Initial speculation from the charter jet crash in New Jersey today swirled around the possibility of frost forming on the wings and causing loss of lift.
From numerous other air disasters, I clearly understand the danger of ice, but frost strikes–that’s new to me. Aviation experts on CNN today said frost can be a killer.
Can someone explain the mechanics involved? Is it issue added plane weight or aerodynamic disruption to the precisely shaped wing, resulting in loss of lift?
Realistically, how heavy can an accumulation of frost weigh on a small charter jet–and how could trained pilots not see a thick accumulation?
To my untrained mind, that a covering of frost can cause a plane to lose lift and crash suggests these wings are operating right on the razor’s edge and have little tolerance for disruption of any kind.
A last point: someone on CNN today claimed that a single deicing of a commercial plane can hit $1,000. Is that true?
IANAP but I am a student pilot. I believe the issue with frost is with aerodynamic disruption of airflow over the wings rather than the weight. Thin layers of regular ice can also have this effect.
This link to AOPAs (Airplane Owners & Pilots Association) website may help give you some insght.
Here is a snippet of the page.
FLIGHT CONTROL PROBLEMS
Ice, snow, and frost don’t just affect the ability of airfoils to generate lift. The additional weight can unbalance control surfaces, which leads to a dangerous aerodynamic condition called flutter. Such was probably the case in the following accident
Jim
“Wind tunnel and flight tests indicate that frost, ice, or snow formations having a thickness and surface roughness similar to medium or coarse sandpaper on the leading edge and upper surface of a wing can reduce wing lift by as much as 30 percent and increase drag by as much as 40 percent.”
The thin layer of ice disrupts the smooth flow of air over the airplane’s wings that creates the lifting force. “Reducing lift” is more dangerous than it might sound. Much more than a slower-than-normal rate of climb is involved. The reduction in lift isn’t likely to be even, to put it in simple terms.
Several accidents have been reported in which airplanes with frost on the wings went out of control — imagine what it would be like close to the ground in an airplane with the right wing unexpectedly developing more lift than the left. Your efforts to level the wings may be fruitless."
[QUOTE=Carnac the Magnificent!]
Is it issue added plane weight or aerodynamic disruption to the precisely shaped wing, resulting in loss of lift?
[quote]
Yep, the frost disrupts the airflow over the wing, reducing lift and adding drag. It takes surprisingly little frost to have a huge effect. The FAA ran wind tunnel tests and found that frost can reduce lift by 30% and increase drag by 40%.
When it comes to frost, the aerodynamic effects are more of a concern than the weight.
Easily. I don’t have any figures from school in front of me, but that sounds maybe a bit on the low side.
It isn’t so much that the frost changes the aerodynamics of the plane from flyable to unflyable as it is the frost turning the plane’s wing into an experimental airfoil. An airfoil that usually has a higher stall speed than the one the pilot thought he had.
Last time I looked Ethyl Glycol cost around $13.00/gal. I would think that it may take several hundred gallons to de-ice a large private jet. In addition to that it has to be heated up before being applied.
Another point, when flying at high altitude aircraft wings are operating fairly close to tolerances. The higher you are flying, the less buffer there is above the stalling speed and so things such as ice can have more of an effect. Also it’s worth noting that a layer of ice/frost on the wings disrupts lift and creates drag which slows the aircraft down further.
The Challenger series (the type that crashed today) has a very efficient wing, which makes a light coating of frost much more dangerous than it would be on something like a Citation II. The Challenger is well-known for its problems with ice, and in fact it was a Challenger that crashed in November taking off from Montrose, Colorado. Ice/frost contamination of the wing is being looked at as a possible cause of that crash as well.
Although I have reason to suspect that putting together “aviation expert” and “CNN” in the same sentence may often result in an oxymoron, in this case the talking heads are correct. In aviation frost can be a killer.
It’s been covered already - frost disrupts the airflow over the wing, leading to less lift generated.
It can also screw up hinges on control surfaces, but I don’t think that’s as much a factor as loss of lift.
You don’t need a heavy accumulation.
Pilots have been told to run their hands over the leading edges of wings - the amount of frost required to affect flight might be hard to see, but it can certainly be felt. I’ve spent many an hour on a ladder rubbing at the frost on Cessna wings (small airplanes like I fly usually don’t use de-icing fluid, we use elbow grease, heated hangars, and if it’s really bad we just don’t bother starting the engine)
Yes, it’s a little counter-intuitive - an airplane that still functions adequately with a big dent can be totally messed up by a light frost. Thing is, a dent only affects one small bit of the wing - frost can affect airflow over the entire wing.
The other thing to remember is that airplanes on take-off and landing are operating a little closer to the edge due to lower speeds and, for take-off, ground friction. The plane in New Jersey yesterday simply never generated enough lift to leave the ground - had there been another 6,000 feet of runway ahead of it, it might have stopped without further damage but that wasn’t the case. There was a highway and a building in the way.
If possible, can you enter this thread with a prejudice about frost? Do we assume frost is something less substantial than ice?
Frost can be quite disruptive, because of the way it forms. Frost happens when nighttime temperatures drop to freezing and dewpoints are below the freezing mark. This provides enough moisture to crystallize over almost the entire airframe. Like other ice, frost must also be dealt with immediately.
Some more information (probably WAAAY too much info for the casual observers).
After the Challenger crash in November the NTSB (National Transportation Safety Board) issued an alert about the hazards of ice and frost accumulation on wings. Here’s part of that warning (bolding mine):
The National Transportation Safety Board has long been concerned about the insidious nature of the effects of small amounts of ice accumulated on an airplane’s upper wing surface. The Safety Board’s preliminary investigation of the November 28, 2004 accident involving a Bombardier Challenger 601-1A in Montrose, Colorado,(1) has revealed that atmospheric conditions conducive to upper wing surface ice accumulation existed at the time of the accident (airplane performance issues, including the possibility of upper wing ice contamination, are being investigated).
