Narrative:

An instrument student and I; a CFI-I; were performing an IFR training flight on an active flight plan to review approach procedures. After completing our first approach; the ILS runway 19 approach; we executed the prescribed missed approach procedures by flying a 160 heading and beginning a climb up to 3;000 feet. After contacting approach; we received instruction to climb to 4;000 feet and were told to expect vectors (as requested) to the VOR runway 28 approach. Within a few minutes; we were given a 'downwind' vector towards the approach course. We continued to fly for approximately 15 miles away from the airport/VORTAC at 4;000 feet; and our 'downwind' was farther away from the airport than is typical for this approach. Before I had the chance to query ATC about our distance; we were given a base turn; and shortly thereafter a heading and instruction to intercept the final approach course. At this point; according to track log data from flightaware; we were still about 18 miles away from the airport. Within the next few miles; we were given the instruction '10 miles from the VOR; cleared VOR runway 28 approach'. At this point; my student began descending from 4;000 feet to the published at-or-above altitude of 2;300 feet that was applicable for the straight-in approach prior to the FAF. During the descent; we broke out of the cloud layer at approximately 3;200 feet. Within a minute or so of going visual; I noticed that our GPS indicated that we were just passing 10 miles from the VOR and we were level at an altitude of 2;300 feet. Now; on the VOR runway 28; the published approach course associated with the 2;300 foot step-down/at-or-above altitude states 'remain within 10 miles' in reference to the procedure turn completion altitude of 3;300 feet; after which an aircraft performing the 'full approach' would re-intercept the inbound course and descend to 2;300 feet. Upon realizing our remaining distance to the VOR; I became concerned that we had descended too low (the applicable MSA prescribes 3;600 feet) for that area of the approach and had descended to the 2;300 feet step-down prematurely (prior to within 10mi of the VOR); placing the aircraft in potential conflict with obstructions and terrain. Subsequent analysis of the flightaware track-log clearly shows my aircraft below the 3;600 MSA at distances greater than 10 miles from the VOR which; within 10 miles; a descent to 2;300 would have been otherwise completely safe. While ATC had implied in our clearance that we were within 10 miles of the VOR; and after we descended made no subsequent mention of our altitude (which may have been perfectly safe in reference to their MVA for that sector as we regularly transit that area at such lower altitudes when receiving vectors); as PIC it was still my responsibility to ensure compliance with all MSA's and step-down altitudes on the approach. Ultimately; my failing to confirm the controller's guidance regarding our aircraft's position and blindly descending on that information represents an unacceptable loss of situational awareness on my part; and it may have put our otherwise uneventful training flight in highly unnecessary and completely avoidable danger. Moving forward; it is necessary to confirm and; when applicable; query ATC when receiving a position report in conjunction with an approach clearance to keep an eye on the big picture and maintain situational awareness. Also; a better understanding of 'when and how far can I descend if cleared...' relating to this scenario dealing with this approach (which; in all other times I have used the procedure; I have been vectored within 10 miles of the station) would have increased my awareness that our descent was premature and hazardous.

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Original NASA ASRS Text

Title: GA flight instructor reported descending below the minimum safe altitude on a practice instrument approach due to confusion and miscommunication with ATC related to distance from the airport.

Narrative: An instrument student and I; a CFI-I; were performing an IFR training flight on an active flight plan to review approach procedures. After completing our first approach; the ILS runway 19 approach; we executed the prescribed missed approach procedures by flying a 160 heading and beginning a climb up to 3;000 feet. After contacting approach; we received instruction to climb to 4;000 feet and were told to expect vectors (as requested) to the VOR runway 28 approach. Within a few minutes; we were given a 'downwind' vector towards the approach course. We continued to fly for approximately 15 miles away from the airport/VORTAC at 4;000 feet; and our 'downwind' was farther away from the airport than is typical for this approach. Before I had the chance to query ATC about our distance; we were given a base turn; and shortly thereafter a heading and instruction to intercept the final approach course. At this point; according to track log data from FlightAware; we were still about 18 miles away from the airport. Within the next few miles; we were given the instruction '10 miles from the VOR; Cleared VOR RWY 28 Approach'. At this point; my student began descending from 4;000 feet to the published at-or-above altitude of 2;300 feet that was applicable for the straight-in approach prior to the FAF. During the descent; we broke out of the cloud layer at approximately 3;200 feet. Within a minute or so of going visual; I noticed that our GPS indicated that we were just passing 10 miles from the VOR and we were level at an altitude of 2;300 feet. Now; on the VOR RWY 28; the published approach course associated with the 2;300 foot step-down/at-or-above altitude states 'remain within 10 miles' in reference to the procedure turn completion altitude of 3;300 feet; after which an aircraft performing the 'full approach' would re-intercept the inbound course and descend to 2;300 feet. Upon realizing our remaining distance to the VOR; I became concerned that we had descended too low (the applicable MSA prescribes 3;600 feet) for that area of the approach and had descended to the 2;300 feet step-down prematurely (prior to within 10mi of the VOR); placing the aircraft in potential conflict with obstructions and terrain. Subsequent analysis of the FlightAware track-log clearly shows my aircraft below the 3;600 MSA at distances greater than 10 miles from the VOR which; within 10 miles; a descent to 2;300 would have been otherwise completely safe. While ATC had implied in our clearance that we were within 10 miles of the VOR; and after we descended made no subsequent mention of our altitude (which may have been perfectly safe in reference to their MVA for that sector as we regularly transit that area at such lower altitudes when receiving vectors); as PIC it was still my responsibility to ensure compliance with all MSA's and step-down altitudes on the approach. Ultimately; my failing to confirm the controller's guidance regarding our aircraft's position and blindly descending on that information represents an unacceptable loss of situational awareness on my part; and it may have put our otherwise uneventful training flight in highly unnecessary and completely avoidable danger. Moving forward; it is necessary to confirm and; when applicable; query ATC when receiving a position report in conjunction with an approach clearance to keep an eye on the big picture and maintain situational awareness. Also; a better understanding of 'when and how far can I descend if cleared...' relating to this scenario dealing with this approach (which; in all other times I have used the procedure; I have been vectored within 10 miles of the station) would have increased my awareness that our descent was premature and hazardous.

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.