De Icing the wings.

[bellevueace]

Flying a couple of days ago the conditions were sub zero with snow and ice. The captain informed us the aircraft was having the wings de iced then we would be taking on more fuel. After re fuelling which took about 15 mins the captain said the wings had iced up again and needed another de icing. On completion we set off but were behind quite a large queue of aircraft because of the conditions. Now if the wings had iced up in the fifteen minutes while refuelling surely they could have iced up during the similar amount of time we were in the queue for take off? How can this be avoided?

[navel_gazer]

Thanks for asking that question! I fly to the cold Midwest a lot in winter, and de-icing concerns are one of my anxiety triggers. I've also wondered about the possibility of icing up while waiting for a slot.

[MathFox]

Many airports have a de-icing platform near the departure end of the runway, so that it is only one minute taxiing before take off. However when the weather is clear (no rain, snow, hail or freezing fog) there will be no fresh ice on the plane after de-icing.

Here is a good blog post by a pilot about de-icing: http://fl250.blogspot.com/2008/11/iceman-cometh.html

[Barb-SAN]

Here is a good blog post by a pilot about de-icing: http://fl250.blogspot.com/2008/11/iceman-cometh.html
Thanks for linking that...he's a very good writer, and explains everything so thoroughly. I haven't flown in winter conditions for about, oh, 25 years or so, so haven't experienced all the de-icing procedures (and flight cancellations due to snowstorms). Guess I know what my next FF challenge should be...but it's so hard to leave sunny S.CA in winter...:angel:

[bellevueace]

An interesting and informative link, thanks.

[tusphotog]

Thanks for linking that...he's a very good writer, and explains everything so thoroughly. I haven't flown in winter conditions for about, oh, 25 years or so, so haven't experienced all the de-icing procedures (and flight cancellations due to snowstorms). Guess I know what my next FF challenge should be...but it's so hard to leave sunny S.CA in winter...:angel:

You want to see fun? Fly to Las Vegas when they have a low pressure system move in and it drops snow. They can't deal with deicing conditions up there.

A few years back (and Sam talks about it in that blog post), I flew into Portland in that ice storm. Driving was terrifying. I ended up being stuck up there for an extra six days after everything melted and flights resumed. This is what happened after the storm moved through: http://www.airliners.net/photo/Airborne-Express/McDonnell-Douglas-DC-9-41/0491116/L/

[Barb-SAN]

A few years back (and Sam talks about it in that blog post), I flew into Portland in that ice storm. Driving was terrifying. I ended up being stuck up there for an extra six days after everything melted and flights resumed. This is what happened after the storm moved through: http://www.airliners.net/photo/Airborne-Express/McDonnell-Douglas-DC-9-41/0491116/L/
I was wondering if anyone was going to point out that part of his blog post! That's quite a photo. I can imagine that driving was terrifying, especially since you probably did not have studded tires. It's scary enough WALKING after an ice storm (I do remember that from living in Michigan).

My question...Sam said there were several inches of ice that accumulated on the airplane DURING THE LAST FEW MINUTES OF THE FLIGHT. Um, what about the de-icing system on the wings? Would the pilot have known he was picking up ice on the body of the aircraft? Was he picking up ice on the windshield, or is that heated? How long could he fly in those conditions before the plane would become too heavy to fly? Wondering how they decide whether to keep going towards the airport, or turn around and try to get out of the storm?

Inquiring minds need to know...:eek:

[tusphotog]

I was wondering if anyone was going to point out that part of his blog post! That's quite a photo. I can imagine that driving was terrifying, especially since you probably did not have studded tires. It's scary enough WALKING after an ice storm (I do remember that from living in Michigan).

My question...Sam said there were several inches of ice that accumulated on the airplane DURING THE LAST FEW MINUTES OF THE FLIGHT. Um, what about the de-icing system on the wings? Would the pilot have known he was picking up ice on the body of the aircraft? Was he picking up ice on the windshield, or is that heated? How long could he fly in those conditions before the plane would become too heavy to fly? Wondering how they decide whether to keep going towards the airport, or turn around and try to get out of the storm?

Inquiring minds need to know...:eek:

The car I drive up in Oregon has stud-less ice tires (just put them on three weeks ago, actually). It's also an all-wheel drive car as well. The tires don't incur the "stud tax" that you pay to the state for destroying their roads, and they work quite well. Getting up and down the hills is a snap with the car, although there are two spots in particular that are a bit hairy. But by and large, driving in ice on hills is absolutely terrifying. Snow isn't so bad.

