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LeCoqFrancais
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Southwest Airlines flight 3472 suffers uncontained engine failure

Sat Aug 27, 2016 10:26 pm

A Southwest Airlines Boeing 737-700, registration N766SW performing flight WN-3472 from New Orleans,LA to Orlando,FL (USA) with 99 passengers and 5 crew, was climbing through FL310 out of New Orleans, about 80nm west of Pensacola,FL (USA) when the front section (engine inlet, fan and compressor section) of the left hand engine (CFM56) separated, debris impacted and punctured the left side of the fuselage causing a loss of cabin pressure. The crew initiated a descent to 10,000 feet and diverted the aircraft to Pensacola for a safe landing. There were no injuries, the aircraft sustained substantial damage.

http://avherald.com/h?article=49d2d7e3&opt=0
--
The pictures are pretty chilling...
Sébastien C. Tourillon
 
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Glidesloper
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Sun Aug 28, 2016 4:15 am

LeCoqFrancais wrote:
A Southwest Airlines Boeing 737-700, registration N766SW performing flight WN-3472 from New Orleans,LA to Orlando,FL (USA) with 99 passengers and 5 crew, was climbing through FL310 out of New Orleans, about 80nm west of Pensacola,FL (USA) when the front section (engine inlet, fan and compressor section) of the left hand engine (CFM56) separated, debris impacted and punctured the left side of the fuselage causing a loss of cabin pressure. The crew initiated a descent to 10,000 feet and diverted the aircraft to Pensacola for a safe landing. There were no injuries, the aircraft sustained substantial damage.

Passengers and crew were indeed fortunate in this case, that the debris didn't sever any hydraulic lines. Control surfaces still had their 'lifeblood' and were able to operate efficiently, resulting in a safe landing. The sobering memory of AA Flight 191 illustrates the vulnerability of hydraulic systems to uncontrolled engine failure/separation and how any impairment of their function can have serious consequences for the aircraft. The people on this flight had a narrow escape and what is scary is the utter randomness of the event. Came literally 'out of the blue'. It must have been a terrifying experience for those on board WN-3472 and I'm sure that others share my relief at the positive outcome.
 
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7BOEING7
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Sun Aug 28, 2016 5:20 am

Glidesloper wrote:
Passengers and crew were indeed fortunate in this case, that the debris didn't sever any hydraulic lines. Control surfaces still had their 'lifeblood' and were able to operate efficiently, resulting in a safe landing. The sobering memory of AA Flight 191 illustrates the vulnerability of hydraulic systems to uncontrolled engine failure/separation and how any impairment of their function can have serious consequences for the aircraft. The people on this flight had a narrow escape and what is scary is the utter randomness of the event. Came literally 'out of the blue'. It must have been a terrifying experience for those on board WN-3472 and I'm sure that others share my relief at the positive outcome.


The 737 flies fine without hydraulics, it just takes a little muscle. Ailerons/elevators are cable driven, stabilizer is electric and the rudder operates off a separate Standby hydraulic system. No big deal. If it was a larger airplane that doesn't have "manual reversion" then you'd be in trouble -- that's why you have more redundant hydraulic systems on larger airplanes.
 
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Florianopolis
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Sun Aug 28, 2016 5:38 am

7BOEING7 wrote:
If it was a larger airplane that doesn't have "manual reversion" then you'd be in trouble -- that's why you have more redundant hydraulic systems on larger airplanes.


Is there any effort made to keep the hydraulic lines for the different systems apart from each other on commercial aircraft?
 
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Glidesloper
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Sun Aug 28, 2016 5:54 am

7BOEING7 wrote:
The 737 flies fine without hydraulics, it just takes a little muscle. Ailerons/elevators are cable driven, stabilizer is electric and the rudder operates off a separate Standby hydraulic system. No big deal. If it was a larger airplane that doesn't have "manual reversion" then you'd be in trouble -- that's why you have more redundant hydraulic systems on larger airplanes.

That's reassuring to know! As for "a little muscle", a bit of sweat and toil would keep pilots in good shape too! :) But seriously, it makes me wonder if there've been any recent instances of 'manual takeover' when loss of hydraulics occurred. Thanks for your informative response!
 
