Tuesday, June 8, 2010
Monitoring What’s Going On
Managing pilot workload
The flight was operating from San Diego International Airport in San Diego, Calif., to Minneapolis. It took off at 2:59 p.m. PST, and the captain was the flying pilot. The takeoff, climb and initial cruise were normal. The flight crew indicated that the planned route programmed into the flight management computer (FMC) was flown during the climb and cruise portions of the flight.
At 6:46 p.m. CST, the flight was being handled by Denver Center, and one controller set up a handoff to another controller. The flight checked in with the second controller, and 10 minutes later, the second controller tried to hand off the flight to a third Denver controller with the radio transmission “one eighty eight contact Denver Center, one three two point one seven.” When there was no response, the second Denver controller again directed the flight to “contact Denver Center, one three two point one seven.”
At 6:57:01 p.m., the flight responded, “Okay, three two one seven, Northwest one eighty eight.” This was the last ATC communication with the flight in Denver Center airspace. The airplane’s flight data recorder (FDR) indicated that after this transmission, there was no radio microphone keying until 8:12:46 p.m.
The flight entered the third Denver sector’s airspace, but didn’t check in on the assigned frequency. The controllers for the fourth and fifth Denver sectors tried to raise the airplane, but it flew into their airspace with no radio contact. ATC radioed the flight to contact Minneapolis Center, but there was no response. Radio calls on several different frequencies were made by Denver and Minneapolis controllers attempting to establish contact, but nothing worked. ATC contacted the airline’s dispatch center and had them send a text message to the airplane. The pilots of other aircraft were asked to contact Flight 188. Controllers transmitted in the blind on ATC sector frequencies and on emergency frequency 121.5 trying to raise the aircraft. They asked for an “ident” on the transponder if ATC could be heard. Controllers in other airspace sectors were advised that the airplane was “no radio” and would be landing at Minneapolis. At least four additional text messages were sent to the airplane by the airline’s dispatchers.
At 8:12:46 p.m., the flight transmitted on frequency 132.125, and advised that they had overflown the destination and needed to turn around and head for Minneapolis. The pilots didn’t know it at the time, but the frequency they used was for Canada’s Winnipeg Area Control Center (YWG), Thunder Bay Low Sector. After establishing the flight’s position over Eau Claire, Wis., at FL370, the YWG controller radioed that the flight was on the wrong frequency and directed the pilots to contact Minneapolis Center on 123.72. At 8:14:06 p.m., Flight 188 established communications with Minneapolis Center.
At 8:14:14 p.m., the flight radioed, “Roger, we got distracted and we’ve overflown Minneapolis. We’re overhead Eau Claire and would like to make a 180 and do arrival from Eau Claire.” They were then given radar vectors to set up for arrival. During the descent, controllers asked several times about the cause of the loss of contact, and each time the pilots indicated that they had “cockpit distractions.”
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