I don't know about specifics on the CRJ, but planes do have anti-ice systems on the wings, engine cowlings, and some control surfaces. The fuselage and the majority of the plane is unheated though. Going off memory from my MD-80 handbooks, the systems take hot air from the engines and send it to the leading edge of the wings, which will melt any and all ice. Cockpit windows are electrically heated (sometimes this system heats them up TOO much and they go pop--that's another story). Same goes for the engine cowls/spinners. Basically ice causes performance penalties for landing aircraft. It is heavy. Very heavy. So, the crew would probably just bump up the landing speed. The long runway at PDX is roughly 10,000 feet long, so there's plenty of room to stop. Taking off with ice buildup all over the airframe isn't good since you incur the same performance penalties. When ice builds up on the wing, it can actually change the shape of the airfoil, again, causing performance penalties, or making it difficult to generate lift.

As for visual clues, you can see it on the windshield, the wipers etc. Some airlines paint black strips on the wings (TWA did this). This black paint makes it easier to detect ice on the wings. I've never had the opportunity to see it in action, but it supposedly works.

I'm sure Hutch can elaborate on operating in icing conditions. Real world and hypothetical data/information are two completely separate things.

One other cool tidbit: A lot of prop planes don't have wing heat systems. Rather they have these "boots" that inflate and break ice off the leading edge. A few years ago, I was on a quick Horizon flight from Seattle to Portland and we were in the tops of the clouds most of the flight. I looked out and could see ice breaking off and flying away when the boots were inflated. Way cool to see.

[Barb-SAN]

The car I drive up in Oregon has stud-less ice tires (just put them on three weeks ago, actually). It's also an all-wheel drive car as well. The tires don't incur the "stud tax" that you pay to the state for destroying their roads, and they work quite well. Getting up and down the hills is a snap with the car, although there are two spots in particular that are a bit hairy. But by and large, driving in ice on hills is absolutely terrifying. Snow isn't so bad.Ah...I'd assumed you were driving a rental car. Late last Oct. I rented a car in Sacramento, and told them I would be driving to Lake Tahoe, and oh, by the way, what kind of tires does the car have? They were just regular (not studded or anything). There was rain one day and snow on the higher peaks, but no icing conditions. BUT...driving around the lake I was thinking that it could be a lot scarier to drive there in snow or ice. :shocked: I've actually never rented a car anywhere when it was snowing...:blush:...I seem to be firmly planted in San Diego during winter months!

Thanks for all the technical details about de-icing! :)

One other cool tidbit: A lot of prop planes don't have wing heat systems. Rather they have these "boots" that inflate and break ice off the leading edge. A few years ago, I was on a quick Horizon flight from Seattle to Portland and we were in the tops of the clouds most of the flight. I looked out and could see ice breaking off and flying away when the boots were inflated. Way cool to see.
Wow...didn't know about that. Were you wondering how much ice was accumulating on other parts of the plane where there were no boots? ;)

[MathFox]

I get that "I'd like to be someplace south" :sunshine: feeling nearly every year... usually comes with the first batch of melting snow. I have driven my bicycle and car through various "icing" conditions... Snow generally has enough friction for driving; ice requires care. I have rode my bicycle a few times over the frozen canals and it is slippery but doable; frozen roads are harder; every slope is dangerous.

BTW, going back to planes. Ice on the body of the plane is additional weight; the fuel savings alone will quickly pay for de-icing. Ice on the wings is more insidious as it changes their aerodynamic shape. For the stabilisers I don't know. Some planes have heating, some don't. Having too much ice on the tail is bad for balance; nice picture tusphotog.

Barb-SAN, I am pretty sure that the pilots knew they were picking up ice, but they also knew that they would land in mere minutes. I would not be surprised if they picked up the last inch of ice while they were taxiing to the gate.

