Frosty Wings

[Miss Terry]

I know the FAA have prohibitted it, but, are there any types of aircraft whose AFM permits departure with frost on the upper surfaces of the wings ?.

I know many permit departure with frost on the underside in the vicinity of the fuel tanks, but what about up top ?.

I don't think there are, anyone know any different ?.

MT.

[BOAC]

737NG if so modified - search for fuel frost. Yeps - it's a Boeing mod.

[zonnair]

Nopes. If it's concerning a significant area it must be removed!!!

[TURIN]

Depends how much (if any) de-icing fluid is left on station. Amazing how the 'rules' change when a lengthy delay is on the cards..........:hmm::suspect:

[777AV8R]

An aircraft may not depart for takeoff if ANY critical surface has contamination adhering to its surface.
Any aircraft may depart with a light covering of frost on the underside of the wing.

Frost on the lifting surface (wing) is a no no. Aside from the usual snow that has fallen, there is a problem with super-cooled fuel sitting in the tanks that make contact with the upper surface of the wing. If the humidity is high or there is light rain, mist or wet snow falling, the result is a frozen mess on the upper side of the wing.

There are a number of ways to try and get rid of the cold fuel, most to no avail except for one.

You can try transferring fuel from the center tanks to the wings. In some cases, the center fuel, if any is left, can be used to warm the fuel remaining in the main tanks. This method doesn't always work, but its a thought.

You can try to transfer fuel across the aircraft and back, thereby mixing the fuel from left and right sides. This method doesn't always work either.

The last thing, which usually works is to wait as long as you can and then fuel the aircraft. I've found that the in-ground/bowser fuel to be warmer by several degrees. The addition of the new fuel will generally warm all the fuel (depending on the temperature difference and quantity to be added) and keep it above freezing. Usually the surface frost around the fuel tank will disappear.

Lastly, I wouldn't think of departing ANY station with ANY contaminate.

Anti-ice and de-icing fluids are OK.

[Tinwacker]

Our procedure on the A330/340 is to transfer the outer wing tank fuel on arrival, if not moved automatically, and then refuel as normal. The warmer induced fuel to the outer tanks rapidly moves any surface frost/ice caused by the humidity.

No delays and done during a one hour transit.

Transferring fuel from the centre or another tank is just moving cooled fuel which will have little or no effect. Space for that fuel has also to be created.

TW

[BOAC]

Miss Terry (I knew your sister...) - ignore the posts above, and you need to look at http://www.pprune.org/tech-log/273577-cold-soaked-fuel-738-a.html in particular post #3.

[Miss Terry]

BOAC, she said she you paid well.

My question relates to any icing on the upper surfaces, not necessarily that caused by cold fuel.

The example would be arrival at an aircraft first thing in the morning to find a heavy frost has formed on the wings. Could departure without deicing be permitted on any type at all ?.

MT

[Tinwacker]

BOAC,
ignore the posts above

Explain as what I have written is a laid down procedure.
Miss Terry post #1 didn't specify any type of aircraft.
The Boeing 737 mod is only the marking of lines on the upper wing for use when calculating the percentage of wing frost.

Airbus also have a letter published that explains CSFF and remedies.

TW

[BOAC]

TW - the question was "are there any types of aircraft whose AFM permits departure with frost on the upper surfaces of the wing" not "what can you do to avoid it."

Answer = 737NG if so modified?

[Tinwacker]

BOAC

Point noted....

TW

[bvcu]

330/340 outer tank transfer was also standard on A300/310 when conditions warranted although normally landing with these empty. Problem on 330/340 is cold soaked main u/c mount area which regularly has a large patch of frost in full view of cabin and doesnt disappear on the standard 2hr longhaul transit !

[TURIN]

TW - the question was "are there any types of aircraft whose AFM permits departure with frost on the upper surfaces of the wing" not "what can you do to avoid it."

Answer = 737NG if so modified?


However, regulatory authority is still required, no?

