Cricri From France, joined Oct 1999, 581 posts, RR: 7 Reply 1, posted (13 years 6 months 2 weeks 1 day 16 hours ago) and read 918 times:
It depends of the aircraft type : on modern airplanes, you'll find an electrical heating system (sort of resistor) for the wings and some other parts. On older planes, it's a kind of pneumatic fender that makes the ice splitting and getting away with the speedwind.
I think, but don't really know, that you have warning horns that prevent crew from icing. A pilot could tell you more about it.
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 23 Reply 2, posted (13 years 6 months 2 weeks 1 day 13 hours ago) and read 915 times:
Hi Gopal, Buzz here. I'm familiar with deice equipment in many ways.
In-flight ice proection? That could go on for pages. Generally, the freezing stuff hits the airplane nose-on, so the forward facing parts get some sort of heat, unless the airplane uses pneumatic boots as previously described.
Heated windshields help the pilots see out, and keep the plexiglass flexible for bird strike proection. Wing leading edges are hot air warmed, bleeding off some engine compressor air. Same idea for engine inlets. Airspeed probes have electrical heaters that will blister your hand before you can let go. (somebody else's experience).
OK, ground deicing: since the freezing rain / snow can come at any direction, the airplane's anti ice stuff is not effective. Air Florida found out the hard way, as did US Air. They crashed.
We hose off the snow / ice with hot antifreeze. The deicer trucks heat the pink juice up to 150 degrees or so, and the poor guy in the bucket plays fireman.... melt off the frozen junk on the airplane. The antifreeze lets the melted snow run off the airplane / out of the nooks and crannys and flow into the storm drains. (ever wonder why Columbia River Pink Salmon won't harden up in the freezer? ) The storm drains generally flow to recovery ponds to keep from poisoning wildlife.
After the airplane is hosed off clean, if more snow /ice is falling we might shoot a layer of green jello (type 4 anti ice) on it. The thick goopy anti-ice lets the snow fall on , then magically blows off at 80 knots or so. Whatever you use, it's an expensive, time consuming mess. But it does get the airplane full of crabby passengers out of town.
A newer way is to taxi the airplane into a special drive through hanger where it bakes for 5 or 10 minutes, infrared heat. I like that idea. But it's not widely used, too new to be cheap .
PerthWA From , joined Dec 1969, posts, RR: Reply 3, posted (13 years 6 months 2 weeks 1 day 8 hours ago) and read 909 times:
The prefered de-icing technique nowadays uses a magnetic field. I forget the name!
But, underneith the leading edge of the wings and other places on teh aircraft lies a magnetic coil, and around this coil are 2 or 3 strips of polarised metal.
When a the coil is charged, these strips repel the coil, hence pushing on the fuselage.
This sequence happens numerous times a second, hence making a vibration, which in turn breaks the ice in many places.
Other techniques like heating and pnuematic systems have proven dangerous as they may de ice the plane, but consequently do it in large chunks instead of breaking them down. These large chunk of ice when falling have damaged wing systems, tail wings etc.
Thats why the prefered de-icer relys on magnetic vibration!
Buff From Australia, joined Mar 2007, 0 posts, RR: 1 Reply 4, posted (13 years 6 months 2 weeks 1 day 5 hours ago) and read 909 times:
Thats why the prefered de-icer relys on magnetic vibration!
The only "system" I've ever heard of that approaches this description is a Goodrich ice detection system. When activated, it alerts the pilots a certain type of ice is forming somewhere on the airframe. Conventional de-icing/anti-icing equipment would then be utilized.
To the best of my knowledge, on commercial airliners, jet and prop driven, all de-icing/anti-icing is still conventional, i.e. heated surfaces, pneumatic boots or alcohol (IPA).
Perhaps Gopal could be more specific with his/her request - are you asking about pre-flight or inflight for instance?
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 23 Reply 5, posted (13 years 6 months 2 weeks 16 hours ago) and read 892 times:
Hi Perth, Buzz here. Magnetic Vibration: hmmm, where can a guy read up on the topic? It's not on any of the aircraft i play with (A320, 727, 737, 747, 757,767, DC-10) Hope i don't have to chase more wire where humans aren't designed to fit.
