5 ms·

> (there is no direct link between the stick/yoke and the flight surfaces) Almost true and oft-repeated. There are still means to somewhat control most FBW air

> (there is no direct link between the stick/yoke and the flight surfaces) Almost true and oft-repeated. There are still means to somewhat control most FBW aircraft in the unlikely event all electrical control is lost; A320 can pitch/yaw with mechanical linkage to stabilizer trim and the rudder, for example (but, to your point, neither involve the sidestick). The flight is very likely headed for an unpleasant end but the intent is to buy time to restore computer control. Landing with trim, rudder, and differential thrust alone is possible (some have landed with less), but it's a big ask for a pilot accustomed to automation. That scenario aside, when a whole lot of things fail an Airbus can also go into a mode called Direct Law, which basically tells the computer to take a hike and puts the pilot in direct control of surfaces proportional to airspeed (and puts structural integrity in jeopardy, because the computer isn't helping to obey design limits). The aircraft is extremely sensitive in this configuration. (If you saw Sully recently, one of the reasons he quickly started the APU was to prevent the aircraft from leaving the relative safety of Normal Law in the absence of electrical power. This was described in the report, if I recall, and was one of the more critical decisions made.) Boeing is entirely different in FBW philosophy from Airbus. A coarse summary might be that Airbus drivers are negotiating with a computer while Boeing drivers are generally flying the airplane. Both have merits and drawbacks and vocal camps.

