C Series Info
01-15-2019, 06:27 AM
#3312
Roll’n Thunder
Joined APC: Oct 2009
Position: Pilot
Posts: 3,855
01-15-2019, 04:43 PM
#3313
Line Holder
Joined APC: Sep 2018
Posts: 49
Interesting article. In the P&W statement section they mentioned the 'knife-edge seal' in the high-pressure compressor.
This seal was the cause of a phenomenon called 'core lock' that occurred on a 2004 CRJ crash (FLG 3701 for those who remember).
In a nutshell, the crew were at altitude, stalled and allowed the core speed to go to 0 RPM. When this happened, the parts of the engine outside the core shock-cooled and shrunk causing the outer portion of the knife-edge seal to contact the core portion which basically got lodged. This was an extreme situation and before 3701 no one had ever heard of core-lock. At first GE denied it could even happen because engines don't generally stop rotation at altitude, even during a flame-out.
The tolerances in this section of the engine must be incredibly tight. I wonder if heating/cooling is causing the same type of core/shell contact in the new engines.
This seal was the cause of a phenomenon called 'core lock' that occurred on a 2004 CRJ crash (FLG 3701 for those who remember).
In a nutshell, the crew were at altitude, stalled and allowed the core speed to go to 0 RPM. When this happened, the parts of the engine outside the core shock-cooled and shrunk causing the outer portion of the knife-edge seal to contact the core portion which basically got lodged. This was an extreme situation and before 3701 no one had ever heard of core-lock. At first GE denied it could even happen because engines don't generally stop rotation at altitude, even during a flame-out.
The tolerances in this section of the engine must be incredibly tight. I wonder if heating/cooling is causing the same type of core/shell contact in the new engines.
01-25-2019, 12:19 AM
#3314
:-)
Joined APC: Feb 2007
Posts: 7,339
Sounds like Airbus has restarted the CS500 program, given comments from their President of Commercial Aircraft. Around 100 of them would fit nicely into fleet renewal for Delta, especially competing directly against the 737max 7/8.
01-25-2019, 03:41 AM
#3315
Gets Weekends Off
Joined APC: Apr 2016
Position: Looking left
Posts: 3,399
I would say the CS-300 competes with the 737-700....both are in the 125 seat range.
01-25-2019, 04:01 AM
#3316
Perennial Reserve
Joined APC: Jan 2018
Posts: 12,159
Interesting article. In the P&W statement section they mentioned the 'knife-edge seal' in the high-pressure compressor.
This seal was the cause of a phenomenon called 'core lock' that occurred on a 2004 CRJ crash (FLG 3701 for those who remember).
In a nutshell, the crew were at altitude, stalled and allowed the core speed to go to 0 RPM. When this happened, the parts of the engine outside the core shock-cooled and shrunk causing the outer portion of the knife-edge seal to contact the core portion which basically got lodged. This was an extreme situation and before 3701 no one had ever heard of core-lock. At first GE denied it could even happen because engines don't generally stop rotation at altitude, even during a flame-out.
The tolerances in this section of the engine must be incredibly tight. I wonder if heating/cooling is causing the same type of core/shell contact in the new engines.
This seal was the cause of a phenomenon called 'core lock' that occurred on a 2004 CRJ crash (FLG 3701 for those who remember).
In a nutshell, the crew were at altitude, stalled and allowed the core speed to go to 0 RPM. When this happened, the parts of the engine outside the core shock-cooled and shrunk causing the outer portion of the knife-edge seal to contact the core portion which basically got lodged. This was an extreme situation and before 3701 no one had ever heard of core-lock. At first GE denied it could even happen because engines don't generally stop rotation at altitude, even during a flame-out.
The tolerances in this section of the engine must be incredibly tight. I wonder if heating/cooling is causing the same type of core/shell contact in the new engines.
