One dead after Southwest Airlines jet engine 'explosion'

[garyc]

The NTSB has found that the failure started due to an internal crack in the fan blade at the point that the blade meets the hub. This failure then caused a second failure half way along the blade.

This could be interesting. Normally fatigue cracks like this are visible on the surface of the blade rather than being completely internal.

 

[Gordon_R]

The NTSB has found that the failure started due to an internal crack in the fan blade at the point that the blade meets the hub. This failure then caused a second failure half way along the blade.

This could be interesting. Normally fatigue cracks like this are visible on the surface of the blade rather than being completely internal.

I don't quite get the actual layout of the fracture and breakup sequence, but it sounds interesting. Someone will post a diagram eventually...

Ultrasonic testing should pick up cracks on the inside. Relying on visual inspection is not good practice.

P.S. We have those tests done on our 50 year old lift motor (I watched the last time). Its rare to find cracks, but the checks must be done.

 

[Jola]

clear air turbulence is definitely a thing,

know its gro$$ but why dont the toilets have seatbelts? I mean if you hit turbulence when you sitting down,
cant you get tossed around the cubicle?

I was on a flight in 2016 when we hit bad turbulence with a passenger in the toilet.

The guy hit the roof and hurt his neck quite badly.

He was carried out of the plane on a stretcher, paramedics had to come and fetch him.

 

[garyc]

Ultrasonic testing should pick up cracks on the inside. Relying on visual inspection is not good practice.

Apparently an AD on ultrasonic testing is imminent. This type of engine has something of a history of throwing fan blades, including the Kegworth crash with 47 fatalities.

 

[Gordon_R]

Apparently an AD on ultrasonic testing is imminent. This type of engine has something of a history of throwing fan blades, including the Kegworth crash with 47 fatalities.

There is already a limited AD. The problem is that there are thousands of B737s flying, and testing all 24 blades on each of those engines will take many months. They won't ground them all, but prioritise those with the most engine hours since last major overhaul.

Edit: Apparently the CFM56 fan blades can be removed without disassembling the engine, but it still takes time in the hangar for each aircraft.

Edit: The CFM56 engine has gone through many variants over 30 years. The model used on the earlier B737-400 at Kegworth was the CFM56-3C series, which had 38 fan blades. The current B737-700 uses the CFM56-7B series, with 24 fan blades. Obviously the design and fatigue testing requirements for each model are very different.

 

[Gordon_R]

Another video from Juan Browne, explaining pilot procedures and teamwork. This includes shutting down the correct engine (at Kegworth they got it wrong). Having two simultaneous issues to deal with, engine fire/failure as well as cabin depressurisation/rapid descent, puts immense strain on the crew workload. Communication from the pilots was complicated by the need to wear full-face 100% oxygen masks.

Because of the unknown condition of the aircraft, descent must not be too rapid to risk further damage. The pilots also need to talk to the flight attendants, who in this case knew things happening in the back, and the condition of the injured pasenger(s). The landing was also unusual, because of potential damage to the wing flap mechanism, and single engine limitations. After landing the coordination with emergency services was also complex.

See: https://www.youtube.com/watch?v=4a4Dw-IbsKg

IMO, the most alarming fact of this incident, is that immediately after the cowling detached, the excess drag caused the wing to bank at an angle of 42 degrees, which is quite scary for a commercial aircraft.

 

[Gordon_R]

The details of the mandatory inspections have been released: http://www.bbc.com/news/world-us-canada-43846660

Almost 700 Boeing 737 engines will need to be inspected worldwide over the next 20 days, regulators say.

"Fan blade failure due to cracking... could result in an engine in-flight shutdown, uncontained release of debris, [and] possible airplane decompression," the US Federal Aviation Administration (FAA) said in a statement announcing the inspections.

Fan blades that have undergone a certain number of flights will be given ultrasonic tests, they added.

FAA details:

The inspection requirement applies to CFM56-7B engines. Specifically, engines with more than 30,000 total cycles from new must complete inspections within 20 days. The EAD becomes effective upon publication. The engine manufacturer estimates today’s corrective action affects 352 engines in the U.S. and 681 engines worldwide.

 

[The_Assimilator]

Apparently an AD on ultrasonic testing is imminent. This type of engine has something of a history of throwing fan blades, including the Kegworth crash with 47 fatalities.

