737 Cold soak Fuel frost

[nnc0]

I notice that some 737 NG operators do not deice when they have fuel frost on the upper surface of their wings but others do and I'm puzzled and obviously concerned. In my mind the clean wing concept is written in sacrosanct.

Is there aircraft certified for t/o with fuel frost on the upper surface and if so why are some operators still deicing. Is this a case of the limits being recognized by some regulators but not accepted by others?

[Johnny F@rt Pants]

There's an outlined area that it is permissible to depart with frost associated with cold soaking, I suppose some operators use this however my operator does not and we must de-ice regardless.

This can cause issues down-route in warm climates where there is no de-icing equipment, then we have to get creative.

[lederhosen]

It is simple, either it is allowed (in limits within the lines on top of the wing) and documented in your OM or you cannot do it. If you are a passenger and see lines on top of a 737 NG wing then you can reasonably expect that the airline you are using has approval. Although as discussed in an earlier thread not all authorities seem to allow it. We have been doing it for years now.

[BOAC]

nn - if you track down the previous threads on this topic I am sure there is a link to the Boeing documentation on CSFF.

[nnc0]

BOAC - there is a bit info there but it doesn't seem to clarify why some regulators seem to allow it and some don't. Apparently the FAA had had approved the no deicing requirement and southwest was not deicing but the FAA later rescinded their approval for some reason.

[BOAC]

In my time the UKCAA accepted it if iaw the Boeing docs, and very useful it was too. Why some do and some don't I do not know. There is a potential 'lawyers' snakepit whereby the icing regs state 'No upper surface contamination' but the CAA at least granted exemption - within limits. Maybe the lawyers are the problem. Did I say maybe???

[RAT 5]

The IAA do not allow any CSFF even though Boeing do. I always wonder why a customer decides to re-write the manufacturer's instruction manual? Do they do that with their car?

[Yeelep]

Some 737NG operators asked Boeing what could be done about CSFF. The result of wind tunnel tests found up to 1/16th of an inch of CSFF had minimal aerodynamic impact. It seems that the FAA was onboard early on and then pulled their approval later. Boeing states their approval of CSFF, but that any operator wanting to operate with CSFF has to gain approval through their Aviation Authority.

If you are a passenger and see lines on top of a 737 NG wing then you can reasonably expect that the airline you are using has approval.

That can't be assumed. From production line 1538 the black lines outlining the CSFF allowable area has been a standard feature regardless of whether the airline is approved for it or not.

I always wonder why a customer decides to re-write the manufacturer's instruction manual?

That's not really the case here. Most airlines would likely want to be able to fly with the allowable CSFF, its certain Aviation Authorities that aren't allowing it.

If you have access 737NG-FTD-12-0001 and SB 737-11-1125 covers this issue.

[BOAC]

.........and for those who want pages of posts to read about this - put CSFF into the PPrune serach engine.