Boeing wing anti-ice

[Birdy767]

When was the last (first) time you used the Wing anti-ice?

[grease7]

this morning, while fixing an wing anti-ice problem on a 744:cool::cool:

[VinRouge]

When decending though an icing layer last week?

Company SOP is anti Ice on with descent checks if you can expect to penetrate a freezing layer in the descent.

Other SOP is wing AI on if Ice Cue on climb.

[STBYRUD]

Yesterday... Collected a nice layer of ice on the LE, blew it off with a half minute burst of WAI.

[411A]

Never on the B707...simply not needed.

[aterpster]

411A:

Never on the B707...simply not needed.

That is your opinion, not a statement from the 707 AFM.

You apparently have never been in a 25 mile downwind for an ILS at ORD during moderate icing and speed restricted to 160 KIAS.

[18-Wheeler]

In a decade of flying 747's ..... never. Not even once.

[exeng]

Once on a 747 classic in 18 years - departing Anchorage and at about 2000 ft entered freezing rain where the front windshields started to 'glaze' over with ice.

Several times on 737's where ice was visually evident on the LE.

Never on a 757, never on a 777 and never on an A320.


Regards
Exeng

[Offchocks]

Three or four times on both 737 and 767, but never on the 747.

[411A]

..25 mile downwind for an ILS at ORD during moderate icing and speed restricted to 160 KIAS.

Fly faster, and don't put up with any guff from ATC.

[Bergerie1]

Once; on a training flight in a VC10 from Prestwick to Shannon when we were held down by ATC over Belfast at around 18,000ft (there was an ATC strike at the time). Ice began to build very rapidly on the windscreen wipers so I immediately put on the wing anti-ice and asked for a higher level which they refused. I argued and eventually got a higher level by saying I would go up anyway if they didn't coordinate with the next ATC facility. We got our higher level, but by then we had nearly 2 inches of ice on the wipers (they were a better ice detector than the official one!).

[de facto]

Any time you use engine anti ice on ground due to atmospherical reasons you need to use wing anti ice except after a deicing/anti icing procedure.
In the air use it at deice unless severe icing for a long time(continious severe icing) use it as antiicing.

[stilton]

'Any time you use engine anti ice on ground due to atmospherical reasons you need to use wing anti ice except after a deicing/anti icing procedure'


Er. what ?


Certainly on the 75 / 67, wing anti ice cannot be used on the ground. And why should you do this 'any time you use engine anti ice' ?

[Denti]

It's the boeing recommended procedure on the 737, so yes, it does not apply to other aircraft. Using it on the ground is a given therefore, but as the 737 packs on quite a lot of ice fast it is used quite frequently in flight as well.

[VinRouge]

Ever heard of "holdover time"? :ugh:

[Denti]

Ever heard of reading comprehension and reading a whole thread before answering?

[shlittlenellie]

Those on the 757/767 generally say that they've never used wing anti ice because they can't see the wing from the flightdeck. There's rarely any sign of ice on the windscreen either. That doesn't mean that the leading edge hasn't iced up. I can't comment on the more exotic types having never flown them.

Now either the 737 is incredibly susceptible to leading edge icing or it's simply that the less aerodynamic profile of the windscreen shows icing more and that we can actually see the leading edge and watch the ice accretion.

I used it a couple of time on the 757 when it became obvious that we were in severe icing conditions. I use it pretty much every day in the winter on the 737.

God wouldn't dare ice up 411A's aircraft: he knows his place.

[BOAC]

I must admit I have NEVER understood Boeing's logic (737) - sticking on wing anti-ice at 9.9 degrees C seems illogical, but hey, stick with the book. I would far rather it were left to my judgement.

God wouldn't dare ice up 411A's aircraft: he knows his place. - I'd be surprised if it ever cooled enough, heat, kitchen etc etc.

[aterpster]

411A:

Fly faster, and don't put up with any guff from ATC.

So, you do have a sense of humor.

[Airclues]

The Boeing 747 anti-ice is actually a de-icer. You should wait until there is a build up of ice on the wing leading edge and then switch it on for about two minutes to break the ice away. Switching it on so as to prevent ice forming can cause water to run back and freeze on the upper surface of the wing.
Having said that, the 747 wing is not prone to icing. In 32 years flying the 747 I never used it, and that included over 100 approaches into Chicago in the winter.

