SWA1380 - diversion to KPHL after engine event
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Knowing and having worked with the FAA for 2/3rds of my career, I'd bet pretty good money the AD's been sitting in someone's in-basket - forgotten - for several months. I'd bet even more money that the responsible person or persons will get nothing worse than a wrist slap.
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According to the NTSB press conference the blade broke in two places, near the root and further up. They have the section nearest the root, they don't have the outboard section. Doesn't that suggest that the section of blade nearest the root went backwards into the engine? If the speculation about the blade shooting forward and clear of the engine was correct, it seems almost certain they wouldn't have either section.
tdracer
A lot to agree on above, except what office issues the AD and under what supporting arguments? After all the engine was safely shut down according to it's certificate. It's only in conjunction with the design of the aircraft certification that it progressed or might have progressed to an unsafe result. If it was an FAA guy in the engine section writing the words in the AD he might have gotten a lot of push back by the operators about the assumptions and had to go back to both Boeing and GE to substantiate responses to comments.
I predict that this will all come out in a public hearing chaired by the NTSB
he who breaks the crockery must pick up the pieces
However, having been involved in several FAA AD's over the years, 8 months and it's still not released is inexcusable. AD's by definition affect flight safety. Normal flow time for a 'routine' AD is a couple months - seldom going much beyond 3 months even if there are lots of comments (emergency AD's don't go through public comment and can go out in a few days). While getting the blade inspection AD released may not have affected this accident, it's pretty clear to me that someone in the FAA dropped the ball.
I predict that this will all come out in a public hearing chaired by the NTSB
he who breaks the crockery must pick up the pieces
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Large Engine Uncontained Debris Analysis
DOT/FAA/AR-99/11
http://www.tc.faa.gov/its/worldpac/techrpt/AR99-11.pdf
Section 4.1.2, page 38 onwards
Much more information besides...
DOT/FAA/AR-99/11
http://www.tc.faa.gov/its/worldpac/techrpt/AR99-11.pdf
Section 4.1.2, page 38 onwards
In a typical fan blade failure event where a large (> 50%) section of the blade is released, the blade tip section fragments and slides forward resulting in a helical trajectory while the root section of the blade is caught by the trailing blade and swept aft.
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There's something that puzzles me.
All over the Planet Earth it's being mentioned Mrs. Tammie Jo Shults as "the hero pilot, bla, bla,bla".
But listening to the radio exchange (brief and complete ones) between ATCs, TWR & AC, there's one thing very clear: THE PIC DURING ALL THE DESCENT WAS F.O. Mr. Darren Ellisor.
Mrs. Shults was in charge of radio and -surely- checklists while Mr. Ellisor was PIC descending and later aligning for a visual long final.
I've got not clear if Mr. Ellisor was PIC at the moment of the engine failure.
All over the Planet Earth it's being mentioned Mrs. Tammie Jo Shults as "the hero pilot, bla, bla,bla".
But listening to the radio exchange (brief and complete ones) between ATCs, TWR & AC, there's one thing very clear: THE PIC DURING ALL THE DESCENT WAS F.O. Mr. Darren Ellisor.
Mrs. Shults was in charge of radio and -surely- checklists while Mr. Ellisor was PIC descending and later aligning for a visual long final.
I've got not clear if Mr. Ellisor was PIC at the moment of the engine failure.
I'm not clear about anything you assert.
The PIC signs the release and is the PIC for the entire flight . Also there is a PF and PNF. As to who flies, that is determined by the PIC for the entire flight.
Who talks on the radio depends on the situation and is, alas, also determined by the PIC. It could be anybody. It could be the jumpseater.
(Pilot In Command)
That is the way it was done where I come from----back in the day.
Is it done differently anywhere?
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The new EAD is signed as follows:
Original signed by
Karen M. Grant, Acting Manager
Engine and Propeller Standards Branch,
Aircraft Certification Service.
Does this mean the previous "manager" has been sacked for not doing his/her job?
Original signed by
Karen M. Grant, Acting Manager
Engine and Propeller Standards Branch,
Aircraft Certification Service.
Does this mean the previous "manager" has been sacked for not doing his/her job?
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OK. Let's try this: the Newtonian physics associated with the air acting on a separated fan blade are completely overwhelmed by the Newtonian physics of the moments of inertia acting on the blade. Kinda like a bullet in air-to-air combat. Sure, aerodynamics will affect the bullet's ballistic trajectory. But those affects are overwhelmed by the moments of inertia acting on the bullet.
Two points:
1. A fan blade that "rotates forward" will almost immediately result in a blade tip/case strike. The resulting forces acting on the blade will cause the blade to fail at the fatigue crack.