Or have FAA etc given it the green light?:confused:

[sbguskje]

SAAB340 AOM II allows dispatch with a thin layer of light rime or hoar frost on upper surfaces e.g. after over night stop. It should be thin enough for you to be able to see markings etc.

"It has negligible effect...."

[BOAC]

Turin - agreed but the 'Q' was asking about AFM approval. The CAA have certainly approved it, don't know about the FAA.

[Mansfield]

The Saab language refers only to the upper surfaces of the fuselage. They are quite clear about insuring that the upper surfaces of wings and tail are free of contamination. This is nearly identical to the language used by Boeing on all models, 737 included.

To my knowledge, there is no manufacturer who recommends takeoff with any amount of contamination on the wing upper surface. There is far too much evidence regarding the serious aerodynamic effects, and the resulting hull losses.

[BOAC]

To my knowledge, there is no manufacturer who recommends takeoff with any amount of contamination on the wing upper surface. - well, your knowledge is partly complete:) While Boeing do not 'recommend' it they do 'approve' it.

[Mansfield]

BOAC - I stand corrected. Had I taken the time to turn the page in the FCOM, I would have seen the reference..obviously I don't fly the type. At least in the generic FCOM that I have, it is under Supplemental Procedures for Anti-Ice and Rain. As you have pointed out, there is a good description of this in a previous thread.

That does not change my comment regarding the Saab. They do not have any such procedure regarding upper wing surface ice.

With respect to Miss Terry's question,

"My question relates to any icing on the upper surfaces, not necessarily that caused by cold fuel.

The example would be arrival at an aircraft first thing in the morning to find a heavy frost has formed on the wings. Could departure without deicing be permitted on any type at all ?."

The Boeing 737 NG procedure refers to 1/16 inch frost within the marked area of the upper wing surface, as well as an outside temperature that is above freezing. I suspect that any frost that forms for reasons other than cold soaked fuel will not lie within the marked areas, and is unlikely to survive long after the temperature rises above freezing. As to whether 1/16 of an inch corresponds to "heavy frost", well, I've sat in way too many industry/authorities meetings to open that can of worms. I would only suggest that the underside frost limit has been 1/8 inch for quite a while now.

Suffice that the only current allowance for upper wing surface frost is in the case of cold soaked fuel, and then is limited to the 737 NG. Further, none of this is allowable under FAR 121.629, so it is a moot argument in the States.

I'll dig around with the certification folks and see if anyone else is approaching this the same way.

[FEHERTO]

Unbelieveable, whta some people interpret into manuals and documents.

ICAO "Clean Aircraft Concept" states clearly that no aircraft shall be operated with "adhering contamination" to the critical surfaces. This includes definitely on all aircraft types the upper wing surface.

The B737NG is the only aircraft type with an exemption. It is possible to operate this model with a thin layer of frost in a clearly defined area of the upper wing (Service Letter shows the exact dimensions). The maximum thickness is 1/16" and to use this opetion requires two items:
- a modification in form of a amrking on the upper wing area
- AFM must included this scenario

No special FAA approval is required, as the AFM must be approved my your FAA representative.

To the SAAB: It does not differ to any other aircraft model (except B737NG): No contamination on the upeprwing surface. Lower wing surface a maximum of 3mm frost (some aircraft models are even not approved for this) and frost on the fuselage as long as markings, door seals and so on are visible. No other contamination type approved.

Using fluids, esepcially which type, depends on the approval of the airframe manufacturer. Basically you can go back and take the FAA document "Hold-Over-Time Tables for Winter Season 2009/2010" and find all fluids, where the manufacturer has submitted the certification documents acc. SAE AMS 1424 (Type I) and SAE AMS 1428 (Type II/III/IV) to the FAA Tech Center.

A lot of airframe manufacturers, especially business jet producers, have brand names listed in their AMM's (chapter 12-30/31), which are very often outdated. Therefore produce your own list and get your winter ops program acc. FAR 121.621 approved.