McDonnell Douglas DC-10-30 accident at US, 23 Dec 1983

Accident narrative

At 1406 Yukon standard time on December 23, 1983, Korean Air Lines Flight 084, a McDonnell Douglas DC-10-30, collided head-on with SouthCentral Air Flight 59, a Piper PA-31-350, on runway 6L-24R at Anchorage International Airport. Both flights were operating under instrument flight rules in dense ground fog. The Piper was destroyed by the collision, and the DC-10 was destroyed by impact and a postcrash fire. Of the eight passengers aboard Flight 59, three were slightly injured, and the pilot was uninjured. The three crewmembers on Flight 084 sustained serious injuries. There were no fatalities.

### The flight

SouthCentral Air Flight 59 (SCA 59) was a scheduled commuter passenger flight from Anchorage to Kenai, Alaska. The pilot was highly experienced.

Korean Air Lines Flight 084 (KAL 084) was a scheduled cargo flight from Anchorage to Los Angeles, California. The flightcrew consisted of a captain, a first officer, and a flight engineer. The captain had logged 12,562 flight hours, including 6,471 in the DC-10, and the first officer had 8,167 hours, with 2,904 in the DC-10. Both pilots were highly experienced at Anchorage; the captain had logged 73 landings and 78 takeoffs there in the preceding eight and a half years.

### The sequence of events

Dense ground fog restricted visibility at the airport to between 1/8 and 1/16 of a mile. The pilot of SCA 59 was delayed by the weather. At 1344, he reported holding short of runway 6L at taxiway W-3, waiting for the runway visual range (RVR) to improve to his minimum of 1,800 feet.

At 1357, the ground controller cleared KAL 084 to taxi from the cargo ramp to runway 32. The captain had selected runway 32 for departure, although KAL operating specifications required a prevailing visibility of 1/4 mile for that runway, and the prevailing visibility was 1/8 mile. Because of the fog, the ground controller could not see the aircraft and asked the crew to report when they entered the east-west taxiway.

The captain of KAL 084 later stated that he could see the yellow taxi lines very dimly through the heavy ice fog. He turned right from the apron onto what he and the first officer believed was the east-west taxiway. At 1401, the crew reported entering the east-west taxiway. They then turned right again onto what they believed was runway 32.

The captain stopped the aircraft and felt unsure that they were on the correct runway. He discussed this with the first officer for three to four minutes. The first officer felt sure they were in the correct location. The captain later stated that because the runway size and lighting appeared correct, he decided to take off.

At 1404, the local controller cleared KAL 084 for takeoff on runway 32. At 1405, the controller advised SCA 59 that the RVR had reached 1,800 feet and cleared the Piper to taxi into position and hold on runway 6L.

At 1406, KAL 084 reported starting its takeoff roll. The DC-10 was actually accelerating on runway 24R, directly toward the Piper holding at the opposite end of the same runway. Seconds before the collision, the KAL captain sighted the Piper. He rotated the DC-10 and applied left rudder, lifting the nose gear and swinging the center main gear to the right.

The DC-10's nose gear passed over the Piper, while its center and left main gears straddled the smaller aircraft's fuselage. The left main gear sheared off the Piper's right wing, and the center gear sheared the left wing. The Piper was pushed backward 125 feet but its fuselage remained intact.

The DC-10 continued off the departure end of runway 24R, demolished seven approach light stanchions, passed through a wooded area, and came to rest in a gully 1,434 feet from the runway end. A fire erupted immediately, consuming the fuselage above the cabin floor and most of the cargo.

### What the investigation found

The National Transportation Safety Board found no evidence of preaccident failure or malfunction in either airplane's structures, systems, powerplants, or flight controls. The KAL 084 digital flight data recorder was recovered but contained no data from the accident flight, having failed on the inbound flight from Seoul. The cockpit voice recorder was not recovered.

The Board determined that the KAL 084 crew most likely turned right onto taxiway W-1 instead of the east-west taxiway, and then turned right again onto runway 24R instead of runway 32. The Board noted that the crew could have determined they were on the wrong runway if they had cross-checked their heading indicators before the takeoff roll.

Calculations showed that based on KAL 084's takeoff weight, the DC-10 required 8,150 feet of runway. Because the aircraft began its roll at the intersection of taxiway W-1 and runway 24R, only 2,400 feet of runway was available. The Board concluded that the takeoff would have failed even if the collision had not occurred. However, the Board noted that the KAL captain's evasive action—raising the nose and turning left—avoided extensive damage to the Piper's fuselage and probable fatal injuries aboard both airplanes.

Investigators examined the airport environment and found that the obscuration of markings by snow, frost, and ice adversely affected the KAL crew. Furthermore, of the four runway and taxiway signs KAL 084 would have passed on its erroneous route, one was unlighted, one was only partially lighted, and two were fully lighted. The lighted sign designating runway 6L/24R was dirty, reducing its contrast. There was no sign at the intersection of taxiway W-1 and the east-west taxiway. The Board also noted that the airport's runway and taxiway signs shared identical shapes, colors, and dimensions, differing only in width, which could contribute to inadvertent runway incursions.

The Board found that the KAL captain failed to exercise proper decisionmaking by relying too heavily on the first officer's belief that they were on the correct runway, despite his own uncertainty.

### Probable cause

The National Transportation Safety Board determined that the probable causes of the accident were "the failure of the pilot of Korean Air Lines Flight 084 to follow accepted procedures during taxi, which caused him to become disoriented while selecting the runway; the failure of the pilot to use the compass to confirm his position; and the decision of the pilot to take off when he was unsure that the aircraft was positioned on the correct runway."

Contributing to the accident was the fog, which reduced visibility to a point that the pilot could not ascertain his position visually and the control tower personnel could not assist the pilot. Also contributing was a lack of legible taxiway and runway signs at several intersections passed by Flight 084 while it was taxiing.