Narrative:

Misinterpreted den ILS runway 35L chart. During approach to den, ILS runway 35L, first officer flying, outside chola at 8000 ft, given turn to final and clearance for the approach. At chola I mistook the bold 7000 ft depicted as a stepdown altitude from which the GS would be intercepted. Approach control asked if we had the airport in sight. We did not due to our passing through a rain shower. Approach informed us that we should be at 8000 ft and directed us to climb to 7500 ft and reclred us for the approach. It should be noted that the chart presentation is confusing as both 9000 ft and 7000 ft are bold type. Commercial chart manual introduction new format 3 states, altitudes in the profile will be in bold type when the altitude is at the FAF on non precision approachs ILS GS intercept altitude ILS GS altitude at the OM despite above, throughout commercial chart manuals one finds charts with non bold ILS GS intercept altitudes, (see den charts). Since our altitude, 8000 ft, was below the bold altitude, 9000 ft, I was drawn to the other bold altitude, 7000 ft. In retrospect, I see the circle #1 note, or as assigned by ATC, and I will be very cautious about such traps in the future. Recommendation: bold type altitudes depicted on ILS charts should be on the GS intercept altitude rather than the dashed line for localizer/GS out. Supplemental information from acn 482689: I was PF, being vectored off of the dandd 3 arrival for the ILS runway 35L at den. Assigned altitude was 8000 ft. We were assigned a heading of 300 degrees. Obviously I will pay much closer attention to GS intercept altitudes.

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Original NASA ASRS Text

Title: MD80 CREW HAD ALTDEV IN DEN CLASS B.

Narrative: MISINTERPRETED DEN ILS RWY 35L CHART. DURING APCH TO DEN, ILS RWY 35L, FO FLYING, OUTSIDE CHOLA AT 8000 FT, GIVEN TURN TO FINAL AND CLRNC FOR THE APCH. AT CHOLA I MISTOOK THE BOLD 7000 FT DEPICTED AS A STEPDOWN ALT FROM WHICH THE GS WOULD BE INTERCEPTED. APCH CTL ASKED IF WE HAD THE ARPT IN SIGHT. WE DID NOT DUE TO OUR PASSING THROUGH A RAIN SHOWER. APCH INFORMED US THAT WE SHOULD BE AT 8000 FT AND DIRECTED US TO CLB TO 7500 FT AND RECLRED US FOR THE APCH. IT SHOULD BE NOTED THAT THE CHART PRESENTATION IS CONFUSING AS BOTH 9000 FT AND 7000 FT ARE BOLD TYPE. COMMERCIAL CHART MANUAL INTRODUCTION NEW FORMAT 3 STATES, ALTS IN THE PROFILE WILL BE IN BOLD TYPE WHEN THE ALT IS AT THE FAF ON NON PRECISION APCHS ILS GS INTERCEPT ALT ILS GS ALT AT THE OM DESPITE ABOVE, THROUGHOUT COMMERCIAL CHART MANUALS ONE FINDS CHARTS WITH NON BOLD ILS GS INTERCEPT ALTS, (SEE DEN CHARTS). SINCE OUR ALT, 8000 FT, WAS BELOW THE BOLD ALT, 9000 FT, I WAS DRAWN TO THE OTHER BOLD ALT, 7000 FT. IN RETROSPECT, I SEE THE CIRCLE #1 NOTE, OR AS ASSIGNED BY ATC, AND I WILL BE VERY CAUTIOUS ABOUT SUCH TRAPS IN THE FUTURE. RECOMMENDATION: BOLD TYPE ALTS DEPICTED ON ILS CHARTS SHOULD BE ON THE GS INTERCEPT ALT RATHER THAN THE DASHED LINE FOR LOC/GS OUT. SUPPLEMENTAL INFO FROM ACN 482689: I WAS PF, BEING VECTORED OFF OF THE DANDD 3 ARR FOR THE ILS RWY 35L AT DEN. ASSIGNED ALT WAS 8000 FT. WE WERE ASSIGNED A HEADING OF 300 DEGS. OBVIOUSLY I WILL PAY MUCH CLOSER ATTN TO GS INTERCEPT ALTS.

Data retrieved from NASA's ASRS site as of July 2007 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.