<< >> NASA ASRS Report 120019, August 1989

Confusion regarding clearance altitude. Descending to 10,000', controller says cleared to 11,000' and descend to 9000' to avoid traffic.

Attributes
ACN	120019
Time
Date	198908
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : pmm
State Reference	MI
Altitude	msl bound lower : 10000 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Heavy Transport, Low Wing, 4 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : zau
Flight Plan	IFR
Person 1
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 last 90 days : 30 flight time total : 15000 flight time type : 1200
ASRS Report	120019
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 120 flight time total : 12000 flight time type : 120
ASRS Report	120174
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : required legal separation other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

Descending into ord for a landing we were cleared via direct pappi, direct ord. We were cleared to cross 'story' intersection at 10,000'. While leveling at 10,000', center called us and asked us our altitude. The first officer told the controller 10,200' for 10,000'. We were then told to descend immediately to 9000' and to do so within 30 seconds. The controller then advised us that our clearance was to 11,000' only, and that we had traffic at 12 O'clock, 6 mi. We leveled at 9000' within seconds, and saw the traffic well ahead and above us.

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Original NASA ASRS Text

Title: CONFUSION REGARDING CLRNC ALT. DESCENDING TO 10,000', CTLR SAYS CLEARED TO 11,000' AND DESCEND TO 9000' TO AVOID TRAFFIC.

Narrative: DESCENDING INTO ORD FOR A LNDG WE WERE CLRED VIA DIRECT PAPPI, DIRECT ORD. WE WERE CLRED TO CROSS 'STORY' INTXN AT 10,000'. WHILE LEVELING AT 10,000', CENTER CALLED US AND ASKED US OUR ALT. THE F/O TOLD THE CTLR 10,200' FOR 10,000'. WE WERE THEN TOLD TO DSND IMMEDIATELY TO 9000' AND TO DO SO WITHIN 30 SECONDS. THE CTLR THEN ADVISED US THAT OUR CLRNC WAS TO 11,000' ONLY, AND THAT WE HAD TFC AT 12 O'CLOCK, 6 MI. WE LEVELED AT 9000' WITHIN SECONDS, AND SAW THE TFC WELL AHEAD AND ABOVE US.

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.