When to de-ice/Anti-ice?
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When to de-ice/Anti-ice?
Hi all,
Not having much experience in cold weather ops (none infact) im asking my self, given different scenarios would I de-ice or anti-ice.
De-icing doesnt seem to hard to understand, if the wing is contaminated then de-ice is needed and there isn't a hold over time, except LOUT if that counts.
So taking a Metar from a UK airfield
12013kt 4900 -SN OCV003 01/01 Q0993
Scenario A : Using the Metar above, the snow melts upon contact, do you Anti-ice?
Scenario B: Using similar conditions but instead its raining. Would you apply any fluid?
I personally would for Scenario A and im not sure for Scenario B but at those temperatures icing will occur??
Part II. Are most fluids applied, done in a one part process or two?
I've only arrived at an aircraft where the de-ice has been done by engineering.
Advise is much appreciated.
Thanks
Not having much experience in cold weather ops (none infact) im asking my self, given different scenarios would I de-ice or anti-ice.
De-icing doesnt seem to hard to understand, if the wing is contaminated then de-ice is needed and there isn't a hold over time, except LOUT if that counts.
So taking a Metar from a UK airfield
12013kt 4900 -SN OCV003 01/01 Q0993
Scenario A : Using the Metar above, the snow melts upon contact, do you Anti-ice?
Scenario B: Using similar conditions but instead its raining. Would you apply any fluid?
I personally would for Scenario A and im not sure for Scenario B but at those temperatures icing will occur??
Part II. Are most fluids applied, done in a one part process or two?
I've only arrived at an aircraft where the de-ice has been done by engineering.
Advise is much appreciated.
Thanks
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Personally I don't look at the ATIS or METAR so much as I do at MY wing. I don't base my decision on what everyone else is doing - only what is on my aircraft. If it is only very light snow and it is melting on contact and the temp is 3 or 4 degrees chances are I'm not deicing but every situation is different. I also consider the current and expected operational status of the airport and location of the deicing pads to determine whether I apply type 2 or 4 fluids.
A clear "It depends".
The METAR is nice to see, but it does not say much about the amount of deposit accumulating on the wing. The best way to find out about what is or is not there is still to get a ladder and climb on the wing to see and feel for Yourself - some ice is only detectable by putting the hand on it.
Some points about estimating the probability of ice accumulation:
-What is Your fuel tank temperature? If You carry lots of sub-zero fuel, beware of fuel-induced ice on the wings that may occur even with well positive temperatures in precipitation. One tell-tale sign may be frost on the wings lower surface.
-The METAR reports some wind. It may well be that the snow is drifting and not sticking to any surface in high wind conditions; mind the little stagnation corners on the leeward side of the fuselage e. g. and also turns during taxi when deciding not to deice.
-What is the weather doing in the longer term? If it is only slightly snowing, but there are dark clouds approaching, remember that deicing will take several minutes and select the required hold-over time and thereby the required fluid mixture with this in mind. A fluid selection that will get You airborne safely with only the odd snowflake falling will see the HOT run out in a flash in heavier precipitation.
-Type dependent, there are other tell-tale signs. On the DH8, when You turn the propellers and find deposit on the blades, You can be certain that the wings look the same. Deposit on the fuselage may be an indication too, but if You see nothing on the fuselage, remember that the cabin is heated unlike the wings. Again, climbing on the wings is the best way to find out what they look like - no need to speculate.
Of course, there is no doubt when it comes to deicing - if You are unsure whether to deice or not, decide for safety and have the plane deiced.
With regards to Your second question:
The selection of a 1 or 2 step procedure depends on whether there is deposit on the wings. Basically, the 1st step is about washing off whatever may be contaminating the wing; for that, hot water with some rather highly diluted fluid is used (refer to tables for exact selection). After this step, the wing is clean, but the HOT is typically nil to rather short. So if there is no precip., You are good to go. But if there is precipitation present, in a 2nd step a (nearly) undiluted Type 2 or 4 liquid is sprayed on to protect against the new contamination and get a usable hold over time. Again, refer to Your companies tables for fluid and mixture selection.
