737-800 wing ice

[Selfloading]

Purely to satisfy my curiosity, would this amount of ice be a problem, I'm guessing in an aerodynamic lift kinda way, would there be any other issues, before anyone starts I've no hidden agenda, don't want to criticise or judge anyone, just curious.

http://i36.tinypic.com/168ivt4.jpg

[Boomerang1]

This is caused by cold soaked wings. The water vapor in the air condenses on the wing and then freezes. For awhile the FAA allowed you to operate the aircraft with this ice as long as it remained within the black lines on the surface of the wing. The FAA then adopted the clean wing rule and no longer permitted you to depart with any amount of ice on the wings.

All you need is warm water spray to remove or refuel with warm fuel and fill the wing tanks.

[frogone]

It's NEI or Non Environmental Icing, caused by cold fuel in the wing tanks by a long cruise at a high altitude.

Boeing have painted Boxes in which if the NEI is within the box it's OK to depart. But some Aviation Authorities have not approved them.

Usually (within reason!) filling the wings with warm fuel, the NEI will melt away.

IR

[Selfloading]

Hmm, I'd guessed the cause, the airport had no de-icing facility (Malaga) I thought that was a bit strange, I know it doesn't get that cold down there but this must happen from time to time, as you said fuel was added (good thinking that) the captain told us that this particular airline's operating procedures did not allow departure with any ice at all on the wings ( won't get an argument from me about that) thanks for the replies :ok:

[Selfloading]

Thanks for the answer, been having a snoop round, amazing how cold that fuel gets, the airline in this particular case has a 25 minute turn around, so I've read anyway and as it was a fairly late flight anyway an extra hours delay was a bit of a bugger, however it's a nice reassuring feeling to find the company adhering to such strict rules, or would it be an aviation authority rule, could we have departed legally with that ice?

[frogone]

Well as Boomerang said, legally NO. In reality you wouldn't have ended up a smoking hole in the ground over that.

And if you're looking to complain, complain to Malaga airport that they don't have a basic de-icing rig!

IR

[Selfloading]

Nah, no complaints, just one of those things I suppose, wouldn't have thought it would have cost Malaga airport a fortune to have something, but hey what do I know :oh:, incidentally do the lines marked on the wing correspond to the outline of the fuel tank or a critical area of the wing?

[PA38]

When I was learning to fly on a very nice PA38, we had a build up of frost on the wings.
We scraped it off and made it into a snowman sitting on the fuel filler cap :O
The exchange from the tower was along the lines of "did you know you have a snowman on your wing??"
It blew off when we started our take off roll ;)

[Selfloading]

Had the captain clambered out onto the wing and started making a snowman, then I would have been worried :)

[Northbeach]

Selfloading,

You are correct. The main problem with ice on the wings is the disruption to the smooth flow of air around the airfoil degrading the wing’s ability to produce lift. This is most critical during takeoff while the airplane is accelerating into the regime of flight, the margin between flying and stalling is small and the ground is close.
As to whether this amount of ice would be a problem; it depends on what the underside of the wings look like, how thick the frost/ice is under the wing, how heavy the airplane is, the length of the runway, obstacles in the departure path and the environmental conditions present during the departure. It could be a problem. Several years ago an SAS MD80 lost both engines to FOD damage when sheets of ice separated from the upper surface of the wings and were ingested into the engines causing them to fail shortly after departure. The 737 engines are mounted in a different place; different airplane different problem.
I have no approved tool available to me to determine how much ice/frost on the upper surface of wing is safe. If it’s present I have to remove it prior to departure. Any ice present degrades performance; with the smallest trace it is inconsequential as you add ice the negative effects get to the point where flight is impossible. I don’t have any approved method to quantify it, therefore I have to remove it or wait until it disperses.
I don’t know the airport where the picture was taken. If the undersides of the wings are clean, it’s above freezing and there is no chance of ice or snow during takeoff what is pictured will most likely disappear long before the takeoff roll. I don’t think it is a problem, but would be technically and legally prohibited from departing with that ice/frost present as pictured.
Thank you for asking an interesting question!

