Air France 447 - On topic only!

[Black Ram]

Are you kidding?
To begin with, it's not FBW. You can program anything into FBW. It's someone's approach to FBW.

No, it's a serious question. I know the airbus load factor flight control system goes into flare mode under 100ft, where pitch control becomes more direct. But what about lateral control? If you've set the wings level and haven't moved the sidestick left or right, would the plane self-adjust to keep the wings where they are? Or does it keep the heading and adjust roll.

Second, the pilot was fighting with the kidnappers.

If that's the reason they hit the water in a left bank, ok.

Or do you think that keeping the wings level is a difficult task in a non-FBW plane?

I don't necessarily think that, I'm just thinking of that extreme and wobbly 727 landing. The Hudson A320 was also on the limit of stall, but didn't wobble. That's the only thing I'm thinking. FBW planes just seem so efficient and precise when executing a maneuver.

[Black Ram]

http://www.youtube.com/watch?v=uTgx0dZ-BAg

http://www.youtube.com/watch?v=PWl0TygaeDw

I hope this helps answering your question.

Actually, it is kind of confusing. They were landing in a crosswind, gustign past the max demonstrated for the a320. Apparently, as for lateral control, ground mode had activated when the left wheel touched down. I don't know what she was doing with the controls, this crabbing and uncrabbing in pretty extreme weather, after all. Probably lots of rudder.

[Gabriel]

AFAIK, lateral control law response to sidestick is roll rate demand.

That means, leaving the sidestick centered means zero roll rate. If an atmospheric disturbance tries to roll the plane, the FBW logic will fight it and try to cancel any induced roll rate. But of course this can't be perfect: by when the sensors detect that the plane is rolling, well, it is already rolling, so the FBW will command as necessary to restore zero roll, but whatever bank is left at this point would remain until there is a pilot input to correct for it (I am of course assuming AP off).

Unless there is something else into the FBW logic that I don't kow, as a "memory" of target bank (what the bank was the last time the pilot centered the sidestick).

[Black Ram]

Check this out:

"The flight data recorder showed, that the airplane started to drift to the left of the runway centerline at 75 feet AGL, to which the first officer reacted by applying right hand sidestick input turning the airplane 10 degrees to the right, reducing the side stick pressure at 50 feet AGL and now applying left hand pressure, at the same time the rudder pedals were moved 28 degrees to the left (align) within the next 5 seconds. The captain applied 4.5 degrees right side stick input at 15 feet AGL, the first officer now also changed her control input from left to the right. The airplane subsequently touched down with the left hand main gear at a roll angle of 4 degrees to the left and got airborne again. The roll angle increased to 23 degrees to the left, first officer and captain each now pushing their side sticks full right, the rudder pedals changed to 14 degrees right. The left hand main gear touched down a second time 2 seconds at a roll angle of 23 degrees and 1.5 degrees nose up pitch at a speed of 144 KIAS. The first officer advanced both thrust levers to TOGA and initiated the go-around, the captain pressed the override button 7 seconds after the first touch down.

Airbus said, that the contact of the left hand wing tip with the ground could have been avoided, if the side stick had been moved to the right earlier. Had the sidestick movement to the right, conducted by the first officer, been applied 1.5 seconds earlier in the present conditions, the left hand bangle would have been limited to 10 degrees (instead of 23 degrees)".

http://avherald.com/h?article=42826d3a

[Leftseat86]

I think you are exaggerating. The "stick and rudder" part of the equation was not tough. I mean, it's quite easy to keep a plane gliding above stall speed, level off a few feet above a plain surface, and smoothly let it mush on it.

Specific gliding skills like holding the best glide speed, taking most out of thermals or other lifting air, planning a glide to reach a specific point on the ground, etc were not applicable here. The Hudson was ling enough and free of obstacles enough that the touchdown point could have been a few miles short or long from the actual touchdown point, and several hundred feet to the sides.

I mean, what would have a "regular", non- "best-in-class Air Force glider pilot", would have done? Pull up and let it stall? (ok, the Airbus itself would have not allowed this) Not flare and dig the nose into the water? Land in a bank to dig a wingtip? Miss the river and land on the ground? Hit a bridge? Avoiding these things are quite easy even for an average pilot.

Try to go for Teterboro? Who knows. I think the fact that he was a seasoned glider pilot must have helped the split second decision required. He knew very quickly that the Hudson represented his best option. I'm not sure other pilots would have been able to deduce that so fast. Given that they missed a bridge by 300ft I'm not really sure I agree with your assessment of the Hudson being an easy choice either.