The METAR is nice to see, but it does not say much about the amount of deposit accumulating on the wing. The best way to find out about what is or is not there is still to get a ladder and climb on the wing to see and feel for Yourself - some ice is only detectable by putting the hand on it.
Some points about estimating the probability of ice accumulation:
-What is Your fuel tank temperature? If You carry lots of sub-zero fuel, beware of fuel-induced ice on the wings that may occur even with well positive temperatures in precipitation. One tell-tale sign may be frost on the wings lower surface.
-The METAR reports some wind. It may well be that the snow is drifting and not sticking to any surface in high wind conditions; mind the little stagnation corners on the leeward side of the fuselage e. g. and also turns during taxi when deciding not to deice.
-What is the weather doing in the longer term? If it is only slightly snowing, but there are dark clouds approaching, remember that deicing will take several minutes and select the required hold-over time and thereby the required fluid mixture with this in mind. A fluid selection that will get You airborne safely with only the odd snowflake falling will see the HOT run out in a flash in heavier precipitation.
-Type dependent, there are other tell-tale signs. On the DH8, when You turn the propellers and find deposit on the blades, You can be certain that the wings look the same. Deposit on the fuselage may be an indication too, but if You see nothing on the fuselage, remember that the cabin is heated unlike the wings. Again, climbing on the wings is the best way to find out what they look like - no need to speculate.
Of course, there is no doubt when it comes to deicing - if You are unsure whether to deice or not, decide for safety and have the plane deiced.
With regards to Your second question:
The selection of a 1 or 2 step procedure depends on whether there is deposit on the wings. Basically, the 1st step is about washing off whatever may be contaminating the wing; for that, hot water with some rather highly diluted fluid is used (refer to tables for exact selection). After this step, the wing is clean, but the HOT is typically nil to rather short. So if there is no precip., You are good to go. But if there is precipitation present, in a 2nd step a (nearly) undiluted Type 2 or 4 liquid is sprayed on to protect against the new contamination and get a usable hold over time. Again, refer to Your companies tables for fluid and mixture selection.
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Thanks guys! Im just trying to get into the right mindset and how people think. Im hoping to be kept on over the winter this year so I can get some experience but until then its just theory.
The aircraft in question is B737.
The aircraft in question is B737.
Don't trust visuals, they don't cover all possibilities for the next few minutes of operation.
Follow the FCOMs they were designed to allow margins for the eyeball or wetted finger-in-the-wind judgements.
Follow the FCOMs they were designed to allow margins for the eyeball or wetted finger-in-the-wind judgements.
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It was discussed briefly during line training, but as it was the summer it wasn't spoken of a lot. I know for sure its covered in the OPC/LPC with LVP's but unfortunately if your one of these summer contract guys you get little AWOP's experience.
Usually im in the tropics, and we dont see a lot of snow or ice there
Usually im in the tropics, and we dont see a lot of snow or ice there
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Typically
Typically, Type I fluid is for de-icing....cleaning off the aircraft....although
it does have to a small degree anti-icing capabilities. "Small degree"is the
key term.
Type II or IV fluids are really for anti-icing, and are to be used after the
aircraft is clean(ed).
Looking at the METAR is good, but there are other factors that must be considered. The bottom line is that there must be no snow/ice adhering
to the critical surfaces of the aircraft....for some operators, the SOPs go
further by requiring all surfaces be free of ice/snow, not just critical surfaces.
(My former company had these more srtict policies.)
Other factors are...and this list is not exhaustive:
1. Wind,
2. Is the aircraft cold-soaked,
3. Temperature of the fuel in the wing tanks,
4. Estimated time from completion of spraying to takeoff,
5. How big a problem would it be to, when getting to the number
one slot for takeoff and determining the aircraft needs more spray,
(You might just want to go with Type IV from the start of things.)
