At 13:13 Alaska time, a Piper PA-31-350 was damaged during a wake turbulence encounter about 3.5 miles northwest of Anchorage. The pilot was not injured. The pilot was in contact with controllers, who pointed out traffic departing the Lake Hood Seaplane Base but did not advise him of a McDonnel Douglas MD-11 that was on final approach to land on runway 14. His flight path was behind and below the MD-11. Shortly after the MD-11 airplane passed his position, the pilot said his airplane encountered wake turbulence from the MD-11 that produced a violent vertical wind shear. The airplanes right winglet mounted landing light cover and the landing light assembly departed the airplane and the gear warning horn sounded. The pilot regained control of the airplane and landed at Merrill Field. A postflight inspection of the airplane revealed upward bending and wrinkling of the upper wing surface at the right winglet attach point. Additional wrinkling was noted on the upper right wing surface at the mid-span/mid-chord area. Slight upward bending was found at the left winglet attach point. Radar data showed the accident airplane crossed the flight path of the MD-11 at a 90-degree angle. The Navajo was about 300 feet below the MD-11 and about 55 seconds later in reaching the point where the flight paths intersected. The MD-11 was on the glide path for runway 14, and the pilot of the MD-11 was in radio contact with the Anchorage Tower.