B747-C/F
Flight Crew Last 90 Days 20; Flight Crew Total 22000; Flight Crew Type 3000
Situational Awareness; Communication Breakdown; Time Pressure
ATC Issue All Types; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors; Procedure
We were being vectored in for an ILS RWY 27 into Mumbai. The weather was reported to be 1900 meters visibility; haze; smoke and light to variable winds. I believe we [were] leading the pack because we were told to maintain Mach .84 or greater and to cross Emrak at a certain time or earlier. When starting our descent we were told to cross Emrak at 18000 or below and continue to 15000. The frequency congestion was very heavy with other carriers and controllers blocking each other and asking to repeat ATC instructions. The communications with controllers was also difficult to understand. We were given a vector to a heading of 255 for the approach into Mumbai. We were also given altitude changes to cross at certain distances. We had complied with these instructions and given a descent to 1900 msl on a heading of 255 to intercept to LOC to runway 27. The captain and I both confirmed the altitude. The captain then read back the clearance for the ILS runway 27. We also had a Jumpseat rider that was also qualified on the aircraft listening in and backing us up. The controller never ever questioned our read back. The approach had gotten busy for us because we were told to keep our speed up in the descent and approach and trying to get down. The heading; altitude and descent that we were given flew us over a mountain ridge that set off the GPWS. I disengaged the autopilot (A/P) had hand flew while starting a climb but we had already passed the conflict. I reengaged the A/P; leveled off at 1900/2000 feet msl. The controller asked about our altitude and said we should have been at 2900 ft. msl. The captain told him he had cleared us down to 1900 ft. msl. The controller didn't say anything other than cleared for the approach and handed us over to the tower. We were cleared to land which we did and taxied in to our assigned spot. We proceeded to shut down and secure the aircraft which we did. At no point in time where we told contact ATC or talk to any ATC representative about what had happened. We as crew members must maintain an even higher level of vigilance when coming into airports such as Mumbai. The low visibility due to smoke/haze; terrain; and hard to understand controllers can make it very challenging. I had briefed what the MSA and GS but not the 2900 ft. msl on the profile. I could have briefed the approach better and asked about the 1900 ft. We had the mountain ridge in sight and clear of the conflict. I should have executed a go around and get vectored back in for another approach.
We had been told to keep speed high all the way from initial descent. We were 295 kt. until 7000 ft. I asked First Officer (FO); pilot flying; to slow quickly then. We had just intercepted 27 LOC about 15 DME from airport. We were cleared to descend to 2900 ft. at 25 DME and cleared ILS 27. As we were approaching 2900 ft. we were told descend 1900 ft. at 15 DME. I repeated it back and set it in window. I then went to look at airport diagram again. I soon heard TERRAIN warning. I looked out window and saw the mountain that is on final approach safely below our altitude. ATC then questioned me about altitude. We then heard 'PULL UP.' I told FO I had terrain below in sight and continue. We intercepted glideslope and landed.
B747 flight crew reports being cleared to descend to 1900 feet during vectors to ILS 27 at VABB. The Controller questions their altitude stating they should be at 2900 feet at about the time a GPWS terrain warning is annunciated. The ridge causing the warning is visible and the approach is continued to landing.