Aircraft X had less than standard separtion from air carrier Y. Pilot deviation.

Attributes
ACN	137050
Time
Date	199002
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : scy
State Reference	TX
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zfw
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other descent other
Route In Use	enroute : direct enroute airway : zfw
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 4
ASRS Report	137050
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 6720 vertical : 100
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft X called on frequency descending to 110. About a min later I cleared aircraft X to 100, he acknowledged, about 2 mins later I cleared aircraft X to 80, he acknowledged. I then gave aircraft X a right 360 degree turn for spacing into the dfw terminal area. About 2 mins later I had to give aircraft X another 360 degree right turn. About 1 min I saw that aircraft X had descended through his assigned altitude and I advised him. I then gave air carrier X an immediate descent to 50. Aircraft X acknowledged for this clearance, I told aircraft X negative climb and maintain 70. I was unable to turn aircraft X because of other traffic. After listening to the voice tapes of the incident several times it was determined that aircraft X asked the question 'do you want us all the way to six?' at the end of this first 360 degree right turn read back. Due to the traffic load, coordination, and poor receivers the question was missed and the question was never asked again. Aircraft X descended to 6000' west/O a clearance. The receivers were garbled and scratchy on this day more so than others, but it is a problem that has been brought up many times before. During the time that I spent on scy low sector on 2-XX-90 I did change the receivers but it did not help. I believe that the frequency problem on 135.25 had a lot to do with this deviation, along with the fact that the pilot of aircraft X not sure of his altitude assignment should have asked his question again to insure the correct altitude.

Original NASA ASRS Text

Title: ACFT X HAD LESS THAN STANDARD SEPARTION FROM ACR Y. PLTDEV.

Narrative: ACFT X CALLED ON FREQ DSNDING TO 110. ABOUT A MIN LATER I CLRED ACFT X TO 100, HE ACKNOWLEDGED, ABOUT 2 MINS LATER I CLRED ACFT X TO 80, HE ACKNOWLEDGED. I THEN GAVE ACFT X A R 360 DEG TURN FOR SPACING INTO THE DFW TERMINAL AREA. ABOUT 2 MINS LATER I HAD TO GIVE ACFT X ANOTHER 360 DEG R TURN. ABOUT 1 MIN I SAW THAT ACFT X HAD DSNDED THROUGH HIS ASSIGNED ALT AND I ADVISED HIM. I THEN GAVE ACR X AN IMMEDIATE DSCNT TO 50. ACFT X ACKNOWLEDGED FOR THIS CLRNC, I TOLD ACFT X NEGATIVE CLB AND MAINTAIN 70. I WAS UNABLE TO TURN ACFT X BECAUSE OF OTHER TFC. AFTER LISTENING TO THE VOICE TAPES OF THE INCIDENT SEVERAL TIMES IT WAS DETERMINED THAT ACFT X ASKED THE QUESTION 'DO YOU WANT US ALL THE WAY TO SIX?' AT THE END OF THIS FIRST 360 DEG R TURN READ BACK. DUE TO THE TFC LOAD, COORD, AND POOR RECEIVERS THE QUESTION WAS MISSED AND THE QUESTION WAS NEVER ASKED AGAIN. ACFT X DSNDED TO 6000' W/O A CLRNC. THE RECEIVERS WERE GARBLED AND SCRATCHY ON THIS DAY MORE SO THAN OTHERS, BUT IT IS A PROB THAT HAS BEEN BROUGHT UP MANY TIMES BEFORE. DURING THE TIME THAT I SPENT ON SCY LOW SECTOR ON 2-XX-90 I DID CHANGE THE RECEIVERS BUT IT DID NOT HELP. I BELIEVE THAT THE FREQ PROB ON 135.25 HAD A LOT TO DO WITH THIS DEVIATION, ALONG WITH THE FACT THAT THE PLT OF ACFT X NOT SURE OF HIS ALT ASSIGNMENT SHOULD HAVE ASKED HIS QUESTION AGAIN TO INSURE THE CORRECT ALT.

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.