Type IV fluid and Air Canada

[ettw]

I thank you all for your responses.

I agree that there was some light snow but at that temp I would not assume that it would stick and therefore be a contaminate but I know from my experience on the ATR that it (type IV) does significantly change the characteristics of the aircraft. In fact we brief that type IV will create considerably increased pitch effects on rotation. The first time I took off with type IV I would have been VERY concerned when I started the rotation due to increased pitch forces required. It just makes me consider the effects of type IV vs. the contamination issue.

I want to emphasize that I am not calling anyone out on this, I am just throwing out a legit question. I suspect that we would not have condsidered use of type IV under these conditions but I am wondering if it would have been the right decision.

My feelings on deice vs. anti ice are that I would use the type IV only if I felt that the current precip would create more of a hazard than the anti ice fluid.

Thanks,

ETTW

[Rockie]

I agree that there was some light snow but at that temp I would not assume that it would stick and therefore be a contaminate

They could have required de-icing with type I because of either adhering snow from earlier showers or accumulated ice build up from the previous descent through cloud.

[xsbank]

If any of you encourage someone to fly without properly dealing with an icing issue because you 'think' that type 4 will hurt you? I suggest that you re-read the Dryden accident report. Yes, hit the books.

Edited to add: in fact, take a moment or two to review the Limitations and de-icing checklists and SOPs as written in your POH, AFM or company ops manual. There is no reason at all that anybody should die this winter because the pilots did not deal with ice properly. If there is any doubt, talk to your CP. I'll bet that 75% of you haven't opened a book since your last recurrent. Guilty?

[Rockie]

I've read back through the thread and nobody is suggesting not using type IV when it is required. If you have active icing conditions and type I doesn't do it then type IV is required...period. Nobody is saying otherwise.

But along with the unnecessary cost incurred (large), type IV does add a contaminate to the wing, that if it is not required for anti-icing you would be silly to inflict on yourself. We have all seen it stuck on the trailing edge of wings in flight. We know that environmental conditions and wing characteristics can have varying effects on its ability to shear off the wing despite the advertised shear speed. So if it's not required don't use it.

Let's not invent an argument where none exists.

edit: Sorry, I just re-read this statement:

My feelings on deice vs. anti ice are that I would use the type IV only if I felt that the current precip would create more of a hazard than the anti ice fluid.

Air regulations are clear on this issue, and have largely removed any ability of the PIC to exercise the kind of discretion this statement implies. Transport Canada publishes holdover tables every year with the applicable times associated with types of active icing conditions. When there is active icing conditions the potential contaminate effect of type IV is not relevant and should not be part of the decision making process. You use whatever is required to ensure an ice free wing.

[mattedfred]

ettw,

please provide us with a few quotes from your employer's ground icing operations section of your COM or AOM

i would be curious to know what they say about operating with type IV

[balfour]

Interesting:

TYPE II AND TYPE IV FLUID REHYDRATION AND FREEZING
Last winter in Europe, restricted elevator movement interrupted the flight of two MD-80 airplanes. In both cases frozen contamination, a gel with a high freezing point, caused the restricted movement. The gel was Type IV fluid residue that rehydrated during takeoff or climbout in rain.

Rehydration can occur when thickened fluid is repeatedly applied in dry conditions, either to prevent frost from forming overnight or for deicing just before flight. The fluid dries out during flight, and a powderlike residue remains in aerodynamically quiet areas, such as balance bays and wing and stabilizer rear spars. If the airplane is not deiced or anti-iced during a subsequent layover and encounters rain on the ground or during climb, the remaining residue absorbs water and turns into a gel. The gel swells to many times its original size and can freeze during the next flight leg, potentially restricting the movement of flight control surfaces.

In the case of both MD-80s, the frozen gel restricted movement of the elevators, which are unpowered flight control surfaces on that model. Both flights were diverted, and elevator movement was restored when the gel unfroze during descent as the airplanes encountered warmer temperatures at lower altitudes. Inspection after the return of one of these flights revealed gel in the area between the elevator and elevator control tabs.

