History of Flight
Continental Airlines Flight 5148 (CAL5148) was conducting an Instrument Landing System (ILS) autoland approach to runway 10L at Chicago O'Hare International Airport (KORD). The approach conditions allowed for an exception under FAA Order JO 7110.65, paragraph 3-7-5a1(a)(2). Envoy Flight 3544 (ENY3544) had departed runway 10L but remained over the ILS critical area during CAL5148's landing attempt. At 0956 CDT, the local controller instructed ENY3544 to line up and wait on runway 10L, while CAL5148 was on a 4-mile final. At 0957, CAL5148 reported inbound on the ILS and was told to continue, with clearance expected about 2 miles out. ENY3544 was cleared for takeoff. At 0958, the controller cleared CAL5148 to land and advised of the departing traffic. CAL5148 crossed the landing threshold at about 700 feet msl (under 100 feet above ground). At 0959, the first officer of DAL2012, holding short of runway 10L, stated "goin off the runway." CAL5148 then reported a go-around due to a "last minute deviation on the runway."
While on short final, CAL5148 drifted left of the runway centerline. The left main landing gear touched down left of the runway but still on the paved surface. The airplane then traveled into the grass between taxiway DD and taxiway N1, leaving deep ground scarring and damaging a windsock. CAL5148 executed a go-around and subsequently landed on runway 9R without further incident at about 1020.
Meteorological Information
KORD had an Automated Surface Observing System (ASOS) supplemented by certified weather observers. The ASOS was at an elevation of 680 feet msl with a 3° westerly magnetic variation. At 0951 CDT, a METAR reported wind from 060° at 12 knots, visibility 2.5 statute miles, moderate rain, mist, overcast ceiling at 600 feet agl, temperature 19°C, dew point 18°C, altimeter 29.78 inHg. Remarks included distant lightning to the east and recent precipitation. The Terminal Aerodrome Forecast (TAF) valid at the time, issued at 0812 CDT, expected wind from 070° at 10 knots, 3 miles visibility, light rain showers and mist, scattered clouds at 500 feet agl, and overcast ceiling 900 feet agl, with temporary conditions of 3/4 mile visibility, heavy rain, and overcast ceiling 500 feet agl.
Wreckage and Impact Information
Deep ground scarring was visible near where the aircraft had touched down left of the runway on the paved surface and extending into the grass between taxiway DD and taxiway N1.
Flight Recorders
The accident airplane was equipped with a Honeywell 4700 solid-state flight data recorder (FDR) containing about 27 hours of data. The accident flight was the last recording, lasting about 5 hours 52 minutes; data were extracted normally. The airplane also carried a Honeywell cockpit voice recorder (CVR) capable of 120 minutes of digital audio. It contained a two-channel recording of the last 120 minutes power was applied, but because power remained on long after the event, all audio from the accident flight was overwritten.
Tests and Research
The FAA's National Resource Engineer for Navigation conducted mathematical modeling of the event. The model could assess how objects like buildings and aircraft affect localizer and glideslope quality but could not evaluate the effects of an aircraft flying directly over the antenna. An analysis was performed with ENY3544 located 2,800 feet from the localizer and 450 feet above the runway. Using several assumptions for aircraft orientation, the model's output was consistent with the localizer deviations determined from the CAL5148 FDR data. The simulation predicted that the location of the departing ENY3544 caused sufficient multipath (signal reflection) to produce a fly-left indication for the arriving CAL5148 during the autoland approach.