Dave

[BOAC]

Having said that, the 747 wing is not prone to icing. - out of interest, how would you know?

[Mad (Flt) Scientist]

Every single wing ever built will accumulate ice in icing conditions. It's basic physics/thermodynamics. Ditto for every other protuberance on the aircraft.

There may be wings out there which are not significantly degraded by ice build up, especially relatively small amounts of ice. But that is not the same as "they don't ice up".

[con-pilot]

Good question. I am trying my best to remember just how many times I used wing anti-ice in 7,000 hours of flying a 727. To be honest I can only remember a couple of time when I was in heavy icing conditions on approaches.

Bottom line is; not that much.

[Spooky 2]

411A you are a piece of work. To long working in the sand box will do that to so I hear. :}

Have used the WAI in every Boeing airplane I have flown. Not often but still have used it. Just depends where you have flown. Restricting your experience to the Middle East and you remain somewhat limited. I guess you never got up to Europe very much, eh?

[d105]

Not sure about the wang anti-ice, but I thought Boeing pollicy of anti-ice below 10°C is valid for Engine anti-ice only? Boeing philosophy on 737 is to let ice build-up on wings and then blow it off with wing anti-ice.

My visual clue for wing anti-ice is when I get build-up on the tightening nut of the windshield wipers.

[411A]

I guess you never got up to Europe very much, eh?

Well, lets see.
FRA, too many times to count.
Stockholm
Copenhagen
Paris
London (yeah I know, not much icing there)
Munich
Vienna
Zurich
Geneva
Amsterdam

the list goes on and on....and on:}
I will repeat, wing anti-ice in a 'proper' swept wing jet transport airplane (possible exception B737, IE, the 'junior' jet) is simply NOT needed.

Heavy jet ops prove same, without a doubt.
Next?:hmm:

NB.
Spooky appears to be 'out to lunch'...:yuk:

[Checkboard]

Ice collects first on small areas, such as window wiper bolts and the like, because small protuberances produce small pressure disturbances ahead of them in the airflow - and small disturbances don't shove aside the supercooled droplets which form ice as well as large ones.

Bigger aircraft have bigger wings, produce larger pressure disturbances ahead of them and so collect less ice. You'll have a lot more of a problem with wing ice in a Navajo or King Air than a 747 (apart from the addition of being forced to cruise in the icing regions for a greater amount of time.)

[411A]

Ice collects first on small areas, such as window wiper bolts and the like, because small protuberances produce small pressure disturbances ahead of them in the airflow - and small disturbances don't shove aside the supercooled droplets which form ice as well as large ones.

Bigger aircraft have bigger wings, produce larger pressure disturbances ahead of them and so collect less ice. You'll have a lot more of a problem with wing ice in a Navajo or King Air than a 747 ...
Bingo....true enough.:ok:

[brakedwell]

Never during ten years on 757/767.

[BOAC]

Not sure about the wang anti-ice, but I thought Boeing policy of anti-ice below 10°C is valid for Engine anti-ice only?- see post #12?

I think it crazy too, but that is what the book said.

[Mansfield]

There is no doubt that scale plays a significant role in the effects of a given ice accretion, but the question that really needs to be asked in these cases is not whether you need the wing anti-ice or not, but rather, when in icing conditions, "What are you doing to maintain the aerodynamic margins that the manufacturer certificated?"

Boeing has avoided ice protection on the tail because they can demonstrate, in actual flight testing and in simulations, that the stabilizer stall margins required for certification are preserved with a three inch ice shape glued to it. This has not been possible to demonstrate in the case of the main wing. hence, TAI is applied to various portions of the main wing on various models.

Generally speaking, Boeing will tell you to operate the wing TAI when ice is detected on window frames, wiper arms or, in the case of the 707, wiper bolts. The "primary" method that they cite is to use it as a de-icer, as they have expressed concern about runback icing if the TAI is not running at a fully evaporative temperature. The exception to this is the 727, due to the pod engines; in this case, they want the TAI run in the anti-ice mode. The 707 also requires the system be operated in the anti-ice mode during approach and landing.

