontained engine failure
ATSB Photo from Av Herald Article
It shows the blades thrown off the IP and Stage I LP turbines -- along with the departure of a good chunk of the stator housing. Perhaps a solid piece got in the way of the blades and sheared them off
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I'll propose another scenario - which may/may not be pertinent to the RB.
The fact that the IP SHAFT is sheared is very worrisome - and in fact that may be the initiating event. If this occured first, then the IPT is suddenly unloaded and very quickly overspeeds, since the N3 system continues to run and provide the gas flow. The overspeeding N2 turbine will at some point fail - and it's possible that the next part to break will be the IPT blade roots. The release of all the blades could rip open the case and the cowl, but then leave the IPT disc without a driving torque, so it does not burst (a very, very good thing!)
Maybe someone more familiar with specific knowledge of RB failure modes can comment.
The fact that the IP SHAFT is sheared is very worrisome - and in fact that may be the initiating event. If this occured first, then the IPT is suddenly unloaded and very quickly overspeeds, since the N3 system continues to run and provide the gas flow. The overspeeding N2 turbine will at some point fail - and it's possible that the next part to break will be the IPT blade roots. The release of all the blades could rip open the case and the cowl, but then leave the IPT disc without a driving torque, so it does not burst (a very, very good thing!)
Maybe someone more familiar with specific knowledge of RB failure modes can comment.
Barit1
Not sure what RB stands for
I do agree that the shaft separation is troubling, more so because the visible unbalance of the IP rotor looks unlikely to to put much of a load on its drive shaft (chicken-egg question)
The battered off LP blades sure look secondary to the IP debris, while the empty blade roots in the IP suggest either severe overspeed or fire and stretching of the disk.
Sucessful design if the shaft was primary and the rotor disk remained intact
I'll propose another scenario - which may/may not be pertinent to the RB.
The fact that the IP SHAFT is sheared is very worrisome - and in fact that may be the initiating event. If this occured first, then the IPT is suddenly unloaded and very quickly overspeeds, since the N3 system continues to run and provide the gas flow. The overspeeding N2 turbine will at some point fail - and it's possible that the next part to break will be the IPT blade roots. The release of all the blades could rip open the case and the cowl, but then leave the IPT disc without a driving torque, so it does not burst (a very, very good thing!)
Maybe someone more familiar with specific knowledge of RB failure modes can comment
The fact that the IP SHAFT is sheared is very worrisome - and in fact that may be the initiating event. If this occured first, then the IPT is suddenly unloaded and very quickly overspeeds, since the N3 system continues to run and provide the gas flow. The overspeeding N2 turbine will at some point fail - and it's possible that the next part to break will be the IPT blade roots. The release of all the blades could rip open the case and the cowl, but then leave the IPT disc without a driving torque, so it does not burst (a very, very good thing!)
Maybe someone more familiar with specific knowledge of RB failure modes can comment
I do agree that the shaft separation is troubling, more so because the visible unbalance of the IP rotor looks unlikely to to put much of a load on its drive shaft (chicken-egg question)
The battered off LP blades sure look secondary to the IP debris, while the empty blade roots in the IP suggest either severe overspeed or fire and stretching of the disk.
Sucessful design if the shaft was primary and the rotor disk remained intact
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lomapaseo - my assumption was that Ppruneists would translate my cryptic RB as RB211. Sorry for the excess brevity.
I also assumed it obvious that the downstream LPT damage is secondary. 99% of the time, that's the way the damage propagates.
In any event, I'll be very curious to learn what the experts think.
I also assumed it obvious that the downstream LPT damage is secondary. 99% of the time, that's the way the damage propagates.
In any event, I'll be very curious to learn what the experts think.
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Interesting. This article on the QF A380 Trent failure seems to confirm my speculation about the QF 747/RB211 failure. The two seem closely related.
Interesting. This article on the QF A380 Trent failure seems to confirm my speculation about the QF 747/RB211 failure. The two seem closely related.
While I might agree with you about what likely happened on the RB211, the only similarity that fits with the Trent incident is the Rotor location.
Of course we could debate things like this in the more general Tech forum
