Why is ice a problem for airplanes?
Ice reshapes the surface of the lift-producing parts of the airplane: the wings and the tail. That roughness is enough to change the aerodynamics of the wing such that there's more drag and less lift.
The amount of lift a wing creates depends on the relative angle that the airstream has to the airfoil. As you increase that angle—the angle of attack—you generate more and more lift. But at some point air cannot flow over upper surface, and you have aerodynamic stall. The point at which aerodynamic stall takes place has to do with the contour of the airfoil. If the surface is contaminated with slight roughness—sandpaper roughness—it will reduce the lift and change the point at which stall takes place.
For scheduled air carriers [including commercial passenger airlines] icing has been a contributing factor in 9.5 percent of fatal air carrier accidents.
How are pilots trained to handle aerodynamic stall?
As you go through pilot training—without icing involved—you practice wing stalls. You bring the nose up and the airplane shakes around because of separated flow. To recover from that, you push the nose down to reduce the angle of attack on the wing and recover. What happens with ice is same principle, but it is happening at a lower angle of attack.
Why would having a plane on autopilot interfere with a pilot's ability to prevent stall?
If a person is hand-flying an airplane and the airplane has a reversible control system, then for every action the pilot makes on the control there is some reaction on the control. There is the ability for the airplane to talk to you.
When the autopilot is engaged, that information isn't being passed onto the pilot. The National Transportation Safety Board recommends against flying with autopilot under icing conditions. [The Federal Aviation Administration recommends against autopilot only under severe icing conditions.] Companies make their own choices on how to present that information to the pilot.
See what we're tweeting about
12 Comments
Add CommentHow unfortunate.
Reply | Report Abuse | Link to thisThe days of heavier than air aircraft are slowly drawing to a close and for good reason. Just takes too much to keep em up in the air.
Really? There are thousands and thousands of airplanes in the air at any given time. How many departures leave Newark on a daily basis? New York State? The United States? It is a staggering number that people do not realize because they only think of flying when they are on an airplane. The safety record of airplanes is impeccable. If we took this kind of approach for automobiles, cars would have been banned in the 20's.
Reply | Report Abuse | Link to thisYeah, I think high speed rail would be much more efficient than airplanes.
Reply | Report Abuse | Link to thisAerospace is "tombstone" technology. Accidents happen, NTSB finds out the causes, then corrections get introduced.
Reply | Report Abuse | Link to thisI am glad NASA and hopefully others are still doing research that can eventually be translated into even safer air travel.
Reply | Report Abuse | Link to thisI have been saying since the day of the accident that the plane was likely on auto pilot and icing had taken place without the pilots knowledge. Its the only obvious conclusion.
Reply | Report Abuse | Link to thisRT
www.anonymity.eu.tc
Mikecimerian is right about the process of the NTSB in a ambiguous way. But if it is totally true, with today's technology, wouldnt you think they would have corrected the pilot error cause of plane accidents? It makes up 59% of all accidents (or the piolts always get blamed for it). Every year we progress the pilot error statistic becomes greater. (unmaned aircraft anybody?) Also the whole Train vs Car vs Plan statistical analysis thingyyy, well its simple. If you want to commute somewhere, do it the way everyone else is NOT. Simple, might be a hell of lot longer commute, but it definately drops your odds of becoming a statistic significately. Basically ride a bike (or walk) if it is down the road, plan long trips in vehicles appropately (go the route that may take the longest), for extremely long trips take the train. If your traveling by air you better be traveling 1500 + miles or over sea and/or ocean. If your the impatiant type or who believe they deseve any means of convience then take the risk of driving your car 2 mins down the road on the busiest road to an airport to get on a plane for a trip to a state that could have been commutable by train. Kinda farfetched especially the nearest airport to me is an hour away :) But dont be that type! and yes i am being a little hypocritical (i walk to work everyday, but i will most likely take the fastest route while driving a car or go where my GPS tells me to... thats all thou! the rest is legit )
Reply | Report Abuse | Link to thisOh and if your going to fly, pick Delta airlines, they have the least fatalities in the world for plane crashes :)
Reply | Report Abuse | Link to thisActually they found out that the pilot took the plane off from auto-pilot when the planes computer system warned him of the ice build up. which is, i wonder, a thing you do not want to do when experiencing those kind of situtations(of what i read from NTSB). The worst part was that the crew noticed significate ice build up before they departed, and...didn't do a thing. WTF right?
Reply | Report Abuse | Link to thisSafety is incremental. There are too many variables.
Reply | Report Abuse | Link to thisTake for instance the Turkish Airways Birgenair Flight 301 accident, one of the pitot tubes which measure air speed had been invaded by a nesting wasp during the two week period the plane was parked in a tropical location.
Conflicting airspeed readings led to a major catastrophe.
Now pitot tubes are covered whenever a plane is parked for any prolonged period in tropical locations.
Falling from the Sky (All Engines Failed)
- British Airways Flight 9 experiences St. Elmo's fire along with smoke smelling like sulfur in the cabin. All four engines on the Boeing 747 start flaming then flame out. With 263 people on board, BA009 starts downward but minutes before its fate in the ocean, the crew successfully restart the engines. The aircraft makes an emergency landing at Jakarta where inspection reveals that it looks as if it has been sandblasted.
The strange happenings were from volcanic ash coming from a volcano in Indonesia. The fine particles of ash melted inside the engines, clogging them and causing all four to fail.
Volcanic ash didn't show up on radar
Those are just two examples of the realm of unexpected things that can happen.
Once the NTSB has done it's forensic studies, new advisories get issued in order to avoid a repeat of the same circumstances.
In 1994, there was a similar turboprop plane, American Eagle Flight 4184, that crashed and killed everyone on board also because of icing.
Reply | Report Abuse | Link to thisIt seems that Continental Express Flight 3407 is a repeat of that disaster.
In 1994, there was a similar turboprop plane, American Eagle Flight 4184, that crashed and killed everyone on board also because of icing.
Reply | Report Abuse | Link to thisIt seems that Continental Express Flight 3407 is a repeat of that disaster.