2. What would cause the fan blade to "rotate forward"? The fan is a compressor section. In other words, in a turbo fan engine the fan blade compresses the air, it does not accelerate the air like a propeller. Further, the huge tension forces resulting from the massive centripetal acceleration of the blade will overwhelm any aero force pushing on the blade. Consider a guitar string. It is under considerable tension. Can you blow on the string to cause it to bend? No. The tension on the fan blade is several orders of magnitude greater than the tension on the guitar string.
Two points:
1. A fan blade that "rotates forward" will almost immediately result in a blade tip/case strike. The resulting forces acting on the blade will cause the blade to fail at the fatigue crack.
2. What would cause the fan blade to "rotate forward"? The fan is a compressor section. In other words, in a turbo fan engine the fan blade compresses the air, it does not accelerate the air like a propeller. Further, the huge tension forces resulting from the massive centripetal acceleration of the blade will overwhelm any aero force pushing on the blade. Consider a guitar string. It is under considerable tension. Can you blow on the string to cause it to bend? No. The tension on the fan blade is several orders of magnitude greater than the tension on the guitar string.
Very true about tensile stresses, which far exceed bending stresses by a significant factor. This actually stiffens the blade considerably in the varying pressure field it operates. one would be very surprised, even at max chat, if a blade would make it outside the cowl without smashing into the edge, as the cetrepetal forces compared to aero forces are massive. My type, you can actually see the fan bending forward at the tips at Max, at least an inch forwards, due to the forces on the blades. The centripetal element is why blades stretch and the cowl has a frangiable seal which wears away as the blades stretch to maintain efficiency. Google turbine creep, the situation is far worse in the hot section.
Naive question: Although the broken fan blade may have been going at ballistic speeds and bounced off of the cowling before its final trajectory through an aft window,
Wouldn't the 500 knot forward speed of the aircraft have some/ a major influence on its being blown backwards midflight?
After all, if a skydiver leaves a plane, they get blown backwards as they are not as aerodynamically sleek as the plane itself nor under power, especially if the plane is going faster than their rate limiting speed in freefall.
Wouldn't the 500 knot forward speed of the aircraft have some/ a major influence on its being blown backwards midflight?
After all, if a skydiver leaves a plane, they get blown backwards as they are not as aerodynamically sleek as the plane itself nor under power, especially if the plane is going faster than their rate limiting speed in freefall.
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According to the NTSB press conference the blade broke in two places, near the root and further up. They have the section nearest the root, they don't have the outboard section. Doesn't that suggest that the section of blade nearest the root went backwards into the engine? If the speculation about the blade shooting forward and clear of the engine was correct, it seems almost certain they wouldn't have either section.
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Nobody knows exactly what the blade hit on its way out, and what else in the cowling was cut off in what direction. It is entirely possible that a piece of something from/in the cowl ricocheted and hit the window. All it had to do was weaken the window enough that the differential pressure could do the rest. Since there was no debris visible inside the cabin, I consider this the more likely scenario.
Also, even a "tight" seat belt is NOT "TIGHT". If you've never strapped into an airplane for planned negative-G acrobatics, you don't know how loose even a normal "tight" seat belt is. Virtually any passenger will have the belt VERY loose in cruise, allowing for significant upward movement if enough force is applied...
Also, even a "tight" seat belt is NOT "TIGHT". If you've never strapped into an airplane for planned negative-G acrobatics, you don't know how loose even a normal "tight" seat belt is. Virtually any passenger will have the belt VERY loose in cruise, allowing for significant upward movement if enough force is applied...
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It's complicated, for sure
DOT/FAA/AR-99/11 "Large Engine Uncontained Debris Analysis" which I posted a link to earlier contains both post-incident analysis and modelling information, and takes into account both the mechanical and aerodynamic forces at play when there is a failure. Even a quick scan makes it clear that the dynamics are very complicated, for example there may be secondary fragments caused by debris being ejected out of the front of the engine, then re-ingested and flung out again. Damage is to be expected both ahead and behind of the point of failure, although from looking at the diagrams it appears that the majority of it will be behind the point of failure.
Should not this accident, coming on the heels of several other surprisingly damaging engine failures, cause a review of our ETOPS requirements?
It certainly appears that large fan engine failures can be more complicated and more damaging than previously anticipated.
It certainly appears that large fan engine failures can be more complicated and more damaging than previously anticipated.
Administrator
Deputy Administrator
Chief of Staff
Associate Administrator Airports
Assistant Administrator Finance and Management
Assistant Administrator Next Gen
And on and on. The previous manager for Engines and Propeller Standards died a couple years ago. Ms Grant has been in that office all this century. They probably don't want to make her position official as she'd go up a notch in pay.
