A CL65 flight crew misunderstands altitude assignment and descended too low until the approach contr...

Attributes
ACN	589547
Time
Date	200307
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : cak.airport
State Reference	OH
Altitude	msl bound lower : 2700 msl bound upper : 3200
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : cak.tracon
Operator	common carrier : air carrier
Make Model Name	Regional Jet CL65, Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 23 other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 3400 flight time type : 1500
ASRS Report	589547
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : overshoot non adherence : far non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued advisory flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Ambiguous

Narrative:

On downwind vector for ILS runway 23. VFR over an overcast (base 2000 ft/top 2500 ft). ATC gave my first officer a clearance with several instructions, among them heading, approach expected, altitude, and distance. First officer misunderstood and made 3 readbacks. After last readback, it was understood that altitude was to be 2500 ft. As we descended through 2800 ft MSL, controller stated 'the altitude was 3200 ft, sir.' we immediately climbed and no further incident occurred. No TCASII/GPWS advisories and no traffic in area. The problem could have been avoided by using two shorter clrncs rather than one long clearance, especially since the first officer made 3 readbacks. There was little radio traffic at the time.

Original NASA ASRS Text

Title: A CL65 FLT CREW MISUNDERSTANDS ALT ASSIGNMENT AND DSNDED TOO LOW UNTIL THE APCH CTLR INTERVENES.

Narrative: ON DOWNWIND VECTOR FOR ILS RWY 23. VFR OVER AN OVCST (BASE 2000 FT/TOP 2500 FT). ATC GAVE MY FO A CLRNC WITH SEVERAL INSTRUCTIONS, AMONG THEM HDG, APCH EXPECTED, ALT, AND DISTANCE. FO MISUNDERSTOOD AND MADE 3 READBACKS. AFTER LAST READBACK, IT WAS UNDERSTOOD THAT ALT WAS TO BE 2500 FT. AS WE DSNDED THROUGH 2800 FT MSL, CTLR STATED 'THE ALT WAS 3200 FT, SIR.' WE IMMEDIATELY CLBED AND NO FURTHER INCIDENT OCCURRED. NO TCASII/GPWS ADVISORIES AND NO TFC IN AREA. THE PROB COULD HAVE BEEN AVOIDED BY USING TWO SHORTER CLRNCS RATHER THAN ONE LONG CLRNC, ESPECIALLY SINCE THE FO MADE 3 READBACKS. THERE WAS LITTLE RADIO TFC AT THE TIME.

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.

A CL65 flight crew misunderstands altitude assignment and descended too low until the approach controller intervenes.