Of course i'm approaching dinosaur age, my kids are teenage. So i've got a lot of knowlage about "the way things have been done".
But that's not a bad thing, comes in handy when keeping a DC-3 flying.
Let me know where i can educate myself on this deice system. Up here at PDX we're on the edge of cold weather country. g'day
Buzz Meyer: Line Mechanic by night, DC-3 crew chief by choice.
Gopal From United States of America, joined Jun 1999, 112 posts, RR: 0 Reply 6, posted (13 years 6 months 2 weeks 14 hours ago) and read 887 times:
Thanks you Buzz, PerthWA, Cricri, Buff for your informative posts. Could anyone explain in detail the functioning of De-icing boots. I read about them in the aviation classic - Fate is the Hunter. I suppose they were present in DC-2s and DC-3s. Since they flew below atmospheric phenomenon, ice accumulation during flight was a big issue. How big in an issue is it for a modern airliner flying at 35000 - 39000 ft?
Pilot21 From Ireland, joined Oct 1999, 1378 posts, RR: 2 Reply 7, posted (13 years 6 months 2 weeks 11 hours ago) and read 882 times:
While most people have already answered the inflight de-icing situation they forgot to mention a new ground based system which Delta has just sign up for in most of it's winter airports. The new system uses about 1/6 of the previously required glycol mixture and a stream of high velocity air. Apparently after tests last winter, it proved to work very well and was much more efficent then the traditional water/glycol mixture which use to come from fireman hoses.
Lonnie From , joined Dec 1969, posts, RR: Reply 8, posted (13 years 6 months 2 weeks 9 hours ago) and read 880 times:
DE-ICING IS NOT FOR INFLIGHT. IT IS APPLIED TO THE AIRCRAFT TO: PUSH, TAXI, HOLD (IF NEED BE), AND TO PREVENT ICING DURING CLIMB SO THE AIRCRAFT CAN CLEAN UP AT THE APPROPIATE ALTITUDE WITHOUT COMPLICATIONS. THERE IS TYPE 1 GLYCOL WHICH IS, OR CAN BE APPLIED PERFERABLY JUST PRIOR TO, OR JUST PUSHED OFF THE GATE WHICH IS MORE COMMONLY USED. THEN THERE IS TYPE 4 GLYCOL WHICH CAN BE APPLIED UPTO 24 HOURS PRIOR, WITHOUT FURTHER SNOWFALL. THIS IS GOOD FOR THE BUSIER AIRPORTS WHERE PRE-SPRAYING IS PRACTISED TO HELP DELAYING FLIGHTS. HOWEVER, REMEMBER THAT THE FLIGHT CREW( (S)
DO THEIR WALK AROUNDS, AND WHATEVER THEY REQUIRE, THEY GET, WHEATHER IT'S ANOTHER SPRAY, OR A HOT MEAL (NOT IN NW SITUATION),
THE FLIGHT CREW ALWAYS HAS IN THEIR INTEREST OF PUTTING THEIR FEET BACK FIRMLY ON THE GROUND, AND IF THEY DO THIS, THEY KNOW THAT THE PEOPLE BEHIND THEM ARE AS WELL, WALKING TO PICK-UP THEIR LUGGAGE. NEVER WORRY ABOUT YOUR TAKE-OFF, THINK ABOUT YOUR LANDING, FOR WHATEVER GOES UP, DOES COME DOWN!
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 23 Reply 9, posted (13 years 6 months 1 week 6 days 17 hours ago) and read 873 times:
Hi Gopal, Buzz again. The short answer is "what ice?". Notice that it's usually fairly clear skies at cruise altitude, you need the moisture to make ice.
So the window and probe heat is normally on inflight, but wing / engine heat is off.
