<< >> NASA ASRS Report 362100, February 1997

Flight crew reads clearance altitude change back incorrectly. Approach controller missed the error until altitude deviation altitude overshot occurs.

Attributes
ACN	362100
Time
Date	199702
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : den
State Reference	CO
Altitude	msl bound lower : 9500 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : den
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 180 flight time total : 3000 flight time type : 800
ASRS Report	362100
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot non adherence : clearance non adherence other other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation Operational Deviation

Narrative:

While cruising from cos to den at 12000 ft MSL, approach cleared us to 'slow to 250 KTS and descend to 9000 ft.' upon passing 9500 ft, controller queried what altitude we were descending to and when I made a positive response that we were cleared to 9000 ft, he responded 'climb back up to 10000 ft.' we immediately complied and nothing further was said by the controller except to switch to the next frequency. There was no incident or terrain clearance problem and both the captain and I were positive of the clearance we had received. It was apparently a case of misunderstanding or misstating the clearance. It reinforces the need for both pilots and controllers to communication and clearly read back all clrncs, and to question them when appropriate.

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Original NASA ASRS Text

Title: FLC READS CLRNC ALT CHANGE BACK INCORRECTLY. APCH CTLR MISSED THE ERROR UNTIL ALTDEV ALT OVERSHOT OCCURS.

Narrative: WHILE CRUISING FROM COS TO DEN AT 12000 FT MSL, APCH CLRED US TO 'SLOW TO 250 KTS AND DSND TO 9000 FT.' UPON PASSING 9500 FT, CTLR QUERIED WHAT ALT WE WERE DSNDING TO AND WHEN I MADE A POSITIVE RESPONSE THAT WE WERE CLRED TO 9000 FT, HE RESPONDED 'CLB BACK UP TO 10000 FT.' WE IMMEDIATELY COMPLIED AND NOTHING FURTHER WAS SAID BY THE CTLR EXCEPT TO SWITCH TO THE NEXT FREQ. THERE WAS NO INCIDENT OR TERRAIN CLRNC PROB AND BOTH THE CAPT AND I WERE POSITIVE OF THE CLRNC WE HAD RECEIVED. IT WAS APPARENTLY A CASE OF MISUNDERSTANDING OR MISSTATING THE CLRNC. IT REINFORCES THE NEED FOR BOTH PLTS AND CTLRS TO COM AND CLRLY READ BACK ALL CLRNCS, AND TO QUESTION THEM WHEN APPROPRIATE.

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.