Air carrier descended below assigned altitude without clearance.

Attributes
ACN	130335
Time
Date	198912
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : rdu
State Reference	NC
Altitude	msl bound lower : 21000 msl bound upper : 27000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 25
ASRS Report	130335
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X descended below the assigned altitude of FL270 down to FL210 into sector 28 airspace west/O a pointout until he was out of FL220. Aircraft had requested lower from high altitude sector because of chop and then just descended on his own. High altitude sector (extremely busy) didn't notice it until aircraft out of FL230 descending. Called low altitude sector after aircraft in low altitudes.

Original NASA ASRS Text

Title: ACR DESCENDED BELOW ASSIGNED ALT WITHOUT CLRNC.

Narrative: ACR X DSNDED BELOW THE ASSIGNED ALT OF FL270 DOWN TO FL210 INTO SECTOR 28 AIRSPACE W/O A POINTOUT UNTIL HE WAS OUT OF FL220. ACFT HAD REQUESTED LOWER FROM HIGH ALT SECTOR BECAUSE OF CHOP AND THEN JUST DSNDED ON HIS OWN. HIGH ALT SECTOR (EXTREMELY BUSY) DIDN'T NOTICE IT UNTIL ACFT OUT OF FL230 DSNDING. CALLED LOW ALT SECTOR AFTER ACFT IN LOW ALTS.

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.