JshWright 10y ago
> Almost true and oft-repeated. There are still means to somewhat control most FBW aircraft in the unlikely event all electrical control is lost; A320 can pitch/yaw with mechanical linkage to stabilizer trim and the rudder, for example (but, to your point, neither involve the sidestick). Yeah, that's why I was specific about the stick/yoke connection. Though, after some research, it appears I was wrong about that as well (as least in the case of Embraer). In the 190, the ailerons are, effectively, directly controlled (there is a hydraulic system in line, but it is directly actuated by cables from the yoke). I was unable to find any conclusive details about the Phenom 300 after a cursory search, but it appears it is "fully" FBW. > Boeing is entirely different in FBW philosophy from Airbus. A coarse summary might be that Airbus drivers are negotiating with a computer while Boeing drivers are generally flying the airplane. Both have merits and drawbacks and vocal camps. Yeah, and both sides can point to major incidents that wouldn't have happened in the other cockpit.
- throwanem 10y ago
  I know of Air France 447 in the "fly the airplane" camp. (An inexperienced copilot stalled the aircraft all the way from cruise altitude to impact, and because the sidesticks aren't linked, no one else could tell that was what was wrong.) What's a good example in the "negotiate with the computer" camp? Perhaps it's merely a tendency on my part, but I don't think I have run across any accident which militates as strongly in favor of Airbus's design as AF 447 seems to militate against it.
  - rockdoe 10y ago
    AA 587, which ironically happened on an early model Airbus before they went FBW. Your perspective will influence how you classify the accidents. Proponents of full FBW will argue AF 447 happened exactly because part of the FBW system was disabled.
  - pedrocr 10y ago
    >I don't think I have run across any accident which militates as strongly in favor of Airbus's design as AF 447 seems to militate against it. The references I've seen to advantages tend to be more subtle than the AF447 tragedy. Things like the Hudson river landing where in that strange situation where you have no power the workload was diminished by having the computer keep the airplane flying most efficiently and thus be able to reach the river instead of crashing by losing airspeed. It also makes sense the advantages are less obvious as the flight envelope protection actively prohibits dangerous situations and you can't report on non-events. The stats also show Boeing and Airbus airplanes pretty evenly matched on safety.
  - TuxerLulz 10y ago
    AF447 is more complicated than just that sidestick issue, if you look at the accident report closely. The contributing factors were loss of outside air temperature and airspeed sensors because of icing, a dark moonless night above the ocean, and flying/falling outside of the operating range of the stall horn (when they pitched the nose down, they started recovering from the stall, airspeed went up, and the stall horn activated. when they pitched up, they went back outside of the operating range, and the horn muted). A big contributing factor as well was that in an airbus, in normal operating conditions, pulling the stick all the way back will configure the aircraft for the best rate of climb (which can be different from just putting the elevator in full climb conditions). Due to the pitot tubes being iced up, the flight computers were in Direct mode (where movement of the sidestick is directly translated in movement of the flight controls, without computer intervention), which didn't help.
userbinator 10y ago
The Boeing 737 is still controllable with no electric or hydraulic operation, since the yoke and rudder are linked with cables to the control surfaces. From what I understand the hydraulics also provide power assist, so it might not be too dissimilar to driving a car without power steering or brakes when that happens. Scenes in movies of pilots physically struggling with the plane are not as unrealistic as they may seem.
- jsmthrowaway 10y ago
  They're not, and you're right. You're literally pulling or pushing a lot of control surface against a lot of fast-moving air, and it doesn't want to go there. There were many inaccuracies in the opening drama of Flight, but the yokes beating the shit out of the crew was quite believable given the scenario.
sgnelson 10y ago
For those who want to know a bit more about a few of these topics, I found this article via HN discussing the role computers, fly by wire, and a lack of training had in the AirFrance 447 crash. Found the article quite interesting. http://www.vanityfair.com/news/business/2014/10/air-france-flight-447-crash http://www.vanityfair.com/news/business/2014/10/air-france-f...
hackuser 10y ago
> A coarse summary might be that Airbus drivers are negotiating with a computer while Boeing drivers are generally flying the airplane. Would you mind taking a moment to spell out what these statements mean to a non-pilot? (For example, I expect that Airbus pilots still operate controls which affect the movement of the airplane; they aren't typing parameters into a computer. And I expect Boeing pilot's actions are still mediated by a computer.)
- jsmthrowaway 10y ago
  Sure. On all FBW systems there's a computer in between the pilot's appendages and the wiggly parts built into the airplane that control its orientation (roll, pitch, yaw, what have you). Airbus systems position the pilot as a suggestive force. At any given time the computer has its idea of what's happening and the pilot influences this calculus within safety tolerances for various bad things that happen to airplanes. One example is a stall, which results from a variety of factors including excessive pitch of the wing against the oncoming air (called angle of attack -- think about tilting your hand back when holding it out of the car and it dropping back on you. that's a stall). Airbus computers typically prevent the pilot from introducing the situation by dampening, modifying, or outright ignoring control input to avoid critical angles of attack. That's one example. Basically, without going alternate law, the Airbus computer will work to make it very hard (not impossible, obviously) to apply control input that would place the flight in jeopardy. Boeing would allow the input and mostly permit the pilot to introduce the situation. That's the difference. They treat the pilot as the end of authority in command. That has compelling merits. So does Airbus. As JshWright said, both sides have incidents on the other they can point to as supporting data.

JshWright 10y ago

> Almost true and oft-repeated. There are still means to somewhat control most FBW aircraft in the unlikely event all electrical control is lost; A320 can pitch/yaw with mechanical linkage to stabilizer trim and the rudder, for example (but, to your point, neither involve the sidestick). Yeah, that's why I was specific about the stick/yoke connection. Though, after some research, it appears I was wrong about that as well (as least in the case of Embraer). In the 190, the ailerons are, effectively, directly controlled (there is a hydraulic system in line, but it is directly actuated by cables from the yoke). I was unable to find any conclusive details about the Phenom 300 after a cursory search, but it appears it is "fully" FBW. > Boeing is entirely different in FBW philosophy from Airbus. A coarse summary might be that Airbus drivers are negotiating with a computer while Boeing drivers are generally flying the airplane. Both have merits and drawbacks and vocal camps. Yeah, and both sides can point to major incidents that wouldn't have happened in the other cockpit.