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SAAFNAV
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Sun Aug 28, 2016 6:39 am

Glidesloper wrote:
7BOEING7 wrote:
The 737 flies fine without hydraulics, it just takes a little muscle. Ailerons/elevators are cable driven, stabilizer is electric and the rudder operates off a separate Standby hydraulic system. No big deal. If it was a larger airplane that doesn't have "manual reversion" then you'd be in trouble -- that's why you have more redundant hydraulic systems on larger airplanes.

That's reassuring to know! As for "a little muscle", a bit of sweat and toil would keep pilots in good shape too! :) But seriously, it makes me wonder if there've been any recent instances of 'manual takeover' when loss of hydraulics occurred. Thanks for your informative response!



Not that recent, but this comes to mind:

https://en.wikipedia.org/wiki/Nationwid ... uth_Africa)#Incidents_and_accidents
CFI/Gr. III, L-382 Loadmaster, ex C-130B Navigator
 
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LeCoqFrancais
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Sun Aug 28, 2016 10:51 am

Some passengers also seem to have been lucky to have not been hit by debris looking at one of the pictures...someone mentioned AA-191, I've read somewhere that if the plane would have kept its speed/increased its speed it might have survived, however the crew followed engine out procedures which where to reduce the speed to its minimums.
Sébastien C. Tourillon
 
Wacker1000
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Aug 29, 2016 12:16 am

There is nothing "uncontained" about it. The entire fan is still there.

Something else let go.
 
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LeCoqFrancais
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Aug 29, 2016 10:54 am

Wacker1000 wrote:
There is nothing "uncontained" about it. The entire fan is still there.

Something else let go.

I'm sorry bu did you look at the pictures? Something clearly breached the fuselage, considering that something breached the fuselage this is an uncontained failure as something did escape the engine casing.
Sébastien C. Tourillon
 
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airmagnac
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Aug 29, 2016 11:47 am

Florianopolis wrote:
Is there any effort made to keep the hydraulic lines for the different systems apart from each other on commercial aircraft?


Yes, and more than that. There is even an effort to determine more precisely what happens in case of e.g. an uncontained engine burst, and design the systems accordingly (either include segregation, or use other means to preserve functionality). It's called a Particular Risk Analysis.

Basically, a model is generated for physical events such as
    an engine burst
    all types of wheel bursts (like Concorde)
    bird strike
    fire
    hydraulic leak
    hydraulic accumulator burst
    bleed duct rupture
    APU burst
    and what not...

Typically, it's a collection of fragment trajectories and/or vulnerability volumes with various energy levels and sizes, depending on the scenario.
For each considered scenario, affected physical components (equipment, pipes, wires...) in the vulnerable areas are identified, and from there it can be determined how the aircraft and its systems will behave. If it's not acceptable, the design has to be improved.
For example, electrical harnesses carrying critical information are usually doubled in the forward fuselage (it can be one route in the floor, and a parallel route in the crown). In case of an engine burst, fragments may cut one or the other, but shall not be capable of cutting both routes at the same time.

It's not perfect, and by no means will the pilots have an easy day, but at least following such events there should remain sufficient functionality to bring the aircraft back on the ground
My goal as an engineer is to fill my soul with coffee and become immortal
 
Slide
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Aug 29, 2016 1:20 pm

LeCoqFrancais wrote:
Wacker1000 wrote:
There is nothing "uncontained" about it. The entire fan is still there.

Something else let go.

I'm sorry bu did you look at the pictures? Something clearly breached the fuselage, considering that something breached the fuselage this is an uncontained failure as something did escape the engine casing.


It is certainly NOT an engine failure. Your original post is editorialized to state "when the front section (engine inlet, fan and compressor section) of the left hand engine (CFM56) separated" - either AVHerald updated the story later, or the "(engine inlet, fan and compressor section)" was added, as the story does not currently state that. The fan and compressor are clearly still intact as is the fan case.

The part that failed is the inlet, which is a structural component of the aircraft that bolts onto the engine forward flange. It's not an engine component, and no part of it is contained by the engine case at any rate. So, to call this an "uncontained engine failure" would be incorrect on several levels.
 
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Moose135
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Aug 29, 2016 1:23 pm

There's a pretty good conversation, with photos, in Civil Av:
viewtopic.php?f=3&t=1341581
KC-135 - Passing gas and taking names!
 
Wacker1000
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Aug 29, 2016 10:44 pm

LeCoqFrancais wrote:
Wacker1000 wrote:
There is nothing "uncontained" about it. The entire fan is still there.

Something else let go.

I'm sorry bu did you look at the pictures? Something clearly breached the fuselage, considering that something breached the fuselage this is an uncontained failure as something did escape the engine casing.


