de-anti icing
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Interesting thread with some positive feedback to it.pilot737.
To answer the original question I believe that the procedure is floored, in that potential would still exist for the melted frost to refreeze prior to take-off. While the uplifted fuel may raise the temperature of the upper wing skin to above the FP, other areas, e.g. where the L/G and engine(s) are attached to the wing, contain large amounts of metal which may have remained below 0 deg. C since the previous flight, or have dropped below that level due to the sub-zero conditions reported. Also if the frost was originally present on the L/E or T/E surfaces, it is unlikely to have been removed by the uplifted fuel. As suggested in the majority of posts, the only safe option would be to have the upper surface of the wings de-iced prior to take-off.
With regard to the Boeing ‘upper wing frost’ alleviation on their 737 NG aircraft, it is my understanding that this only comes into play under very closely defined conditions. For example, when ‘normal’ de-icing conditions exist at an Airport, i.e. when surfaces of all/the majority of departing aircraft have been contaminated by frost, ice slush and snow and require de-icing, standard procedures will apply and the upper wing surfaces of all aircraft, including the 737 NG, will receive a full de-ice.
However, due to the design of the 737 NG it is not uncommon for frost to be found on specific areas on the upper wing surface, even though the OAT may be above 0 deg. C and the majority of other aircraft types do not require de-icing. Don’t have any details but assume it’s associated with the design of the wing. I believe the alleviation allows for take-off with frost in these relatively small areas, provided it is within the painted lines. Must say that I have also seen similar small areas of frost on the wings of A320 series aircraft under the same conditions but presumably Airbus have not been pressurised by customer airlines into introducing a similar alleviation for these aircraft.
A significant number of the above posts quite rightly question the advisability of allowing take-off with frost patches, albeit small ones, on the upper surfaces of the wings. However, one aspect that hasn’t been discussed is the aerodynamic effect of the de-/anti-icing fluid residues that remain on the wings following treatment.
Following work they carried out during the late 80’s Boeing stated, “Flight tests show that both Type I and Type II (Type III and Type IV fluid did not exist at that time) de-icing/anti-icing fluids do flow off the wings of a treated aircraft in significant amounts during initial take-off ground run. However, the residual fluid is sufficient to cause a temporary decrease in lift and increase in drag during rotation and initial climbout....” They subsequently confirmed that sufficient performance margins were available on their aircraft to offset the effects of the fluids but there was still a detrimental effect on performance.
It’s possible that the aerodynamic effect of the small frost patches on 737 NG aircraft was found to be less than that of the de-/anti-icing fluid flowing off a fully de-iced wing, so there would appear to be some justification for introducing the alleviation.
To answer the original question I believe that the procedure is floored, in that potential would still exist for the melted frost to refreeze prior to take-off. While the uplifted fuel may raise the temperature of the upper wing skin to above the FP, other areas, e.g. where the L/G and engine(s) are attached to the wing, contain large amounts of metal which may have remained below 0 deg. C since the previous flight, or have dropped below that level due to the sub-zero conditions reported. Also if the frost was originally present on the L/E or T/E surfaces, it is unlikely to have been removed by the uplifted fuel. As suggested in the majority of posts, the only safe option would be to have the upper surface of the wings de-iced prior to take-off.
With regard to the Boeing ‘upper wing frost’ alleviation on their 737 NG aircraft, it is my understanding that this only comes into play under very closely defined conditions. For example, when ‘normal’ de-icing conditions exist at an Airport, i.e. when surfaces of all/the majority of departing aircraft have been contaminated by frost, ice slush and snow and require de-icing, standard procedures will apply and the upper wing surfaces of all aircraft, including the 737 NG, will receive a full de-ice.
However, due to the design of the 737 NG it is not uncommon for frost to be found on specific areas on the upper wing surface, even though the OAT may be above 0 deg. C and the majority of other aircraft types do not require de-icing. Don’t have any details but assume it’s associated with the design of the wing. I believe the alleviation allows for take-off with frost in these relatively small areas, provided it is within the painted lines. Must say that I have also seen similar small areas of frost on the wings of A320 series aircraft under the same conditions but presumably Airbus have not been pressurised by customer airlines into introducing a similar alleviation for these aircraft.
