A Continental Connection Bombardier Q400 similar to the one flown on Flight 3407
Image: RUDI RIET VIA WIKIMEDIA
Last Thursday, Continental Express flight 3407 was just five miles (eight kilometers) short of the runway in Buffalo, N.Y., when it suddenly pitched, rolled, and plunged into a house outside of town, killing all 48 passengers and crew and one man inside the house.
Media reports have suggested that the pilot may have violated company guidelines—but no federal laws—by engaging autopilot on the propeller-driven Bombardier Dash 8 Q400 airplane under severe icing conditions. In December, the National Transportation Safety Board (NTSB) had warned that "using the autopilot can hide changes in the handling qualities of the airplane that may be a precursor to premature stalling or loss of control." The Federal Aviation Administration has not made such recommendations mandatory.
The pilot of flight 3407, which was operated by Colgan Air, had turned on the de-icing system just 11 minutes after taking off from Newark Liberty International Airport in New Jersey and had discussed "significant" ice buildup on the windshield and wings of the plane. One other plane on the same route landed after flight 3407 without incident, after reporting severe icy conditions. Still, NTSB member Steven Chealander warned yesterday against "jumping to conclusions" about icing being the primary cause of the crash, which occurred just 26 seconds after an antistall system disengaged the autopilot.
Ice typically builds up when tiny cloud droplets impact and freeze on the leading edges, or front surfaces, of the plane. The ice alters airflow over the wing and tail, reducing the lift force that keeps the plane in the air, and potentially causing aerodynamic stall—a condition that can lead to a temporary loss of control. The Dash 8 was fitted with pneumatic de-icing boots that inflate and deflate to break off the crust that forming on the wing's leading edge during flight, but if the plane is pelted with larger droplets, they may freeze farther back on the wing where ice cannot be effectively removed. (The IceController, a device not yet in use on planes, zaps ice off with a pulse of electricity).
To find out more about the dangers of icing, we spoke to Thomas Ratvasky, who has worked as an engineer at the Icing Branch of the NASA Glenn Research Center for the last 19 years.
[An edited transcript of the interview follows.]
How does ice build up on airplanes?
Ice builds up on aircraft in two ways: in flight or on the ground. On the ground, precipitation falls onto the airplane and freezes on upper surfaces much like what happens if you leave your car out overnight. On planes, ground icing forms on the upper surfaces of the wing and tail. That type of ice is managed by de-icing the plane with a fluid [typically propylene glycol] at the airport.
In flight icing is where the airplane is flying through clouds made up of small liquid water droplets. These liquid water droplets can be sustained as liquid below the freezing point. Everybody knows that 32 degrees Fahrenheit (0 degree Celsius) is where water freezes. It turns out that if the water is very pure—if it is condensed out of the atmosphere—and there is nothing for that water to freeze on, it can be sustained below the normal freezing point. What we find in the wintertime is clouds that are made up of small water droplets where the water temperature can be as low as negative 40 degrees C. Here comes this plane flying through the cloud, and the water droplets impact the airplane and then freeze because now they have a surface to freeze on. Ice builds up in flight on the frontal surfaces: leading edge of the wings, the nose and the tail surfaces. There are systems to prevent ice or to remove ice. The de-icing system works on the basis of allowing ice to form before being broken off [using pneumatic boots that inflate to crack the ice]. The anti-icing system prevents ice from forming by blowing hot air from within the compressor of the engine.
We have here at NASA an Icing Research Program with folks who do computer codes to predict ice growth, and we have a wind tunnel in which we can recreate icing conditions on a model.
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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
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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.