Honest De-Icing Question

[thirdtimecharm]

Hello,

I work on the ramp in a northern town that sees two competing Boeing 737-200's landing at basically exactly the same time six times per week. The company that we are associated with has us prep for de-icing if the ground temperature is under +15 degrees while the other guys don't. We have had to de-ice several times in what has been our warmest summer in a long time, even when it was over 10 degrees on the ground and there was no visible ice on the wing.

While we would never question a Captain's decision to request de-icing (we get paid basically to sit around waiting) the difference in SOPs between the two companies is interesting and we were just curious as to why there was such a big difference considering we are talking about the same aircraft type flying the same routes on the same day. The one Captain we asked took the question the wrong way and thought that we were questioning his decision... we weren't- we are just curious.

None of us have ever been on an aircraft down south that de-iced when it was +15 on the ground. Is there implied pressure when one 737 scoots out to the runway and takes off while the competition takes a 45 minute de-icing delay on a sunny +10 day?

I need to stress that I am not trying to imply someone is being unsafe. Just trying to understand the thought process behind the decision.

Thanks!

[DHC2eater]

Different pilots do different things...... Common sense and experience play a large role in day to day operations. One should never take off with wing contamination as you know.....I can't maintain a frosty beer glass in above freezing temps.

Eater

[Rockie]

If an aircraft lands with a lot of fuel in the tanks after a prolonged cruise at high altitude the fuel remaining can be very very cold. If the aircraft is then filled up close to the top of the tanks the fuel in the tanks can still be well below freezing and cause the temperature on the top of the wing to freeze. If there is moisture in the air it can condense, freeze and cover the wing over the tanks in frost even in very warm outside air temperatures.

I don't know if this was the issue but it is certainly possible. When tankering gas to Mexico or the Caribbean I have on occasion almost had to wait for the frost on top of the wing to soften and melt before taking off on a short turn, and it was much warmer than 15 degrees.

[pdw]

... the fuel in the tanks can still be well below freezing and cause the temperature on the top of the wing to freeze.

OK; in the scenario where the one aircraft has five tonnes fuel still remaining upon landing at a -30C cold-soaked fuel-temp:
In the pilot's quickturn/stopover time, say the fueler provides another five tonnes at +10C for the next flightplan; now the whole load is warmed/averaged only to -10C. There any moisture contacting that wing's surface (behind which that fuel is being loaded-in/stored) can get below freezing ...esp if dark/cloudy and calm wind during that quickturn. Lately it seems there have been cases where optics really mattered too.

With a zero tolerance for frost, when a pilot's calculation result shows there's chance for frozen material, then he/she is simply making a right decision to spray on some anti-ice fluid as prevention ... or de-ice as the remedy for even the smallest amounts.

If there is moisture in the air it can condense, freeze and cover the wing over the tanks in frost even in very warm outside air temperatures.

Knowing when an appropriate anti-ice application is necessary ... is maybe not always so easily predictable as to being right on / accurrate. Under some circumstances it's understandable that shooting fluid onto the aircraft might seem like a waste. So how much prevention volume does it take when ice/frost is not yet visible ? A bit less ? Or is there some effort to recycle the product ... so that the waste isn't so great when the whole generous helping hits the pavement/drains below ?

[justwork]

esp if dark/cloudy and calm wind during that quickturn.

[pdw]

(lol) Just saying, with sun on the wings or overcast ... is like night and day for the situation described. I doubt frost can form on that minimally cold-soaked wing if there's enough of a breeze at 10-15C .. or in bright sunshine, although interesting combinations are known to be possible.

[thirdtimecharm]

Thanks for the replies... and again I wasn't trying to criticize- just seemed like very different SOPs and not saying one is better than the other.

[Rockie]

Thanks for the replies... and again I wasn't trying to criticize- just seemed like very different SOPs and not saying one is better than the other.

It isn't really a question of different SOP's since the clean wing regulations apply equally to all operators (exception being the frost exemption WestJet has).

More than likely it was a difference in circumstances between airplanes or the pilot decision making. It is not likely a company SOP will dictate de-icing when none is required since it costs a lot of money.

[FICU]

I guess one company has 737s with magical wings that won't allow frost to form on cold soaked wings and one doesn't?