And then, the "rudder skills" part was not the best of Sully's performance, as he run out of airspeed to soon and too high, making a somehow hard touchdown instead of "skimming" the water.

The moment of truth in this accident was when Sully said "We will be in the Hudson". As himself said in an interview: "The Hudson was the only surface long enough, wide enough and smooth enough that I knew I could reach".

He had three nearby airports, simulations have shown that one of them within reach (barely) and the other two not. But he didn't have this piece of information up there. He might have thought (and he probably did) "I may reach one of them". When you face an emergency, having three airports nearby that may be within reach is a big temptation. You can save the airplane landing there.

And I would expect a not small fraction of the pilots trying to reach one of them because they thought they may reach it. Instead, Sully went for the sure thing, for a hard but survivable place that he knew he could reach. Tough but good decision.

Indeed, and I think the fact that he was such an experienced glider pilot must have had a bit to do with making that decision so quickly. I'm not saying he demonstrated any particularly crazy skills with the actual piloting of the aircraft, or trying to exaggerate in this respect, but I think my point stands, if any pilot would have been suited to their jetliner turning into a massive engine-less glider, he was up there...

[Deadstick]

Check this out:

"The flight data recorder showed, that the airplane started to drift to the left of the runway centerline at 75 feet AGL, to which the first officer reacted by applying right hand sidestick input turning the airplane 10 degrees to the right, reducing the side stick pressure at 50 feet AGL and now applying left hand pressure, at the same time the rudder pedals were moved 28 degrees to the left (align) within the next 5 seconds. The captain applied 4.5 degrees right side stick input at 15 feet AGL, the first officer now also changed her control input from left to the right. The airplane subsequently touched down with the left hand main gear at a roll angle of 4 degrees to the left and got airborne again. The roll angle increased to 23 degrees to the left, first officer and captain each now pushing their side sticks full right, the rudder pedals changed to 14 degrees right. The left hand main gear touched down a second time 2 seconds at a roll angle of 23 degrees and 1.5 degrees nose up pitch at a speed of 144 KIAS. The first officer advanced both thrust levers to TOGA and initiated the go-around, the captain pressed the override button 7 seconds after the first touch down.

Airbus said, that the contact of the left hand wing tip with the ground could have been avoided, if the side stick had been moved to the right earlier. Had the sidestick movement to the right, conducted by the first officer, been applied 1.5 seconds earlier in the present conditions, the left hand bangle would have been limited to 10 degrees (instead of 23 degrees)".

http://avherald.com/h?article=42826d3a

This sounds like some seriously fucked up cockpit management. Two people flying the plane at the same time? What happened to "it's my airplane?" This is like the automation they're putting into cars these days with auto braking and other programs. I want to drive my car myself, and I would want to fly my airplane myself without being restricted as to what I know needs to be done.

[Deadstick]

Try to go for Teterboro? Who knows. I think the fact that he was a seasoned glider pilot must have helped the split second decision required. He knew very quickly that the Hudson represented his best option. I'm not sure other pilots would have been able to deduce that so fast. Given that they missed a bridge by 300ft I'm not really sure I agree with your assessment of the Hudson being an easy choice either.



Indeed, and I think the fact that he was such an experienced glider pilot must have had a bit to do with making that decision so quickly. I'm not saying he demonstrated any particularly crazy skills with the actual piloting of the aircraft, or trying to exaggerate in this respect, but I think my point stands, if any pilot would have been suited to their jetliner turning into a massive engine-less glider, he was up there...

I was a 300 hour glider pilot before I took my first lesson in SEL. It drove my instructor nuts that he couldn't shake me with a simulated engine failure. Having gliding experience is a huge advantage in a power out situation.

[Gabriel]

I don't deny that flying gliders have a special skill. I know for fact that the average glider pilot is much more precise than the average Cessna (or Pipper) pilot. But I don't think that spilt-second is one of those special skills that glider pilots get.

Look again at link in the post #2409. Those are a lot of gliding & ditching accident, to which we could sum several gliding (non-ditching) more.

I bet that most of those pilots (including most of those that took the plane to a successful outcome) were not glider pilots.

I think that the ability to remain calm, assess the data available, and make a rational decision is independent of the glider experience. Maybe his involvement with the Air Force, his big experience and his age had more to do with it. But we must take into account the individual personality and ability to manage stress, and why not a bit of luck and an moment of brilliance.

