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Not necessarily, I try to put myself in the cockpit and imagine this:
Lose engines, lose generators. Lose generators lose hydraulics. I have been out of aviation a long time and dont have experience with this aircraft but if partially or completely fly by wire, you lose all that too.
So, on battery power, there is the radio , an MCDP that illuminates everything that has failed, horns, aural warnings blaring, a standby attitude indicator that is doing things that would nauseate anyone on an x box in their living room, let alone a real situation like this, and they are being tossed violently by a thunderstorm with no engines and no electrics in the dark.
I dont know about you, but sending out a distress call would be secondary to saving my behind. I know the flight data and voice recorders will let the world know what happened if I failed.
personally, I think flame outs are pretty catastrophic.
It would be a chaotic onslaught of failures and ECAM messages requiring cool nerves and practiced CRM discipline, but a dual engine flameout would not deprive you of essential hydraulics or power. First, the APU would come online. If that failed as well you would have the RAT, which is actually a backup hydraulic pump that also drives an auxiliary electrical generator. If you lost the RAT somehow you would still have direct law FBW functionality on battery as well as left seat displays but of course no hydraulics. Without any hydraulics you would have mechanical rudder linkage for yaw and roll and manual stabilizer trim for pitch. But you are never going to get there because losing both engines, the APU and the RAT are never going to happen unless you are also losing parts of the aircraft in a very hopeless scenario.
The real danger is lack of practice with piloting the aircraft in a degraded condition and a lack of practiced CRM leading to task overload, disorientation and panic.
(edit: sorry Gabriel, I guess we were posting at the same time)
There have been several cases of losing all engines that were not so catastrophic, including the miracle of the Hudson and the AirTran glider to mention two notable cases that were FBW.
If memory serves, Sully did not lose the engines, just the effective thrust, so I think he still had main generators and hydraulics.
If [the APU] failed as well you would have the RAT, which is actually a backup hydraulic pump that also drives an auxiliary electrical generator. If you lost the RAT somehow you would still have direct law FBW functionality on battery as well as left seat displays but of course no hydraulics.
What's "FBW functionality without hydraulics"?
The plane saying "If I had hydro power, in response to your stick input I would move the ailerons like this and the elevator like that"?
Without any hydraulics you would have mechanical rudder linkage for yaw and roll and manual stabilizer trim for pitch.
Hmmm.... Double check that Evan. I'm quite sure that both the manual trim and the rudder require hydro power. No hydro? No control whatsoever. Even if you have all engines, the APU and the RAT all working perfectly.
But you are never going to get there because losing both engines, the APU and the RAT are never going to happen unless you are also losing parts of the aircraft in a very hopeless scenario.
A single failure can get rid of most of these systems at once: run out of fuel and you've lost all engines and the APU. Now all your bets are on the RAT. Lose that and Newton has the plane.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
What's "FBW functionality without hydraulics"?
The plane saying "If I had hydro power, in response to your stick input I would move the ailerons like this and the elevator like that"?
It means that the essential FBW systems are still alive. But yes, of limited use using accumulator reserves until you can restore hydraulics. The aircraft is still controllable with the stab trim and rudder but it is not intended to land this way, just to provide time to restore the lost systems. But this is never going to happen to an aircraft that is not in catastrophic shape.
Hmmm.... Double check that Evan. I'm quite sure that both the manual trim and the rudder require hydro power. No hydro? No control whatsoever. Even if you have all engines, the APU and the RAT all working perfectly.
You've lost the hydraulic pumps but not the fluid. You still have some hydraulic pressure in the accumulators to move the control surfaces for a short time. But again... this is never going to happen to an aircraft that is not in catastrophic shape. And remember, the RAT IS a hydraulic pump.
A single failure can get rid of most of these systems at once: run out of fuel and you've lost all engines and the APU. Now all your bets are on the RAT. Lose that and Newton has the plane.
Not true, you can still fly it but landing is a risky proposition. But in what zilliion-to-one scenario do you lose the engines, the APU and the RAT?
Pangkalanbun: Recovery crews believe they have found part of the wreckage of the downed AirAsia jet in 29 metres of water.
The news is a major breakthrough and came late on Friday night, just as authorities were beginning to worry that the wreck would break up in strong undersea currents.
The commander of the Indonesian navy ship Banda Aceh confirmed the find, saying it had come both from sonar on board an Indonesian ship, the Bung Tomo, and the American USS Sampson. The two ships recorded similar but slightly different sites.
