The main runway of the Mumbai airport was shut for about 40 minutes on Sunday after pilots observed low friction levels due to rubber deposits on the surface. The deposits had to be removed on a war footing to avoid skidding of aircraft. Operations were shifted to the secondary runway, which along with poor visibility and winds led to some flight delays.
An airport spokesperson said that the main runway remained unavailable between 3.43 p.m. and 4.17 p.m. during which flights were routed to the secondary runway. During this period, a Jet Airways flight from Dhaka carried out a go-around (aborted landing at the last minute) twice. A Kozikode-Mumbai Jet Airways flight also carried out a go-around.
Officials said that the greater the accumulation of materials is, the lower the friction levels. Each time an aircraft lands, its tires deposit approximately 1 to 1.5 pounds (454g) of rubber onto the surface. The build-up of these heavy deposits can over time, if not treated properly, reduce the friction levels of the surface, potentially causing the aircraft to lose braking capabilities and directional control.
As per requirements of aviation regulator, Directorate General of Civil Aviation, runways should be periodically cleaned of rubber deposits to regain friction. “Cleaning of rubber deposits at the touch down zone on the runway will increase the friction levels. This procedure is strictly followed and the friction coefficient given to the crew during adverse weather conditions, as a part of the standard practice,” an airport official said.
During 24 hours ending at 8.30 a.m. on Sunday, the airport recorded 31.7 mm of rainfall. According to aircraft and airline monitoring website flightradar24, this led to an average 11 minute delay in arrivals with 87 flights arriving late and one flight being cancelled. On the departure front, the airport reported an average 46 minute delay affecting 250 flights and two flights being cancelled.
According to procedure laid down by the International Civil Aviation Authority (ICAO), it is obligatory on the part of airport operators to thoroughly inspect the runway and taxiways immediately before the monsoon or during the dry spell. “With the present technology we were able to identify the weak spots well before the monsoons. The runway surface conditions during the monsoon period are informed to the pilots, i.e. whether the runway is damp/wet or contaminated and if contaminated, the depth of the contaminant, so that appropriate performance penalties may be applied before a take-off or approach is initiated,” the official said.