[Captain Hutch]

Good question, Bellevueace,

The blog by Sam was pretty good and gives a nice summary of the whole procedure. To summarize, de-icing fluid clears off what snow, ice, or frost has accumulated on the aircraft, and anti-icing fluid protects the aircraft from additional accumulation, the time of which is dependent on air temperature and type of precip as the biggest factors. We use type one for deicing and type IV for anti-icing. This morning in Albany NY the temperature was -3 degrees centigrade and light snow was falling. We pushed off the gate a few yards, stopped, configured the aircraft for deicing and made contact with the person in the deicing truck, requesting type one and type IV because of the temperature and the fact that light snow was still falling. I used my handy-dandy deicing sheet as a guide to determine what type fluid I needed and also to calculate my Hold Over Time. I calculated an H.O.T. of 1 hour and 15 minutes. The HOT's are given in ranges usually and it's up to the pilots to narrow that number down to one specific time. I based mine on the fact that the snowfall was very light and the flakes small. We taxied out and took off in about ten minutes so we had plenty of extra leeway. Had our HOT been exceeded, I would have sent the co-pilot back to the cabin to look through the windows and visually confirm that the wings were clean. The FAA absolutely prohibits an aircraft from taking off with any contamination whatsoever adhering to the wings or any part of the aircraft. Had we noticed any snow sticking to the wings we would have returned to the gate for more de/anti-icing.

If the HOT hasn't been exceeded, we can observe from the cockpit part of the wings and the windshield if there is any precip sticking. I'm not sure what the situation was that you were talking about, but I can only think that the pilots observed from the flight deck after all that time in the queue the wings were clean and so they decided to take off.

In flight the aircraft has deicing protection on the parts of the airplane that are susceptible to ice buildup. I think MathFox covers most of these. On the 737-300 and -400 the recommended procedure inflight is to wait for ice build-up on the leading edge devices of the wings before applying wing heat, at which time pieces of ice will break away and the wing will be clean. However on approach the wing and engine anti-ice will be on in light icing conditions. We are not permitted to land in moderate or heavy icing conditions.

I'm glad that you brought this up as it is of interest to everyone, and I hope this helps somewhat.

Hutch :tiphat:

[bellevueace]

More good insight, thanks Captain. The other thing i always had a doubt about was the actual landing in icy conditions. Driving in these conditions is hairy let alone landing an aircraft. I still find it amazing how a plane can come in at the speed it does and touchdown in icy conditions without being thrown into a skid. Surely the runways cant be totally free of ice all the time? Recalling the Munich air disaster that wiped out the Manchester United team that was caused by icy conditions always brings these thoughts. I know that was over 50 years ago was deicing done then? Also for fear of flyers Bobby Charlton who survived that crash has since flown all around the world without incident, thats something else i think about and get confidence from.

[MathFox]

A plane has three systems to lose speed:

The airbrakes and flaps on the wings
Putting the engines in reverse
Brakes on the wheelsOnly the last braking system is influenced by slippery runways, the other two work on iced runways too. (and there is anti-skid on the wheelbrakes.)

[Captain Hutch]

Once I am configured for landing, i.e. gear down, and flaps in landing position, I concentrate totally on making sure that the aircraft is tracking exactly straight down the runway. It is hard to emphasize how important this is. When landing in icy or blizzard-like conditions I basically count on no wheel braking but I want the momentum of the aircraft to be headed specifically down the runway because the track that you have prior to touchdown will be your track once on the runway. Once the wheels touch, I put the trust levers in the idle position but do not deploy them right away since any uneven acceleration of reverse thrust could cause a skid one way or the other. The speed brakes deploy automatically (providing they are set that way by the pilot) and are pretty reliable as far as deploying evenly. I ease the reverse thrust in very delicately so as to cause no asymmetrical thrust. Gusty conditions make the approach and landing more difficult as you could imagine, but still this procedure works well enough. If I detect any sliding one way or the other when on short final then I will just go around. The crosswinds make it tricky but headwinds, even very strong ones, are very helpful in that they shorten the landing roll. Hairy sometimes--yes. You can't count on runway condition reports because they cannot keep up with actual conditions, however, we do have reduced crosswind limits when the braking action reports, "mu" readings which come from a truck rolling down the runway, are less than good. The best indicator of braking action is an airliner landing in front of you. And yes, in snowy conditions or right after the runways are never free of patches of snow or ice. Landing in these conditions are not my favorite, and yes, I do breathe a sigh of relief when I have slowed down enough to turn off the runway. In my humble opinion pilots are never underpaid!

Hutch :)

[Captain Hutch]

Whoops, I meant to say "pilots are never OVERpaid!" :D

[bellevueace]

Thanks again, i really have total confidence in the ability of the pilots to do their job and agree they certainly arent overpaid, they carry a lot of lives in their hands. My next flight is to Las Vegas in May so shouldnt have to be worrying about snow and ice on that one:D But there again with my luck lol.