Narrative:

We had just come off of the ANCHR3 RNAV arrival into denver and were being vectored for a visual approach to 35R. Approach called out traffic to us and we followed them on the visual after we had been given a heading to intercept the 35R localizer. When cleared for the visual approach; the captain extended the centerline in the box off of fronz and set the altitude select window to the fronz altitude of 7000 ft. The captain then began a fairly rapid descent to 7000 ft which caught me a little off guard since we were still quite a ways from fronz. However; it wasn't gross; just much more rapid of a descent than I was contemplating; since there was no hurry to descend. Approaching 7000 ft; ATC gave us an altitude alert and said 'check altitude; min altitude in this area 7500 ft.' during the descent; I was checking the approach plate to see if there were any obstacles; and noted a tower at 6236 ft which was more than 500 ft below the altitude we were descending to (7000 ft). The captain then climbed back to 7500 ft and continued the approach; the remainder of which was uneventful. After the flight; we discussed this and the captain told me he had descended rapidly to correct for decaying airspeed vs pushing up the throttles. We thought perhaps ATC called us because of our rapid descent rate. My recollection was that we were just inside of drumm (14 DME fix on final) on the dogleg. The final had been extended off of fronz so the visual representation on the navigation display didn't show our location on the dogleg in relation to drumm which had an altitude of 9000 ft. I had previously put the runway on the fix page; but didn't have that page up at the moment to see our distance from the runway. We were transferred to tower freq and the rest of the approach was normal.while on a visual approach; extra caution should be exercised to ensure we don't descend too early. The captain could have verbalized his intent to descend rapidly to correct for decaying airspeed; and I could have asked him about it. We should both have made sure we didn't descend early by crosschecking DME restrictions on the ILS; even though we were on a dogleg and cleared for the visual approach.

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Original NASA ASRS Text

Title: Air carrier First Officer reported being surprised when his Captain began a premature descent to 7;000 feet while being vectored towards FRONZ. ATC alerted the crew; now below the minimum vectoring altitude; so the Captain returned to 7;500 feet.

Narrative: We had just come off of the ANCHR3 RNAV Arrival into Denver and were being vectored for a visual approach to 35R. Approach called out traffic to us and we followed them on the visual after we had been given a heading to intercept the 35R Localizer. When cleared for the visual approach; the Captain extended the centerline in the box off of FRONZ and set the altitude select window to the FRONZ altitude of 7000 ft. The Captain then began a fairly rapid descent to 7000 ft which caught me a little off guard since we were still quite a ways from FRONZ. However; it wasn't gross; just much more rapid of a descent than I was contemplating; since there was no hurry to descend. Approaching 7000 ft; ATC gave us an Altitude Alert and said 'check altitude; min altitude in this area 7500 ft.' During the descent; I was checking the approach plate to see if there were any obstacles; and noted a Tower at 6236 ft which was more than 500 ft below the altitude we were descending to (7000 ft). The Captain then climbed back to 7500 ft and continued the approach; the remainder of which was uneventful. After the flight; we discussed this and the Captain told me he had descended rapidly to correct for decaying airspeed vs pushing up the throttles. We thought perhaps ATC called us because of our rapid descent rate. My recollection was that we were just inside of DRUMM (14 DME fix on final) on the dogleg. The final had been extended off of FRONZ so the visual representation on the navigation display didn't show our location on the dogleg in relation to DRUMM which had an altitude of 9000 ft. I had previously put the runway on the Fix page; but didn't have that page up at the moment to see our distance from the runway. We were transferred to Tower freq and the rest of the approach was normal.While on a visual approach; extra caution should be exercised to ensure we don't descend too early. The Captain could have verbalized his intent to descend rapidly to correct for decaying airspeed; and I could have asked him about it. We should both have made sure we didn't descend early by crosschecking DME restrictions on the ILS; even though we were on a dogleg and cleared for the visual approach.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.