The issue of rehydration was discussed at the Society of Automotive Engineers (SAE) G-12 Fluids subcommittee meeting last May. The subcommittee also discussed related occurrences on other types of airplanes with unpowered flight controls and the deicing/anti-icing procedures used by the operators attending the meeting. These discussions led the subcommittee to conclude that the residue builds up when a one- or two-step deicing/anti-icing procedure is followed using Type II fluid, Type IV fluid, or both, in either neat or diluted form. This practice is prevalent in Europe.

The SAE G-12 Fluids subcommittee recommended including a caution note in the next revision of SAE ARP 4737 to address this issue. The SAE G-12 Methods subcommittee agreed and is including the following note in SAE ARP 4737D, scheduled to be released in late 1999.

CAUTION: The repeated application of Type II or Type IV, without the subsequent application of Type I or hot water, may cause a residue to collect in aerodynamically quiet areas. This residue may rehydrate and freeze under certain temperature, high humidity and/or rain conditions. This residue may block or impede critical flight control systems. This residue may require removal.

This caution note is similar to Precaution Note Number (6) of the MD-80 Aircraft Maintenance Manual (12-30-01):

After prolonged periods of deicing/anti-icing, it is advisable to check aerodynamically quiet areas and cavities, like balance bays and rear spars of wing and stabilizer, for residue of thickened fluids.

Boeing will address these issues in a service letter to be released in late 1999.

[HavaJava]

If I was forced to guess, I'd say that it's an SOP thing where taking Type IV is a move on the side of caution.

Not an Air Canada SOP...nor a CYOW SOP since I've been through there with only a "type one, wings and tail".

As a previous poster mentioned, it could very well have been that the pilots thought that precip was likely and opted for the type 4 to preclude a return to the de-icing pad. If the original poster had the TAF and not just the METAR perhaps it would explain things better.

Dude, you quoted me and those aren't my words... re-read my posts. It was Linecrew you should be quoting.

Sorry dude...don't know how that happened. My bad

[xsbank]

Balfour, all the cautions for Type 4 clearly state that it should NOT be re-applied without the thorough cleaning of surfaces with Type 1 (or hot water depending upon what is required) first. That article is probably the reason for this caution as its over 10 years old.

[xsbank]

I forgot to add: Type 4 only becomes a contaminant if it is overheated by leading edge heat (or similar) then it can cook on the wings. I am sure that you are all aware that if you use Type 4, you have leading edge heaters that you do not turn them on until you are ready for takeoff, that the heat will change the viscosity of the fluid and it will lose its ability to adhere, before it reaches the contaminant stage?

[ettw]

Alright. I've dug out the HOT for type I and at -10 and light snow you would have 11 min from the time of the start of final application to departure. The colder aircraft skin temp may have reduced this somewhat but I would have thought in YOW with the deice crew they have there that you could accomplish that.

Anyways, type IV in this case would not have hurt but it must be expensive.

ETTW

[Liquid Charlie]

The other major consideration for guys flying "smaller" aircraft -- turbo props and such -- make sure your aircraft is certified to use type 4 -- just as a little useless information a C-130 is not certified for type 4 -- just because type 4 is available does not mean you can use it.

[invertedattitude]

When I was working the ramp, non contract de-icing prices were somewhere in the vicinity of:

$2.50-$3.00 per litre of Type I

$8 for Type IV

Now factor that Type IV has a defined limit on an airframe unlike Type I... if my long term memory serves for a 737-700 the Type IV application maximum 140 Litres, go over that and you gotta spray all over again Type I then Type IV because it's now a contaminant.

Type I on the other hand can be sprayed to unlimited amounts, or in other words what ever is required to take the fluid off.

Worst I have ever seen:

2130 at night, noone is flying, but a "727" operator was going to attempt departure... the aircraft had sat in Freezing rain and Ice Pellets for about 5 hours, and at the time it was still coming down with Ice Pellets in buckets...

We sprayed 6000 Litres of Type I to get the airframe clean, and it was NOT an overspray, this aircraft was head to toe covered in about an inch and a half of thick hard ice, followed by a regular Type IV spray (727 was around 150 litres I think)

They taxiied out, despite the RFI of something foolishly low but just above mins, in a hurry of course to beat the likely 5 Minute HOT in Ice pellets, lost their HOT as snow clearing equipment left the runway and came back in.

