Southwest 737-300 Emergency Landing After Fuselage Tears Open

[Evan]

As for the procedure, its pretty simple. Wind down the altitude window, press FLCH, set the speed to what you want it, pull the speedbrake, ensure the thrust levers are at idle.

Thank you MCM. That just leaves me with one lingering question. What speed are you setting in the IAS/MCH window? Do you ever approach Vmo/Mmo?

[3WE]

...the descent rate was not dissimilar to a normal descent....an "emergency descent" is not that much different to a normal descent... passengers, have quite possibly been in an aircraft doing an "emergency descent" style arrival, and not even known it!

Care to give us some numbers of the upper end of "normal" descent rates? and prescribed descent rates for depressurization?

Also, I am thinking there is a reasonably big area that lies between "passenger comfort" and a "prompt-though-gentle-but-not-messing-around" response.

Given that folks are keeling over with some halfway serious health threats, I'd think Otto would be commanded (or even helped) with a good push over where you would get a little light in the seat....again- not shoving the yoke- but applying deliberate, sustained pressure while the plane rolls over.

Again- during normal flight- there are those guys who seem to have a goal of having totally undetectable vertical acceleration.....There's a wide range where you can smoothly make someones stomach levitate while putting the plane under no significant stress.......

[guamainiac]

This was not answered but in a push over what of the pax and crew who are standing or not belted; what of the galley service carts and such?

It does not sound like there is time to order and wait for folks to get out of the head, out of aisles and securing objects such as carts and such.

How much push are you recommending?

[Highkeas]

The FAA EAD applies to 737-300, -40, and -500 series aircradft. Here is the EAD:

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/77979606b642117286257869006afb63/$FILE/2011-08-51_Emergency.pdf

[Gabriel]

This was not answered but in a push over what of the pax and crew who are standing or not belted; what of the galley service carts and such?

It does not sound like there is time to order and wait for folks to get out of the head, out of aisles and securing objects such as carts and such.

How much push are you recommending?

Normal straight and level flight is 1G.

As long as you don't go below 0G, no butt will get off its seat.
Below 0G, like -0.2Gs, the roof becomes the new floor, and everything not secured (passengers, carts, coffee) will go up the new floor, and secured passengers will be hanging from the belt with their butts off the seat and the cell-phone dropping up from the shirt pocket.

Now, between 0G and 1G there is a range that is perfectly safe for the plane (it's subject to even lower loads than a straight and level flight) and for the passengers, but which may be very uncomfortable, scaring, and vomit-inducing. It's the semi-weightless floating-stomach feeling that you feel in the first drop of a roller-coaster, the further from 1G towards 0G the stronger the feeling.

3WE is "recommending" a push within this range, probably closer to 1G than 0G.

By the way, if you are going to go fom zero fpm to -5000 fpm without banking the plane, you HAVE to make the transition at less than 1G, there's no way around this. Now, if you make it at 0.9Gs the discomfort will be minor in intensity but longer in time since it will take some 25 seconds to build that -5000 fpm sink rate at 0.9Gs. Make it 0.5Gs and it'll take just 5 seconds, but probably a few passengers will have already vomited by then (however, nobody will be hurt, nothing will fly towards the roof, and the coffee will stay in its cup).

Here you have a video of a short maneuver at around zero Gs, that included a brief excursion to slightly below zero Gs too (aknowledged, this manuver started with a possitive Gs pull up and the passenger "discomfort" had started already there, bfore the zero G part):

(WARNING: not nice, view at your own risk)

http://www.youtube.com/watch?v=rbvIbdTUd2k

[Fear_of_Flying]

The FAA EAD applies to 737-300, -40, and -500 series aircradft. Here is the EAD:
http://rgl.faa.gov/Regulatory_and_Gu..._Emergency.pdf

The facile reassurance here seems to be that these regulations pertain to a specific model and vintage of aircraft, with a minimum number of cycles, and a particular manufacturing process.

The concerns to me (who doesn't know any better) are the urgency with which this AD came about, the aggressive inspection regimen that has been mandated, and the fact that no less than five aircraft with cracks have now been discovered. Also, the safeguards against cracking were not effective on the recent Southwest incident, as the crack extended five feet, past two of the metal strips that were intended to stop the crack from spreading.

So is this an unforeseen anomoly due to a manufacturing process, or is this the first of what could be a succession of metal fatigue issues that emerges in the next several years? One suspects that's the underlying concern of Boeing.

[Alessandro]

The facile reassurance here seems to be that these regulations pertain to a specific model and vintage of aircraft, with a minimum number of cycles, and a particular manufacturing process.

