Malaysia Airlines Loses Contact With 777 en Route to Beijing

[guamainiac]

Actually the Boeing "struggling to maintain altitude" isn't too far off reality. What glider jocks have called and been taught as "speed to fly" and there is even a "McCreedy Speed Ring" designed to calculate it, is simply a way of taking in all of the factors of lift and sink and trimming to maximize the distance that it's possible to keep the bird in the air.

I'm sure powered aviation has a similar concept and device for pilots to use during engine shut down (Miracle on the Hudson), or fuel starvation.

[Gabriel]

Actually the Boeing "struggling to maintain altitude" isn't too far off reality. What glider jocks have called and been taught as "speed to fly" and there is even a "McCreedy Speed Ring" designed to calculate it, is simply a way of taking in all of the factors of lift and sink and trimming to maximize the distance that it's possible to keep the bird in the air.

I'm sure powered aviation has a similar concept and device for pilots to use during engine shut down (Miracle on the Hudson), or fuel starvation.

I think that "struggle" means "done with dificulty", but done.
A 777 has a special feature called "conservation of energy" that it CANNOT keep altitude when out of fuel. Unless you are lucky wnough to catch a +2000fpm lift, that is. Something quite improbable in the middle of the ocean where there are not thermal differences in the surface nor mountains for "ridge lift".

If you really struggle to keep altitude in this situation you will stall and then NOT keep altitude. But that's just in a 777.

[BlueMax]

Interesting post on PPRUNE by a 777 pilot where, using a full motion simulator they flew 777 until tanks emptied to see results. Starting at FL250, plane dived, RAT engaged so flight displays came alive, picked up speed and then flew back up to FL210 and repeated process again. He described it as series of "phugoid oscillations"

Link to this post is below.

http://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost-432.html#post8407235

[jfojoe]

Interesting post on PPRUNE by a 777 pilot where, using a full motion simulator they flew 777 until tanks emptied to see results. Starting at FL250, plane dived, RAT engaged so flight displays came alive, picked up speed and then flew back up to FL210 and repeated process again. He described it as series of "phugoid oscillations"

Link to this post is below.

http://www.pprune.org/rumours-news/5...ml#post8407235

Thanks BlueMax. Its amazing that the AP can get stable with an engine out, even more so that the stability of the design results in said oscillation. great link. thanks again. What this says to me is that unless a person remained at the helm to perform a miracle ditch, and that if the AC is in the water....that there ought to be flotsam eventually found from breakup. But given that we dont ""yet know" either of those cases...I'm left either looking for the logo'ed plastic cup described earlier or back to one of the conspiracy theories.

[BoeingBobby]

Actually the Boeing "struggling to maintain altitude" isn't too far off reality. What glider jocks have called and been taught as "speed to fly" and there is even a "McCreedy Speed Ring" designed to calculate it, is simply a way of taking in all of the factors of lift and sink and trimming to maximize the distance that it's possible to keep the bird in the air.

I'm sure powered aviation has a similar concept and device for pilots to use during engine shut down (Miracle on the Hudson), or fuel starvation.

Max L/D

[Peter Kesternich]

Speaking of engines and fuel, if one runs out of fuel before the other...does the 77 autopilot have the authority to keep the plane in the air until the other exausts? thanks.

Wouldn't the fuel be cross-fed from one wing to the other under normal circumstances, to ensure that both engines have the same amount of fuel available? In that case, they would both starve within a few moments of each other once all fuel on board is used up and the autopilot authority question becomes moot.

[Peter Kesternich]

Interesting post on PPRUNE by a 777 pilot where, using a full motion simulator they flew 777 until tanks emptied to see results. Starting at FL250, plane dived, RAT engaged so flight displays came alive, picked up speed and then flew back up to FL210 and repeated process again. He described it as series of "phugoid oscillations"

Still - the end of each dive would be lower than the starting point and the plane would eventually end up at ground level/sea level. The only question is what will take the plane farther, the "oscillations" described a bove, or a gentle descent. And actually, the answer doesn't make a big difference in the middle of the Indian Ocean.