[Leftseat86]

Alright, I'll concede as much, but you can't say that him being a seasoned glider pilot couldn't have helped! :P

[3WE]

I was a 300 hour glider pilot before I took my first lesson in SEL. It drove my instructor nuts that he couldn't shake me with a simulated engine failure. Having gliding experience is a huge advantage in a power out situation.

The transition from something that has a great glide ratio to something that had an 'average' ratio strikes me as very very interesting.

Was it a quick mental recalibration to the gliding abilities, or is it more that you are a pro at visualizing your glide, and then arriving at a good place for a nice, proper, reasonable dive (with brakes) down to a landing.

[Gabriel]

Alright, I'll concede as much, but you can't say that him being a seasoned glider pilot couldn't have helped! :P

Deal!

Even more, I have great sympathy and admiration for glider pilots that spend 5% of their flying time in close-formation flight and the remaining 95% in what for us would be an emergency!

I did just one flight in a glider (with an instructor) and I was horrible in the tow part (definitively I would have not wanted to be the tow pilot of that flight), I almost vomit during the tow (the instuctor who, given my performance, had the controls during most of the tow, was making a lot of short but brisk corrections to keep the glider in the exact position and that upset my stomach), and while I was quite good during the free flight part, my coordination was less than perfect and there was some movement of the ball (with the instructor the ball seemed to be glued to the tube).

In another case where I took a glider pilot to fly with me in the Tomahawk, despite him having never flown this type and having minimum experience in anything powered, he showed extreme precision in coordination, keeping airspeed, an keeping a very stable path for example during the approach: we made a long final and at the very beginning of it he adjusted the power to keep the desired speed and glidepath, and no further adjustments of power or glidepath were needed for the remaining of the approach and the airspeed remained nailed at 70 until the flare.

So in both cases I was amazed (nearly humiliated) with the precision of these glider pilots, but precision was not a critical skill in the Hudson case. Effectiveness was by far more important than efficiency, if you get what I mean. Don't stall, don't hit any obstacles, keep a good airspeed to have enough reserve energy for the flare, keep the wings level, and skim the water with minimum forward and vertical speed. In my opinion, Sully was good enough in that part (maybe barely), and brilliant in his decision making and managing of the emergency as a whole.

[Gabriel]

The transition from something that has a great glide ratio to something that had an 'average' ratio strikes me as very very interesting.

Was it a quick mental recalibration to the gliding abilities, or is it more that you are a pro at visualizing your glide, and then arriving at a good place for a nice, proper, reasonable dive (with brakes) down to a landing.

Hehe... yes, best glide in the Tomahawk is like a dive with full spoilers in a glider: 70 knots and some -600fpm, for an L/D of some 12:1.

[Deadstick]

The transition from something that has a great glide ratio to something that had an 'average' ratio strikes me as very very interesting.

Was it a quick mental recalibration to the gliding abilities, or is it more that you are a pro at visualizing your glide, and then arriving at a good place for a nice, proper, reasonable dive (with brakes) down to a landing.

The best way I can describe it is you "just feel it." I never flew high performance gliders. Mostly Schweitzer 1-26's and Blaniks, so having a huge L/D was not something I had to transition from going into power off 152's. I once had a biennial where the instructor was so frustrated with my failure to panic over pulling the power that he pulled the mixture, raised the nose and put us into an over the top right spin entry then said "your airplane." (We were required to demonstrate right and left three turn spins in our glider club before we could solo) So I recovered from the spin and asked him what he'd like me to do with the dead engine. We were at 5000 feet over the Ramona CA airport and he said "land it." I said "deadstick?" (Hence my screen name) and he said no, go ahead and restart but don't use any power. So I put it on the numbers with the engine idling.

You watch your airspeed and sink rate and mentally calculate your pattern. After 300 hours of never going around you get pretty good at it.

[Gabriel]

After 300 hours of never going around you get pretty good at it.

Yea, sure. But how many landings short of the runway, long of the runway, or off airport, that you would have gone around if only you had been able to?

[Deadstick]

Yea, sure. But how many landings short of the runway, long of the runway, or off airport, that you would have gone around if only you had been able to?

Two off airport landings that were intentional. (Competition flights, knowing you wouldn't make the airport but getting more points for getting closer and knowing good places to put down enroute.) None long or short of a runway.