Bridge Toll
 

PTH

Bridge toll wouldn't have been very high. They charge by axle:D

I flew floats in Canada for awhile. On glassy water, we set up a shallow descent in touchdown attitude and waited.

As for the brick, that only works if you have power to go around and make another approach to the newly disturbed water.

What would you have done engine off?

I cant help thinking that expecting a ditching aircraft to be able to accurately flare is unrealistic in most circumstances - that was the only point I was trying to make. Given the (fortunately) minor injuries received in this incident, it seems that a 'best glide' descent is entirely survivable, and working on this assumption has got to be the starting point for any changes sought as a result.

Think you make your own luck.

These guys had three and a half minutes in which to diagnose and attempt to rectify an emergency, select an area to land, run the checklist as far as it would take them, inform ATC and pax and then successfully ditch an aircraft at an almost MAUW of 150,000 lbs.

This is not a "best glide" landing. L/D was over 200 kts(220 KIAS +/-?).

The report says they were 15-19 knots below 'V sub LS' (Vls) and at AOA limit and touchdown was at 750 FPM (12.6 fps).

Having some energy to flare might have reduced the impact damage.

IcePack – you are correct. While one engine was inoperative, the other one was still operating although not producing much, if any, thrust. It was the continued operation of that engine that prevented reversion to direct law – and thereby prevented any last minute “flare” capability.

air rabbit

wouldn't the plane allow a flare in a normal landing? is this change in law dependent upon gear down as well as radio altitude?????

Of course a normal flare would be allowed under normal law - but as IcePack correctly notes - in normal law there is a maximum angle of attack that is allowed (called Alpha Floor) regardless of where the airplane is at the moment. This "protection function" is disabled in "direct law" and the pilot has complete authority over the pitch attitude of the airplane. Because in this situation, both engines were not shut down (i.e., even though the one engine running was producing very little, if any, viable thrust) the computers were still "in control," and alpha floor could not be exceeded. In other words, the pilot could have had (and I understand that Sully DID have) the side-stick controller at the full aft position, but the alpha floor protection would allow only the computed maximum angle of attack. In this case, had the airplane actually been in "direct law," the pilot would have had the ability to pull the nose up even farther than was allowed here, and that may have allowed a more shallow descent and thereby a less impacting touchdown. Of course that is speculative by any measure. Under most circumstances there would be little, if any, need to exceed a designated angle of attack very close to the ground. For example, landing an A-320 in a full stall cannot be accomplished under "normal law" - but it can be accomplished under "direct law." Why? Because there are precious few reasons why someone would want to land a commercial jetliner in a full stall, and limiting the angle of attack also protects from a tail strike (infrequent, but more frequent than other circumstances) - but it also prevents what would otherwise have been an "over rotation" in this case to, I believe in Sully's mind anyway, lessen the touchdown force for the inevitable water landing. However, loss of envelope protection means all loss of envelope protection; i.e., the bank angle protection would be lost as well.

The "law" that is operational at any given time is related to the status of the computers and the malfunctions or combination of malfunctions existing at any given time. Even though the aircraft OEM cites the probability of a complete computer failure being less than 10, raised to the -9 power, the FAA still requires the pilots to be trained on certain tasks when operating in Direct Law (i.e., without envelope protection), and the simulators used for training must be tested in a representative number of those conditions. There are several sets of circumstances that will put the airplane into operation without envelope protection - "direct law" - notice, I said "sets" of circumstances - that means a combination of circumstances - and I think there are about 10 - 12 such combinations. Unfortunately, some of those combinations can be reached quite quickly in some cases.

Sorry for the "ramble." But I think it important that those who are interested should know ALL the available facts. I think Sully and his FO did a wonderful job of maintaining control of the airplane - but, in my estimation, the most significant thing he did was, make a reasonable decision, and he stuck to it - even when others were offering other alternatives. My hat was off to him and his first officer - and will stay that way - particularly knowing the predilictions of the airplane under the conditions that crew was facing - and that just makes that hat position more appropriate.

thanks rabbit

yes, the right thing to do is stick with your plan, as other options are constantly getting worse while the plan you are on increasingly becomes the only choice.

certainly, if a giant aircraft carrier with a mile long flight deck had risen from the hudson, sully could rightly have changed his mind. ;-)

I don't care for the airbus and its control laws. I actually could have been captain on the A320 series (for more money) but elected to fly the 737 instead ( also a POS).

but that's that.

I do think he would have been better off at speed plus 10 to give a better flare (note speed at stick full aft, add ten knots and hold that till flare regime)

Actually there is a time when both engines were shut down.
That's the early start of the APU by the captain that kept the aircraft in normal law.