The CFM56-3C was never tested on a flying 737, only on a test bench, because Boeing and CM cheaped out. End result, a design flaw with the engine was not discovered, until surfaced by the Kegworth incident.

However, that does not excuse the operator British Midlands for not giving their pilots enough training, nor does it excuse the pilots for assuming which engine was problematic and not using their instruments, nor the cabin crew for not communicating with the flight crew - especially after the captain made a broadcast mentioning the right engine, when the passengers and cabin crew could clearly see the left engine was on fire.

 

[Gordon_R]

The NTSB report calls for retrospective reinforcement of B737 NG engine cowls after this fatal incident: https://www.reuters.com/article/us-...-after-fatal-southwest-accident-idUSKBN1XT1EK

The U.S. National Transportation Safety Board on Tuesday called on Boeing Co to redesign the fan cowl structure on all 737 NG planes and retrofit existing planes after an April 2019 incident in which a woman was killed on a Southwest Airlines plane after an engine failure caused by a fan blade.

The board said the U.S. Federal Aviation Administration should require Boeing to determine the fan blade impact location or locations on the engine fan case and redesign the structure to minimize the potential of a catastrophic failure. The board did not fault Boeing’s analysis in the mid-1990s when it developed the case.

NTSB Chairman Robert Sumwalt acknowledged the retrofit could be expensive.

“This accident underlines the vulnerability of the fan case to become separated when the fan blade detaches at a location that was not anticipated,” Sumwalt said after the hearing.

The NTSB did not call for the planes to be grounded and noted that airlines are now inspecting the fan blades on a more regular basis.

The accident occurred 20 minutes into the flight when a fan blade fractured as a result of a fatigue crack on a Boeing 737-700 jet powered by two CFM International CFM56-7B engines after taking off from New York’s LaGuardia Airport. The plane, bound for Dallas, diverted to Philadelphia International Airport. Eight of the 144 passengers suffered minor injuries.

The NTSB had been investigating a 2016 engine failure on another Southwest 737-700 at the time of the fatal incident. The incidents in both flights were what is known as a “fan blade out” (FBO) event.

The board noted that there are 14,600 CFM56-7B engines in service with 356,000 fan blades on the Boeing planes, with 400 million flights over more than two decades and two reported engine failures.

CFM International, the engine manufacturer, is a transatlantic joint venture between General Electric Co and France’s Safran SA.

 

[Gordon_R]

Lengthy NTSB presentation (2 hours) with images and technical details:

Report overview, executive summary and probable cause: https://www.ntsb.gov/news/events/Pages/2019-DCA18MA142-BMG.aspx

https://www.ntsb.gov/news/events/Documents/2019-DCA18MA142-BMG-abstract.pdf

The National Transportation Safety Board (NTSB) determines that the probable cause of this accident was a low-cycle fatigue crack in the dovetail of fan blade No. 13, which resulted in the fan blade separating in flight and impacting the engine fan case at a location that was critical to the structural integrity and performance of the fan cowl structure. This impact led to the in-flight separation of fan cowl components, including the inboard fan cowl aft latch keeper, which struck the fuselage near a cabin window and caused the window to depart from the airplane, the cabin to rapidly depressurize, and the passenger fatality.

 

[Priapus]

I know someone who was on this very flight when it happened. Southwest did a lot to help the passengers move on from this. But probably not enough.

 

[MidnightWizard]

There are 3 errors in your single sentence post! Congratulations, comment of the day award is in the mail.

As is YOURS
For NOT explaining what the errors are -- for the rest of us dumbasses ...

 

[Gordon_R]

CFM56 is not a Rolls-Royce which is extensively tested for compressor blade failure containment.

I have been asked to explain the three errors which you made in one sentence:
1. The blade that failed was a fan blade, not a compressor blade.
2. Fan blade containment is mandatory, while compressor blades are low energy, and usually exit the rear of the engine.
3. Fan blade testing is done by all manufacturers (as per #2), it has nothing to do with GE or CFM vs RR engines.

The NTSB report makes it clear that the fan blade was contained, and did not strike the aircraft. In fact pieces making up 75% of the blade were found inside the engine, and examined by the NTSB.

What failed was the latch holding the two halves of the cowling, which flew open in the high speed airstream, and impacted the passenger window.

