Narrative:

The captain called toronto approach. Toronto gave us a new frequency and upon checking in we were immediately cleared for the profile descent runway 24L/right (attachment 2). At this time I pulled out the profile descent runway 24L/right. I immediately initiated a descent to cross 38 DME between 17000-13000'. When we checked to ensure that we were just inside the 38 DME ar, the captain then directed a descent to 10000'. At this time I continued the descent, and then checked the profile to confirm the altitude. I made the same mistake as the captain and read the 25 DME restriction which was listed adjacent to the 38 DME restriction we had just used (attachment 2). Approximately 25 NM out from toronto. The controller asked us if we had been cleared to 10000' and the captain replied that we had already been cleared the profile descent to runway 24. The controller then gave a vector for traffic sep. At this point we realized that something was wrong and the captain discovered that we had read the restriction for the improper quadrant. We had descended to 10000' instead of 11000'. The arrival procedure at toronto requires pilots to rapidly transition through a number of in-flight documents. First the pilot must be reading his low chart to navigation to the arrival procedure. Then he must have out the arrival procedure and determine which profile he will be assigned. When the profile is assigned, the pilot must have both the profile and the arrival procedure in front of him and refer to both since the profile and the arrival procedure in front of him and refer to both since the profile has no course instructions. In addition, he must have out the proper approach plate so that the approach can be studied and briefed. All of this occurs within 40 NM of toronto at the same time that the controllers are constantly on the radio (requiring extra vigilance to hear your call sign) and when the descent check must be accomplished. New charts had been issued within the week. Both pilots had all updated information on board and in use at the time of the incident. Unfortunately the new profile descent is not portrayed in an easily understandable format. Upon close study, you can see that the arrival is divided into sectors. However, these sectors are not emphasized either graphically or in writing. Both the captain and I made the mistake of reading the 25 DME restriction which is closest to the proper 38 DME restriction. The restriction that we should have used is located at the bottom of the chart. Also, the 25 DME line depiction is not segmented or otherwise obviously divided into sectors. This helps lead to the conclusion that the 25 DME restriction is uniform throughout. Supplemental information from acn 108306: I was captain erie, PA, to toronto/pearson int'l. The copilot was flying en route to brany. On contact with arrival we were given the brany 4 arrival with profile descent runway 24 and a frequency change to toronto approach control. We were in the descent runway 24 and a frequency change to tor approach control. We were in the descent to 10000' and I contacted approach and advised them that we were leveling 10000' with information. Approach asked if we had been cleared to 10000' by arrival and I said yes, we were cleared the profile descent runway 24. We were then given a vector for traffic sep. At that moment I suspected something was wrong and realized that when comparing the courses on the brany 4 and the altitude restrictions on the runway 24 profile descent which was in my hand (not the 6 pages away from the brany 4 in the manual nor on the yoke with the 24 runway approach plate) that the copilot and I had misread the altitude as 10000' from the above quadrant and had not seen the 11000' restriction applying to the quadrant for our entry. Corrective action: 1) put more emphasis to sector division lines on profile descent in relation to DME and altitude restriction 2) offset 25 DME arc within the different quadrants for arrival. Relation of restrictions to quadrants should be close to one another 3) combine course and altitude restrictions on one chart, or have more continuity between the brany 4 and runway 24 profile descent--they look like 2 totally unrelated arrs.

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Original NASA ASRS Text

Title: ACR MLG ALT DEVIATION OVERSHOT ON PROFILE DESCENT INTO YYZ.