I grew up with the DC-8's and they have a lot of old thinking on them. They had tail deice, and the whole length of the wing is also heated, which was found to be unnecessary. Imagine my suprise when i go to classes on 'newer' airplanes and the inflight antiice system is missing on much of the airplane! The hot air plumbing and valves aren't installed. And this is on Boeing... it rains up here guys. And rain at the ground means you can find ice several thousand feet up.
It seems that the shape of some of the leading edges deflects the semi-frozen rain / cloud bits from sticking to the airplane. Thus, no tail deice is needed and the wings inboard of the engines are not heated either.
Then again, pilots are taught not to loiter in ice. Use the magnificent rate of climb to get above the temperature level where it's sticking if you have to wait for a runway. g'day
JETPILOT From United States of America, joined May 1999, 3130 posts, RR: 32 Reply 10, posted (13 years 6 months 1 week 6 days 16 hours ago) and read 879 times:
As long as I've been flying jets for....about 3 years.... I have never had to use wing de-ice. The 727 doesn't even have a de-iced tail.
Engine anti-ice is used anytime you're in visible moisture and the temp is below 10c. You don't want your inlets to ice up. This will change the airflow into the engine and could cause compresor stalls, or a flameout.
The best way to tell if your picking up ice in a jet is to watch you're EPR guage. If the plane is picking up ice the EPR will rise dramatically indicasting your sensor has iced over. It's 100% accurate.
Hmmmm... From Canada, joined May 1999, 2089 posts, RR: 5 Reply 11, posted (13 years 6 months 1 week 6 days 4 hours ago) and read 875 times:
What concerns me the most about the ice problem is the interval between the time the plane is de-iced at the gate and the actual time that the wing gets into the air. Under icing conditions, that is often longer than it takes for ice to accumulate again. And returning for more de-icing is not the answer if it means waiting all over again. So shoot down this idea:
At the end of every taxiway where planes hold short before turning onto the runway, a series of poles spray a sheet of de-icing fluid through which the plane must pass as it positions for take-off. After the aircraft has passed through, sensors then lower the poles back down into the ground automatically where they await the next aircraft.
Do away with icing trucks, booms, and frozen humans all together. And bag guys who don't know what they are doing. Years ago, when my brother was a baggage guy, he was ordered to fill the role of a de-icer and go de-ice an aircraft. He retorted that he was just a bag guy. Go de-ice that plane, he was told. He did it. Hadn't a clue what he was doing. I doubt anybody ever checked. He just shook his head.
AC183 From Canada, joined Jul 1999, 1532 posts, RR: 2 Reply 13, posted (13 years 6 months 1 week 6 days 1 hour ago) and read 868 times:
Regarding the chemicals, I believe there are several of them. I think they use ethylene glycol for one.
Because these chemicals are expensive, and potentially harmful if they are just dumped, more and more airports are setting up de-icing areas where the glycol is sprayed onto the airplanes, and is contained and collected for recycling.
Also, newer de-icing trucks, (I saw AC's new ones at YYC, for example) have enclosures around the bucket on the end of the boom, which would make the job a little better for the guy spraying the glycol.
One thing I wanted to add about de-icing. Usually de-icing is required in conditions where the dew point and the outside temperature are close together (ie-moisture will condense on the wings), and the temperature is cold enough for this condensation to form ice on the wings.
I believe that in-flight ice prevention measures are known as anti-icing equipment. De-icing usually refers to removing of ice on the ground, or at least that is my understanding. Now to explain the de-icing boots a bit. I believe they are primarily used on turboprops. At least as I understand it, the leading edge has a rubber material on it with this system. This can be inflated just a bit, which causes ice to break off. It is my understanding that it uses compressed air from the engines. It would be like forming ice on a rubber balloon, then inflating it more to break the ice up. Is this correct, can anyone confirm it?
Buff From Australia, joined Mar 2007, 0 posts, RR: 1 Reply 14, posted (13 years 6 months 1 week 5 days 3 hours ago) and read 862 times:
The balloon analogy is a good one. Also true about boots being primarily on turboprops. An old style jet that used to have boots was the Lockheed Jetstar. An old breed indeed.