Whole lot more to that mishap than just close tolerances to the engines, including EXTREME lack of professionalism on the part of the crew on a repo flight, misuse and/or lack of understanding of what the aircraft could deliver at an altitude they had no business being at when they (finally) got there, not following the procedure for two engine failure (which they caused by being cowboys), lying to ATC that they only had single engine failure, and failing - over a considerable period - to actually pilot the aircraft to any of the half dozen airfields they could have landed at (you can glide a h€|| of a long ways from FL410, even if you had no business being there in the first place).
https://www.ntsb.gov/investigations/...ts/AAR0701.pdf
The bottom line:
Evidence indicated that the critical human performance failures during the flight were the result of intentional behavior and were not consistent with typical errors (slips, lapses, and mistakes) found in most flight crew-involved accidents involving Part 121 operators. Although the pilots demonstrated some performance failures and deficiencies in basic airmanship that were consistent with the more typical errors found in accidents, such as their failure to achieve required airspeeds during the descent (see section 2.2.3), the pilots’ overall actions during the accident flight were not consistent with the degree of discipline, maturity, and responsibility required of professional pilots. The Safety Board concludes that the pilots’ unprofessional operation of the flight was intentional and causal to this accident because the pilots’ actions led directly to the upset and their improper reaction to the resulting in-flight emergency exacerbated the situation to the point that they were unable to recover the airplane.
Last edited by Excargodog; 01-25-2019 at 04:21 AM.
01-25-2019, 04:36 AM
#3317
Gets Weekends Off
Joined APC: Sep 2015
Posts: 438
In defense of the original poster, I didn’t see anywhere that he stated that caused the accident. I did see where he said it caused the core lock, which it did. A matter of legal record that the seal caused the core lock. Ask me or K-Dobbs how we know. No disputing what caused that accident, but K-Dobbs said the seal caused the core lock not the accident.
01-25-2019, 04:43 AM
#3318
Line Holder
Joined APC: Aug 2013
Position: Home
Posts: 44
If anyone needs to slow down its you. The post you quoted never indicated that the cause of that accident was core lock. He was simply relating how close engine tolerances can sometimes delay the rollout of new engine types and airframes. Slow your roll dude
01-25-2019, 05:25 AM
#3319
:-)
Joined APC: Feb 2007
Posts: 7,339
01-25-2019, 06:46 AM
#3320
Perennial Reserve
Joined APC: Jan 2018
Posts: 12,159
[
The seals which had been stressed by the engines being required to operate on the back side of the power curve for a prolonged period of time despite the stick shaker going off five (5) times before a dual engine flameout that then was GROSSLY mishandled including never coming within 40 knots of the recommended dual engine restart speed despite having seven MILES of altitude to give up, hence not ever providing the engines with the airflow needed to turn to avoid a core lock.
I mean, when you either negligentally or intentionally push things to destruction through unprofessional actions, yeah they are going to fail.
Blaming the failure on not being able to stand abuse that they should have never been exposed to in the first place and we’re out of their known envelope is sort of silly, don’t you think?
Like saying, yeah, I landed in a left wing low bank, in a slip to the left, on my left main gear, at a descent rate of 2000 fpm..., and the damn left gear failed.
Who’da thunk???
In a nutshell, the crew over stressed and overheated the engines by climbing to the edge of the operating envelope by dialing in a rate of climb on the autopilot that was inconsistent with the performance charts they were given for that altitude, remained at that altitude at an excessively high AOA, despite deteriorating airspeed, ultimately managed to stall the aircraft and flameout both engines, then totally mismanaged the restart while lying to ATC about the extent of their problem and never lowering the nose long enough to attain an airspeed capable of windmilling their badly abused engines before core lock occurred.
There, fixed it for you.
In defense of the original poster, I didn’t see anywhere that he stated that caused the accident. I did see where he said it caused the core lock, which it did. A matter of legal record that the seal caused the core lock. Ask me or K-Dobbs how we know. No disputing what caused that accident, but K-Dobbs said the seal caused the core lock not the accident.
I mean, when you either negligentally or intentionally push things to destruction through unprofessional actions, yeah they are going to fail.
Blaming the failure on not being able to stand abuse that they should have never been exposed to in the first place and we’re out of their known envelope is sort of silly, don’t you think?
Like saying, yeah, I landed in a left wing low bank, in a slip to the left, on my left main gear, at a descent rate of 2000 fpm..., and the damn left gear failed.
Who’da thunk???
In a nutshell, the crew were at altitude, stalled and allowed the core speed to go to 0 RPM
There, fixed it for you.
Last edited by Excargodog; 01-25-2019 at 06:59 AM.
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