Narrative:

We were being in the middle of radar contact and a non-radar environment. We had been cleared to FL180 and reported level. I believe we were radar identified and then cleared to 12;000 ft. On the descent we were cleared to what we heard as 11;000 ft. My co-captain read back 11;000 twice and neither read back was acknowledged. We were then told to maintain what my co-captain read back as 7;000. The controller said no one seven thousand. I was already out of 14;000 descending and immediately initiated a climb. The controller then said maintain your altitude and heading. We were summarily vectored for a visual approach onto runway 21 at sequ (quito; ecuador). I wrote a report for the aero in quito explaining the situation. I requested a copy of the tape recording for my own benefit. Two things that come to mind are 1) the lack of response from the quito controller; and 2) poor english annunciation of multiple numbers. Although we were VMC at the time I hate to think of the problems that may have ensued had we been IMC. Even though I believe we took every precaution; the system failed us. As a former air traffic control specialist who has trained multiple nationalities; my major emphasis was always on strict adherence to proper verbiage and enunciation. Although I have traveled to many nations and expect some variability; nothing is more important than the proper pilot controller verbiage. It is even more important when in such hostile terrain. There was never any change in the controllers voice. No indication that anything was wrong until we read back 7;000.

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Original NASA ASRS Text

Title: IFR corporate jet on approach to Quito; Ecuador; descended below ATC assigned altitude; reporter claiming poor ATC adherence to proper verbiage and enunciation as causal factors.

Narrative: We were being in the middle of radar contact and a non-radar environment. We had been cleared to FL180 and reported level. I believe we were radar identified and then cleared to 12;000 FT. On the descent we were cleared to what we heard as 11;000 FT. My Co-captain read back 11;000 twice and neither read back was acknowledged. We were then told to maintain what my Co-captain read back as 7;000. The controller said no one seven thousand. I was already out of 14;000 descending and immediately initiated a climb. The controller then said maintain your altitude and heading. We were summarily vectored for a visual approach onto Runway 21 at SEQU (Quito; Ecuador). I wrote a report for the Aero in Quito explaining the situation. I requested a copy of the tape recording for my own benefit. Two things that come to mind are 1) the lack of response from the Quito controller; and 2) poor English annunciation of multiple numbers. Although we were VMC at the time I hate to think of the problems that may have ensued had we been IMC. Even though I believe we took every precaution; the system failed us. As a former Air Traffic Control Specialist who has trained multiple nationalities; my major emphasis was always on strict adherence to proper verbiage and enunciation. Although I have traveled to many nations and expect some variability; nothing is more important than the proper pilot controller verbiage. It is even more important when in such hostile terrain. There was never any change in the Controllers voice. No indication that anything was wrong until we read back 7;000.

Data retrieved from NASA's ASRS site as of April 2012 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.