For years most pilots have understood that visible ice contamination on a wing can cause severe aerodynamic and control penalties; however, it has become apparent that many pilots do not recognize that minute amounts of ice adhering to a wing can result in similar penalties. Research results have shown that fine particles of frost or ice, the size of a grain of table salt and distributed as sparsely as one per square centimeter over an airplane wing’s upper surface can destroy enough lift to prevent that airplane from taking off. The Safety Board has commented on the hazards of upper wing ice accumulation in several previous aircraft accident reports; some excerpts from these reports follow:
* According to.wind tunnel data, a wing upper surface roughness caused by particles of only 1-2 mm [millimeter] diameter [the size of a grain of table salt], at a density of about one particle per square centimeter, can cause lift losses.of about 22 and 33 percent, in ground effect and free air, respectively.(2)
* Research has shown that almost imperceptible amounts of ice on an airplane's wing upper surface during takeoff can result in significant performance degradation. Therefore, the Safety Board has urged pilots to conduct visual and tactile inspections of airplane wing upper surfaces in past safety recommendations (including Safety Recommendation A-04-66, which was issued to the FAA on December 15, 2004).(3)
* Ice accumulation on the wing upper surface is very difficult to detect..It may not be seen from the cabin because it is clear/white.and it is very difficult to see from the front or back of the wing..The Safety Board believes strongly that the only way to ensure that the.wing is free from critical contamination is to touch it.(4)
* Accident history shows that nonslatted, turbojet, transport-category airplanes have been involved in a disproportionate number of takeoff accidents where undetected upper wing ice contamination has been cited as the probable cause or sole contributing factor.(5)
* The industry acknowledges that it is nearly impossible to determine by observation whether a wing is wet or has a thin film of ice..a very thin film of ice or frost will degrade the aerodynamic performance of any airplane.(6)
* The Safety Board believes that even with the wing inspection light, the observation of a wing from a 30- to 40-foot distance, through a window that was probably wet from precipitation, does not constitute a careful examination..the Safety Board acknowledges that the detection of minimal amounts of contamination, sufficient to cause aerodynamic performance problems, is difficult and may not be possible without a tactile inspection.(7)
* The Federal Aviation Administration's (FAA) Environmental Icing National Resource Specialist (NRS) indicated that he was concerned that most pilots were not aware that a slight amount of frost or ice accumulation could result in a significant degradation of airplane performance. The Icing NRS stated, 'pilots may observe what they perceive to be an insignificant amount of ice on the airplane's surface and be unaware that they may still be at risk because of reduced stall margins resulting from icing-related degraded airplane performance.'(8)
* From an aerodynamic viewpoint, there is no such thing as "a little ice." Strict attention should be focused on ensuring that critical aircraft surfaces are free of ice contamination at the initiation of takeoff.(9)
* Strange as it may seem, a very light coating of snow or ice, light enough to be hardly visible, will have a tremendous effect on reducing the performance of a modern airplane. (Jerome Lederer, M.E., 1939) (10)
I can see from the above posts that in aviation, frost and ice appears to be a very big and important issue. The question is that if it is indeed such a big issue as we know, then why don’t we have planes fitted with some sort of de-icing systems. To my non-flying mind, all it takes is to have some arrangement that can can heat surfaces that are critical and keep them hot.
Yes, I have seen the de-icing activity sitting inside a plane and hoping that that guy doing the de-icing does not leave any part of the surface unsprayed. Then I have also fretted after the de-icing wondering what if the ice forms again while we waited for clearance on the runway.
So why don’t they have some sort of a heating system that keeps the wing surface temperature warm all the time, rather than spend so much money in de-icing each time the plane takes off and run the risk of fatalities. I know there must be a reason, just wondering what it is.
The frosty equivalent of one grain of salt per square centimeter can be enough to prevent an airplane from taking off? OK, that’s got me completely freaked out and not ever wanting to fly if it’s less than 50 degrees now.
I can understand bizjets being much closer to their limits, but how about the big birds like 757s and A320s? Are they similarly at risk or do they generate so much lift that there’s a lot more margin of error available?
So, would this mean the larger jets have inefficient wings? What exactly is wing efficiency?
Ice bringing down planes seems to be all too common (relatively).
This begs the question of why no planes seem to come equipped with wing defrosters? I have a rear window defroster on my car…why couldn’t one be put in a wing? Something, anything, to warm the wing up a bit and melt the frost/ice. Is there some engineering reason why these would not work? Seems simple enough even if it would have to be more heavy-duty than a car defroster but then I am not an aeronautical engineer so can’t really say.
I understand that this would add to the cost of a plane but all things considered in the cost of a plane I cannot imagine the price increase would be all that dramatic. If you add in $1,000+ per de-icing treatment seems the cost should pay for itself quick enough if you fly in areas where you might expect ice conditions. Certainly it is a cheaper than crashing the plane.
The equipment needed to defrost a whole wing would add a great deal of weight and complexity to the aircraft. Even if you did add the defrosting equipment, you would need a great deal of power to run it. Adding the hardware to produce that power would drive up the weight even more. Too much more for a system that would only be used occasionally.
Aircraft already have de-ice/anti-ice systems that are usually powered by bleed air or electricity. Heated areas are usually limited to antennas, leading edges, windscreens, air inlets, etc. Heating larger areas of the airframe with on-board equipment is impractical.
