Can anybody tell me something about these inflatable exit ramps and why they can not be designed to be something able to float the passengers?

It seems that with them being inflatable to begin with they should be easy to make into a temporary raft type thing if you had to ditch.
Maybe not a perfect answer, but a better answer than dunking old folks with weak hearts into freezing water.

Hi and welcome,

To take the points I can in order.

Pilot skill was pretty much the key here, as to what percentage could have pulled it off under the same identical circumstances I think you will see a pretty tight bell curve (at least in the US pilot population, it varies a bit more across the globe) with the pilot of this flight at or near the top end of the scale. Your more typical pilot (center of the curve) would probably done nearly as well, maybe a bit harder landing, a few more injuries, a bit faster sink rate after "landing"). The other end of the scale might have broken up or flipped on impact since ditching is a very narrow margin situation. US aircrews (all airlines) are a pretty highly trained and skilled group and most are very professional and proud of their abilities. Keep in mind it was an average flight crew that did such a great job getting that crippled DC-10 into Sioux City Iowa several years ago.

Another factor was the type of aircraft involved. I am not a huge fan of Airbus planes (If it ain't Boeing, I ain't going) but the A320 series is designed for hard use (lots of cycles per day) and is reasonably sturdy. A 737 would have probably done as well while larger planes might not have fared as well. For those speculating on the effect of the water temperature, it doesn't really matter at the speed the plane was going. I am pretty sure the investigation will show the initial impact managed to open up the outer fuselage at the impact point. Hitting water at those speeds is like hitting concrete since water is not compressible.

The number and size of slides are dictated by airplane evacuation times not their secondary use as floatation devices and trust me, you want to keep it that way. Adding more exits & slides just to have more "rafts" would increase the cost and weight of the plane considerably and drive ticket prices even higher. Making the slides longer (to float more people) would have a negative impact on evacuation times and safety. Flights over larger bodies of water carry dedicated rafts based on their rated passenger capacity. In this situation I don't think it would have helped a lot and most passengers are already upset at the overhead compartment space dedicated to the flight crew and safety items. Adding in life rafts would just increase the frustration and operating costs of the airplane for no measurable improvement in safe outcomes over the continental US.

Adding any sort of a non-slip surface to the wing just for emergencies is not a good cost benefit trade. You are adding weight, drag (think increased operating and maintenance costs) and additional risk (icing, changes in stall behavior/margin) under normal operating conditions to offset a minor risk (slippery surface) during an emergency situation (loss of aircraft/major damage is a roughly 10E-9 type of event).

Can't help with the other ponderings.

- Eric

The ramps do float and are designed as a detachable floatation device. They are not sized to carry everyone on the plane but to ensure rapid and relatively safe exits for a wide variety of emergency conditions. Preliminary information is that they performed well and as designed. Probably won't hear anything significant about them until the NTSB publishes their final report in 6 months to a year.

- Eric

Regarding the Flight Control software on Airbus airplanes. It really hasn't changed since the Airshow incident. That was a specific case of the pilot getting too low and slow, with the engines powered waaay back and the flight controls not allowing the airplane to maneuver up to the real stall attitude or into the post stall region of flight. Various people have claimed that by pulling up either closer to the edge of a stall or even into an intentional stall the crew could have gained enough altitude and time for the engines to finish spooling up enough thrust to climb out. The flight controls operated as planned and they flew the airplane into the trees with the crew hauling back on the stick as hard as they could.

That is actually one of the big philosophy differences between Boeing and Airbus designs - who has the final say on what the plane can do, the pilots who are on the plane or the engineers who are sitting at their desks. I am an engineer and all told I would rather trust the guy up in the front of the plane most of the time.

Airbus flight control laws still prevent the pilot from intentionally performing radical maneuvers (like large bank angles or approaching a stall). They have hard limits that the pilot cannot fly through. Those limits do not seem to have had any impact (positive or negative) on this incident.

- Eric

Thanks. I kind of suspected that but didn't know.
As you say, the real news will likely be in about a year when they finally have it all figured out and can make recommendations.

Captain Al Haynes was also coincidentally about 57 years old, just like Captain CB "Sully" Sullenberger. This Sioux City accident also had an additional DC-10 pilot/flight instructor in the cockpit, adding to the amount of experience in the cockpit.

I think that perhaps having a medium length of time for the incident may have allowed greater focus. Less chance that stray thoughts get in the way and the adrenaline is up as high as it can go.



Usually, they're to protect the airframe from undue stress, right?

Actually from the stories Captain Al Haynes tells and the NTSB writeups that crew performed a minor miracle keeping their wounded bird in the air. They were flying along minding their own business when BAM! - they get a big jolt followed by indications of engine problems and flight control problems. They fought a several minute battle where things kept going from bad to worse after which they had to relearn to fly using only the throttles!! I am willing to bet their adrenaline levels were right up there - but yeah after the initial crisis they had some time to think. Personally I think that crew pulled off a much harder set of miracles since the A320 only lost engines (not flight controls).



Thats one of the arguments but not really a good one - there are lots of things that an airplane can do that are low/no stress that the Airbus primary flight control laws don't allow. My favorite example is a 1G roll. No stress on the airframe at all - heck done correctly the airplane never really knows it is upside down . Another one is stalling - no real airframe stress.

It really is a philosophy thing that ties into cultural tendencies and who should have the final say. If you assume the pilots are good and know what they are doing you warn them where the limits are (and the warnings are usually loud/obvious) but let them choose to spill the drinks and maybe abuse the airframe a bit if they need to. Airplanes have impressive design margins so letting a good pilot push the envelope can be the difference between an incident and an accident.

On the other hand if you assume the crew is under trained (by comparison to say the typical US commercial crew) and a bit ham handed you let the flight controls protect the plane from the pilots. Of course that assumes that the engineers designing the thing have managed to figure out everything that can go wrong and design in the right response - yeah, that's going to happen.

I guess I'll fess up here too. I am an engineer and I work on avionics systems, including flight control systems once upon a time ago. The teams I have worked with have all been very good but I would rather put my faith in the pilots. If nothing else the guy in the front seat has the added incentive that he is usually the first to arrive wherever the airplane is going.

- Eric

I don't recall if it was an Airbus placard or not, but I have certainly seen pictures on an emergency placard of exit slides being used as a raft during a water landing.

One reason that passengers had to stand on the wing instead of being in one of the rafts is because the tail section immediately submerged, so the two tail exits were never opened and those two slides were never deployed. The cabin crew directed the passengers away from the tail exits.

With several boats close by, I also wonder if the crew was calculating the danger of overloading the rafts by piling everyone on the rafts versus waiting on the wing in anticipation of imminent pick up?

Surveillance tapes from the shore show the plane's landing. Amazingly, it looks *almost* routine.

http://www.cnn.com/2009/US/01/17/usair.splash.video/index.html

The NY Times article says that initially all of the passengers rushed to the rear exits, then the flight crew told them to come forward. Could that initial weight shift have been the reason (or contributing factor) for why the tail sank? The article doesn't explicitly say so, but presumably, the flight crew initially directed the passengers to go to the rear - if so, was that a mistake? What if someone had managed to get the rear exit open before it sank - wouldn't that have been disasterous?

Along those line, is it possible to open the exit doors if the plane is submerged? (The wing doors, it says, are the push-out kind, not pull-in; presumably the rear exit is the same.) If yes, doesn't that pose a risk of sinking the plane if a panicy passenger opens one under water? (And if no, what about entrapment risk in a fast-sinking plane?)

Also, one thing I saw hinted that there might have been flotation rafts stored inside the plane (closets and overhead) that were not deployed. Does anyone know if that's true?