By the time they decided they were going to try again, 30 minutes elapsed, and it took another 2500 Litres of Type I to clean the plane (Type IV doesn't go on the fuselage!) followed by of course another Type IV spray.

They taxiied out, lost their HOT AGAIN! On top of this the runway was so icy when they taxiied off of 29 onto C taxi they couldn't make the turn and plowed the nose gear into a snowbank.

Now after the airplane was tugged out of the bank, they waited 5 hours for the weather to stop, which it did after about 4 hours but it took another 6500 Litres of Type I to get the incredibly caked on ice off again!


You don't have to be a financial guru to run the numbers on that! Needless to say, I think that flight was operated at a net loss!

[Dockjock]

The high profile of Air Canada owing to its size is also a factor.

All it takes is a passenger with cellphone camera and, "Air Canada jet departs with frost on wings" is the frontpage headline on the Globe and Mail. It's not like there aren't thousands of people out there looking to take AC down a notch at any possible opportunity. Crews use extra caution and as the old video says, WHEN IN DOUBT...

So, we could save olympic swimming pools of money every year pushing the HOT times in situations like the one above (can you taxi from the CDF in YOW to the threshold of 32 and takeoff in 7 mins?). But we err on the side of caution.

To trot out another old saw, IF YOU THINK SAFETY IS EXPENSIVE TRY HAVING AN ACCIDENT.

[whiteguy]

The high profile of Air Canada owing to its size is also a factor.

All it takes is a passenger with cellphone camera and, "Air Canada jet departs with frost on wings" is the frontpage headline on the Globe and Mail. It's not like there aren't thousands of people out there looking to take AC down a notch at any possible opportunity. Crews use extra caution and as the old video says, WHEN IN DOUBT...

So, we could save olympic swimming pools of money every year pushing the HOT times in situations like the one above (can you taxi from the CDF in YOW to the threshold of 32 and takeoff in 7 mins?). But we err on the side of caution.

To trot out another old saw, IF YOU THINK SAFETY IS EXPENSIVE TRY HAVING AN ACCIDENT.

Just like the AC A319/320 that departed BOS a couple years ago. Plane was sprayed then the crew was called away to spray another aircraft before finishing. They forgot to return and the aircraft departed with the left wing covered with ice & snow. Thats why AC crews must perform a visual inspection after a spray.

[whiteguy]

Now factor that Type IV has a defined limit on an airframe unlike Type I... if my long term memory serves for a 737-700 the Type IV application maximum 140 Litres, go over that and you gotta spray all over again Type I then Type IV because it's now a contaminant.

I've seen charts that show the amount of Type IV that should be on an aircraft if done properly but never heard of a maximum amount!

[ahramin]

I forgot to add: Type 4 only becomes a contaminant if it is overheated by leading edge heat (or similar) then it can cook on the wings. I am sure that you are all aware that if you use Type 4, you have leading edge heaters that you do not turn them on until you are ready for takeoff, that the heat will change the viscosity of the fluid and it will lose its ability to adhere, before it reaches the contaminant stage?

Sounds like it's time to hit the books yourself my friend. The Boeing paper by David Kotker that balfour refers to is quite clear that the problem encountered was with type II or type IV drying out in aerodynamically quiet locations. You're not going to get aerodynamic heating in quiet locations. In certain dry conditions the fluid dries out to a gel and then if the airplane sits in light rain or high relative humidity the gel can rehydrate, then freeze in flight. In 2 cases this caused restricted elevator movement.

[Liquid Charlie]

you have leading edge heaters that you do not turn them on until you are ready for takeoff

Not many (none that I know off but maybe exceptions) airplanes allow ground operation of wing and empennage (if they even have this installed) heat -- over heating is one thing but "run back" would be the worst concern and of course performance the other.