I did and I know what I'm seeing. Slide is right - uncontained failure means rotating parts left the engine case (and its very clear from the pictures that a fan blade did not penetrate the containment ring).
 
KC135Hydraulics
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Tue Aug 30, 2016 2:57 pm

Without question, for reasons already mentioned above, this is NOT an uncontained engine failure. This is an uncontained engine inlet/cowl failure!
MSgt, USAF
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LeCoqFrancais
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Wed Aug 31, 2016 10:45 am

I'm sorry for all of you saying that this is NOT a uncontained engine faillure, but a friend of mine who works at the FAA and has access to the reports of this flight has told me that all this damage was caused by a single fan blade breaking off, so yes since the fan blade did not exit the rear of the engine and that parts of the engine fell off this is a uncontained engine faillure.
Sébastien C. Tourillon
 
freakyrat
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Thu Sep 01, 2016 2:02 am

It was confirmed earlier on another forum that the aircraft engine did loose a fan blade. Also unusual atmospheric conditions for late summer required aircraft departing MSY to use anti icing systems so we may have a failure there or a series of events that started the whole sequence. I'm sure the NTSB will figure things out.
 
oldannyboy
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Thu Sep 01, 2016 11:42 am

Pretty chilling pictures. A narrow escape me thinks. Never mind the discussion about the technical definition of what seems to me a pretty serious accident which could have had potentially fatal consequences.
 
rcair1
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Thu Sep 01, 2016 2:34 pm

This article in aviation week disputes the fan blade loss. Neither of these (aviation week or the 'friend of a friend' post) are authoritative.

"Given the absence of evidence of damage to the fan stage and the intact fan case flange, it is likely the U.S. National Transportation Safety Board (NTSB) investigation will focus initially on the inlet cowl mounting structure and potential failures of the few systems that are located within it. Prime suspects are likely to include an overpressure of the inlet anti-ice system, possibly due to a TAI valve failure, a duct or vent failure in the pressurization system itself, or a mechanical failure of the fasteners. However the root cause and failure sequence could also be difficult to identify given the impact of air loads on the structure and the accelerated break-up this force would cause."

http://aviationweek.com/commercial-avia ... cdd546fd42
rcair1
 
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fr8mech
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Fri Sep 02, 2016 1:22 am

LeCoqFrancais wrote:
I'm sorry for all of you saying that this is NOT a uncontained engine faillure, but a friend of mine who works at the FAA and has access to the reports of this flight has told me that all this damage was caused by a single fan blade breaking off,


The pictures do not support this theory. A single fan blade does not simply depart a running engine without tearing up the fan case and ripping apart the rest of the fan. The pictures I have seen show all the blades in place and the case itself intact.

As for the fuselage puncture, I suspect a large piece of the nose cowl became a play thing for the airflow and "walked" its way inboard and hit the fuselage. Look at the second picture in the avherald link. Look at the reflection in the fuselage. There is damage to the wing panels immediately aft of the leading edge.

As I posited in the CivAv thread, a pneumatic over-pressure event that caused the cowl fail. That's my opinion.
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Apprentice
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Wed Sep 07, 2016 9:00 am

Question: Does B737-700 have a Pneumatic Press Regulating Valve, incorporated to Engine anti-ice circuit like PW's A330?
Any engine antiice system schematic?
Rgds/
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OMP777X
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Sep 12, 2016 8:19 pm

Turns out it was a fatigue crack in the fan blade after all.

"According to an investigative update issued Monday, the initial engine examination revealed that one fan blade separated from the fan disk during the flight and the root of the separated fan blade remained in its hub; however, the NTSB has not recovered the remainder of the blade. Metallurgical examiners found that the fracture surface of the missing titanium-alloy blade showed curving crack arrest lines consistent with fatigue crack growth."

http://www.ntsb.gov/news/press-releases ... 60912.aspx

http://www.ainonline.com/aviation-news/ ... -fan-blade

Best,

OMP777X
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rmilstre
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Re: Southwest Airlines flight 3472 suffers uncontained engine failure

Mon Sep 12, 2016 11:48 pm

The NTSB report was very factual (thanks for the link!). It merely said the fan blade was found broken. It stopped short of claiming the inlet separation was due to the blade separation. My money is actually on fr8mech's pneumatic overpressure event. I guess we'll see when NTSB releases more data.

Rgds,
Rob

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