B727 crew descends below assigned altitude on approach to BIL after runway change, triggering a GPWS warning and necessitating an escape maneuver.
Synopsis
B727 crew descends below assigned altitude on approach to BIL after runway change, triggering a GPWS warning and necessitating an escape maneuver.
Narrative
Rewritten in plain English from NASA’s original all-caps telegraphic report — facts, figures, and terminology preserved.
During approach to runway 10L at Billings, the runway was changed to runway 28. This placed our aircraft high and fast for the approach. In an effort to get the aircraft down and slowed, the captain asked for a vector, which was received.
We were then vectored back to a dog-leg, 3 miles outside the marker. The aircraft was still high and was not configured. We were given a descent to 5300 feet and a turn to intercept the localizer. During this maneuver, the first officer, an IOE student, lost situational awareness of his descent rate and the fact that he had the speed brakes deployed. I informed him that he was about to descend below 5300 feet.
As we descended through 5500 feet, the captain took the airplane and recovered at 5100 feet. At this point, we received a GPWS 'whoop whoop terrain' warning and were forced to execute an escape maneuver. This resulted in a climb to 7000 feet MSL.
We informed approach, who asked us to stop climb at 6000 feet MSL. We were already nose high passing 6600 feet at the time, which we communicated to approach control. Due to our altitude and an impending conflict with other traffic, we were told to turn north and 'expedite' the turn. We complied and then were vectored back around for another, uneventful approach.
Show the original NASA report (verbatim, telegraphic)
DURING APCH TO RWY 10L AT BILLINGS; THE RWY WAS CHANGED TO RWY 28. THIS PLACED OUR ACFT HIGH AND FAST FOR THE APCH. IN AN EFFORT TO GET THE ACFT DOWN AND SLOWED; THE CAPT ASKED FOR A VECTOR; WHICH WAS RECEIVED. WE WERE THEN VECTORED BACK TO A DOG-LEG; 3 MILES OUTSIDE THE MARKER. THE ACFT WAS STILL HIGH AND WAS NOT CONFIGURED. WE WERE GIVEN A DSCNT TO 5300 FT AND A TURN TO INTERCEPT THE LOCALIZER. DURING THIS MANEUVER; THE FO; AN IOE STUDENT; LOST SITUATIONAL AWARENESS OF HIS DSCNT RATE AND THE FACT THAT HE HAD THE SPD BRAKES DEPLOYED. I INFORMED HIM THAT HE WAS ABOUT TO DSND BELOW 5300 FT. AS WE DSNDED THROUGH 5500 FT; THE CAPT TOOK THE AIRPLANE AND RECOVERED AT 5100 FT. AT THIS POINT; WE RECEIVED A GPWS 'WHOOP WHOOP TERRAIN' WARNING AND WERE FORCED TO EXECUTE AN ESCAPE MANEUVER. THIS RESULTED IN A CLB TO 7000' MSL. WE INFORMED APCH; WHO ASKED US TO STOP CLB AT 6000 FT MSL. WE WERE ALREADY NOSE HIGH PASSING 6600 FT AT THE TIME; WHICH WE COMMUNICATED TO APCH CTL. DUE TO OUR ALT AND AN IMPENDING CONFLICT WITH OTHER TFC; WE WERE TOLD TO TURN NORTH AND 'EXPEDITE' THE TURN. WE COMPLIED AND THEN WERE VECTORED BACK AROUND FOR ANOTHER; UNEVENTFUL APCH.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.