throwanem 10y ago
I know of Air France 447 in the "fly the airplane" camp. (An inexperienced copilot stalled the aircraft all the way from cruise altitude to impact, and because the sidesticks aren't linked, no one else could tell that was what was wrong.) What's a good example in the "negotiate with the computer" camp? Perhaps it's merely a tendency on my part, but I don't think I have run across any accident which militates as strongly in favor of Airbus's design as AF 447 seems to militate against it.
- rockdoe 10y ago
  AA 587, which ironically happened on an early model Airbus before they went FBW. Your perspective will influence how you classify the accidents. Proponents of full FBW will argue AF 447 happened exactly because part of the FBW system was disabled.
- pedrocr 10y ago
  >I don't think I have run across any accident which militates as strongly in favor of Airbus's design as AF 447 seems to militate against it. The references I've seen to advantages tend to be more subtle than the AF447 tragedy. Things like the Hudson river landing where in that strange situation where you have no power the workload was diminished by having the computer keep the airplane flying most efficiently and thus be able to reach the river instead of crashing by losing airspeed. It also makes sense the advantages are less obvious as the flight envelope protection actively prohibits dangerous situations and you can't report on non-events. The stats also show Boeing and Airbus airplanes pretty evenly matched on safety.
- TuxerLulz 10y ago
  AF447 is more complicated than just that sidestick issue, if you look at the accident report closely. The contributing factors were loss of outside air temperature and airspeed sensors because of icing, a dark moonless night above the ocean, and flying/falling outside of the operating range of the stall horn (when they pitched the nose down, they started recovering from the stall, airspeed went up, and the stall horn activated. when they pitched up, they went back outside of the operating range, and the horn muted). A big contributing factor as well was that in an airbus, in normal operating conditions, pulling the stick all the way back will configure the aircraft for the best rate of climb (which can be different from just putting the elevator in full climb conditions). Due to the pitot tubes being iced up, the flight computers were in Direct mode (where movement of the sidestick is directly translated in movement of the flight controls, without computer intervention), which didn't help.

userbinator 10y ago

The Boeing 737 is still controllable with no electric or hydraulic operation, since the yoke and rudder are linked with cables to the control surfaces. From what I understand the hydraulics also provide power assist, so it might not be too dissimilar to driving a car without power steering or brakes when that happens. Scenes in movies of pilots physically struggling with the plane are not as unrealistic as they may seem.

jsmthrowaway 10y ago
They're not, and you're right. You're literally pulling or pushing a lot of control surface against a lot of fast-moving air, and it doesn't want to go there. There were many inaccuracies in the opening drama of Flight, but the yokes beating the shit out of the crew was quite believable given the scenario.

sgnelson 10y ago

For those who want to know a bit more about a few of these topics, I found this article via HN discussing the role computers, fly by wire, and a lack of training had in the AirFrance 447 crash. Found the article quite interesting. http://www.vanityfair.com/news/business/2014/10/air-france-flight-447-crash http://www.vanityfair.com/news/business/2014/10/air-france-f...

hackuser 10y ago

> A coarse summary might be that Airbus drivers are negotiating with a computer while Boeing drivers are generally flying the airplane. Would you mind taking a moment to spell out what these statements mean to a non-pilot? (For example, I expect that Airbus pilots still operate controls which affect the movement of the airplane; they aren't typing parameters into a computer. And I expect Boeing pilot's actions are still mediated by a computer.)

jsmthrowaway 10y ago
Sure. On all FBW systems there's a computer in between the pilot's appendages and the wiggly parts built into the airplane that control its orientation (roll, pitch, yaw, what have you). Airbus systems position the pilot as a suggestive force. At any given time the computer has its idea of what's happening and the pilot influences this calculus within safety tolerances for various bad things that happen to airplanes. One example is a stall, which results from a variety of factors including excessive pitch of the wing against the oncoming air (called angle of attack -- think about tilting your hand back when holding it out of the car and it dropping back on you. that's a stall). Airbus computers typically prevent the pilot from introducing the situation by dampening, modifying, or outright ignoring control input to avoid critical angles of attack. That's one example. Basically, without going alternate law, the Airbus computer will work to make it very hard (not impossible, obviously) to apply control input that would place the flight in jeopardy. Boeing would allow the input and mostly permit the pilot to introduce the situation. That's the difference. They treat the pilot as the end of authority in command. That has compelling merits. So does Airbus. As JshWright said, both sides have incidents on the other they can point to as supporting data.