<< >> NASA ASRS Report 555068, July 2002

A B737 crew, in descent to mdw, misinterped ATC's descent clearance resulting in an unattainable crossing restr.

Attributes
ACN	555068
Time
Date	200207
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : jot.vortac
State Reference	IL
Altitude	msl bound lower : 17000 msl bound upper : 19000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc tower : lfpg.tower
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 24000 flight time type : 240
ASRS Report	555068
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : undershoot non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

First officer flying the aircraft and captain off frequency getting ATIS for mdw. First officer received a clearance to cross 6 mi southwest of jot at 17000 ft and no response from the controller. Captain reported back from getting ATIS and first officer informed the captain that we had a clearance to cross 6 mi southwest of jot at 17000 ft and it had been entered into the FMC. We were at FL290 and the clearance was given when we were 93 mi from jot. At 72 mi southwest of jot, the center controller asked if we were going to make the restr. We responded we would make 6 mi southwest of jot at 17000 ft. The controller said he said '60' mi southwest of jot at 17000 ft. The first officer said he read back 6 mi southwest at 17000 ft and entered it in the FMC and wrote it down and received no response from the controller. The controller then responded to us 'I need you to expedite down' and we did. The next response from the controller was a handoff to the next center controller. Cause: busy controller, similar if not improper terminology, single pilot operation and no response from controller about the correct crossing restr. Cure: perhaps when 1 pilot is off frequency and a clearance is given, the pilot returning to the frequency should verify the clearance with the controller as well as the PF. Also, terminology: '60 (six zero) instead of 60 (sixty) could have prevented the problem.

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Original NASA ASRS Text

Title: A B737 CREW, IN DSCNT TO MDW, MISINTERPED ATC'S DSCNT CLRNC RESULTING IN AN UNATTAINABLE XING RESTR.

Narrative: FO FLYING THE ACFT AND CAPT OFF FREQ GETTING ATIS FOR MDW. FO RECEIVED A CLRNC TO CROSS 6 MI SW OF JOT AT 17000 FT AND NO RESPONSE FROM THE CTLR. CAPT RPTED BACK FROM GETTING ATIS AND FO INFORMED THE CAPT THAT WE HAD A CLRNC TO CROSS 6 MI SW OF JOT AT 17000 FT AND IT HAD BEEN ENTERED INTO THE FMC. WE WERE AT FL290 AND THE CLRNC WAS GIVEN WHEN WE WERE 93 MI FROM JOT. AT 72 MI SW OF JOT, THE CTR CTLR ASKED IF WE WERE GOING TO MAKE THE RESTR. WE RESPONDED WE WOULD MAKE 6 MI SW OF JOT AT 17000 FT. THE CTLR SAID HE SAID '60' MI SW OF JOT AT 17000 FT. THE FO SAID HE READ BACK 6 MI SW AT 17000 FT AND ENTERED IT IN THE FMC AND WROTE IT DOWN AND RECEIVED NO RESPONSE FROM THE CTLR. THE CTLR THEN RESPONDED TO US 'I NEED YOU TO EXPEDITE DOWN' AND WE DID. THE NEXT RESPONSE FROM THE CTLR WAS A HDOF TO THE NEXT CTR CTLR. CAUSE: BUSY CTLR, SIMILAR IF NOT IMPROPER TERMINOLOGY, SINGLE PLT OP AND NO RESPONSE FROM CTLR ABOUT THE CORRECT XING RESTR. CURE: PERHAPS WHEN 1 PLT IS OFF FREQ AND A CLRNC IS GIVEN, THE PLT RETURNING TO THE FREQ SHOULD VERIFY THE CLRNC WITH THE CTLR AS WELL AS THE PF. ALSO, TERMINOLOGY: '60 (SIX ZERO) INSTEAD OF 60 (SIXTY) COULD HAVE PREVENTED THE PROB.

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.