<< >> NASA ASRS Report 449600, September 1999

Flight crew of an air carrier mdt jet overshot assigned intermediate altitude during a profile descent due misunderstanding of clearance.

Attributes
ACN	449600
Time
Date	199909
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : yyz.vor
State Reference	ON
Altitude	msl bound lower : 10500 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : cyyz.tracon
Operator	common carrier : air carrier
Make Model Name	Medium Transport, Low Wing, 2 Turbojet Eng
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	descent : intermediate altitude
Route In Use	arrival : profile descent
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 175 flight time total : 3090 flight time type : 260
ASRS Report	449600
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	atc equipment other atc equipment : radar other controllera
Resolutory Action	controller : issued alert none taken : detected after the fact other
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared as follows: 'descend 7000 ft profile descent.' this was unclr to us because the profile required an intermediate stop on the way to 7000 ft. I queried the controller to ask if he wanted us to fly the profile or descend to 7000 ft. The response was '7000 ft profile.' therefore, we started a descent to 7000 ft following the horizontal (course) profile. When we crossed the yyz 35 DME at approximately 10500 ft, the controller asked us why we weren't at 11000 ft per the profile. I responded that I understood our clearance as being descend to 7000 ft following the profile. He said no. In my opinion, this confusing situation could be avoided by the clearance being issued as simply 'fly profile descent,' omit the 7000 ft discussion. After speaking with other line pilots. I discovered this is a very common occurrence.

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Original NASA ASRS Text

Title: FLC OF AN ACR MDT JET OVERSHOT ASSIGNED INTERMEDIATE ALT DURING A PROFILE DSCNT DUE MISUNDERSTANDING OF CLRNC.

Narrative: WE WERE CLRED AS FOLLOWS: 'DSND 7000 FT PROFILE DSCNT.' THIS WAS UNCLR TO US BECAUSE THE PROFILE REQUIRED AN INTERMEDIATE STOP ON THE WAY TO 7000 FT. I QUERIED THE CTLR TO ASK IF HE WANTED US TO FLY THE PROFILE OR DSND TO 7000 FT. THE RESPONSE WAS '7000 FT PROFILE.' THEREFORE, WE STARTED A DSCNT TO 7000 FT FOLLOWING THE HORIZ (COURSE) PROFILE. WHEN WE CROSSED THE YYZ 35 DME AT APPROX 10500 FT, THE CTLR ASKED US WHY WE WEREN'T AT 11000 FT PER THE PROFILE. I RESPONDED THAT I UNDERSTOOD OUR CLRNC AS BEING DSND TO 7000 FT FOLLOWING THE PROFILE. HE SAID NO. IN MY OPINION, THIS CONFUSING SIT COULD BE AVOIDED BY THE CLRNC BEING ISSUED AS SIMPLY 'FLY PROFILE DSCNT,' OMIT THE 7000 FT DISCUSSION. AFTER SPEAKING WITH OTHER LINE PLTS. I DISCOVERED THIS IS A VERY COMMON OCCURRENCE.

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.