Southwest Airlines Emergency Landing at PHL

I'm curious to know too.

Does anyone know what GE did with maintenance intervals, if anything, after this other fanblade incident? https://en.wikipedia.org/wiki/Southwest_Airlines_Flight_3472

The photos of that engine failure look very similar to the this most recent one and the fuselage damage thankfully wasn't as bad as this time around. I hope they did something to prevent more from happening if it was preventable...

 

The woman died of blunt force trauma to the head and body.

She WAS wearing her seatbelt.

 

I'm not pointing fingers at SWA so please don't class me as some kind of cheap shot guy. I have been associated with the engine problem thing in the past and worked in the Boeing gas turbine lab and I know what can happen when the stresses of operation can raise their ugly heads and do bad things to you. The JT-9 on the 747 had a terrible start with shaft failures and other gremlins but after aggressive and consistent inspections P&W was able to solve the problem. The CFM is a great engine and is proving its durability every day on something like 20,000 installations. All I was saying is that after three failures of the same type on this engine there has to be an increase in blade inspections. The stress on the blades is tremendous and after thousands of hours of constant loading something has to give. There are signals and they must be detected early. I remember when a blade let go on the 11.5 compressor of the engine that we were testing at 36,000rpm and the impact on the test cell walls. The energy of that blade was the same as a cal. 50 bullet and the rig was completely destroyed. I imagine that the energy of a five foot long blade at 15,000rpm might have the energy of a 20mm cannon shell or more. I see on TV that the FAA has ordered ultra sound inspection of all CFM's in service. Again, no shots at SWA . Just examining what has been done and what should be done.

 

Blending nicks on those fan blades is as much art as science. Will be interesting to see if the errant blade had any nicks resurfaced.

 

They have part of the blade... the part that joined the hub. It failed. It is cracked internally, not visible to the eye.
I'm assuming it stayed in the case.

The outer 3/4 of the blade is missing and it failed also.

According to the press conference today.

 

I'm amazed to see how big some of the blended nicks are on some of the fans, much larger than I ever saw in the military on the KC-135s.

 

FAA orders random ULTRASONIC testing of 200 engines fan blades. Also looking into the "casing" containment area of this particular CFM-56-->why did it break down???

 

If you're the pilot of this plane, what is the sequence of the first 5 things you do after a catastrophic engine failure? A non pilot guess.

I assume the first is to get control of the plane and fly it.

start to Descend

shut the fuel off to that side.

Damage assess

Figure out a place to land.

 

The key words in an emergency is "Aviate" , "Navigate", "Communicate"

The first priority is to fly the plane and assess the situation, then look for a safe place to land and avoid other traffic, then communicate the situation with ATC.
If you watch this video it was over 2 minutes before the Captain before she contacted ATC about the engine failure even though ATC was trying to make contact with them.

 

The blade went forward when it failed... in front of the casing.
It went beyond the front of the casing, so the casing could not contain it, so in that sense the casing did not fail.

Also, saying this, a friend asked and didn't know... the blades are hollow, like flattened curved metal straws. The crack on the interior of the blade was never visible. They have part of the blade that broke.
So ultrasonic testing is necessary.

 

So, the 'casing' did not fail... it's still intact. The exterior covers came off and hit the wing and window...

 

Actually it is mostly science nowadays... Back in the mid 70's when I wrote the nick and blend limits for the F100 we based them a lot on experience and what was then the early finite element analysis techniques. By the late 70's we were modeling the notches that we could remove and not have a major effect on stress or on the dynamic response (vibration characteristics) of the blade. The location and the depth of blend is strictly defined in the nick and blend limit procedures and if a blade exceeds those limits it is gone. Highest stress areas generally are in the blade root, and the stress concentration at the root fillet is what usually sets blade life. This is why you can take a pretty big bite out of the blade outboard of the 50% span and not have a stress problem. The root stress profile of a blade like this looks like a butterfly, with the high stress occurring on one side caused by the bending of the blade from the aero forces and this generally occurs near mid chord at the root, and on the other side there are two peaks near the LE an TE of the blade. The structural engineer will tilt the blade to minimize the bending stress caused by the aero loads... One problem with the 737 is that the engines are close to the ground and you can get more FOD than is typical of other engines. It doesn't take much damage in the root area to cause problems. A small scratch back from the leading edge on the pressure side can wreak havoc with the life calcs, and it's almost impossible to see that area without some kind of borescope or a mirror, and any scratch could be easy to miss. Not making excuses, and it's the job of the inspectors to find those things, but is isn't an easy job by an means.

