Water Ditching

[muduckace]

Did not dig through the thousands of posts reguararding the sucessfull Hudson River landing.

I had allways immagined a water landing to be High AOA (tail impact first at a slow as possible IAS, being speed as the enemy)

Question is observing servailance video showing a low AOA impact that obviously created a stable landing (have seen video of a wing tip digging in and cart-wheeling an aircraft in other failed water ditchings). The engines (one lost) seemed to stabilize the the impact at low AOA that was more or less a three point landing... Tail and wing engines.

Question... Is this SOP at your operator as it was very sucessfull?

[Spooky 2]

You would need to read your aircraft specific FCOM for the exact procedure but anything resembling a stall or close to a stall is not a recomended procedure as will stave in the fuselage at impact. I suspect there is as much luck as skill in the outcome of this event.

[CommandB]

Taken from the Boeing QRH:

"Maintain airspeed at VREF. Flare the airplane to
achieve the minimum rate of descent at touchdown.
Maintain 200-300 fpm rate of descent until the start
of the flare.
At flare, rotate smoothly to a touchdown attitude of
10-12°. Maintain airspeed and rate of descent with
thrust.
At touchdown, reduce thrust to idle."

But as Spooky 2 said - it really involves alot of luck as well as skill AND conditions on the day. There are a lot of variables!

[cribble]

There are some non-type specific things also.

Lots of luck picking these (especially in an Atlantic storm), but the perceived wisdom was (may not be now, I stand to be corrected) to ditch parallel to the primary swell, as close to into wind as possible(on the back side of a particular swell :))

Results may vary.:ok:

[jeff64]

One thing disturbs me.
I have in mind four cases where an airliner did a ditch landing
- Cactus 1549
- A jetstream on takeoff from a northern country where both engines stopped cause ice accumulated during stop, or something else
- The Tunintair ATR
- Ethiopan 767 after the hijack

And a fifth where the aircraft almost did a ditch landing
- Air Transat A330 who landed in acores

All of these flights ditched because of no more power --> (3/5 - no more fuel ; 2/5 loss of power on both engines due to ice / birds)

And in all my aviation knowledge, I don't have any (or a very few maybe) cases of airliners (> 20 pax) who did a controlled and voluntereed crashed with fuel remaining.
Generally speaking, when an aircraft crash outside an airfield area, it's because
- the pilots can no longer control the aircraft
- loss of spatial and geographical orientation
- loss of ability to maintain speed and altitude (generally induced by loss of power)

So my question is : Am I the only one to find the procedure described is totally useless. Because it seems to need to have power (Vref and -300 fpm) and in mostly cases, when ditching, you have no more power ?

[Clandestino]

Am I the only one to find the procedure described is totally useless?

I certainly hope so, sir.

I have never flown a Boeing but on all types I did there were separate procedures for ditching with and without power. I assume the quoted paragraph is for "precautionary" ditching - when there's no chance of reaching the suitable airport, ditching under power is generally considered to be more survivable than glide to the sea.

[muduckace]

Ok, hate to take a stab at the guy but most of you seem to feel luck played a large part.

Logic tells me that he still had airspeed on his side and possibly a RAT deployed to provide crude control. It just seems SO logical to me to impact water with the wing engines at a low AOA (seeing is believing). A good old saying I thrive on is that luck is where opportunity meets preparedness.

I would be disappointed if this experience does not influence future training, understand that not all water ditching have the opportunity to land in a bay or river. I was just amazed to be able in my opinion to call this a controlled crash if the crew had less control over the aircraft than I give them credit for.

Hey, another factor that I neglected to consider is that most jet engines provide full hydraulic power from 5-10% N2 or N3. Keeping the A/S dumping into the engines (low AOA) may have provided better control if the spool driving the gearbox was able to spin.

[Clandestino]

Excuse me sir, but even the impeccable logic applied to false premises cannot result in conclusion that is true by anything else but by a chance.

I'm unable to find explicit reference to the specific accident in your posts but if you are referring to USAir A320 Hudson ditching when writing about "RAT deployed to provide crude control" and "observing servailance video showing a low AOA impact" then your notions, while possibly logical, are factually very incorrect. RAT did not deploy. Control law remained normal until water contact. No hydraulic or flight controls fault was recorded. All main electric busses remained powered. Finaly, attitude at touchdown was 10° ANU, very near manufacturer's recommendation of 11° and definitively inconsistent with idea that low AoA splashdown was achieved.

