I’m not going to touch the “what would happen if a non-pilot was suddenly in control” question. WAY too hypothetical. W-A-M, your description of a slip is close but not quite.
“a sideslip is where the plane is moving in one direction while the nose is pointed in another.”
Flying in anything other than an exact head- or tail-wind causes this condition. A slip is a cross-control configuration that the pilot deliberately induces. Normally, the rudder controls the direction the aircraft points and goes the same direction as the turn (left turn, left rudder, etc.) In a slip, the pilot lowers a wing, then puts in a bootfull of opposite rudder. This configuration has the effect of banking the plane without turning, causing the nose to point away from the track of the plane, but most importantly, increases the induced drag and sink rate without increasing airspeed. While you are correct that in a crosswind landing, the pilot must bank into the wind to compensate, what the pilot in the Gimli Glider story was doing was a deliberate cross-control to lose altitude without picking up airspeed.
So what you said is basically true, but a slip does not induce a roll, it’s the roll countered by the rudder that causes a slip.
av8rmike is correct about slips, but I’d like to add a description of when you would commonly experience a slip with a crosswind in a commercial plane.
As the plane approaches the runway in a crosswind, it would normally be flying with its nose pointed into the wind, so that its nose is pointed directly into the airstream. Another way to say this is that a plane flying normally will look like it’s pointed slightly sideways to an observer on the ground with a crosswind, but the plane is flying directly into the airstream.
As the plane gets very close to the runway, they need the wheels to point down the runway, not at an angle to it. Imagine a crosswind coming from your left, so the plane’s nose looks like it’s angled to the left of the runway center line. The pilot will then kick right rudder, to point the nose down the runway, while at the same time banking the wings to the left, so that the crosswind doesn’t push it sideways. Now the plane will be going straight down the runway, with its left wing dipped down, so the left wheel will hit first.
i think given the powerful computers on board them these days, the practically land themselves
I have to think about getting out of here for my lunch break and I’ve only scanned the posts.
Flying magazine asked this question about a year or two ago. They put one of their pilots into a Jumbo simulator. Even though this guy had stacks of hours, he still crashed. The article concluded that even an experienced GA pilot would have a hard time landing a large transport jet.
Of course, I could do it if I had to.* 
[sub]*I have an enormous ego.[/sub] 
This question has been asked before on the boards, and I think the general consensus was no.
Having landed small planes and having been in the cockpit during landings in larger planes, I’ve been amazed at the difference in the sight picture and when pilots start the flare in different planes. Assuming a non-flyer could even get through the approach (doubtful, but possible, I think) to the airport, I’m convinced he’d either not flare at all and prang it in or flare too early. Either way, you’re putting the person in a real bad situation where he’ll probably panic. Even if he keeps calm, he won’t have the necessary experience and judgement to safely control the plane once it hits the runway and comes airborne again, or stalls in a premature flare. Not only won’t you get a nice smooth landing, but my guess is you’ll wind up with a Sioux-City-type cartwheel, and then it’s just luck as to whether anyone walks away or not.
If you add in a nice crosswind, poor visibility, or some type of mech/hydraulic/electrical failure, I doubt he’d ever even get it on the runway.
Just out of curiosity did they just plop a GA pilot in the simulator and let him have at it or did they have someone on the ground (so to speak) talk him through various procedures to get the plane landed?
I keep hearing over and over that the newbie pilot will flare too early or too late. While I agree with the general consensus that a crash is more likely than not is there anything ground control can do to help the poor pilot out? Assuming the pilot doesn’t have to contend with any other weirdness such as crosswinds and the like can’t ground control get the guy on the proper glide slope (flaps set at X, throttles Y, pitch Z and so on) and then tell him when to flare the plane at the appropriate time? Can that even be judged sufficiently from the control tower? The plane might go skipping down the runway but the longer they can keep the plane slowing down and mostly on the ground before cartwheeling or swerving off the runway the better chance those inside will have of surviving (I would think).
I think at 225 mph water at is not as soft as all that. Have you ever seen a racing boat lose control and disintegrate? Plus even if you don’t break up you probably drown.
Would the response to this question from pilots be summed up as, “Surely you can’t be serious,” then? (And as for the GA pilot attempting a jumbo jet landing, they should know it’s an entirely different kind of flying altogether.)