[jfojoe]

Hi Peter, thanks for the comment. The train of my question is to eliminate, at least in my mind, a structurally intact water landing such that the debris might be more contained by the intact fuselage and carried down as opposed to a breakup that would lay down far more floating stuff. My uneducated thinking was that maybe the wind-turbine could power the autopilot in such a way that after the 2nd flameout there might be a possibility of a fuselage intact water impact (ie...non tumbling). If the simulator does reflect what the AC would do (does it?) then it seems my idea becomes toast...there would be a breakup on water impact.
To finish my thought...if there were a bad-guy actually working to ensure nothing was ever found....I would think that person would attempt to keep the fuselage intact at the end in order to minimize debris. To my knowledge there is no fact supporting fuel starvation actually happened....so if the goal were that nothing ever be found....when fuel became critically low an attempt at a fuselage-intact ditching would be in order.

[BoeingBobby]

So if the goal were that nothing ever be found....when fuel became critically low an attempt at a fuselage-intact ditching would be in order.

Is that verses putting it in the water at 500+ knots and pretty much breaking up the entire aircraft?

[Peter Kesternich]

Hi Peter, thanks for the comment. The train of my question is to eliminate, at least in my mind, a structurally intact water landing such that the debris might be more contained by the intact fuselage and carried down as opposed to a breakup that would lay down far more floating stuff. (...)
To finish my thought...if there were a bad-guy actually working to ensure nothing was ever found....I would think that person would attempt to keep the fuselage intact at the end in order to minimize debris. To my knowledge there is no fact supporting fuel starvation actually happened....so if the goal were that nothing ever be found....when fuel became critically low an attempt at a fuselage-intact ditching would be in order.

Well - that brings up another question. Let's say you manage to get a 777 down on the ocean surface with minimal damage and with near-empty (i.e. air-filled) wing tanks, then how long would the aircraft stay afloat with all doors closed?

[EconomyClass]

I'm curious. Assuming a plane of this type has any ability to glide, without power how much height does it lose per kilometer of forward motion? I once took a ride in a very light reconnaissance plane, and we pretty much floated in to a landing. They had to minimize all power and depend on the wings to make an accurate landing. There's some sort of equation of weight and lift that determines that (and I won't even attempt it). A jet airliner has to maintain some power to control loss of altitude, right? With no power, how close does it have to be to a useful landing spot?

[Gabriel]

The only question is what will take the plane farther, the "oscillations" described a bove, or a gentle descent.

A constant descent at green-dot speed (best lift-to-drag = best glide angle) will take the plane farther.

[jfojoe]

BoeingBobby...yes. Recovery of flotsam improves chances of the recovery of aircraft, black boxes, evidence of wrongdoing...So if my goal were to have minimum floating stuff...wouldn't I try to keep as much of the cushions, bags, floating parts contained inside an intact as possible in a sunken fuselage?

[Gabriel]

Interesting post on PPRUNE by a 777 pilot where, using a full motion simulator they flew 777 until tanks emptied to see results. Starting at FL250, plane dived, RAT engaged so flight displays came alive, picked up speed and then flew back up to FL210 and repeated process again. He described it as series of "phugoid oscillations"

Link to this post is below.

http://www.pprune.org/rumours-news/5...ml#post8407235

It also answers the question of the single-engine-out. The AP together with the rudder autotrim manage it.

And to this question, also in pprune:

Fascinating - since the net effect was a gradual descent, was it possible to project how far, or for how long, you would have flown in total doing all the phugoid oscillations ?

And also linked to Peter's question.

The 3 to 1 rule comes handy. The plane will go about 3 nautical miles for every 1 thousand feet of altitude. For example, at 33000ft, it will glide some 100 NM. Not enough to reach anywhere from any of the latest search zones.

[Gabriel]

Is that verses putting it in the water at 500+ knots and pretty much breaking up the entire aircraft?

Well, I think that managing to ditch and sink the plane laregely intact (re: Hudson) will guranatee that everything will sink together. Honeycomb bulkhead and seats would remain attached even of the fusealge is breached at depth.

On the other hand, a nearly vertical dive at nearly the speed of sound will leave thousands of debris floating on the surface, albeit few if any more than an inch long, what would make them very diffcult to spot.

Both strategies have their risks.