The concerns to me (who doesn't know any better) are the urgency with which this AD came about, the aggressive inspection regimen that has been mandated, and the fact that no less than five aircraft with cracks have now been discovered. Also, the safeguards against cracking were not effective on the recent Southwest incident, as the crack extended five feet, past two of the metal strips that were intended to stop the crack from spreading.

So is this an unforeseen anomoly due to a manufacturing process, or is this the first of what could be a succession of metal fatigue issues that emerges in the next several years? One suspects that's the underlying concern of Boeing.

Or result of rogue subcontractors? B had issue with a rogue subcontractor with bolts and nuts not up to specs on the B737-NGs.

[Evan]

The facile reassurance here seems to be that these regulations pertain to a specific model and vintage of aircraft, with a minimum number of cycles, and a particular manufacturing process.

The concerns to me (who doesn't know any better) are the urgency with which this AD came about, the aggressive inspection regimen that has been mandated, and the fact that no less than five aircraft with cracks have now been discovered. Also, the safeguards against cracking were not effective on the recent Southwest incident, as the crack extended five feet, past two of the metal strips that were intended to stop the crack from spreading.

So is this an unforeseen anomoly due to a manufacturing process, or is this the first of what could be a succession of metal fatigue issues that emerges in the next several years? One suspects that's the underlying concern of Boeing.

One has to wonder if the NG's are structurally different in this area. I doubt it. Why then is the AD only addressing the "classics"?

In any case, with proper inspections enforced every 500 cycles, the problem should lead to increased maintenance instead of terrifying plunge.

[Horatio]

Call me cynical, but I think all airlines drag their feet with these kinds of inspections because it would cost them more $$$ to do the inspections than it would cost to pay off the families of those killed in a crash.

[Highkeas]

Today was the first day I saw a good picture showing the damaged area location relative to the main landing gear. I have seen damage in the upper fuselage of aircraft caused by hard landing.
So it is possible that multiple hard landings combined with pressure cycling accelerated the fatigue. I'm hoping AW&ST will have details of the joint on Monday (or if the NTSB will issue a report with these details).

[MCM]

G'day - sorry for the slow reply.

Evan - yes, in fact Boeing say to set MMO/VMO, and so you fly at that speed. How to handle a minor overspeed when manually flying is covered in the depressurisation information, so they obviously intend for you to fly at this speed.

3WE - I would not assist otto at all. I would allow it to pitch over at the rate it usually commands. Manually, I would pitch over at the rate I normally do (although I'm sure adrenaline would mean you pitched a little quicker than normal).

As for rates of descent - I do not know of any published figures, but based on the minimum oxygen requirement for passengers I'm figuring it is a minimum of about 2500fpm. Realistically you'd be getting more like 4000, higher initially while you accelerate, and 5000 + with the gear down (although that is not the preferred procedure for a couple of reasons... but might be used if you need to keep the speed back for structural considerations). It will of course vary between aircraft types.

I'll have a closer look at the actual rates next time I'm in the sim.

[Alessandro]

The FAA EAD applies to 737-300, -40, and -500 series aircradft. Here is the EAD:
http://rgl.faa.gov/Regulatory_and_Gu..._Emergency.pdf

They are going to check all classics with more than 30k cycles.

[Curtis Malone]

Thank you MCM. That just leaves me with one lingering question. What speed are you setting in the IAS/MCH window? Do you ever approach Vmo/Mmo?

That's two lingering questions, isn't it? And is this really the sort of thing that keeps you awake at night?

[3WE]

Quote = Gabriel:

Now, between 0G and 1G there is a range that is perfectly safe for the plane (it's subject to even lower loads than a straight and level flight) and for the passengers, but which may be very uncomfortable, scaring, and vomit-inducing. It's the semi-weightless floating-stomach feeling that you feel in the first drop of a roller-coaster, the further from 1G towards 0G the stronger the feeling.

3WE is "recommending" a push within this range, probably closer to 1G than 0G.


/quote.

Thank you sir- you get the concept.

The average "push over for descent" is "detectable" but....BIG BUT that's about it (and sometimes with really really smooth pilots it's undetectable.)

But beyond "detectable" is a push over that is going to be structurally gentle, but which gives passengers a good feeling of "significantly falling".

Restating- if passengers and FA's are going to pass out from the altitude, I hope my pilot does not do (nor command) a normal, extra-gentle, barely-detectable push over....

Instead, gently, yet-deliberatly, positively, and promptly get the thing going down even means putting some overly-sensitive intenstinal acelerometors into the red arc.

[MCM]

If Boeing and Airbus say that a standard push over by the autopilot is acceptable, then that is good enough for me.