ARTCC controller misjudged spacing while descending an small transport through the altitude of anoth...

Attributes
ACN	90770
Time
Date	198806
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : rwf
State Reference	MN
Altitude	msl bound lower : 5900 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Operator	general aviation : corporate
Make Model Name	Small Transport
Flight Phase	descent other
Route In Use	enroute airway : zmp
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 3 controller non radar : 1 controller radar : 17
ASRS Report	90770
Person 2
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation
Independent Detector	atc equipment other atc equipment : unspecified
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 21000 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

Both aircraft were in straight and level flight before the error. Small transport X at 7000' was descended to 4000' to meet the msp approach restriction. The aircraft were to pass laterally, but not 5 mi or more. My lack of experience in the low altitude sectors caused me to misjudge the range being used at the time. I do believe that many of these type of errors are taking place across the country because of the hi/low concept. There is usually a cause written down, but the unwritten cause can be working high altitude or vice versa most of the time. I have yet to meet a controller who can work high and low and be good at both. Usually, a person is comfortable in one or the other, but not both. Hi/low has caused a decrease in the service we provide to the flying public and the closer to the major airports a person works, the more this becomes a problem. Callback conversation with reporter revealed the following: during callback type aircraft was given. Reporter was working a combined position operation with light traffic vol. Traffic advisory was not given nor did the aircraft indicate that they saw each other. ARTCC has been transitioning to the high/low concept for the last 2 yrs. Reporter does not like this confign, even though most of the ARTCC have converted to it. Reporter old timer who has not been at this facility too long and facility transferred from had not yet gone to this confign.

Original NASA ASRS Text

Title: ARTCC CTLR MISJUDGED SPACING WHILE DESCENDING AN SMT THROUGH THE ALT OF ANOTHER SMT AND HAD LESS THAN STANDARD SEPARATION.

Narrative: BOTH ACFT WERE IN STRAIGHT AND LEVEL FLT BEFORE THE ERROR. SMT X AT 7000' WAS DSNDED TO 4000' TO MEET THE MSP APCH RESTRICTION. THE ACFT WERE TO PASS LATERALLY, BUT NOT 5 MI OR MORE. MY LACK OF EXPERIENCE IN THE LOW ALT SECTORS CAUSED ME TO MISJUDGE THE RANGE BEING USED AT THE TIME. I DO BELIEVE THAT MANY OF THESE TYPE OF ERRORS ARE TAKING PLACE ACROSS THE COUNTRY BECAUSE OF THE HI/LOW CONCEPT. THERE IS USUALLY A CAUSE WRITTEN DOWN, BUT THE UNWRITTEN CAUSE CAN BE WORKING HIGH ALT OR VICE VERSA MOST OF THE TIME. I HAVE YET TO MEET A CTLR WHO CAN WORK HIGH AND LOW AND BE GOOD AT BOTH. USUALLY, A PERSON IS COMFORTABLE IN ONE OR THE OTHER, BUT NOT BOTH. HI/LOW HAS CAUSED A DECREASE IN THE SVC WE PROVIDE TO THE FLYING PUBLIC AND THE CLOSER TO THE MAJOR ARPTS A PERSON WORKS, THE MORE THIS BECOMES A PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: DURING CALLBACK TYPE ACFT WAS GIVEN. RPTR WAS WORKING A COMBINED POS OPERATION WITH LIGHT TFC VOL. TFC ADVISORY WAS NOT GIVEN NOR DID THE ACFT INDICATE THAT THEY SAW EACH OTHER. ARTCC HAS BEEN TRANSITIONING TO THE HIGH/LOW CONCEPT FOR THE LAST 2 YRS. RPTR DOES NOT LIKE THIS CONFIGN, EVEN THOUGH MOST OF THE ARTCC HAVE CONVERTED TO IT. RPTR OLD TIMER WHO HAS NOT BEEN AT THIS FAC TOO LONG AND FAC TRANSFERRED FROM HAD NOT YET GONE TO THIS CONFIGN.

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.

ARTCC controller misjudged spacing while descending an small transport through the altitude of another small transport and had less than standard separation.