Narrative:

The first officer was intercepting the localizer to runway 27 at san. At 210 knots; 4000 AGL and 15 DME; he asked for and I selected flaps 5. We felt what we thought was wake turbulence; aircraft roll which eventually dampened out; and heard what we thought were the flight attendants securing the forward galley; as they had been told to do several minutes before. I later learned the flight attendants also heard and felt something at the same time. Sometime later during the approach; I noticed some yoke displacement to the left; which I have seen before at higher flap settings; but I remember thinking it was quite large. After arriving at the gate and the completion of the parking checklist; I remarked to the first officer that I was going to inspect the airplane for bird strikes; as we had flown past some birds on the right side of the aircraft on takeoff roll in ZZZ. I walked out onto the deck of a catering truck; which had pulled up to the forward service door. I immediately noticed a red discoloration on the top of the right wing; just aft of the number 6 slat. I went down to the ramp and a ramp supervisor pulled a belt loader up to the wing so I could take a closer look. I found that a 10 foot by 4 inch strip of wing material was missing just aft of the number 6 slat; exposing honeycomb material. It is my opinion the aircraft's flight characteristics would have been more compromised in the clean; flaps up configuration which we never had to experience; except momentarily. I contacted dispatch and maintenance control who wanted pictures; which I took and forwarded with my cell phone camera. A logbook entry was made. Eventually we swapped planes and continued our scheduled flights. I would like to point out that we don't necessarily inspect the top of the wing; nor is it visible from a walkaround at ground level. In this case; I was looking for something else; and the honeycomb was disturbed so much that you could see it from the ground. I assume that boeing is going to figure out why this strip came off and come up with an inspection criteria and interval.

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Original NASA ASRS Text

Title: A B737-300 Flight Crew experienced a roll axis upon lowering flaps for approach and landing. Subsequent inspection revealed a 10 foot by four inch strip of skin material had separated from the top of the right wing aft of the #6 slat.

Narrative: The First Officer was intercepting the Localizer to Runway 27 at SAN. At 210 knots; 4000 AGL and 15 DME; he asked for and I selected flaps 5. We felt what we thought was wake turbulence; aircraft roll which eventually dampened out; and heard what we thought were the flight attendants securing the forward galley; as they had been told to do several minutes before. I later learned the flight attendants also heard and felt something at the same time. Sometime later during the approach; I noticed some yoke displacement to the left; which I have seen before at higher flap settings; but I remember thinking it was quite large. After arriving at the gate and the completion of the Parking Checklist; I remarked to the First Officer that I was going to inspect the airplane for bird strikes; as we had flown past some birds on the right side of the aircraft on takeoff roll in ZZZ. I walked out onto the deck of a catering truck; which had pulled up to the forward service door. I immediately noticed a red discoloration on the top of the right wing; just aft of the number 6 slat. I went down to the ramp and a Ramp Supervisor pulled a belt loader up to the wing so I could take a closer look. I found that a 10 foot by 4 inch strip of wing material was missing just aft of the number 6 slat; exposing honeycomb material. It is my opinion the aircraft's flight characteristics would have been more compromised in the clean; flaps up configuration which we never had to experience; except momentarily. I contacted Dispatch and Maintenance Control who wanted pictures; which I took and forwarded with my cell phone camera. A logbook entry was made. Eventually we swapped planes and continued our scheduled flights. I would like to point out that we don't necessarily inspect the top of the wing; nor is it visible from a walkaround at ground level. In this case; I was looking for something else; and the honeycomb was disturbed so much that you could see it from the ground. I assume that Boeing is going to figure out why this strip came off and come up with an inspection criteria and interval.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.