A significant number of the above posts quite rightly question the advisability of allowing take-off with frost patches, albeit small ones, on the upper surfaces of the wings. However, one aspect that hasn’t been discussed is the aerodynamic effect of the de-/anti-icing fluid residues that remain on the wings following treatment.
Following work they carried out during the late 80’s Boeing stated, “Flight tests show that both Type I and Type II (Type III and Type IV fluid did not exist at that time) de-icing/anti-icing fluids do flow off the wings of a treated aircraft in significant amounts during initial take-off ground run. However, the residual fluid is sufficient to cause a temporary decrease in lift and increase in drag during rotation and initial climbout....” They subsequently confirmed that sufficient performance margins were available on their aircraft to offset the effects of the fluids but there was still a detrimental effect on performance.
It’s possible that the aerodynamic effect of the small frost patches on 737 NG aircraft was found to be less than that of the de-/anti-icing fluid flowing off a fully de-iced wing, so there would appear to be some justification for introducing the alleviation.
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To add to 'it.pilot's' query and to explain a little more of the 'problem' to 'Ice-bore', with reference to the 737 NG the 'frost' occurs due to fuel cold soak during prolonged cruise in cold upper temperatures. The 'thin wing' then allows the cold fuel to cool the wing surface, and cause condensation (obviously humidity related). If the fuel temperature in the wing is below zero, this dew can/will then freeze to produce a thin 'frost'. The thermal capacity of the cold fuel prevents the wing from warming up in line with the rest of the aircraft, even in OATs of 14-15 degrees C or more. I have had the problem at 20 deg C.
It affects ONLY the wing - the rest of the structure (no fuel contained therein - eg
is not affected. They normally 'warm-up' on a t/round. If I elect to de-ice in these conditions I will de-ice only the wing upper surface. The addition of 'warm' fuel in an uplift [beware it is 'warm' - I have like a previous poster, seen sub-zero fuel loaded (in Krakow)] will, providing there is sufficient uplift, raise the tank fuel temperature to above zero. The 'frost' will melt, leaving 'dew'. In the OATs we are looking at (10 deg C plus), there is NO WAY the 'dew' will refreeze and it will obviously disappear during take-off and flight.
The upper surface is the problem - lower surface ice is allowed in controlled conditions. If you have arrived in Egypt in summer and ask to be de-iced, it proves a little difficult.
This is, IMO, a reasonable attempt (with testing) to review the age-old philosophy of a 'clean upper wing.
I have not looked in detail at the Boeing lnk above, but I'm pretty sure there is no 'condition' that de-icing is not available? I cannot see why people are getting so 'heated' about this - if Boeing have tested it, the 'frost' is withing the defined area and is the 'correct' type PLUS it does not affect the handling/performance any more than a coating of de-icer, what is the issue?
It affects ONLY the wing - the rest of the structure (no fuel contained therein - eg
other areas, e.g. where the L/G and engine(s) are attached to the wing, contain large amounts of metal which may have remained below 0 deg. C )
The upper surface is the problem - lower surface ice is allowed in controlled conditions. If you have arrived in Egypt in summer and ask to be de-iced, it proves a little difficult.
This is, IMO, a reasonable attempt (with testing) to review the age-old philosophy of a 'clean upper wing.I have not looked in detail at the Boeing lnk above, but I'm pretty sure there is no 'condition' that de-icing is not available? I cannot see why people are getting so 'heated'
about this - if Boeing have tested it, the 'frost' is withing the defined area and is the 'correct' type PLUS it does not affect the handling/performance any more than a coating of de-icer, what is the issue?
The issue BOAC is that not all airport personnel are as educated as yourself.
Pressure will be applied by those in positions of authority (IE the ones holding the purse strings) to accomodate the B737NG philosophy on all aircraft types, irrespective of safety procedures. It happens now even with a simple 'no ice on upper surface rule'. Station managers and the like insist that they know better. I have witnessed an uninformed station manager tell a captain that his aircraft didn't need de-icing when clearly it did (that one got an MOR).
Keep it simple.
Pressure will be applied by those in positions of authority (IE the ones holding the purse strings) to accomodate the B737NG philosophy on all aircraft types, irrespective of safety procedures. It happens now even with a simple 'no ice on upper surface rule'. Station managers and the like insist that they know better. I have witnessed an uninformed station manager tell a captain that his aircraft didn't need de-icing when clearly it did (that one got an MOR).
