KBUF737 From United States of America, joined Dec 2003, 779 posts, RR: 3 Posted (12 years 3 weeks 2 days 7 hours ago) and read 1723 times:
I recently flew a 757 with UA from ORD-FLL. We were up around FL390 and I noticed an ice formation on the middle of the flaps inboard of the engine. It seemed to be one single round spot and I think ive noticed this before on 757s and 737s. Is this a common area for ice buildup on these planes?
Mender From United Kingdom, joined Feb 2004, 250 posts, RR: 0
Reply 1, posted (12 years 3 weeks 2 days 4 hours ago) and read 1666 times:
Ice formation on a composite surface is usually due to delamination of the composite allowing water to accumulate inside the flap. This water freezes and then attracts moisture from the outside air. This then freezes on the outside of the flap.
You are allowed a certain amount of delamination/water ingress and still be serviceable. When water or delam is found during maintenance the surface will be x-rayed to work out if it within limits.