It's believed to be about 23 metres long, and crews "strongly suspect it's the tail part of the plane", according to a report in Tempo online.
The find means that, for the first time, a combined crew of 67 navy and search and rescue agency divers will be able to descend to begin organising a search — with some teams focusing on the "black box" flight recorder and others searching for victims.
I know. I was thinking in a scenario like United DC-10 in Sioux City, JAL 747, or the A310 of a cargo company in Iraq. All of them lost all hydro fluid. The AA DC-10 that crashed out of O'Hare did so before losing all hydraulics. One system had totally depleted and the other two were leaking.
Not true, you can still fly it but landing is a risky proposition.
Risky? Unless you don't touch the controls during the now uncontrolled descent, you'll have no hydro pressure in the accumulators by when you reach the ground.
But in what zilliion-to-one scenario do you lose the engines, the APU and the RAT?
I've already said this: It takes two independent failures: Fuel and RAT. You run out of fuel and having 19 engines and 14 APUs will not help. You depend on the RAT.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
There have been several cases of losing all engines that were not so catastrophic, including the miracle of the Hudson and the AirTran glider to mention two notable cases that were FBW. Sully could start the APU, the AirTran pilots not because the reason of the failure was precisely fuel exhaustion.
I wonder how much the pressure in the accumulators will last. My guess is about nothing.
[...]
I've already said this: It takes two independent failures: Fuel and RAT. You run out of fuel and having 19 engines and 14 APUs will not help. You depend on the RAT.
In any case the RAT powered EMER GEN isn't really generating power below 100-140kts but is providing some hydraulic pressure all the way down. When the EMER GEN is lost the static inverter transfers battery DC to the AC Essential bus. Flight control is preserved via the HOT busses. But I think that the blue electric hydraulic pump is only powered by the NORM AC bus.
So, if you lose all turbine power and the RAT you apparently have little (residual pressure) or no flight control actuation. At that point you have defeated three levels of redundancy.
Level 1: You lose Engine 1 ~ You have Engine 2
Level 2: You lose Engine 2 ~ You have the APU
Level 3: You lose the APU ~ You have the EMER GEN (RAT + BLUE SYS)
Level 4: You lose the RAT ~ You still have flight control systems and whatever residual power is left in the accumulators.
In 23 years of service no Airbus FBW aircraft has ever got to Level 4. There is therefore very little documentation describing the functionality of it. Everything I wrote above is deduced from FCOM bus lists and system schematics but I suspect there is more to the story.
However, AFAIK this loss of flight control is true of all Boeings as well. The 737 has two main hydraulic systems plus a dedicated system for the rudder but still requires AC power to pressurize it. The rest have a triplex hydraulic system somewhat like the A320. In all cases, no AC power=no hydraulic pumps=no flight control. Both FBW and traditional mechanical linkage control require hydraulics to move flight surfaces due to the enormous forces required.
The A380 uses Electric Backup Hydrostatic Actuators (EBHA) that are independent of the hydraulic systems. This allowed them to eliminate the blue system for redundancy. I assume the A350 also has this architecture. This is known as Power By WIre. You might find this interesting:
Hmm. Apparently the airline has had this route suspended by the authorities as they didn't actually have permission to fly it on the day of the accident.
Originally posted by http://www.bbc.co.uk/news/world-asia-30658877
In another development, it has emerged that AirAsia did not have official permission to fly the Surabaya-Singapore route on Sunday - the day of the crash - but was licensed on four other days of the week.
The Indonesian authorities are suspending the company's flights on this route with immediate effect pending an investigation, a transport ministry statement said.
No doubt that will cause some legal and financial wrangling if insurers/government/whoever use that to get out of paying compensation?
A bit strange though that an airline can fly a route between two major airports without anyone checking or noticing that they didn't have permission to do so.
EDIT: In any case the RAT isn't really generating power below 100-140kts but is providing some hydraulic pressure all the way down. When the EMER GEN is lost the static inverter transfers battery DC to the AC Essential bus. Flight control is preserved via the HOT busses. But I think that the blue electric hydraulic pump is only powered by the NORM AC bus.
I think that maybe the yellow system has an electric pump that can be operated on the battery. It also has a manual pump (to open the cargo doors when the plane is "cold and dark"), but I very much doubt that you can have enough "manual power" to power the flight controls, if such pump is accessible from the inside at all.