My apologies if you were referring to something else.

[muduckace]

[QUOTE][All main electric busses remained powered. Finally, attitude at touchdown was 10° ANU, very near manufacturer's recommendation of 11° and definitively inconsistent with idea that low AoA splashdown was achieved.

/QUOTE]

I claim ignorance as I have not followed the investigation and clearly stated that the scenario possibly required a RAT deployment. Thanks for the facts.. Oh yeah, just one more question... Your reference to 11deg anu... Was it to a water or runway landing?

By high AOA in reference to ditching, I had the probable false perception that a tail strike into the water was the safest scenario prior to the Hudson ditching. Your caustic sentiment to a humble question provided no enlightenment.

A standard AOA in a water ditching is what I perceived as a relatively low AOA. Still no response from the high timers. Is this SOP/tribal knowledge or just a good landing that no one wants to imagine themselves having to perform???

[Clandestino]

Very well sir, I'll try to enlighten you as far as my limited abilities and knowledge allow.

11° ANU is taken from A320 Ditching checklist and per Merriam-Webster "to ditch" means "to make a forced landing (of an airplane) on water". All the ditching checklist I've came across dealt with forced alighting on water therefore "water ditching" looks to me as a good example of redundancy in writing. Now when I've touched the subject of checklists, different aircraft operators have different ideas how the aeroplane should be flown in normal circumstances and that's what the SOPs are about - normal procedures. When it comes to emergency and abnormal (alternatively called: "following failures, non-normal etc.") procedures, everyone is interested in following the procedure that gives the best chance of survival and this usually boils down to one and only procedure promulgated by the aeroplane's manufacturer. I don't know whether Airbus Industries' just calculated the optimum ditching attitude and technique or actually experimented with A320 scale models but it seems that capt Sullenberger's successful ditching has validated the procedure, whatever it was.

To make it even more clear: there's no SOP regarding the ditching. There's no tribal knowledge regarding the ditching. Ditching is dealt within emergency sections of the flight manuals and not a single one I've come across makes emphasis on alighting with low AoA. It seems that "perception that a tail strike into the water is the safest scenario" is actually the correct one.

Incidentally, 10° AoA is not much for aerobatic aeroplane but is sure a lot for transport one.

If I may be so free, I'd like to ask you: which part of my post did you find caustic, sir?

[Dani]

Actually, Manu Chao, errr Clandestino, I find your posts here very sophisticated, polite and extremly friendly. I really like the way you write lately. If just all Pprune members would write so elegantly. :ok:

A great compliment from
Dani

[rudderrudderrat]

Hi,

There's a link to a Synopsis of the above here. (http://www.ntsb.gov/Publictn/2010/AAR1003.htm)

[Neptunus Rex]

jeff64,
There is a classic case of a well executed ditching, with 3 of the 4 engines running and plenty of fuel in the tanks. The aircraft was a Northwest Orient Douglas DC-7CF, with Wright Cyclone radial piston engines, and it happened on 22 OCT 62, in the Gulf of Alaska.

The flight was a military charter from Washington to Anchorage, with 102 POB (7 crew/95 PAX) mostly service personnel with wives and children. Three hours into the flight, the #2 engine lost power, quickly followed by the propellor overspeeding. The overspeed could not be controlled, resulting in massive drag, noise and vibration. With no suitable airfield close by, ditching became inevitable.

The flight engineer was able to monitor the engine oil level, but the crew knew that when the oil ran out, the engine would overheat, resulting in a massive fire. The Captain descended to 500 feet over the sea, continuing to fly towards Anchorage at that level. The weather was benign, with conditions of good visibility, light winds and little or no swell. A 'Mayday' call had been made and rescue services were on their way to the likely ditching area. The oil lasted for 50 minutes, giving the cabin crew time to brief and organise the passengers, with plenty of fit young servicemen to assist.

When, inevitably, the oil supply ran out, the Captain ditched at a speed of 96 knots. All 102 made it safely into the liferafts without significant injury. The DC7 stayed afloat for 24 minutes and everybody was rescued in due course and in good health. Many years ago, I heard a tape by the Captain, describing the whole event. He came across as calm, assured and utterly professional, and described the beaming smile of a young child who greeted him as he, last of all, boarded his liferaft to take command of his new 'ships.'