Aircraft X descent through assigned altitude had less than standard separation from aircraft Y. Pilo...

Attributes
ACN	261532
Time
Date	199311
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mdt
State Reference	ND
Altitude	msl bound lower : 12000 msl bound upper : 13000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	descent other
Route In Use	enroute : direct enroute airway : zmp
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : non radar
Qualification	controller : radar
Experience	controller radar : 8
ASRS Report	261532
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : required legal separation non adherence : clearance
Independent Detector	other controllera
Resolutory Action	other
Consequence	faa : investigated
Miss Distance	horizontal : 3000 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft X was en route to mot at 17000 ft requesting lower. Aircraft Y also en route to mot at 12000 ft. The radar controller issued descent to 13000 ft to aircraft X. Aircraft X descended to 12500 ft where radar controller observed the mode C below the cleared altitude and queried the pilot. Aircraft X climbed back to 13000 ft. I believe the pilot's inattn to flying the aircraft was responsible for this incident. If the pilot of aircraft X had adhered to readback procedures and remained vigilant this incident could have been avoided. By reading back the altitude, it might have reinforced in the pilot's mind there was a restriction.

Original NASA ASRS Text

Title: ACFT X DSCNT THROUGH ASSIGNED ALT HAD LTSS FROM ACFT Y. PLTDEV.

Narrative: ACFT X WAS ENRTE TO MOT AT 17000 FT REQUESTING LOWER. ACFT Y ALSO ENRTE TO MOT AT 12000 FT. THE RADAR CTLR ISSUED DSCNT TO 13000 FT TO ACFT X. ACFT X DSNDED TO 12500 FT WHERE RADAR CTLR OBSERVED THE MODE C BELOW THE CLRED ALT AND QUERIED THE PLT. ACFT X CLBED BACK TO 13000 FT. I BELIEVE THE PLT'S INATTN TO FLYING THE ACFT WAS RESPONSIBLE FOR THIS INCIDENT. IF THE PLT OF ACFT X HAD ADHERED TO READBACK PROCS AND REMAINED VIGILANT THIS INCIDENT COULD HAVE BEEN AVOIDED. BY READING BACK THE ALT, IT MIGHT HAVE REINFORCED IN THE PLT'S MIND THERE WAS A RESTRICTION.

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.

Aircraft X descent through assigned altitude had less than standard separation from aircraft Y. Pilot deviation.