The yellow system is the primary source just for one spoiler in per wing, but also provides backup power to one elevator, the horiz stab, other 3 spoilers per wing, and I don't know the rudder.
However, AFAIK this loss of flight control is true of all Boeings as well. The 737 has two main hydraulic systems plus a dedicated system for the rudder but still requires AC power to pressurize it.
I think that the B737 was fly-by-cable in the 100 and 200 versions and became hydraulic since the 300 but it retains a manual reversion with cables.
That's why the 373 doesn't have a RAT (I think).
In all cases, no AC power=no hydraulic pumps=no flight control. Both FBW and traditional mechanical linkage control require hydraulics to move flight surfaces due to the enormous forces required.
Not sure what you mean with "traditional linkage".
With some very notable exception (that I don't even remember), all hydraulic controls in airplanes are full hydraulic controls, meaning that the hydraulic provides all the power and the control. In the conventional control airplanes with hydraulic controls, the pilot just move hydro valves. Yes, the 747 has an array of cables and pulleys that go from the cockpit to the control surface (nearby in fact), but that's to put the hydraulic control valves close to the control surface and avoid routing hydro pipes all around the plane (cables are easier, especially these ones that handle a very small force, just to move a valve). In the FBW the steel cable is replaced by an electric wire that sends signals to said valve. In other words, in both cases there is NO mechanical linkage between the control surface and the yoke. If a DC-10 looses all the hydro power, the pilot can freely move the yoke all around. He will still even feel the "control forces" (which is done by an artificial feel system, although I don't know if it depends on hyro too), but full deflection of the yoke will translate in nothing in the control surface. This is different from a "hydraulically ASSISTED" system, like the steering wheel of your average car, that is mechanically linked to the direction mechanism and the hydro power relieves the force needed to operate it, but if you lose the hydro you can still operate it (with much more effort).
Smaller planes (but still airliners jets) used to have real mechanical linkage.
These days most planes are going hydraulics (even some small bizjets), in some cases because they are being fitted with FBW.
In a fully mechanical system the "hinge moments" are big, yes, but this is offset by using "servo tabs". Servo tabs are small control surfaces in the trailing edge of the main control surface that is mechanically liked to the airframe so as it's movement is opposite of that of the control surface.
For example, if you pull the elevator up, there will be a big aerodynamic force trying to push it back down. However, this force will act more or less near to the hinge. The servo tab will move in the opposite direction, and there will be an upward aerodynamic force on it. While this force is much smaller than the one on the elevator, it's acting very far from the hinge and hence produce a relatively large moment that partially compensates the moment of the force of the force in the elevator. You don't want to fully cancel it. What's left is the part that the pilot has to put, which is also his feedback so while you don't want the control forces to be too hard, you don't want the m too light either. In any event, you can design the servo tabs so as the control forces are what you want.
This servo tabs concept was taken to the extreme in some planes like the MD-80 (and others), where the pilot actually only moves the servo tab (now called control tab), and the servo tab provides the hinge moment to move the main control surface. It's the same concept than the trim tab in small planes like the Cessna 172, only that linked to the yoke not the trim wheel. I call this "aerodynamically powered controls). In these planes, the controls are not linked to the main control surface. Moving the yoke on the ground, for example, moves the control tabs but not the control surface because there is no aerodynamic force acting on the tab. This generates the "odd looking" split-elevator many times seen on MD-80s on the ground (each elevator has its own servo tab and they are not mechanically lined one to the other so if one jams the other keeps working. Only the aerodynamic force, not available when parked on the ground, keep them "aligned"). It also produces the scaring (well, it scared me once before I knew this) "full aileron during the take-off run" sight from the passenger window. Of course the pilots have the yoke centered, but until there is enough speed to "float" the elevators to center they remain at whatever position they were.
These two kind of planes with mechanical linkage (controlling the main control surface or the control tab) don't need any hydro power to be flown. While in some cases they have hydro power to boost the manual system, the plane is still flyable without it.
For example, the the MD-80 has two hydraulic systems. One of them is powered by the engine pump and a backup electric pump (only with AC, not from battery). The other one is powered by the other engine's pump and a one-way pressure transfer pump powered by the first system. There is no APU-driven hydro pump (although the APU can provide electric power for the electric pump) and there is no RAT. A you see, not a very redundant design.
