Apologies, I got lost in the fog of life recently and haven't had the time to write anything. Work continues to be quiet after the holidays have subsided, and I've been managing to get other things done in life with the time off I have.
I was doing well this winter to avoid the messy business of de-icing, but my luck ran dry shortly after Christmas and I ended up with more than my fair share. I started off in the business as a seasonal worker, covering the busier times of year during the summer and so managed to avoid anything to do with de-icing for a long time in the job. As such, it's not one of my areas of expertise so I can't give you a short lesson on it, other than the basics I know and the mess it causes for us.
There are a few different types of de-icing fluid that range in the time they remain effective for before de-icing would be required again. The Type II fluid we use I'm told is little more than a more expensively priced version of sugar and water, and is sticky stuff. After being applied to the wings it tail, it drips off onto the ramp forming puddles. I end up walking through it while doing my job, my trousers get covered in it, my headset gets covered in it, and I end up back in the office feeling somewhat like a school glue stick.
Those of you who follow Flightlevel390.com will have seen Capt Dave's recent two posts on de-icing at JFK, and the specially built 'house' for it. At my lesser equipped airport, we have no such facility and the de-icing is carried out on the apron where the aircraft park.
A fancy cherry-picker type truck drives around the aircraft. One ramp guy is in the basket of the cherry-picker with the nozzle, directing it at the required areas, while a driver in the truck moves around the aircraft as necessary. The two of them communicate via an intercom system in a 10-4 Rubber duck type lingo similar to that in the 1970s film, Convoy. Or so I like to imagine anyway.
The fluid is heated before being sprayed on, to around 80 degrees Celsius. It can be used at lower temperatures but is most effective around 80. It's heated within the de-icing rig, and can take about 10 minutes to heat up. The rig then moves around the aircraft to allow a good position to spray the required surfaces. De-icing usually takes about 10-15 minutes, depending on what areas need de-icing and the size of the aircraft.
A gauge in the truck records the amount of de-icing fluid used for each aircraft, and this is used to work out the billing for the airlines. Some typical values are around 200 litres to de-ice the wings and tail of a 737 or A320 sized aircraft.
It's a surreal image standing freezing on the ramp watching an aircraft get de-iced. In the darkness of early morning you watch the steam rise from the aircraft as the heated de-icing fluid hits the wings and tail. The sight always reminds of giving my dog a wash, while scratching behind his ears to keep him happy.
Thankfully, in my climate, we don't get the more extreme cold temperatures that New York get and so the fluid tends to last unless it's significantly colder than usual or it's snowing/raining. I can only remember a select few occasions where aircraft have left the ramp for departure but had to return due to exceeding the hold-over time.
It can lead to delays, which we always try best to avoid but sometimes just happen. We can't de-ice during boarding, unless the aircraft is on a jetty/airbridge. Spraying 80 degree hot fluid over the tops of passengers would lead to around 150 law suits per flight, and that would put us out of business rather quickly. Instead, if it's 'warm' enough with no rain/snow, we can try and de-ice before the passengers start to board. This means we need to get an early call from the crew to say they need de-icing, and what areas they want done. It might just be the wings and tail, it may be over most of the fuselage too. If we can't find out early enough, it will have to wait until after boarding and the doors are closed.
Don't let my ignorance of de-icing worry you, the crew and de-icing guys know much more about it than I do, in this situation I'm merely the messenger boy between crew and ramp guys. I'll stick to smaller tasks of trying to de-ice my windshield when I return to the car after a cold shift.
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3 comments:
De-icing is not a simple topic.
At the introductory level it is the act of spraying a hot liquid one an aircraft to melt all the frozen stuff off it, and since there is a little bit of anti-freeze in it then you get a little bit of protection against the de-icing fluid just becoming the newest layer of ice.
When you get into the four types of de-icing fluids, the ambient temperature, the temperature of the fluid when applied, whether it is precipitating (and whether it is rain, sleet, or snow), and the time elapsed before take-off, it gets a bit more complex. There are charts and tables which must be used to determine a go.nogo decision for the time period after de-icing.
Then there is anti-icing (as opposed to de-icing) spray, which if used is applied after the de-icing. It's a sticky substance which doesn't drip off, but adheres to the surfaces until 100KMPH is reached on the take-off run at which time it peels off, leaving a bare and dry wing. It too has a maximum holdover time (it can only absorb so much precip before it will fail to peel off).
Here in Canada the major airports all have de-icing pads, we never spray the aircraft at the gate. The key benefits are the the optimal use of the spraying hardware (you don't need to have enough hardware to spray all the airplanes on-demand, you only need to be able to spray them at a rate higher than the runways can handle). And environmental - the de-icing pads have sumps under them which collect all the de-icing fluid which drips off the aircraft, instead of having it go into the local environment. The collected fluid is re-processed and recycled into other industries, it never gets collected, re-heated and re-used on airplanes since it's level of dilution, and therefore the level of anti-ice performance, is now unknown.
Jim,
Many thanks for the detailed post, certainly gives me more an insight into a grey area for me.
De-icing areas had been discussed at ours, but still haven't been introduced. Unfortunately the airport weighed up the cost of introducing them versus the number of days and volume of traffic that's being de-iced, and haven't gone with it yet. Hopefully someday, as it'll be efficient and leave the ramp cleaner for us to work on.
200 L on A320 or B737 that is probably only anti-icing procedure not both: de-icing/ anti-icing. 200 L it is used on SF34.
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