Wiper bolt ice can be extremely hard to see, particularly at night. As I believe I have posted in other threads, there can be situations in which the wing has accumulated significant ice before anything shows up on the bolt. With respect to the de-ice mode, the glaring problem that Boeing has left unanswered is how to decide when to cycle to system the second time...since you can't see the wings, and the ice on the wiper is still there from the first time.

The 707 and 727 required a ten knot speed additive to Vref when ice was on the airframe. I believe you'll find that most, if not all, Boeings require significant penalties to both approach-climb and landing-climb weights when icing conditions have been encountered and the surface temp is 8C or less.

At the end of the day, the goal is to preserve the certification margins. That's pretty much what the pax think they're paying for...those that think, anyway.

[de facto]

411a writes'boeing 737,the junior plane'...thanks!:-)

[L337]

Lots of times on the 737.

Once.. I think... maybe in 15 years on the 747 and its variants.

I am never too sure if it is because I cannot see it, or it is just never there. The tailplane has no anti-ice anyway, so maybe I worry to much!?

[Mad (Flt) Scientist]

Ice collects first on small areas, such as window wiper bolts and the like, because small protuberances produce small pressure disturbances ahead of them in the airflow - and small disturbances don't shove aside the supercooled droplets which form ice as well as large ones.

Bigger aircraft have bigger wings, produce larger pressure disturbances ahead of them and so collect less ice. You'll have a lot more of a problem with wing ice in a Navajo or King Air than a 747 (apart from the addition of being forced to cruise in the icing regions for a greater amount of time.)

In addition to the scale effect on accretion, as mentioned, there's also the scale effect on the aerofoil itself. It takes longer for the bigger wing to build that 3" ice shape, AND 3" of ice does more damage aerodynamically to a smaller wing. So smaller aerofoils get a double whammy in icing conditions.

[411A]

In addition to the scale effect on accretion, as mentioned, there's also the scale effect on the aerofoil itself. It takes longer for the bigger wing to build that 3" ice shape, AND 3" of ice does more damage aerodynamically to a smaller wing. So smaller aerofoils get a double whammy in icing conditions.
Bingo...another true statement.

Now, lets look at when it is prudent to use wing anti-ice, on a swept wing jet transport airplane.
IF you are going to use it, do so when the wing has no slats/leading edge devices extended, as....with many designs, the anti-icing is far more effective when the wing is clean, aerodynamically (devices retracted).

NB.
Some might say...'well, if smaller aircraft use the three inch criteria, larger aircraft should use...more.
One aircraft manufacturer did just that...five inches.
Lockheed.
And, still found no anti-icing required on the tailplane.
TriStar.

[Mad (Flt) Scientist]

The "three inch" rule was justified on the basis (assumption really) that a larger lump would blow off, and that is a function more of the size of the ice than the aerofoil it is stuck on.

The advisory material keeps evolving, though, and I think the current interpretation is that you build the ice (analytically) for the specified time - typically 45 minutes - and what you get, you use.

[VJW]

wow, I learnt something new today. 747 is an awesome piece of kit still. Shame I'll probably never fly it, and for now I put up with the 737 and putting my wing anti ice on anytime we use eng anti ice on the ground (expect after de-icing with type II)....

[galaxy flyer]

The mighty C-5 had NO TAI for the wings and apparently didn't need it. I've flown trainers for 4 hours in winter conditions, at 0C, with no accumulation. And approaches in Germany, in heavy wet, cold weather with no icing.

OTOH, ice in a Beech Baron, flying checks in the lee of Lake Ontario, was a fearsome problem. Scaler properties, I guess.

The manufacturer of the GLEX says CAI and WAI ON in icing conditions, I don't go against the book, turn it on and haven't seen any ice.

GF

[stilton]

'OTOH, ice in a Beech Baron, flying checks in the lee of Lake Ontario, was a fearsome problem. Scaler properties, I guess'


Been there, done that. In another life I flew checks in a Baron and picked up an astonishing amount of ice despite my best attempts to avoid it.



Other than losing a fair amount of speed (with full power) it kept flying with no problems.


One particular night I had so much all over the Aircraft I flew a zero flap approach (not wanting to change the aerodynamic shape any more) at the highest speed I dared before plunking it down on the runway.



With no heated windshield I could barely see to taxi as it was almost completely opaque.



A superb Aircraft.


