ANC00LA120 · Piper PA-31-350

An airline transport pilot was returning from a charter flight in a twin-engine airplane and was in radio and radar contact with an FAA TRACON approach controller in Class C airspace. The pilot was given air traffic advisories for airplanes departing a satellite airport, but was not given an advisory about a McDonnell Douglas MD-11 airplane that was on final approach to land at the Ted Stevens Anchorage International Airport. The pilot said he did not specifically recall seeing the MD-11. The accident airplane encountered wake turbulence from the MD-11 that produced a violent vertical wind shear. The pilot then noticed the MD-11 airplane. After landing at a satellite airport, he notified the FAA of the wake turbulence event. Radar data revealed the MD-11 was on the glide path for landing at Anchorage, and the pilot of the MD-11 was in radio contact with the tower. The accident airplane crossed the flight path of the MD-11 at a 90 degree angle, about 900 feet msl, and about 55 seconds after the MD-11. When the accident airplane encountered the wake turbulence, it was 300 feet below the flight path of the MD-11 and separated by 2.47 miles. A postflight inspection of the airplane revealed substantial damage to the right wing. The Anchorage International Airport is within Class C airspace, which has a high volume mix of air carrier, general aviation, and military aircraft. Class D, Class E, and Class G airspace surround, and underlie the Class C area. In addition, the airspace is subject to Federal Aviation Regulation Part 93 (FAR 93). FAR 93 outlines geographic segments and special rules for operating at airports within the area. An air traffic controller is required to separate small aircraft operating behind heavy aircraft by 5 miles, and issue traffic advisories, and safety alerts including wake turbulence cautionary advisories. The TRACON utilizes certain prearranged coordination procedures to improve the traffic flow of aircraft through TRACON radar segments. Controllers are required to view a full data block on their radar screen when using prearranged coordination. The air traffic controller did not have a full data block displayed. The TRACON procedures manual does not contain a procedure for challenging, and verifying, the use or non-use of prearranged coordination between controllers. The air traffic controller did not notice that an aircraft designation symbol displayed on his screen indicated a heavy aircraft, and he did not issue a wake turbulence advisory. A heavy aircraft designator ('H' if assigned) is displayed on all radar data blocks (full or partial).

Verbatim NTSB analysis and probable cause from the NTSB dataset