The same way a human would.

As a pilot myself I can tell you that in EP there are really only a handful of criteria you look for when determining a place to land:

1. Minimize risk of ground personnel 2. Minimize obstructions between air and ground (ie. poles, trees and wires are bad) 3. Maximize straight and flat ground 4. Maximize featureless ground etc...

Given where Newark is, and Sully's flight condition, there was really only one place that would show maximum differentiation in human density and allow for landing: Hudson. The trick is knowing how to land on water with *a passenger jet - something remarkably simple to compute given environmental parameters (CG, load, wind, etc...) and a few simulations.

As was rightly pointed out, the key to success here was calm - something Sully learned starting at the USAF Academy (I'm a fellow grad as well, shout out where you can take it!) and was what let him do computer level calculations so quickly.

Nit picking: Sully was flying an A320, not a widebody.

Granted. Fixed

> Can a computer land in the Hudson?

Well it did. One of the (probably lifesaving) actions that Sullenberger did was to deploy the RAT which meant electrical power was maintained. This was not a checklist item, merely something he though useful. This meant the computers were still firmly in control when the aircraft ditched and the stall protection they gave certainly helped the ditching.

Interestingly after the accident the NTSB and Airbus made a number of ditching simulations and it showed just how hard it was for pilots to achieve the correct entry mandated by the ditching certification (minimum speed, -1 degree approach). However one pilot, an Airbus test pilot, managed to do much better than this by levelling out at high speed and very low using the radar altimeter. He the allowed the speed to decay until the aircraft touched the 'water'. This unusual proceedure probably couldn't be done by many pilots but it could be done by a computer.

RAT is automatic. APU was started manually which allowed full electrical power and flight envelope protection.

I think the RAT deploys automatically. The flight computers most likely run on a backup battery for a good while, but without the RAT there'd be no way to even move the control surfaces.

That so much does not in any way describe "the computer landed the plane". At all.

For the Hudson, interesting question. Probably you need humans in that loop. However, you can probably preprogram the scenario (I recall that Sullenberger actually did practice it).

For TransAsia, the point is that a computer wouldn't have needed to land. It still had engine power and could have moved the plane to a stable situation.

The problem is that the TransAsia-type pilots and situations far outnumber the Sullenberger's.

Capt. Sully actually did practice glide landings in the simulator after a dual engine failure after takeoff. He had expressed concerns about bird strikes before. It was thought that the chance of both engines being destroyed (engine core failure) was minimal. There are plenty of cases where an engine with a damaged fan blades keeps producing some thrust until shut down.

One thing that most people don't realize is that if Capt. Sully had lost one engine, and turned hard into the dead engine to return to LaGuardia, chances are he would have crashed. He made the right call to confirm (dual) engine failure.

Its also well known that a controlled crash landing is better than trying to stretch the glidepath, and loosing control.

I suspect that "automated" airliners will be programmed with crash landing areas for the 0.00001% its actually needed. There was a mishap when a F/A-18D crashed on final, both engines out, and its theorized that if the pilot had flown the pattern higher the jet would crashed away from the houses. A lot of factors lead to the crash, and 4 people in the houses died.

Of course, flying dead-stick instrument approach with low clouds is almost unheard of.

> The problem is that the TransAsia-type pilots and situations far outnumber the Sullenberger's. That is a huge problem. A lot of training programs are very scripted, regimented, and do not encourage pilots to make decisions like intentionally putting a jet into the water.

NASA trained the shuttle crews for unrecoverable situations (that don't result in an emergency landing) so the crew would still keep functioning and hopefully bailout.

If there were an infallible procedure for a computer to detect which engine is malfunctioning, the fly-by-wire system could already refuse to switch off the wrong engine.

I don't see why this is an argument for full automation.

> how does the computer decide where to land?

The same way a human does: by assessing all the options, running little simulations to see which is the best one, and then picking that one. When you're over a densely populated area and lose all power, landing on water is kind of a no-brainer actually because all other possibilities lead to certain disaster.

> When you're over a densely populated area and lose all power

So your powerless computer is going to land the plane?

Sorry, I was being a little fast and loose with my terminology. If you really lose all power in a jet you're simply screwed. But that never ever happens, unless you have the kind of catastrophic failure that makes power loss the least of your worries. Losing all power means losing all engine power. You still have many layers of backups that keep the flight control surfaces and avionics working even if all the engines quit.

Nothing fast and loose about it. "Lose all power" is a perfectly normal way to mean all of your engines quit. "Power" in an airplane refers to propulsion by default.

And just to be clear, if you somehow lose all electrical power on a modern airliner you are completely screwed no matter what or who is flying it, because the controls won't work anymore. The pilot, whatever its nature, immediately becomes a passenger.

Not a pilot, don't know anything about flying. Got it.

This is the problem. In an emergency, you need a trained and experienced pilot who can find a way out. If you replace pilots with computers (well, software), even if you have a pilot sitting there, they will have less experience (because they just sit and watch) and they'll have less immediate understanding of a situation when they're called upon to take over the controls.

You can put your pilots in a flight simulator.

If you provide enough if else branches, it could land anywhere.