Keep it simple.
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BOAC
As mentioned by Turin keep it simple.
Regarding training for winter operations we work off our company procedures (keeping it simple) based on AEA etc and the many customer requirements. Our annual training includes aerodynamics and videos with examples like the BHX crash a couple of years ago included in it.
In my experience it is shocking how many pilots (unlike you) are worryingly under trained on this subject. It. pilot737 or any other pilot should have this basic knowledge.
How many of you de-icers reading this have had to explain to crews why they must turn of the air-con when we de-ice?
The worse e.g. I have is pleading with a skipper to get out of the flight deck and look at the inch long ice stalactites under just one side of his wing. After a heated debate he gave us the go ahead to clear it. I am sure if he had gone that would have been a disaster.
Us idiots, who take responsibility and freeze our tits off de-icing aircraft, take onboard a moral responsibility after our experience and training. Some say we just push for company profits. This could be true but I bet it is rare?
There are people also who de-ice who are sadly chucked in the deep end with very little training.
The whole subject should be better regulated and improved or the luck one-day will run out?
BOAC that is the heated issue I think!
I probably have de-iced you i/b from Gambia?
As mentioned by Turin keep it simple.
Regarding training for winter operations we work off our company procedures (keeping it simple) based on AEA etc and the many customer requirements. Our annual training includes aerodynamics and videos with examples like the BHX crash a couple of years ago included in it.
In my experience it is shocking how many pilots (unlike you) are worryingly under trained on this subject. It. pilot737 or any other pilot should have this basic knowledge.
How many of you de-icers reading this have had to explain to crews why they must turn of the air-con when we de-ice?
The worse e.g. I have is pleading with a skipper to get out of the flight deck and look at the inch long ice stalactites under just one side of his wing. After a heated debate he gave us the go ahead to clear it. I am sure if he had gone that would have been a disaster.
Us idiots, who take responsibility and freeze our tits off de-icing aircraft, take onboard a moral responsibility after our experience and training. Some say we just push for company profits. This could be true but I bet it is rare?
There are people also who de-ice who are sadly chucked in the deep end with very little training.
The whole subject should be better regulated and improved or the luck one-day will run out?
BOAC that is the heated issue I think!
I probably have de-iced you i/b from Gambia?
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De Icing training
Have just got to read the threads on this subject having been away in warmer climates.
Its no surprise that there exists a great deal of ignorance on both the aviators side as to when to de ice and on the ground side as to what deicing means.
Many years ago I lost a lot of fellow aviators when a Britannia crashed in the USA and which deicing, or the lack of it, played a part. Therefore, now building and selling aircraft de icers as well as being involved in training on their use, the subject is somewhat 'personal' for me.
The KISS principle revails. Make clean and keep it clean, a statement from a previous thread. If its ice or looks like ice, get it off.
On the ground side, and this is a proven area of the cause of possible invertion after take off due incorrect deicing, an airport in the UK who wanted to introduce deicing for its customers this season laboured under the impression that you just ordered the vehicle, sat a short course and then went deicing!! No consideration of the regulations, fluids, training and so on. It even got to the point of enquiring one afternoon half way through a second classroom course if they would be ready to deice that night!!
Yes, training is the key for both those who fly and those who spray as the next accident is, unfortunately fast approaching the ground I fear.
Its no surprise that there exists a great deal of ignorance on both the aviators side as to when to de ice and on the ground side as to what deicing means.
Many years ago I lost a lot of fellow aviators when a Britannia crashed in the USA and which deicing, or the lack of it, played a part. Therefore, now building and selling aircraft de icers as well as being involved in training on their use, the subject is somewhat 'personal' for me.
The KISS principle revails. Make clean and keep it clean, a statement from a previous thread. If its ice or looks like ice, get it off.
On the ground side, and this is a proven area of the cause of possible invertion after take off due incorrect deicing, an airport in the UK who wanted to introduce deicing for its customers this season laboured under the impression that you just ordered the vehicle, sat a short course and then went deicing!! No consideration of the regulations, fluids, training and so on. It even got to the point of enquiring one afternoon half way through a second classroom course if they would be ready to deice that night!!
