B727 flight crew descends below cleared altitude due to hearback readback problem.
Synopsis
B727 flight crew descends below cleared altitude due to hearback readback problem.
Narrative
Rewritten in plain English from NASA’s original all-caps telegraphic report — facts, figures, and terminology preserved.
I was the first officer acting as pilot monitoring. On approach to Grand Forks (GFK) we were instructed to descend to 3000 feet and contact approach. Grand Forks approach acknowledged our check-in; asked for a pilot report and gave us a clock position for the field to report the runway for a visual.
I asked that he contact the tower and ask them to turn up the runway lights to help with spotting the runway 35L. The ground was snow covered and blended with a deck of clouds south of the field that I did not previously notice. We were given a heading of 300 degrees to intercept the LOC and I heard and read back descend to 2000 feet. The new altitude was placed in the altitude alert window and acknowledged per company FOM.
In the descent I transmitted the tops were at 3000 feet and the base was at 2400 feet; no turbulence or icing. At approximately 2200 feet we were asked what our altitude was and I reported our altitude and descending to 2000 feet. Approach stated the minimum vector altitude for our position was 2800 feet and to climb to that altitude.
We complied and intercepted the LOC from 2800 feet. We subsequently broke out of the deck at 2800 feet and were cleared for a visual approach to runway 35L at GFK. There was no indication from ATC that there was any conflict or problem; however the captain contacted the tower later that day to ask if there were any unresolved issues; which there were none.
Show the original NASA report (verbatim, telegraphic)
I WAS THE FO ACTING AS PLT MONITORING. ON APCH TO GRAND FORKS (GFK) WE WERE INSTRUCTED TO DSND TO 3000 FT AND CONTACT APCH. GRAND FORKS APCH ACKNOWLEDGED OUR CHK-IN; ASKED FOR A PIREP AND GAVE US A CLOCK POS FOR THE FIELD TO RPT THE RWY FOR A VISUAL. I ASKED THAT HE CONTACT THE TWR AND ASK THEM TO TURN UP THE RWY LIGHTS TO HELP WITH SPOTTING THE RWY; 35L. THE GND WAS SNOW COVERED AND BLENDED WITH A DECK OF CLOUDS S OF THE FIELD THAT I DID NOT PREVIOUSLY NOTICE. WE WERE GIVEN A HDG OF 300 DEGS TO INTERCEPT THE LOC AND I HEARD AND READ BACK DSND TO 2000 FT. THE NEW ALT WAS PLACED IN THE ALT ALERT WINDOW AND ACKNOWLEDGED PER COMPANY FOM. IN THE DSCNT I XMITTED THE TOPS WERE AT 3000 FT AND THE BASE WAS AT 2400 FT; NO TURB OR ICING. AT APPROX 2200 FT WE WERE ASKED WHAT OUR ALT WAS AND I RPTED OUR ALT AND DSNDING TO 2000 FT. APCH STATED THE MVA FOR OUR POS WAS 2800 FT AND TO CLB TO THAT ALT. WE COMPLIED AND INTERCEPTED THE LOC FROM 2800 FT. WE SUBSEQUENTLY BROKE OUT OF THE DECK AT 2800 FT AND WERE CLRED FOR A VISUAL APCH TO RWY 35L AT GFK. THERE WAS NO INDICATION FROM ATC THAT THERE WAS ANY CONFLICT OR PROB; HOWEVER THE CAPT CONTACTED THE TWR LATER THAT DAY TO ASK IF THERE WERE ANY UNRESOLVED ISSUES; WHICH THERE WERE NONE.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.