I have landed at coastal airports with cold soaked wings and clearly visible white frost formed immediately under sunny skies and mild temps and it didn't melt by the time we were ready to depart.

Someone questioned me once after landing in YHM with cold soaked wings at +7 and light rain. When he saw the nice layer of ice that formed on the wings he understood why we called them out on a quick turn.

[Rockie]

WestJet's exemption for cold soak fuel frost was a result of Boeing testing and is subject to very strict limitations. Bear in mind this is only for cold soaked fuel frost and not frost resulting along the entire wing from atmospheric conditions. Hardly worth it in my mind since it would happen only under certain unusual conditions and would not be a factor in anything but the shortest turnarounds after having tankered fuel and filled up close to capacity.

Takeoff is not permitted if:

1. The cold soaked fuel frost exceeds 1/8 inch (3 mm) in
thickness on the lower wing tank surfaces.

2. There is cold soaked fuel frost on the upper wing tank
surfaces:

(a) That exceeds 1/16 inch (1.5 mm) or
(b) That is not of similar extent on both wings or
(c) That is beyond the outer edge of the black lines
defining the cold soaked fuel frost area
(in accordance with Boeing Service Bulletin
737-11-1125, or the production equivalent).

3. There is cold soaked fuel frost on the upper wing tank
surfaces:

(a) And the ambient air temperature is below freezing
(0o C, 32o F)or

(b) There is precipitation or visible moisture (rain, snow,
drizzle, or fog with less than 1 mile visibility).

[thirdtimecharm]

I guess one company has 737s with magical wings that won't allow frost to form on cold soaked wings and one doesn't?

Maybe that's an agenda item for the merger discussions?

1.0 Aircraft types
1.1 Wings
1.1.1 Magic
1.1.2 Non-Magic

[ODA]

I guess one company has 737s with magical wings that won't allow frost to form on cold soaked wings and one doesn't?

Maybe that's an agenda item for the merger discussions?

1.0 Aircraft types
1.1 Wings
1.1.1 Magic
1.1.2 Non-Magic

LOL

Thanks for the laugh!!

[FICU]

[midwingcrisis]

Rockie, Timely and great response. Thanks

[Bede]

WestJet's exemption for cold soak fuel frost was a result of Boeing testing and is subject to very strict limitations. Bear in mind this is only for cold soaked fuel frost and not frost resulting along the entire wing from atmospheric conditions.

Because of course cold soak fuel frost affects the wing much differently than normal frost; )

I was flying with the guy who was the CP when WJ got this exemption. Boeing data showed that type 4 fluid has a greater adverse affect than frost to 1/8". WJ was supposed to get a complete exemption for frost but TC balked at the last minute because of potential legal ramifications and only permitted the cold soaked frost exemption which we almost never rely on like Rockie mentioned.

Contamination should me taken seriously but I think tc should allow operators to rely on flight test data from the manufacturer rather than blanket bans on the slightest skiff of ice. There are adverse health effects of deice fluid.

[thirdtimecharm]

Great responses, thank you....

Just an observation from someone who has come from other parts of the industry to the ramp:

A little "why" goes a long way when you are dealing with your non-pilot colleagues. Sometimes it isn't all that obvious if you aren't wearing the Ray-Bans.

[pelmet]

Hello,

I work on the ramp in a northern town that sees two competing Boeing 737-200's landing at basically exactly the same time six times per week. The company that we are associated with has us prep for de-icing if the ground temperature is under +15 degrees while the other guys don't. We have had to de-ice several times in what has been our warmest summer in a long time, even when it was over 10 degrees on the ground and there was no visible ice on the wing.

None of us have ever been on an aircraft down south that de-iced when it was +15 on the ground. Is there implied pressure when one 737 scoots out to the runway and takes off while the competition takes a 45 minute de-icing delay on a sunny +10 day?

I need to stress that I am not trying to imply someone is being unsafe. Just trying to understand the thought process behind the decision.

Thanks!

De-icing on a sunny +10°C day. Can't say I have ever had to do it and wouldn't even bother to check the top of the wings on such a day. I wonder if there are even de-icing guys around at most southern airports when it goes down to 10°C at night.

