Created Saturday, May 21st 2022 18:19Z, last updated Saturday, May 21st 2022 18:19Z
A China Airlines Boeing 747-400 freighter, registration B-18711 performing freight flight CI-5148 from Anchorage,AK to Chicago O'Hare,IL (USA) with 4 crew, was on an ILS approach to runway 10L at 09:57L (14:57Z) when the crew advised they were going around having had a last minute deviation on the runway. The crew of another aircraft on the ground advised the aircraft had gone off the runway, a third crew advised tower the runway needed to be inspected. A runway inspection found debris on the runway, the windsock (WDI) to the left (north) of the runway between taxiway DD and N1 was found damaged, the runway was closed for about 50 minutes. In the meantime B-18711 positioned for another approach and landed safely on runway 09R about 25 minutes after the go around.
The FAA reported the flight touched down in the grass, went around and returned to land. None of the 4 occupants was injured, the aircraft sustained minor damage.
On Jul 25th 2018 the NTSB reported the Boeing 747-400 "experienced a runway excursion off the left side of runway 10L shortly after touchdown and subsequently conducted a go around". None of the 4 crew were injured, the aircraft was not damaged. The occurrence was rated an incident and is being investigated.
The occurrence aircraft remained on the ground in Chicago until Jul 4th 2018 (for 13 days) before returning to service.
On May 21st 2022 the NTSB released their final report concluding the probable causes of the incident were:
Interference with the localizer signal resulting in a Multipath condition experienced by CAL5148 while conducting an ILS CAT III (autoland) approach. This condition resulted in a runway excursion and subsequent go-around. The interference was most likely caused by a previous departure flying through the ILS critical area while departing the same runway.
The NTSB analysed:
CAL5148 was conducting an ILS autoland approach to runway 10R. Instrument meteorological conditions prevailed at the time of the incident, with an overcast ceiling of 600 feet above ground level (agl), and visibility of 2 and 1/2 miles with moderate rain. These conditions required protection of the ILS critical area by ATC which they did according to FAA Order JO 7110.65, Air Traffic Control. ATC issues control instructions to protect ILS critical areas and avoid signal interference from vehicle traffic and taxiing aircraft when the reported weather is a ceiling of less than 800 feet or visibility of less than 2 miles. However, this restriction does not include consideration for preceding arriving or departing aircraft.
While a previously departed aircraft was airborne and over the ILS critical area, CAL5148 experienced localizer deviations while on short final. In math modelling analysis of this event conducted by the FAA; the results were consistent with the localizer deviations determined from CAL5148 flight data recorder (FDR) data. Specifically, the modelling indicated the deviation beginning at 1/4 mile from threshold would lead the aircraft to turn left to continue to follow the localizer course line during an autoland approach. The FAA National Resource Engineer for Navigation who performed the modelling wrote “I am 90% confident that the location of departing ENY3544 caused sufficient Multipath (signal deflection) to produce a fly left indication to arriving CAL5148.”
“Multipath” is a term used to describe the distortion of the radiated signal which is caused by the signal being deflected off either stationary or moving objects such as aircraft or vehicles in the localizer or glide slope critical area(s).
Related NOTAMs:
ORD 06/887 ORD RWY 10L/28R CLSD 1806211501-1806211600
ORD 06/889 ORD RWY 10L/28R SAFETY AREA IRREGULAR SFC N SIDE BTN TWY DD AND TWY N1 1806211540-1807141100
ORD 06/890 ORD AD AP WDI FOR RWY 10L OUT OF SERVICE 1806211547-1807262300
ORD 06/892 ORD NAV ILS RWY 10L OUT OF SERVICE 1806211633-1806222200
ORD 06/893 ORD RWY 10L ALS OUT OF SERVICE 1806211723-1806222359