One thing that could be an issue here is that they are saying that there were two cracks in the blade... What could have happened is that one crack changed the dynamic response of the blade, that could soften the mounting so to speak, and if the frequency response changed then it could have resulted in a different dynamic response that could have led to serious vibration or even flutter, which would cause rapid failure of the blade. Similarly, in hollow fan blades, if there is any delamination of the blade the dynamic response can change and that can create vibration or flutter and all bets are off. Ultrasound is good, but it isn't perfect, and there's skill involved too. As I understand it there's an AD on some CFM56 fans calling for repeated inspections at periodic intervals so there could be a variation of a known problem or issue here and until we get the NTSB report we're just all speculating, but there are several ways this could have played out and it will be interesting to find out what happened. Once they get a good look at the root there will be finite element models made and run and it will all become known, and then they'll address it. Unfortunate that someone lost their life in this incident, but it's pretty close to impossible to know all the unknowns when you're designing things.

 

Aviate, Navigate, Communicate is always a good rule. However, in this case not only did the engine fail but you had a loss of pressurization. So the very, very first thing you need to do is get your oxygen mask on. Then you need to get started down, and figure out what's going on.

 

From what I can discern, the fan case is intact, the fan is still there but missing a blade. The blade that failed took out the inlet duct, inlet, and associated cowling. A lot of trash flying around.

 

One thing that struck me in the videos/audios - I don't remember them telling ATC that they had a pressurization issue. When she asked to descend initially, they only gave her down to 11,000. I've always thought that you wanted to get below 10,000 as soon as possible.

 

I noticed same, but I am just a layman/YouTube jockey. I also noticed nobody wasted time telling or asking if an emergency was being declare

 

Not really wasted time to actually state that you have an emergency. Most importantly, saying the words 'Southwest XXX declaring an emergency' ensures that certain protocols are enacted. Also broadcasting such not only alerts ATC but also everyone else on frequency, who then will not waste time inquiring why they are being put in a hold or told to delay descent, reduce speed, etc.

 

My motto from many years of flying. "WHEN IN DANGER OR IN DOUBT, RUN IN CIRCLES, SCREAM AND SHOUT!"

 

I completely understand what you mean. That's why I was surprised that the emergency declaration was not requested by ATC.

I am curious about how the controller community sees it. If the controller has enough info to know seconds are precious, are they to be commended for cutting a procedural corner, or reprimanded for breaking an important protocol?

 

It is the responsibility of the pilot to declare an emergency. ATC can, and I've heard them, ask a pilot if they would like to declare an emergency. Having a declared emergency can also shift duties between controllers, without which other controllers not in the know could continue to hand-off aircraft into the sector with the emergency. I'm not a controller so as you requested would be good to hear directly from someone trained for these things.

 

Actually, ATC can declare an emergency for you. Unless the crew did so at some point that isn't on YouTube (which is entirely possible), that's probably what happened here.

 

You can nitpick anything. Sully and Skiles didn't activate the ditching switch on the A320, which would have resulted in less water coming into the aft cabin...

You could also make the point that any pilot flying at Southwest could have managed the same event... also probably true.

All of that said, "any pilot flying at Southwest" wasn't in the hot seat that day. Tammie Jo Shults was, and she managed the situation calmly and with grace and professionalism. She demonstrated that her first concern was for her crew and passengers, by checking on them as soon as it was safe. And I'm sure the fact that her flight had a passenger killed (first passenger fatality on Southwest ever) will weigh on her for the rest of her life.

 

I listened to the tape pretty closely. Again, I'm not a pilot but it was pretty clear immediately, maybe even on the first transmission that it was an emergency. I would think when you're on one engine and say part of the plane is missing, saying you have an emergency would be redundant?

 

Well, it is helpful to have someone declare an emergency. That way the other controllers know that there is something going on. But I'd be really surprised if the controller didn't do it. In fact, I am 100% certain that someone did, because that's why the controller, at one point, asks about souls on board and fuel. That's part of declaring an emergency.

 

Just to be clear - I wasn't nitpicking - more like asking "I wonder why they didn't ..." . She/they got the job done just fine without my input.