I’ve seen an arcade game that apparently is nothing more than a simulation of landing a large passenger airplane (You take off, the flight lasts 3 seconds, and then you have to land). You don’t have much you need to control (a yoke, maybe rudders but I’m not sure on that, and one button to press when it lights up). I suppose it gives some idea for the feel of the plane, but at the same time there’s little circles on the screen to guide you in.
[Leslie Neilsen] Of course they’re serious. And don’t call them Shirley. [/Leslie Neilsen]
Yes. And don’t call me Shirley.
They should know it’s an entirely different kind of flying!
What is flaring?
Generally speaking, it’s the last phase of the landing before the touchdown and rollout. The technique is slightly different for smaller, prop-driven GA aircraft than for larger, jet- and turboprop-driven aircraft, but it’s raising the nose of the aircraft so that it settles on the main gear first. As I said above, in either case of aircraft, flaring too soon or too quickly raises the aircraft out of ground effect and you start climbing again. Flaring to late or too slowly results in a hard landing at best. As you can probably imagine, proper flare technique is key to successful landings; therefore, I don’t think it would be possible to have a “spotter” telling our hapless passenger-turned-pilot when to flare. He wouldn’t know how to do it properly.
IIRC, there was an instructor in the right seat… But it’s been a while since I read the article.
Flaring is raising the nose prior to landing to reduce your airspeed and rate of descent. When you flare, you’re trading some of your energy (speed) for different energy (lift). If you keep flaring, you will eventually not have enough speed to develop enough lift to stay airborne. The idea is for this to happen as your mains touch the runway. By holding the nose gear up during the roll-out, you are braking the aircraft aerodynamically. (This works better if you retract your flaps.)
Oh Lord! We are screwed harder than we thought. I told you that you were completely screwed before you admitted that you don’t even know what flaring is. I don’t have anything left to give.
Flaring is the transition that a pilot makes from descent down to the runway down to a nice smooth landing. You can’t just down fly onto the runway. Well , you can but will just bounce back up again and then you have got problems because you need to get everything set up for a good landing again very quickly or decide to go around if you are in danger of floating to the end of the runway.
Here is basically how you flare. Smoothly descend down towards the runway on your approach. After you are safely past the runway threshold, cut the power. You are probably about 50 feet high at this point. Keep descending nice and smooth until your rear landing gear is only a foot or two above the runway. Now hold it there by pulling back on the stick or yoke, The plane will slow so you will need to pull back even more. That is fine. When you have slowed enough after just a few seconds, the plane will not want to fly anymore and should gently touch down on its rear landing gear. Continue pulling the stick back to hold the front landing gear off of the runway as long as you can. After a couple of more seconds, it too will touch down and the plane is now firmly planted on the ground. That is how to flare.
Does that affect the aircraft’s center of gravity?
Ok I got flaring down, now if only I can figure out how to turn on those damn thrust reversers. 
Just out of curiosity has there ever been a situation anywhere, anytime that the OP describes?
I can land everything but the 747 in MS Flight Sim - Since I can’t figure out the navigation info, I can never find the airport in time. Without an Interstate highway leading straight to the runway, I’m dead.
Yeah, everything revolves around me!
[sub]Hey, if you can’t poke fun at yourself, who CAN you poke fun at?[/sub]
No there hasn’t because the scenario is very unlikely and it is pretty much impossible to land a 767, a 747, or any large transport jet without very intensive training on that particular plane and hundreds if not thousands of hours of practice. CANNOT BE DONE!
There have been several successful landing in smaller planes but the landing passenger is usually a frequent buddy on flights in that plane. That is very different because the plane is much smaller and the passenger has already sat with the controls between their legs for many hours (most small planes have dual controls for the pilot and passenger/co-pilot). The passenger has usually had a chance to fly the plane before during straight and level flight because the pilot might get tired and let them. There is nothing strange or illegal about that.
I can tell you are just begging to try. Flight Simulator 2002 is actually pretty good at demonstrating this concept. You have to crank up the realism to “full” in all areas to be fair but it should show you how difficult it is and is a pretty good teaching tool for what you want to learn. The program X-Plane is almost perfectly realistic and will let you model your exact scenario the best way any computer can (it is used to virtually test planes by the Department of Defense) but it is not as user-friendly.
I’m just imagining pulling out of my side slip just in time to flare.