Yes, training is the key for both those who fly and those who spray as the next accident is, unfortunately fast approaching the ground I fear.
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When Boeing introduced its alleviation allowing you to get airborne with a small amount of frost on the upper wing I was very suspicious of the whole thing and refused to do it for a time while I tried to understand what was behind it. After all if you stall after take-off low down your not coming back, unless you have a rocket seat, as has been tragicaly proven many times.
Now I'm quite happy with it as it has all been tested, is well documented and trained for and can only be done in very specific circumstances. My company have never and will never put pressure on people not to de-ice and I have never heard of a decision to de-ice queried.
At the end of the day you have to know your type and the manufacturers recommendations for how to operate it and why, you also need to be totaly familiar with winter ops and if in doubt de-ice. If you still not happy do it again until you are happy or don't go its not an area to take chances with. Keep reviewing your decisions until you take-off so you know they remain valid and all will be well.
Anyone assuming snow will simply blow away is on their way to an early grave, get it brushed off then inspect it and proceed from there. I once had to do a 2 stage de-ice in these circumstances as the bottom layer of snow had compacted into some very nasty ice and that was in sub zero conditions without a refuel.
Now I'm quite happy with it as it has all been tested, is well documented and trained for and can only be done in very specific circumstances. My company have never and will never put pressure on people not to de-ice and I have never heard of a decision to de-ice queried.
At the end of the day you have to know your type and the manufacturers recommendations for how to operate it and why, you also need to be totaly familiar with winter ops and if in doubt de-ice. If you still not happy do it again until you are happy or don't go its not an area to take chances with. Keep reviewing your decisions until you take-off so you know they remain valid and all will be well.
Anyone assuming snow will simply blow away is on their way to an early grave, get it brushed off then inspect it and proceed from there. I once had to do a 2 stage de-ice in these circumstances as the bottom layer of snow had compacted into some very nasty ice and that was in sub zero conditions without a refuel.
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...and yet again... Two 737's, operated by a large European LCC took off today, one with roughly 6-8 square meters of 2 mm + coarse ice on the right wing, and the other with 2 mm + coarse ice covering about 50% of the fueltanks on both wings (RASN on coldsoaked wings in both cases)...
Both crews decided that it was just water, without performing a tactile check, even though ladder was provided. When informed that there was in fact ice on the wings, they simply denied it, claiming it was water...
Both crews decided that it was just water, without performing a tactile check, even though ladder was provided. When informed that there was in fact ice on the wings, they simply denied it, claiming it was water...
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I have seen a very thin layer of frost removed completely from the top surface of the wing by filling the fuel tanks with relatively warm fuel. There was no moisture left at all on the wing - completely dry, so nothing to refreeze back on.
An unusual situation.
What about the tailplane, though? Well, the tail provides lift in the opposite direction (i.e. downward) on most aircraft. Therefore, a very light dusting of frost on the upper surface of the tailplane is the equivalent of the same dusting of frost under the main wing, and may therefore be acceptable, depending on the manufacturer's limitations.
An unusual situation.
What about the tailplane, though? Well, the tail provides lift in the opposite direction (i.e. downward) on most aircraft. Therefore, a very light dusting of frost on the upper surface of the tailplane is the equivalent of the same dusting of frost under the main wing, and may therefore be acceptable, depending on the manufacturer's limitations.
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BOAC. Yes, I think I've got it.
But the very thin layer of frost I mentioned had occurred overnight (not due to a cold soaked wing in flight) with the aircraft parked outside.
The warmer fuel de-frosted the wing, and the rising sun evaporated any dew immediately.
But the very thin layer of frost I mentioned had occurred overnight (not due to a cold soaked wing in flight) with the aircraft parked outside.
The warmer fuel de-frosted the wing, and the rising sun evaporated any dew immediately.
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That is by no means uncommon, and often a fuel uplift is not even necessary. As the wing warms up in the morning sun................
If the tailplane is 'frosted' and there is no sign of it melting, I would guess the wings are the same and therefore = de-ice. This again is a separate issue to cold-soak frost.
If the tailplane is 'frosted' and there is no sign of it melting, I would guess the wings are the same and therefore = de-ice. This again is a separate issue to cold-soak frost.