Narrative: THE CAPT CALLED TORONTO APCH. TORONTO GAVE US A NEW FREQ AND UPON CHKING IN WE WERE IMMEDIATELY CLRED FOR THE PROFILE DSCNT RWY 24L/R (ATTACHMENT 2). AT THIS TIME I PULLED OUT THE PROFILE DSCNT RWY 24L/R. I IMMEDIATELY INITIATED A DSCNT TO CROSS 38 DME BTWN 17000-13000'. WHEN WE CHKED TO ENSURE THAT WE WERE JUST INSIDE THE 38 DME AR, THE CAPT THEN DIRECTED A DSCNT TO 10000'. AT THIS TIME I CONTINUED THE DSCNT, AND THEN CHKED THE PROFILE TO CONFIRM THE ALT. I MADE THE SAME MISTAKE AS THE CAPT AND READ THE 25 DME RESTRICTION WHICH WAS LISTED ADJACENT TO THE 38 DME RESTRICTION WE HAD JUST USED (ATTACHMENT 2). APPROX 25 NM OUT FROM TORONTO. THE CTLR ASKED US IF WE HAD BEEN CLRED TO 10000' AND THE CAPT REPLIED THAT WE HAD ALREADY BEEN CLRED THE PROFILE DSCNT TO RWY 24. THE CTLR THEN GAVE A VECTOR FOR TFC SEP. AT THIS POINT WE REALIZED THAT SOMETHING WAS WRONG AND THE CAPT DISCOVERED THAT WE HAD READ THE RESTRICTION FOR THE IMPROPER QUADRANT. WE HAD DSNDED TO 10000' INSTEAD OF 11000'. THE ARR PROC AT TORONTO REQUIRES PLTS TO RAPIDLY TRANSITION THROUGH A NUMBER OF INFLT DOCUMENTS. FIRST THE PLT MUST BE READING HIS LOW CHART TO NAV TO THE ARR PROC. THEN HE MUST HAVE OUT THE ARR PROC AND DETERMINE WHICH PROFILE HE WILL BE ASSIGNED. WHEN THE PROFILE IS ASSIGNED, THE PLT MUST HAVE BOTH THE PROFILE AND THE ARR PROC IN FRONT OF HIM AND REFER TO BOTH SINCE THE PROFILE AND THE ARR PROC IN FRONT OF HIM AND REFER TO BOTH SINCE THE PROFILE HAS NO COURSE INSTRUCTIONS. IN ADDITION, HE MUST HAVE OUT THE PROPER APCH PLATE SO THAT THE APCH CAN BE STUDIED AND BRIEFED. ALL OF THIS OCCURS WITHIN 40 NM OF TORONTO AT THE SAME TIME THAT THE CTLRS ARE CONSTANTLY ON THE RADIO (REQUIRING EXTRA VIGILANCE TO HEAR YOUR CALL SIGN) AND WHEN THE DSCNT CHK MUST BE ACCOMPLISHED. NEW CHARTS HAD BEEN ISSUED WITHIN THE WEEK. BOTH PLTS HAD ALL UPDATED INFO ON BOARD AND IN USE AT THE TIME OF THE INCIDENT. UNFORTUNATELY THE NEW PROFILE DSCNT IS NOT PORTRAYED IN AN EASILY UNDERSTANDABLE FORMAT. UPON CLOSE STUDY, YOU CAN SEE THAT THE ARR IS DIVIDED INTO SECTORS. HOWEVER, THESE SECTORS ARE NOT EMPHASIZED EITHER GRAPHICALLY OR IN WRITING. BOTH THE CAPT AND I MADE THE MISTAKE OF READING THE 25 DME RESTRICTION WHICH IS CLOSEST TO THE PROPER 38 DME RESTRICTION. THE RESTRICTION THAT WE SHOULD HAVE USED IS LOCATED AT THE BOTTOM OF THE CHART. ALSO, THE 25 DME LINE DEPICTION IS NOT SEGMENTED OR OTHERWISE OBVIOUSLY DIVIDED INTO SECTORS. THIS HELPS LEAD TO THE CONCLUSION THAT THE 25 DME RESTRICTION IS UNIFORM THROUGHOUT. SUPPLEMENTAL INFO FROM ACN 108306: I WAS CAPT ERIE, PA, TO TORONTO/PEARSON INT'L. THE COPLT WAS FLYING ENRTE TO BRANY. ON CONTACT WITH ARR WE WERE GIVEN THE BRANY 4 ARR WITH PROFILE DSCNT RWY 24 AND A FREQ CHANGE TO TORONTO APCH CTL. WE WERE IN THE DSCNT RWY 24 AND A FREQ CHANGE TO TOR APCH CTL. WE WERE IN THE DSCNT TO 10000' AND I CONTACTED APCH AND ADVISED THEM THAT WE WERE LEVELING 10000' WITH INFO. APCH ASKED IF WE HAD BEEN CLRED TO 10000' BY ARR AND I SAID YES, WE WERE CLRED THE PROFILE DSCNT RWY 24. WE WERE THEN GIVEN A VECTOR FOR TFC SEP. AT THAT MOMENT I SUSPECTED SOMETHING WAS WRONG AND REALIZED THAT WHEN COMPARING THE COURSES ON THE BRANY 4 AND THE ALT RESTRICTIONS ON THE RWY 24 PROFILE DSCNT WHICH WAS IN MY HAND (NOT THE 6 PAGES AWAY FROM THE BRANY 4 IN THE MANUAL NOR ON THE YOKE WITH THE 24 RWY APCH PLATE) THAT THE COPLT AND I HAD MISREAD THE ALT AS 10000' FROM THE ABOVE QUADRANT AND HAD NOT SEEN THE 11000' RESTRICTION APPLYING TO THE QUADRANT FOR OUR ENTRY. CORRECTIVE ACTION: 1) PUT MORE EMPHASIS TO SECTOR DIVISION LINES ON PROFILE DSCNT IN RELATION TO DME AND ALT RESTRICTION 2) OFFSET 25 DME ARC WITHIN THE DIFFERENT QUADRANTS FOR ARR. RELATION OF RESTRICTIONS TO QUADRANTS SHOULD BE CLOSE TO ONE ANOTHER 3) COMBINE COURSE AND ALT RESTRICTIONS ON ONE CHART, OR HAVE MORE CONTINUITY BTWN THE BRANY 4 AND RWY 24 PROFILE DSCNT--THEY LOOK LIKE 2 TOTALLY UNRELATED ARRS.

Data retrieved from NASA's ASRS site as of August 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.