No way he was trying to do anything like it.

Alpha Max could not be exceeded.
What is surprising is that absolutely no graph from the FDR has been published.
Technically speaking Alpha Max has not even been approached during the flare despite the full back stick action by the captain.

Finding 24 remains pretty vague :I'd like to know more on that "may be attenuated"

:oh:
Sorry about using the wrong term - I'm not a "bus" guy - just under the impression that AFloor was driven by an AoA that when approached disallowed any further increase in AoA and would command an increase in thrust (to TOGA - regardless of throttle position) and a retraction of any speed brake extended. In that there were no speed brakes deployed and (virtually) zero thrust available, the only thing that was accomplished was the disallowance to further increase AoA - regardless of the sidestick position.

A comment , if I may, from a private pilot. I fly an amphibian and note that being unable to flare more forcefully may have been a saving grace. Aircraft that land in water nose high and in stall tend to touch down tail first and then the nose drops suddenly and forcefully enough to submarine. Note that the fulcrum point for a stall on , U/c up is not around the main U/c position (just aft of the CG,) but further back at the tail. Aft end touch downs cause a strong rotational moment.

Float planes have narrow pontoons with pronounced V which penetrate the surface and act as a cushion. If I stall on my plane, a rather flat hull, it causes pronounced and rather scary porpoising even though the step is only about three feet behind the CG.

Just my very humble opinion but attitude is more important that 10 to 20 knots of speed at this point.

I just read 'Fly by Wire' by William Langewiesche, and can thoroughly recommend it. He describes in a very balanced way what happened not just during the flight but also during the hearings.

He makes clear his view that the crew did a great job and he argues compellingly that the design of the plane also helped. Interestingly there are very few differences between his version of events written last year and the official report just published.

no one is advocating a full stall landing in this case, but a descent rate of less than 750 fpm would have been better.

lederhosen, as I mentioned a long time ago...other comparable airplanes have done better water landings without any electronic gadgets.

Are we sure this '750fpm' is correct at 'touchdown'? What I recall of the actual video did not look like a full blown, no arrest ILS rate of descent!

Protectthehornet I gather we are both 'if its not Boeing I'm not going' captains. I have no axe to grind about Airbus aircraft. The gist of my post was to recommend Langewiesche's book.

Have you read it? It is available in e-book format. If I have any criticism it is that it is a little short. But then again I guess that shows I would have enjoyed reading more.

Not being funny but can you list some examples of more successful comparable aircraft ditchings?

lederhosen, check out Tu-124 on the Neva in 1963. The landing itself was even more successful than Sully's, but yeah — they had more time for pondering the situation. On the other hand, the Neva is more of a slalom course than the straight and wide Hudson.

Tupolev 124 ditching in Neva River - Wikipedia, the free encyclopedia

Let's see:

Since the aircraft was in "Normal Law" (one engine is enough to keep it in that mode) it should have behaved as designed, i.e., when crossing 50', it progressively must have changed into Flare Mode, therefore allowing a further increase of the AoA, during those few seconds from 100', (protections lost) till ditching.
IMHO - (and this is not to say that Sully made a bad landing, there is still room for proving that there is a better way to ditch an A320) - the best way to glide a FBW aircraft into a ditching, is to fly it stick neutral, once you were able to set-up a glide speed (as we usually do for a landing), in order to allow for (further stick movement) to flare.

lederhosen

I am thinking of a JAL DC8 at San Francisco, CA USA late 1960's or so...landed in the bay...gear down! plane was recovered and started flying again after repairs.

Lederhosen - PTH
 

JAL DC-8 at San Francisco 1968

http://libraryonline.erau.edu/online...s/AAR70-02.pdf

Don't remember that one. But I can remember the JAL DC8 with the unstable captain who deliberately crashed into the bay short of Haneda. The poor flight engineer who was trying to restrain the suicidal captain was sadly killed. I don't think the airplane was reusable on that occasion, at least in part due to the interaction with the approach lights. However I think we can all agree that Douglas built strong airplanes.

The successful examples from nearly fifty years ago show this is an unusual enough occurance for airlines to have been seriously considering if they could save weight by ditching the survival gear. The regulators thank heavens saw things differently. I personally was unconvinced up to the Hudson event that a landing on water might be a survivable option, particular given that apart from a non normal checklist in the QRH this is not something normally covered in training. In open waters I still think a happy outcome is not very likely.

I was aware of the Russian ditching, again in sheltered waters, the Neva is actually pretty wide for at least a couple of kilometres either side of the Hermitage. You might want to avoid the bridges though! Again they built solid machines.