 

[nightjar]

Ahead of the release of her new book “Nerves of Steel: How I Followed My Dreams, Earned My Wings, and Faced My Greatest Challenge” (out Oct. 8), Shults sat down with ELLE.com to talk about the fatal flight.
https://www.elle.com/culture/books/a29355725/tammie-jo-shults-book-interview/

 

[ArtyLoop]

I have been asked to explain the three errors which you made in one sentence:
1. The blade that failed was a fan blade, not a compressor blade.
2. Fan blade containment is mandatory, while compressor blades are low energy, and usually exit the rear of the engine.
3. Fan blade testing is done by all manufacturers (as per #2), it has nothing to do with GE or CFM vs RR engines.

The NTSB report makes it clear that the fan blade was contained, and did not strike the aircraft. In fact pieces making up 75% of the blade were found inside the engine, and examined by the NTSB.

What failed was the latch holding the two halves of the cowling, which flew open in the high speed airstream, and impacted the passenger window.

OK boss... Won't comment here again

 

[Ivan Leon]

NTSB recommends Boeing redesign and retrofit engine casing on thousands of 737s - Seattle Times

After investigating an engine blowout that killed a Southwest Airlines passenger last year, federal safety officials on Tuesday said Boeing should be required to redesign the engine casing on its 737 NG airplanes, and airlines should retrofit more than 6,800 planes currently in service worldwide.

In a terrifying incident in April 2018, the left engine of the 737 exploded and flying metal broke a passenger window. Jennifer Riordan, 43, the mother of two children, was partially sucked out of the airplane.

The cause was a fan blade in the left engine that broke off and sent metal shrapnel ripping through the engine casing, piercing the fuselage and causing the cabin to decompress.

Part of the engine cowl struck and broke the window by Riordan’s seat. She died as a result of her injuries, the sole fatality on board a U.S. airline in the past decade.

The tragedy raised questions about safety oversight because of a similar engine explosion on a different Southwest flight 19 months earlier.

After that earlier incident the Federal Aviation Administration (FAA) mandated inspections of engine fan blades — but the inspections failed to detect the cracked fan blade that caused the fatal accident.

At a public hearing Tuesday, the National Transportation Safety Board (NTSB) laid out its investigation into Southwest flight 1380, which departed from New York City bound for Dallas, but diverted to Philadelphia after the engine explosion.

The NTSB issued a series of recommendations, including that the FAA require Boeing to redesign the casing around the engine to prevent penetration by hot metal shrapnel in the event of an engine explosion.

Read the full article at the link below (may be pay-walled):

NTSB recommends Boeing redesign engine casing on thousands of 737s after passenger death

After investigating an engine blowout that killed a Southwest Airlines passenger last year, federal safety officials on Tuesday said Boeing should be required to redesign the engine casing on its 737 NG airplanes, and airlines should retrofit more than 6,800...

www.seattletimes.com

 

[ForceFate]

...it pours at Boeing HQ.

 

[ponder]

The NTSB report calls for retrospective reinforcement of B737 NG engine cowls after this fatal incident: https://www.reuters.com/article/us-...-after-fatal-southwest-accident-idUSKBN1XT1EK

I'm getting mixed messages from that article.

The NTSB said the engine failure was caused by a broken fan blade, and the board said the U.S. Federal Aviation Administration should require Boeing to determine the fan blade impact location or locations on the engine fan case and redesign the structure to minimize the potential of a catastrophic failure.

If it's the cowl then it's boeing, if it's the fan case then it's cfm unless it's both. Trying figure out who's gonna pay for this retrofit.

 

[Gordon_R]

I'm getting mixed messages from that article.



If it's the cowl then it's boeing, if it's the fan case then it's cfm unless it's both. Trying figure out who's gonna pay for this retrofit.

It is complicated, since the fan blade hit the casing, and then ricoched into the cowl, causing the latch to fail. The fan casing did not fail, so its not a CFM problem. The engine cowl is purely a Boeing design, so they take the can...

Edit: The Seattle Times article is much clearer (I had not read it when I made my post).

On Flight 1380, it was the disintegration of the fan cowl that did most damage. That’s the middle part of the pod that wraps around the engine; a part that opens up on hinges to allow access for maintenance.

The design requirements for the engine casing — known as the nacelle — are developed by Boeing. The 737 NG nacelles are then designed and built by a division of United Technologies.

 

[Jola]

Wow, seems that only the pre-ng 737's are safe to fly in, and those are getting quite old !