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Regarding the passenger partially exiting the window: Can anyone provide an analysis of the Bernoullie forces involved? Most of the analyses seem to assume that the only force is due to the pressure differential between the cabin interior and the aircraft exterior. However, a 500 knot airflow past an open window must create substantial additional pressure differential. Might this help explain the difficultly in retracting the passenger from the window?
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Now there are only 20 days (!) left to check the Blades with more than 30.000 FC on the 737 NG:
FAA AD 2018-09-51
FAA AD 2018-09-51
Last edited by IFixPlanes; 21st Apr 2018 at 06:39. Reason: Not all blades...
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During conversion and routine refresher training both Engine Severe Damage Separation and Depressurisation exercises are flown. Both events require prompt memory actions. What is unique(?) in this event was that both situations occurred either simultaneously or very close together.
Due to the vagaries of the media circus there was comparatively little media interest in that one, probably because nobody died. We don't even know the names of the crew involved (not made public, that I can find) - they got everyone down safely but apparently they weren't heros. We do, however, know from published selfies that things were very different in 2016 in that pax could fit oxygen masks correctly back then
, no really: https://www.thesun.co.uk/wp-content/...0017.jpg?w=960
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There's something that puzzles me.
All over the Planet Earth it's being mentioned Mrs. Tammie Jo Shults as "the hero pilot, bla, bla,bla".
But listening to the radio exchange (brief and complete ones) between ATCs, TWR & AC, there's one thing very clear: THE PIC DURING ALL THE DESCENT WAS F.O. Mr. Darren Ellisor.
Mrs. Shults was in charge of radio and -surely- checklists while Mr. Ellisor was PIC descending and later aligning for a visual long final.
I've got not clear if Mr. Ellisor was PIC at the moment of the engine failure.
All over the Planet Earth it's being mentioned Mrs. Tammie Jo Shults as "the hero pilot, bla, bla,bla".
But listening to the radio exchange (brief and complete ones) between ATCs, TWR & AC, there's one thing very clear: THE PIC DURING ALL THE DESCENT WAS F.O. Mr. Darren Ellisor.
Mrs. Shults was in charge of radio and -surely- checklists while Mr. Ellisor was PIC descending and later aligning for a visual long final.
I've got not clear if Mr. Ellisor was PIC at the moment of the engine failure.
Only one PIC in the cockpit. Who is PF and PM may change several times during a flight.
I have never had an emergency like this, but in the simulator I will give control to my Effoh when there is a problem. Managing and flying at the same time is a bad combination.
I take back control for the landing. Only myself to blame if something goes wrong at that stage.
FL5 landing is not dictated by any non normal checklist. I say it was a good call. You look out and see damage to the leading edge. You want to slow down as much as possible, but are unsure if you can get control problems when you extend your leading edges. You try FL 5 and LE in mid position. It works.
You land with this configuration. I don’t know the runway length but a -700 is not that hard to stop on a normal length runway even in a flapless configuration.
This emergency involved multiple priority checklists, non normal configuration, compromises, etc.
You can all keep digging for mistakes and look for ways to criticise this crew, but they did a great job.
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With the SW 3472 incident in 2016, plus the SW 438 incident in 2007, and now this, I think the focus of attention needs to be as much on the cowl as the blade. In two (perhaps all three) cases the root of an N1 fan-blade failed (due to fatigue on the 2016 incident) and the blade separated.
But in all three cases the blade appears to have missed the containment ring and struck the cowl instead, causing a complete failure of the cowl, and all the attendant risks with all that material flying off into the slipstream. If you look at the N1 containment ring on the recent incident, it appears to be untouched all the way around. But the cowl took the full force of the departing blade, and disintegrated.
The N1 blade is under considerable aerodynamic forward pressure in flight, and will naturally spring forwards when released. But in static testing for cerification the blade still seems to hit the containment ring. Yet here it appears that the blade moved forward enough to miss the containment ring, and strike the cowl. Perhaps an engineer on this board might suggest why that might be. Why would the forward speed of the aircraft have any effect on the trajectory of the departing blade?
ST
But in all three cases the blade appears to have missed the containment ring and struck the cowl instead, causing a complete failure of the cowl, and all the attendant risks with all that material flying off into the slipstream. If you look at the N1 containment ring on the recent incident, it appears to be untouched all the way around. But the cowl took the full force of the departing blade, and disintegrated.
The N1 blade is under considerable aerodynamic forward pressure in flight, and will naturally spring forwards when released. But in static testing for cerification the blade still seems to hit the containment ring. Yet here it appears that the blade moved forward enough to miss the containment ring, and strike the cowl. Perhaps an engineer on this board might suggest why that might be. Why would the forward speed of the aircraft have any effect on the trajectory of the departing blade?
ST