ea306

A question for Boeing guys out there:

In light of the A320 dual engine failure ditching in the Hudson River,
as a B737-800 pilot, what items would you want to accomplish in the 6 minutes to
prepare for ditching the aircraft in an attempt to have the best possible
outcome?

There are some significant differences in design. There is no RAT,
no Ditching button to press.

If engines are wind milling you would have some Hydraulic
Pressure...other wise you would be in manual reversion. Certainly not
a desrable situation to be in.

- Boeing checklist says to have the APU off for ditching ( the APU inlet door
would let a lot of water in the tail.) On the other hand, the electrical power
could be useful to run some hydraulic systems...which in turn will
greatly improve aircraft handling for more precise control.

-Alternate flaps system will extend leading edges to makes for a better
gliding wing and also activate the standby hyfraulic pump which will
help with rudder of course.

-Engine Bleeds Off
-Outflow valve comfirm closed (close manually if time permitted)
-Flap/Gear configuration warning switches to Inhibit

Again, if you had just a few minutes to prepare for this scenario, what items
would you want to look after with engines windmilling or not windmilling
due to damage?


I always enjoy reading this section of PPRUNE and I look forward to
reading every one's feed back.

.

misd-agin

Leading edge devices to make a better gliding wing?

Until Boeing changes their manual a clean wing is your best L/D for gliding.

Leading edge devices have a huge reduction in stall speed. The first notch of flaps is typically about 50% of the total stall reduction you get from flap extension.

1. Fly the airplane. Airspeed towards target dual engine failure speed. Evaluate energy available(altitude and speed).
2. Try engine restart or any other immediate action steps.
3. While attempting #2 continue with plan of action, which right now, with no engines means to head towards landing area. - 1. runway 2. clear ashpalt/concrete 3. smooth open land 4. water 5. best available
4. Get as much done as possible. Checklist or wing it, your choice if time is very critical.

If you can't start the engines, immediate action items are done, radio calls are made, I'd notice the crew or passengers.

Bleeds? Packs? Outflow valves? This accident shows how those are nice to do things, but not necessary in a time critical situation.

misd-agin

They didn't have 6 minutes. They had 3-4 minutes from failure to landing.

Empty Cruise

ea306,

You state in your profile that you're a 738 captain...

I am sorry, but it appears that a lot of people suddenly have become very interested in 2-engine-out procedures, ditcing procedures and A320 technicalities (for those that operate that aircraft).

Have we reached that state already? That it takes an accident to get us thinking about how we'd handle it if we were the unfortunate ones? I know we're talking a minority, and your efforts to get up to speed are commendable, ea306 - but us not having the imagination to imagine all the things that could and sooner or later will happen, that's not what the fare-paying public expect.

My tuppence worth - while you call for the "loss of thrust on both engines recall items", reach up and initiate an APU start while you declare the emergency and wind it back towards UP-speed (and once the APU start is going, you pop the trim handle for manual reversion). If at high altitude, you'll be calling for masks on as well, and once it was determined that the engines were not relighting immediately, you'd call for the memory items for emergency descent, followed by the checklist for loss of thrust on both engines. Your radios, your airplane

If you were flying... if your FO was flying, you'd prompt him/her to do the same if no immediate plan of action was forthcoming.

Once you have the APU, you have all sorts of goodies - hydraulics and normal gear extension, but only after remembering to switch the DCMPs off before getting the APU GEN on line, and then on again afterwards.

Edited after spotting that you DO have a ditching button to press! It's called the outflow valve, and you need to close it manually to ensure it'll stay closed.

Empty

ea306

1. Yeah a clean wing is the best for glide...
I am thinking more towards prepaing for ditching..after all other options
considered.

Not getting the best gliding
range of a clean wing...but rather the best handling configuraion for a water landing.
Boeing say use flaps 40. That is with thrust though. In this scenerio you would be
limited from an operating systems point of view. Towards that end would you not
agree to extending the leading edge devices??

ea306

Thank you for the responses so far.

Yes my profile does state that I am an NG captain. Been a captain on
A good many types including some older Airbus types as well..my CV is
not point of topic.

I pose the question as was posed to us in a CRM class today by our training
department. Apologies if my question appears amaturish. Maybe I should of
mentioned that?