The hydro is used for the rudder, the landing gear, brakes, nose wheel steering, flaps/slats and spoilers. Also for elevator boost when pushing all the way nose down (that's to help recover from a stall, where the elevator can be floating up regardless of the control tabs position).
So if you lose both hydros, you still have normal ailerons (but no roll spoilers) and normal elevator. No rudder, but that's not so important. No flaps or slats (it will be a fast landing, as a comparison the 737 has backup electric actuators), no nosewheel steering (and no rudder, so challenging lateral control on the landing roll, use differential brakes). you have brakes with a specific brakes hydro pressure accumulator (actuate the brakes only once and keep them, don't pump on them or you'll lose the pressure, don't use antiskid for the same reason, and keep differential braking at minimum, when you stop call for the tow truck). Landing gear must use the alternate extension (and the doors will drag on the runway).
Not nice but still safe.
By the way, returning to the A320, I do realize that loosing all three hydro system is highly unlikely to the point that it never happened. Today, even a scenario like the United DC-10 at Sioux City is almost impossible because after that accident the certification was upgraded to require automatic shutoff valves to isolate damaged parts of the hydro system, so all the fluid is not lost and the system can keep feeding the good parts of the plane (in this DC-10 case I don't know what would have been available on the tail). A "run out of fuel" (that would kill all and any engines and APUs at once) is rare enough. So you need a very very bad luck to have a RAT failure in the same flight (although the reliability of the RAT is hard to judge because it's almost never used).
I just meant to say that, while extremely unlikely, it's not so unlikely as it looks when you say "you have to lose one engine, and then the other engine, and then the APU and then the RAT". The first three can and has happened (more than once) at once for one single (and unlikely) reason.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
Hmm. Apparently the airline has had this route suspended by the authorities as they didn't actually have permission to fly it on the day of the accident.
No doubt that will cause some legal and financial wrangling if insurers/government/whoever use that to get out of paying compensation?
A bit strange though that an airline can fly a route between two major airports without anyone checking or noticing that they didn't have permission to do so.
It doesn't seem to be a technical measure. Rather an administrative (market regulation) measure. I can't imagine why an airline is safe to fly one route on tuesdays but not on sundays.
Because of that, I doubt that the victims, the government, the justice or whoever can use that against the airline in terms of liability or responsibility regarding the accident.
But I do see the insurer denying to cover the airline for liability for damages during an illegal flight. That could be a major problem for the continuity of AirAsia, if the accident alone wasn't enough.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
Hi I'm no expert but I've been examining all the information so far and I'm surprised why no real "experts" have been discussing the possibility of some sort of mid-air breakup or explosion of the plane. We have seen nude bodies, bodies still strapped in their seats, and there's also reports of pieces of wreckage seen scattered on an island. This all seems very similar to China Airlines 611, which was a mid air structural failure. Just wondering why there's been very few discussion of such a possibility and why instead people keep focusing on the AF447 stall scenario.
Hi I'm no expert but I've been examining all the information so far and I'm surprised why no real "experts" have been discussing the possibility of some sort of mid-air breakup or explosion of the plane. We have seen nude bodies, bodies still strapped in their seats, and there's also reports of pieces of wreckage seen scattered on an island. This all seems very similar to China Airlines 611, which was a mid air structural failure. Just wondering why there's been very few discussion of such a possibility and why instead people keep focusing on the AF447 stall scenario.
Because:
1- Most of the things you mention are neither confirmed nor reliable info (some of them have even been denied), and
2- The "real experts" don't go about speculating with no factual info.
With the RELIABLE info known so far, about anything is possible (stall and in flight break up among many others).
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
I think that maybe the yellow system has an electric pump that can be operated on the battery. It also has a manual pump (to open the cargo doors when the plane is "cold and dark"), but I very much doubt that you can have enough "manual power" to power the flight controls, if such pump is accessible from the inside at all.
Naw, that pump is also on the AC NORM bus. The blue system is the designated 'emergency' system with the RAT. The yellow system can feed the green system (driving the other elevator, etc.) via the PTU. The yellow system hand pump is in the main gear fairing so that would be quite a feat in the air.
Not sure what you mean with "traditional linkage".
Conventional mechanical linkage. I guess 'traditional' wasn't the right word. I am referring to modern aircraft, so the NG's, not the classics or the MD's. The 737NG has no manual rudder reversion.
Did you check out the links at the bottom? I think Power By WIre is the new solution.
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