Those were the days..:eek:

[Mansfield]

I dug around a bit to see whether I could find anything useful with regard to the question about the 737 wing TAI operation while on the ground. I am not rated on the airplane, so my comments must be so considered.

In the October 1977 issue of Airliner magazine, the following was stated:

During flight testing of a 737, unsymmetrical formations of clear ice occurred on leading edge devices during ground operations involving use of thrust reversers in light snow conditions with crosswinds. These formations, which were difficult to see, occurred in temperature conditions at or moderately below freezing; it appears that snow melted due to hot engine gasses and then refroze on contact with the cold leading edge devices, which are not anti-iced during ground operations. The presence of ice resulted in a tendency to roll at high angles of attack during subsequent takeoffs.

In the fall of 1981, Boeing reported the results of an extensive flight test program to evaluate the effects of frost and a heavier “corn” ice on the leading edge slats of the 737. One of the outputs was an increase in stall speed, over the clean wing 1g speed, of approximately 10 knots with frost, and 14 knots with corn ice, while in the flaps 1 configuration. These stall speed degradations were significantly improved at flaps 40 (approximately 4 knots for frost and 8 knots for corn ice). This is attributed to the differences in airflow between the “sealed” configuration between the slats and the main wing at flaps 1, and the “gapped” configuration at flaps 40.

In the fall of 1983, none other than Alan Mullaly reported in Airliner on an extensive flight test program using two variations of simulated frost. This was carried out on the 737 (similar testing was later extended to the 757 and 767). The entire upper surface was coated, as well as the portions of the slats and flaps that would be exposed during ground operations with the flaps retracted. Increases in the stall speed above the clean, 1g speed were in the 8 to 12 knot range for all three airplanes with flaps 5. The utility of the wing TAI system in ground operations was also tested, by using frost simulant applied to the slats based on the wing TAI predicted capability at both 0F and 20F. This may be the genesis of the 737 procedure.

Although most of this work was done with respect to the takeoff icing threat, in 1992 Gene Hill described testing with only the slats coated with a frost simulant. The results showed, approximately, a 15% loss in maximum lift capability for the 737 with flaps 5, compared to about 19% for the same airplane and flap position with frost simulant applied to both the slats and the entire upper wing surface. These results can be applied to both the takeoff and the inflight icing situations.

I am aware of only three large jet icing accidents involving ice (other than takeoff events). One is the 767 tailstrike at Halifax, the second a DC-8 landing accident at Edmonton, and the third is an Airbus upset near West Palm Beach. All had more than one contributing cause, but in each case the wing TAI was not operated. I am also aware of a handful of buffet encounters and a couple of stick shakers apparently due to a failure to operate the wing TAI. The concern that I have had with respect to larger jets has been the go-around with a contaminated wing; the lift degradations and stall speed increases reported in the Boeing work suggest a quite a bit of margin erosion is possible, and that go-around is where an erosion of margins may show up.

Regarding the statement that wing anti-icing is less effective with slats extended, we have an open question on another thread concerning the Airbus procedure, and I have no information to add to that discussion yet. In the case of the 757/767, for example, the slats are equipped with telescoping ducting for bleed air supply to the protected surfaces, and the 757 AMM states that “Bleed air can be fed to the leading edge slats regardless of slat position.” I don't believe there is any difference in thermal performance regardless of slat position, but there is the above-mentioned difference between sealed and gapped airflows.

If anyone is interested in the Airliner articles and does not have access to them, drop me a note and I can email them to you.

[EW73]

My understanding of the 737 NG WAI system is....

a/ Works well on the ground as well as inflight.
b/ The outboard LE Slat (on each side) is not heated at all.
c/ The anti-ice system works with slats in any position.
d/ On the grnd, the system is temperature sensitive, i.e., when they get up to the thermostat temp setting (either side), both supply valves close, and cycle around that temp. In flight, the thermostats play no part.
e/ When takeoff power is set, (beyond config switch setting) both supply valves close (and both blue valve position lights go bright), the switch stays ON until liftoff, when it goes OFF, and the blue indicator lights go off. Further normal inflight operation is at the discretion of the pilot.
f/ If an RTO occurs, when the thrust levers are returned below the takeoff setting, both valves will reopen and continue to be controlled by the thermostats.

Works well, costs a lot of money!!

EW73