In any case, the group I am working with are trying to see what can we
learn from this scenerio with the NG being the subject airplane. I do not see
taking an event and applying it to your aircraft type as being entirely reactive.
It is in a sense, however we could be proactive as well.

Your comment on the outflow valve was certainly my first response in the
classroom.

Other points mentioned in order to quickly configure:

APU. - ON/OFF?
Out Flow Valve- Closed
Engine Bleeds Closed
Guarded Proximatey switches.
Landing Gear - UP

You have wind milling engines that will provide hydraulic pressure
to about 170 kts... However maybe not available as Eng damaged
due to bird ingestion.


Common sense stuff should always prevail.

1. Always fly the plane. Drills checklist etc. As time premits. Certainly,
all the nice little window dressing items don't mean much if the aircraft
Is not flown firstly and foremeost.


I am not a prolific poster on PPRUNE.. I can see that one has to be
very careful in how one posses ones questions.

So back to the question:

Intruder

On what airplane?

On the 747 there is a 20 KT reduction in stall speed (or maneuvering speed, however that may technically be defined) for each of the first 3 "notches" of flap -- 1, 5, and 10. There is another 20 KT for the last 2 increments (through 25 to 30). While the 747 Classic and 747-400 have completely different wings and LE/TE flap extension profiles (e.g., the Classic has some TE extension at Flaps 1; the 744 does not), the speed reduction increments are retained.

misd-agin

Intruder -

757/767 has almost exactly 50% reduction in stall speed for the flap movement.

However, we operate in 20 kt speed reductions allowable per flap configuration, which is not the same thing as the actual reduction in stall speed.

Are you positive the you're commenting on actual stall speeds vs. SOP speeds per flap configuration? They're two different situations. I'm asking because a 747 classic pilot told me that the stall reduction for the first notch (or two?) of flaps on the 747 had a similar impact(high percentage of total stall speed reduction).

757 - 200K 767-300 320K

0 - 151 0- 172
1- 125 53% decrease 1- 142 56% decrease
5- 118 5- 130
15- 113 15- 127
20- 109 20- 125
25- 104 25- 120
30- 102 30- 118

Empty Cruise

Unaware if flaps were used on the Hudson, but for kinetic energy reduction purposes, I would deffo go with F40, even without looking at the checklist. Emer extension would only come into play if we couldn't get the HYD press from windmilling and the APU failed to start so we could use the DCMPs.

Even if you only reduce your impact speed by 10%, you've reduced your kinetic energy by 21%, so F40 gets my vote.

Empty

Jinkster

Only problem with deploying flaps is the chance on impact the water will hit, the flaps and cause control problems.....not trying to state the obvious at all but a boat is very streamlined and sticking flaps down will make the boat shaped hull or fuselage of the aeroplane un-boat shaped!

Conan The Barber

How much control do yo think you have once you hit the water? None, I should think.

I would be much more concerned with the amount of energy I'm carrying on impact, than whether or not my aircraft is boat shaped.

Jinkster

Well you still have your rudder, would be sort of like a float plane I imagine, never tried it!!

Would be nice to read the accident report just to see what actually happened! I can see both points of view

Empty Cruise

Agreed, you'll probably need the "Boeing push" more than ever - but Boeing recommend F40 for ditching. If you stay clean (or clean-ish), the engines will strike the water first, but the speed is now some 30-40 kts higher than the speed the ditching criteria were build around.

I see it as two seperte problems: Forward speed (impact forces and severity of any loss of control) and pitch-down-moment from dragging the aeroplane through the water (since a high pitch-down-force could break the fuselage forward of the wing box). The pitch-down-moment will occur no matter what, only we're now talking slightly less moment arm (only engines, no flaps worth mentioning), but at a higher speed. How much difference would that generate from the standard ditching scenario, where you hve a greater pitch-down-arm (flaps and engines), but the speed is lower?

I think the two above scenarios more or less balance eachother out - i.e. we end up with roughly the same pitch moment, but with less forward speed and thus energy to dissipate - or, if the water is less smooth than the Hudson and it's not your day, to take into the cartwheel.

