Misinterpreted profile descent procedure and began descent early.

Attributes
ACN	93803
Time
Date	198809
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : yyz
State Reference	ON
Altitude	msl bound lower : 9000 msl bound upper : 9000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : yyz
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Route In Use	arrival : profile descent
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 225 flight time total : 4900 flight time type : 600
ASRS Report	93803
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : cfi pilot : atp
Experience	flight time total : 10000
ASRS Report	93933
Events
Anomaly	altitude deviation : crossing restriction not met inflight encounter : weather non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared for the profile descent for runway 06 into yyz. The captain (not flying) misinterpreted the DME associated with davni intersection. As a result, I was instructed to descend early to meet a modified crossing restriction, issued by the approach controller. I explained the location of davni intersection and he realized his mistake. WX was IFR, rain and turbulence. Contributing factors: controller modification of an already complex and confusing profile descent into yyz, a mileage (DME) mistake on the profile descent plate and the yyz VOR becoming out of service during the descent. While this arrival may decrease workload of the controllers, the workload is evermore increased for pilots during this critical and very busy phase of flight.

Original NASA ASRS Text

Title: MISINTERPRETED PROFILE DESCENT PROC AND BEGAN DESCENT EARLY.

Narrative: CLRED FOR THE PROFILE DSCNT FOR RWY 06 INTO YYZ. THE CAPT (NOT FLYING) MISINTERPRETED THE DME ASSOCIATED WITH DAVNI INTXN. AS A RESULT, I WAS INSTRUCTED TO DSND EARLY TO MEET A MODIFIED XING RESTRICTION, ISSUED BY THE APCH CTLR. I EXPLAINED THE LOCATION OF DAVNI INTXN AND HE REALIZED HIS MISTAKE. WX WAS IFR, RAIN AND TURB. CONTRIBUTING FACTORS: CTLR MODIFICATION OF AN ALREADY COMPLEX AND CONFUSING PROFILE DSCNT INTO YYZ, A MILEAGE (DME) MISTAKE ON THE PROFILE DSCNT PLATE AND THE YYZ VOR BECOMING OUT OF SERVICE DURING THE DSCNT. WHILE THIS ARR MAY DECREASE WORKLOAD OF THE CTLRS, THE WORKLOAD IS EVERMORE INCREASED FOR PLTS DURING THIS CRITICAL AND VERY BUSY PHASE OF FLT.

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.