[Rotten Apple #1]

I forgot to add: Type 4 only becomes a contaminant if it is overheated by leading edge heat (or similar) then it can cook on the wings. I am sure that you are all aware that if you use Type 4, you have leading edge heaters that you do not turn them on until you are ready for takeoff, that the heat will change the viscosity of the fluid and it will lose its ability to adhere, before it reaches the contaminant stage?

xsbank, for WJ operations, WAI is not required following Type IV fluid application, but neither is it prohibited. (Approved by both TC and Boeing).

[xsbank]

The a/c I fly, limitations prohibit use of WAI on the ground after application of Type 4 until just before take-off.

[xsbank]

There are no limitations or restrictions in any of the aircraft manuals I have for the use of anti/de-ice fluid except as I have mentioned above. There are specific checklists for pre- and after anti-icing, also places you are not supposed to spray, etc., but I can assure you that I am current on all my pubs.

The bottom line is that you are responsible to know the esoterica of winter ops and you remain ignorant at your and your passenger's peril. I apologize if this sounds pompous, but the fact remains that compromising on de/anti-icing because of a perceived problem with Type 4 or its cost (if it's too expensive, leave the a/c in the hangar and wait for summer) you are cutting your margins too fine.

[Bede]

I think the whole thing is reasonably simple: if you take a type 1 only, get airborne before the HOT expires. If you think it will be longer than the type 1 HOT, get a type 4 spray.

BTW, there is still plenty of type 4 on the trailing edge of the RJ even after a 3+ hr flight. The reason it is still there is because the boundary layer on the trailing edge is relatively thick so the fluid remains undisturbed.

[invertedattitude]

Now factor that Type IV has a defined limit on an airframe unlike Type I... if my long term memory serves for a 737-700 the Type IV application maximum 140 Litres, go over that and you gotta spray all over again Type I then Type IV because it's now a contaminant.

I've seen charts that show the amount of Type IV that should be on an aircraft if done properly but never heard of a maximum amount!

Type IV according to Dow Chemicals when I worked the ramp, said that Type IV should NEVER be applied thicker than 1-3MM or about the thickness of a dime, going over this and you risk turning it into a contaminant, and of course you never apply Type IV on anything other than a fresh coat of Type I, with the exception of an "overnight" spray of Type IV when nasty precip was expected, but in that case regardless of any precip that fell, even none you still had to use Type I to remove all Type IV fluid remaining.

I doubt they have fluid max numbers for every aircraft, but when I worked the ramp several airlines did, WestJet being one of them, if we went over we had to respray Type I and start all over again. (Never actually seen it happen)

The math worked out that at 3MM thickness on the wing and horiz stab was 140 Litres (Roughly 737-700)... I'm sure there is some fudge factor built in there as well.


All of this being said, my favourite quote was when I pulled up to a Saab 340 that had been flying in some nasty weather when everyone else was staying home, I asked

"You want Type I and IV?"

"I don't give a shit buddy, I'm not paying for it soak the F**KER!"

[C-GGGQ]

I've never seen absolute max amounts i have seen charts saying that it "SHOULDN'T" take more than x amount. But we also recently (within the last 4 years) switched type 4 fluids, different company different viscosity so stats probably changed. and about type 4 on the fuselage no type for should not be required for the fuselage but it is now law for all US carriers after the colgan crash to get type 4 on the fuselage. Its a waste but its required for them now. Also as a deicer we can suggest what to use but the pilots have final say even if we have to report them for a violation (snowing like a bastard and they still only want type 1). Pilots can always request type 4, however sometimes its a mental thing and not an actual necessity.

[RampGurl]

140 L is a minimum amount for the 737-700. That is a baseline for the Ice man to know if they have full coverage. As for type IV being a contaminant - it has the ability to gel as your article stated but it is standard procedure to begin with Type I and finish with Type IV. Taking a type IV for blowing snow seems over the top - Type IV is normally reserved for active precipitation - if your wings are dry and cold there should be no issue. Also, the hold over time for Type I is longer than you think - when I was working the ramp for WJ we would spray the headstarts an hour before departure to remove morning frost. A tactile would always be completed just before departure but I cannot recall a single aircraft that required a re-spray.

[C-GGGQ]

yes and no, holdover for type one is actually only around 3 minutes, however frost is not likely to reform (at least not within a matter of minutes)