That's more or less my reasoning for staying with F40 - but have no hard testing data or other evidence to back that up

Empty

misd-agin

Total energy reduction demands as much flaps as possible.

And any parts being torn off will reduce the ultimate G force. Shedding parts is good.

BOAC

Good to see the initiative, ea. From the comfort of my computer seat, here's a 'first shot':-

PF: Look for somewhere to land/crash. Tell ATC. Best clean glide speed.
PNF Frantic hot restart attempts + light APU then on buses ASAP. Cabin emergency call. Flap as called by PF, either with lever or as much on standby as possible if no APU. GPWS inhibit (although not really too important!). Outflow closed. Engine bleeds if time. Engine start levers closed. Brace call.

PF meanwhile calls for flaps as appropriate and crosses everything. Touchdown as slow as possible.

BOTH: Harnesses so tight you squeal. APU may as well stay running, since there is no real danger of significant water ingress through the inlet and I guess the APU bleed will be off.

Not in any checklists/text as far as I am aware, but what do folk think of trying to 'fly' the nose up to avoid it 'diving under' once impact has occurred? There will certainly be lots of 'Q' for the elevator. I think I'd prefer that to getting 160kt Hudson through the nose into my face.

Callsign Kilo

Something I thought about in regards to the PF. If you are to ditch, what will you aim for? You are looking to minimize the break up of the airframe's structure in order to increase the chances of survivability. I remember from my PPL days that the CAA produced around 14 documents relating to all levels of airmanship matters (see a copy of UK LASORS, I believe they are all included here). One I believe included 'ditching.' Although relating to GA aircraft types, it did take into consideration the effect of swell and waves and what the dangers were when preparing for a landing on water. I understand the most recent copy of Flight talks about this as well, including the possible outcome to the Hudson A320, had conditions on the day been different and indeed if the crew hadn't done such a spectacular job.

Graybeard

I would go for least rate of descent until a landing spot is chosen, then go for best glide range if needed.

I would worry that flaps 40 would require excessive speed and rate of descent in order to leave enough energy for the deadstick flare. The greater the R/D, the more exacting the flare required.

The last half of flaps is typically more drag than lift, not what you really want until maybe in the flare.

GB

stator vane

the good well outweighted the bad.

bad luck for the bird strike.

everything else was good--

the timing of the strike--if earlier--less time to get to the height to make the river to begin with.

good weather--just about cavok from what i could see in the pictures. had some winds, but not too bad. curious if he turned into a head wind.

day time--and even enough to get the people into the boats.

amazing to think about--

could almost make those passengers get religion!!!

certainly impresses one to start looking all about the regular departure airports and have good ideas of where to turn. might be a bit late to start looking once the birds get you.

what's the score now? birds 2--airplanes--?

Intruder

I don't know where I'd find stall speed vs flap configuration published for the 747 (or any other transport airplane, for that matter). Therefore, I can only assume that flap maneuvering speed is based on a consistent margin above the stall speed for that configuration.

The "or two?" comment you make, however, is also relevant. The second increment of flaps on a 747 gives a total of 40 KT reduction in maneuvering speed, of the grand total of 80 KT reduction from clean to Flaps 30. So, in the case of the 747 it IS likely accurate to state that 50% of the stall speed reduction is attained in the first TWO "notches" of flap. Likewise, 75% is attained by the third "notch," with 3 "notches" remaining.

Port Strobe

For NG at least there's a 65 knot spread in the minimum speeds one can normally expect to fly between clean and F40. The first 40 knots (c60%) of this reduction in minimum manoeuvring speed (not stall speed but I don't have that info) is attained by the time F5 is extended, so just like most aircraft, any flap beyond roughly half scale deflection tends to do little if anything for stall speed reduction and a lot for dragging you up. Which one may argue would lead to a steep flight path when there's no thrust available to flatten it out and that means there's less margin for error in a situation presenting a different visual aspect to what one has ever seen before (anyone done it twice yet actually?).
As for the ditching button on the bus it appears to seal everything up below the waterline. Scratching away at very feint memories here but on the NG doesn't the overboard exhaust valve open when there's low cabin diff and/or the flaps are not up? Hence it can't be completely sealed? Same story for the ram air doors? Personally I don't think I'd be hanging about long enough for these items to be of practical significance