[Selfloading]

Thank you for taking the time to give such a detailed answer :ok:

At the time I was thinking it was ironic that having been a passenger quite a few times from Scandinavia during the winter I'd never been delayed by ice, but I guess the air in Southern Spain being relatively warm contains more moisture than the cold Scandinavian air, maybe this would make this kind of ice accumulation more likely?

[Groundloop]

incidentally do the lines marked on the wing correspond to the outline of the fuel tank or a critical area of the wing?

The lines indicate where ground crew are allowed to walk on the surface of the wing. Almost everything outside the lines are moveable surfaces ie forward of the line are the leading edge slats, aft of the line are the ailerons, spoilers and flaps. Therefore the black lines almost correspond to the position of the fuel tanks.

You can see the wording "NO STEP" on the photograph just aft of the black line.

[Northbeach]

Selfloading,

Again you are correct. It is the temperature of the air, not its geographic location that determines how much moisture a body of air can contain. Warm air can “hold” more moisture in suspension than cold air. Surely you have been in some hot humid location where you can “feel” the moisture on your skin and with every breath. You will never “feel” that same moisture content at the top of a ski slope in winter will you? Additionally, if the airport is close to a significant body of water then the surrounding air will usually have a higher moisture content. Under such conditions you will quickly develop moisture on the outside of a drinking glass if you have a cold liquid and ice cubes inside the glass. So it is with the jet you observed. During the inbound flight the fuel in the wing became cold saturated. I suspect that you know that the standard temperature at 35,000’ (10,600 meters) is -55C. The longer the fuel is exposed to those temperatures the colder it gets. Upon arrival, some hours later, you still have several thousand kilos of remaining cold fuel, really cold (-20C +/-). That several thousand kilo mass of cold fuel is transmitting that low temperature to the surface skin of the wing. Outside you have moisture laden air also touching the wing. As the moist air comes into contact with the very cold wing it is forced to “give up” the water suspended in it. If the temperature of the wing is cold enough then the moisture will freeze resulting in what you saw. Different countries’ regulatory authorities deal with this in different ways. The aircraft’s manufacturer has their recommendations. But two different airlines flying the very same model parked next to each other on same ramp may have to deal with exactly the same phenomenon differently because of the regulations each is bound under.

[Selfloading]

Well, thanks to all for taking the time to reply, could not have asked for a better explanation :ok:

[BOAC]

Just to add a little more for selfloading, even the 'alleviation' for the 737NG to which Rainboe refers has 'conditions' applied to it. I.E You cannot ALWAYS depart with upper wing ice on a 'modified/approved' 737NG.

[Sky Wave]

To expand on BOAC's comments.

My company uses Boeings procedures.

These state:

Light Coatings of frost are allowed on the upper wing provided:

It is less than 1.5mm thick
It's the same on both wings
It's within the defined allowable cold soaked fuel area (the thick black lines)
The ambient air temperature is above 0 degrees
There is no precipitation or visible moisture.

You're also allowed to depart with up to 3mm of frost on the lower wing.

So there's every chance that any operator using Boeings procedures would have been allowed to depart from Malaga judging by the photos.

As has been said, different operators have different rules.

SW

[Selfloading]

Excellent thanks again, apparently the airline in this case don't allow departures with any ice at all (better safe than sorry :)) who says loco's cut corners with safety, ice was only on one wing on this occasion so that's another no go then :ok:

[Seat62K]

"The airline in this case". Mmmmm........let me guess.....737-800 operator......25 minute turnarounds.......Lots of airlines to choose between, then...:}

[TheCosmicFrog]

Ryanair B737-800?

[BOAC]

Poor old RyanAir (again!). Sterling used to operate into AGP with 800s on 25 min t/rounds as well! I have no idea what their rules were on CSFF, but quite a lot of airtlines do NOT use the Boeing alleviation.

[Selfloading]

"The airline in this case". Mmmmm........let me guess.....737-800 operator......25 minute turnarounds.......Lots of airlines to choose between, then...:}
Well done Sherlock :}:ok: