De-icing
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Join Date: May 2006
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De-icing
OK, so say you get de-iced to remove snow from the aeroplane - assuming they use a mixture of hot water and type 2 fluid and they don't apply a second anti ice coat.
If it then begins to snow as you're on your way to the holding point, am I right in thinking that if you've just been de-iced, you only have minimal protection against further contamination and therefore don't really have any holdover times to rely on???
If it then begins to snow as you're on your way to the holding point, am I right in thinking that if you've just been de-iced, you only have minimal protection against further contamination and therefore don't really have any holdover times to rely on???
Join Date: Jun 2006
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De - icing / Snow / Change of weather
Yep, de-icing is an unpredictable thing with weather changes!
You could be de-iced for frost and be given a hold over time of five hours. BUT when it's / starts snowing, the fluid is being diluted and the hold-over time is reduced significantly to 15-20 mins! Thats why some smaller airports can't/won't de-ice in snow as they can't complete in time. as crew (if you are/were) you should have all the relevant information in the cockpit about holdover times according to the known fluid types used.
Otherwise the a.c should not be flown. Holdover times are guidelines only and are subject to change! I do hope training reflects this throughout the industriy!
Better safe than sorry, despite the thousands of extra pounds put on the bill!! Keep Safe!!!!
Take care
Deal
You could be de-iced for frost and be given a hold over time of five hours. BUT when it's / starts snowing, the fluid is being diluted and the hold-over time is reduced significantly to 15-20 mins! Thats why some smaller airports can't/won't de-ice in snow as they can't complete in time. as crew (if you are/were) you should have all the relevant information in the cockpit about holdover times according to the known fluid types used.
Otherwise the a.c should not be flown. Holdover times are guidelines only and are subject to change! I do hope training reflects this throughout the industriy!
Better safe than sorry, despite the thousands of extra pounds put on the bill!! Keep Safe!!!!
Take care
Deal
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Maybe is the answer. From what you saying, it looks like you were deiced and anti-iced in a single step procedure with less than 100% fluid. The other factors influencing your hold-over time (which commenced in your case when the treatment started) are the temperature, the type of precipitation and the de-icing fluid type. Using this information, you look your company's Ops manuals books to get the hold-over time range. Then you read the small print and find out that no-one is guaranteeing anthing!
PM
PM
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"Quote: If it then begins to snow as you're on your way to the holding point, am I right in thinking that if you've just been de-iced, you only have minimal protection against further contamination and therefore don't really have any holdover times to rely on???"
It depends on the OAT, rate of precipitation and the concentration of the Type II fluid used. If your company publishes the generic Type II holdovertime table in their Ops. manual and a 75/25 mix was used for the de-/anti-icing operation, guideline times in falling snow would have been between 15 to 30 minutes at 3 deg. C and above (15 minutes in moderate snow to 30 minutes in light snow) and 15 to 25 minutes at below 3 deg. C to 14 deg. C. Should a two-step operation have been carried out and concentrate Type II fluid used for the second step, the guideline times would have been 20 to 45 minutes at 3 deg. C and above and 15 to 35 minutes at below 3 deg. C to 14 deg. C.
Holdovertime tables are available for individual Type II fluids (these are used when compiling the generic table) and there is an option for companies to publish one or more of these fluid specific (brand name) tables in their Ops. Manuals, as well as the generic tables. There are benefits to this in that the table published for the most widely used Type II fluid in the UK shows the guideline times for a 75/25 mix as 30 to 65 minutes at 3 deg. C and above and 25 to 50 minutes below 3 deg. C to 14 deg. C. For concentrate fluids the times are 30 to 60 minutes at 3 deg. C and above and 25 to 45 minutes below 3 deg. C to 14 deg. C.
It depends on the OAT, rate of precipitation and the concentration of the Type II fluid used. If your company publishes the generic Type II holdovertime table in their Ops. manual and a 75/25 mix was used for the de-/anti-icing operation, guideline times in falling snow would have been between 15 to 30 minutes at 3 deg. C and above (15 minutes in moderate snow to 30 minutes in light snow) and 15 to 25 minutes at below 3 deg. C to 14 deg. C. Should a two-step operation have been carried out and concentrate Type II fluid used for the second step, the guideline times would have been 20 to 45 minutes at 3 deg. C and above and 15 to 35 minutes at below 3 deg. C to 14 deg. C.
Holdovertime tables are available for individual Type II fluids (these are used when compiling the generic table) and there is an option for companies to publish one or more of these fluid specific (brand name) tables in their Ops. Manuals, as well as the generic tables. There are benefits to this in that the table published for the most widely used Type II fluid in the UK shows the guideline times for a 75/25 mix as 30 to 65 minutes at 3 deg. C and above and 25 to 50 minutes below 3 deg. C to 14 deg. C. For concentrate fluids the times are 30 to 60 minutes at 3 deg. C and above and 25 to 45 minutes below 3 deg. C to 14 deg. C.