6. Dewpoint,
7. Geography (are you near water? See point #6),
8. Number of planes in line for takeoff....will ATC ask you
to snuggle up...thereby having the aircraft in front of you blow
off all your protection with his jet blast,
There are more factors....I'm sure we have numerous experienced
guys reading this who can add to the list (make a few changes and
suggestions).
Personally, if there was any precip falling, I'd almost always opt
for cleaning with Type I, and ask for Type IV. It's more expensive
for the company, but it's the safe thing to do. (maybe overkill, but
safe)
it does have to a small degree anti-icing capabilities. "Small degree"is the
key term.
Type II or IV fluids are really for anti-icing, and are to be used after the
aircraft is clean(ed).
Looking at the METAR is good, but there are other factors that must be considered. The bottom line is that there must be no snow/ice adhering
to the critical surfaces of the aircraft....for some operators, the SOPs go
further by requiring all surfaces be free of ice/snow, not just critical surfaces.
(My former company had these more srtict policies.)
Other factors are...and this list is not exhaustive:
1. Wind,
2. Is the aircraft cold-soaked,
3. Temperature of the fuel in the wing tanks,
4. Estimated time from completion of spraying to takeoff,
5. How big a problem would it be to, when getting to the number
one slot for takeoff and determining the aircraft needs more spray,
(You might just want to go with Type IV from the start of things.)
6. Dewpoint,
7. Geography (are you near water? See point #6),
8. Number of planes in line for takeoff....will ATC ask you
to snuggle up...thereby having the aircraft in front of you blow
off all your protection with his jet blast,
There are more factors....I'm sure we have numerous experienced
guys reading this who can add to the list (make a few changes and
suggestions).
Personally, if there was any precip falling, I'd almost always opt
for cleaning with Type I, and ask for Type IV. It's more expensive
for the company, but it's the safe thing to do. (maybe overkill, but
safe)
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If visually nothing is 'adhering' to the aircraft(ie 2c and -snow)and after tactil check then no deicing/anti icing.
Keep your distance from other aircraft to avoid blow off as described above.(50 meters are usually standard).
If precip increasing and temp dropping during taxi,ask a crew to have a look from the cabin.
FCOM SUPP Procedure cold weather is a good start...
Cold soak information in your FCOM is NOT a guarantee that your Airline is approved by your state authority to allow for such contamination.
Your airline must advise crew if cold soak or clean wing concept is to be followed.
Keep your distance from other aircraft to avoid blow off as described above.(50 meters are usually standard).
If precip increasing and temp dropping during taxi,ask a crew to have a look from the cabin.
FCOM SUPP Procedure cold weather is a good start...
Cold soak information in your FCOM is NOT a guarantee that your Airline is approved by your state authority to allow for such contamination.
Your airline must advise crew if cold soak or clean wing concept is to be followed.
Last edited by de facto; 11th Feb 2013 at 05:09.
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"If there's doubt there is no doubt. " If in doubt anti-ice. The time interval between making the decision NOT to anti-ice and taking off is indeterminate, as is the fickleness of the weather. The next decision is if you need to de-ice first. Sitting at the end of the rwy wondering if this takeoff is going to be safe, or should we have anti-iced, is not healthy. It is not possible to see the wings from the cockpit. Delays? It's better to be 10 minutes late on departure than 20 years early upstairs.
I do understand the technicalities in your question, but it is not an exact science. However, there are solid guidelines and legal boundaries.
I do understand the technicalities in your question, but it is not an exact science. However, there are solid guidelines and legal boundaries.
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Thanks guys and girls! I forgot to mention in my OP about visually checking the wings.
As some of you said its not an exact science, and seems experience does play a big part.
As some of you said its not an exact science, and seems experience does play a big part.
As some of you said its not an exact science, and seems experience does play a big part.
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Roughness, not quantity, kills.
Aircraft Icing Training - A Pilot's Guide to Ground Icing
Helps with insomnia before an early report too.
Helps with insomnia before an early report too.
