gopal
Posts: 167
Joined: Thu Jun 03, 1999 3:05 am

De-Icing

Thu Dec 09, 1999 6:21 am

What are the latest de-Icing techniques available to Airline pilots /Maintenance teams. What is currently being done on Modern aircraft to prevent ice from jamming the control surfaces during flight?
 
cricri
Posts: 540
Joined: Sat Oct 02, 1999 12:10 am

RE: De-Icing

Fri Dec 10, 1999 12:32 am

Hi Gopal!
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.
Regards.
 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: De-Icing, Part 3

Fri Dec 10, 1999 2:59 am

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 .
g'day
 
Guest

RE: De-Icing, Part 3

Fri Dec 10, 1999 8:37 am

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
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: De-Icing/Anti-Icing

Fri Dec 10, 1999 11:15 am

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?

Best Regards,

Buff
 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: De-Icing, Part 5

Sat Dec 11, 1999 12:08 am

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
Posts: 167
Joined: Thu Jun 03, 1999 3:05 am

RE: De-Icing

Sat Dec 11, 1999 2:07 am

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
Posts: 983
Joined: Sun Oct 24, 1999 8:28 am

RE: De-Icing

Sat Dec 11, 1999 5:29 am

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.
Aircraft I've flown: A300/A310/A320/A321/A330/A340/B727/B732/B733/B734/B735/B738/B741/B742/B744/DC10/MD80/IL62/Bae146/AR
 
Guest

RE: De-Icing

Sat Dec 11, 1999 7:27 am

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
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: De-Icing, At Cruise

Sat Dec 11, 1999 10:52 pm

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
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: De-Icing

Sun Dec 12, 1999 12:25 am

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...
Posts: 1959
Joined: Tue May 18, 1999 8:32 am

De-icing

Sun Dec 12, 1999 11:50 am

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.
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1stClassFlyer
Posts: 183
Joined: Sat Nov 13, 1999 5:10 am

What Chemicals

Sun Dec 12, 1999 12:26 pm

why chemical mixture do they use to de-ice the planes?
 
AC183
Posts: 1496
Joined: Tue Jul 06, 1999 10:52 am

RE: What Chemicals

Sun Dec 12, 1999 3:02 pm

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
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: De-Icing/AC183/Hmmm..

Mon Dec 13, 1999 12:53 pm

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.

Best Regards,

Buff
 
Guest

RE: De-Icing, At Cruise

Tue Dec 14, 1999 9:47 am

Since when do you need moisture to make ice!?
Hasnt anyone done basic chem?
 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: Huh?

Tue Dec 14, 1999 12:46 pm

Hey Perth WA, could you explain what you mean? Hope you're keeping in mind the question asked was about aircraft icing...

Best Regards,

Buff
 
Guest

RE: Huh?

Tue Dec 14, 1999 2:42 pm

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
Posts: 1965
Joined: Tue Dec 07, 1999 12:35 pm

RE: De-Icing

Tue Dec 14, 1999 3:03 pm

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
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: De-Icing

Tue Dec 14, 1999 4:42 pm

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!

Best Regards,

Buff
 
akelley728
Posts: 1965
Joined: Tue Dec 07, 1999 12:35 pm

Infra-tek System

Sun Dec 19, 1999 1:20 pm

I landed at Newark yesterday, and saw the Infra-tek structure all lit up at the north end of the runway. I guess it's ready to go whenever we get our first icing conditions here in New Jersey!
 
NKP S2
Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am

RE: De-Icing

Mon Dec 20, 1999 3:46 am

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
Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am

RE: De-Icing

Mon Dec 20, 1999 3:55 am

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.
 
AC_A340
Posts: 2196
Joined: Wed Sep 08, 1999 12:01 pm

Dry Ice

Mon Dec 20, 1999 4:28 am

Frozen Carbon Dioxide freezes close to 100 kelvin. According to my chem teacher.

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