There are some aircraft that are vulnerable to clear ice forming on top of the wings when raining on cold soaked wings from very cold fuel on a long previous flight. The MD-80 comes to mind.

[pdw]

The poster's location is Rankin, ... and the day posted the +10C is very short-lived, .. the daytime high at 3pm.

Calling for the spray is likely also from previous experiences ... and who knows, can it also serve as a practice run for a de-ice crew, for the days coming where surface temps fluctuate much more around/nearest the freezing points ?
There (Rankin Inlet) is definitely a place for an ultimate example where things will change in a hurry (an inlet at the edge of Hudson's Bay) at this time of year, with regards to de-icing needs. The bay is warmest now, and in spring it's the opposite; a big factor for rapid changes if operating close to that shore. Interesting to hear about the challenges from that area, when down south in the same Country we're still enjoying the summer temps ...

[tbaylx]

The ones with the blue tail spray if there is frost on the top of the wing...full stop. Cold soaked wings from the flight in from YFB often generate tank frost on the top of the wings. One of those operators will remove it, the other either never gets tank frost or chooses to look the other way.

There is a bit of a cultural difference in the operations.

[ettw]

Is it possible that one operator carries more fuel through YRT than the other?

I might think that if, for sake of this discussion, the wing was pretty much full of cold soaked fuel there would be more of the upper surface of the wing in contact with or under the influence of the cold fuel. If on the other hand you were carrying min gas through Yrt or up lifting more of the warm fuel clearly the upper surface would be less affected.

I doubt that there is a cultural difference between these operators.

Lawyer induced disclosure: I work for the company that according go this thread does not deice. ie. the ones with the magic wings

ETTW

[pdw]

Cold soaked wings from the flight in from YFB often generate tank frost on the top of the wings.

North into YFB already gets cold-soaked, then back out at altitude chills some more; if adding some cold stored at YFB for the trip home likely isn't adding any significant/lasting warmth to the tanks if its only a bit warmer than the already cold soaked fuel-remaining (esp if it re-chills on that next leg). Also, the increasing in-tank airspace above a very cold fuel also stays at the fuel's temperature ... probably til well after landing at the warmer airport.

[pdw]

... that was actually with reference to this:

I might think that if, for sake of this discussion, the wing was pretty much full of cold soaked fuel there would be more of the upper surface of the wing in contact with or under the influence of the cold fuel. If on the other hand you were carrying min gas through Yrt or up lifting more of the warm fuel clearly the upper surface would be less affected.

Yeah .. if frost on upper laminar surfaces forms when well above freezing from a cold soaking where wing-tanks are at half or less, the fuel in them would have to be very cold to make the air above it a heat sink as well .. for it to become a cooling power capable of drawing enoujh heat out of the highly conductive wing aluminum under those cirumstances.

[onspeed]

Regarding the cultural difference are you trying to insinuate 5t doesn't deice all the time with frost? Because I'm certain the competition does.

You do realize they are paid by the hour and therefore get paid more money to get a spray then not? I have flown on those 737 many times and everytime it was required we deiced.

[Jean-Pierre]

You do realize they are paid by the hour and therefore get paid more money to get a spray

Maybe instead of thinking about padding their own paycheck they are thinking about saving the company some money. That is another company culture that is foreign to many.

[pelmet]

The ones with the blue tail spray if there is frost on the top of the wing...full stop. Cold soaked wings from the flight in from YFB often generate tank frost on the top of the wings. One of those operators will remove it, the other either never gets tank frost or chooses to look the other way.

There is a bit of a cultural difference in the operations.

So how do you explain this part of a post from what appears to be a person with de-icing training....

"We have had to de-ice several times in what has been our warmest summer in a long time, even when it was over 10 degrees on the ground and there was no visible ice on the wing."

No issue if there is frost on the wing, as it is the law.

Of course, one could reply that clear ice can be invisible to the eye and it certainly can. This is what happened to the SAS MD-80 that crashed when its cold-soaked wings(due to the fuel tank design on that aircraft) had rainfall freeze on it.

But frost is normally pretty easy to see. After all we see it on the bottom of the aircraft wing on a regular basis. And the original poster mentioned a nice warm sunny day. Frost can form but I would think it would be noticeable to most who have dealt with the issue.

Could the present day cultural difference be something different than what you are suggesting.