Aircraft are equipped with de-ice equipment as well as anti-ice equipment. As implied by the terms, de-icing equipment removes accumulated ice (pneumatic wing boots, propeller heat) and anti-icing equipment prevents ice from forming (pitot heaters, jet engine inlet heaters).
Regarding the deicing spray at the end of the taxiways just prior to entering the runway, this is The Best Solution. Unfortunately, it has taken many deaths over the last couple of decades to get airlines/aviation specialists to realize that more efficient means are necessary in this day of increased air travel. And of course, the idea to build these towers would be vetoed by the bean counters - too long to recoup costs. The same old, same old.
PerthWA From , joined Dec 1969, posts, RR: Reply 17, posted (13 years 6 months 1 week 4 days 2 hours ago) and read 850 times:
Yeah, I know, someone said when you are flying at such high altitudes, there is no moisture, therefore, you cannot have an ice problem, but people forget, water isnt the only thing that can freeze.
High alt. extremely low temperature, therefore you can have gases that freeze aswell, dry ice is a problem on aircraft cruise aswell you know!
AKelley728 From United States of America, joined Dec 1999, 2105 posts, RR: 6 Reply 18, posted (13 years 6 months 1 week 4 days 1 hour ago) and read 853 times:
Just read in Continental's in-flight magazine that there is a new ground deicing system that was just installed at Newark called the "Infra-tek". It uses infrared rays to melt the ice. While planes are on the taxiway before take off they are supposed to go through this device to melt the ice on the surface They still get a wash of glycol before they takeoff, however. Sounds pretty neat! Does anybody have more info on this system and whether or not they will be installing it on more airports?
Buff From Australia, joined Mar 2007, 0 posts, RR: 1 Reply 19, posted (13 years 6 months 1 week 4 days ago) and read 857 times:
Frozen carbon dioxide on an airframe is not a problem in commercial aviation. Moisture can very well invade the higher altitudes. It is not common, but even Concorde can leave a contrail at FL590. Moisture forming on particulates from its exhaust.
Generally, the temperature up to 100,000 feet does not go below -60C (It can, but ISA above the tropopause is -56C at 40N/S Lat).
If memory serves, dry ice or frozen CO2 sublimates to a gas at about -100C. Hope you'll correct that if it's wrong!
NKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 6 Reply 21, posted (13 years 6 months 5 days 13 hours ago) and read 835 times:
I have de-iced multiple times (I'm not a "bag" person--not that there's anything wrong with them ) and we use a hot Propylene glycol/water mixture (type 1) to de-ice and a thick green fluid applied cold to extend holdover times _only after de-icing with type 1_ (type 4). Most of the de-icing is just removing overnight frost,or removing contamination after precipitation has ended. There are charts that determine the length of holdover times depending on the temperature,amount and type of precipitation,and final type of fluid shot. The mixture of water/glycol is varied depending on temperature. The mix with the lowest freezng point is a 50/50 mix (not 100% glycol!),so a mixture is used to provide an adequate "buffer zone" below the actual ambient temp to conserve gloycol. (we don't need a mix with a freeze point of -35F to de-ice an A/C in 30F ambient temps). The freeze point of the mix is not what does the de-icing---It is the heat (180F) and pressure that really does most of the work,in fact plain old hot water will de-ice fine in theory. The reason we use glycol is to lessen the loss of heat loss from the nozzle to the A/C,and to provide additional holdover protection to: a) cover the gap between type 1 to type 4 applications and b) provde holdover if no type 4 is shot. Type 4 is not always needed. Sorry for the book,hope this answers your questions.
NKP S2 From United States of America, joined Dec 1999, 1714 posts, RR: 6 Reply 22, posted (13 years 6 months 5 days 12 hours ago) and read 831 times:
Just to add to the previous post,the guy in the bucket and in the truck cab communicate via a headset and boom mike,usually switched to "hot mike" so the guy in the boom can talk and give instructions and have his hands free to shoot and operate the boom/bucket. The guy in the cab can also control the boom/bucket arrangement and he also talks to the pilot via radio. A good team really makes it easier on both people.