Air carrier Y unauthorized descent through occupied altitude descent to wrong altitude had less than...

Attributes
ACN	207766
Time
Date	199204
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : msp
State Reference	MN
Altitude	msl bound lower : 11000 msl bound upper : 12000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other
Route In Use	enroute : direct enroute airway : zmp
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other descent other other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 3 controller radar : 3
ASRS Report	207766
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 12000 flight time type : 5000
ASRS Report	207848
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 28500 vertical : 100
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Pilot Deviation Operational Error

Narrative:

Metering, holding with approximately 12-13 min delays for msp. Approximately 13-16 aircraft on the frequency. Small transport X was an overflt through the sector at 110. Air carrier Y was cleared out of hold and issued 120. Pilot read back 100 and I missed it. At the time of his readback, I was searching around the sector for the listing of AWOS frequencys as I had 2 different aircraft going into 2 different airports within the sector and the WX wasn't very good. Air carrier Y probably wasn't listening up very well either as I had to issue a previous clearance to him 2 times. But that's no excuse. Supplemental information from acn 207848: during the initial outbound turn as I entered the holding pattern at meinz intersection, center said to continue turn to 310 degrees, intercept the arrival, maintain 10000 ft and increase speed to 270 KTS (had previously been maintaining 250 KTS per ATC). I read back the clearance and complied. (First officer was on the PA advising passenger we were now cleared to continue to msp). Passing 11000 ft, center asked if we were at 12000. Told first officer to reply negative descending to 10000 and did they want us to return to 12000. Center told us to descend and maintain 10000. A little later, he advised us there was a 'possible altitude deviation' and gave a telephone number to call if problems arose because of 2 things: 1) 4 items of instruction in 1 string, 2) flying plane and responding on radio at same time in busy phase of flight. I could have prevented the situation by telling first officer to hold up on PA until we were well established in holding, and querying center on altitude assigned as the arrival says to expect to cross pepper intersection at 10000 ft to maintain 9000 ft landing on runway 29. April 92 -- after writing the above, I found out today that msp center had pulled the tapes on this incident. Apparently, controller had in fact cleared me to 12000 ft. I read back 10000 ft and they did not catch the error in my readback.

Original NASA ASRS Text

Title: ACR Y UNAUTHORIZED DSCNT THROUGH OCCUPIED ALT DSCNT TO WRONG ALT HAD LTSS FROM SMT X. PLTDEV. RADAR CTLR FAILED TO HEAR ACR Y INCORRECT READBACK OF WRONG ALT. SYS ERROR.

Narrative: METERING, HOLDING WITH APPROX 12-13 MIN DELAYS FOR MSP. APPROX 13-16 ACFT ON THE FREQ. SMT X WAS AN OVERFLT THROUGH THE SECTOR AT 110. ACR Y WAS CLRED OUT OF HOLD AND ISSUED 120. PLT READ BACK 100 AND I MISSED IT. AT THE TIME OF HIS READBACK, I WAS SEARCHING AROUND THE SECTOR FOR THE LISTING OF AWOS FREQS AS I HAD 2 DIFFERENT ACFT GOING INTO 2 DIFFERENT ARPTS WITHIN THE SECTOR AND THE WX WASN'T VERY GOOD. ACR Y PROBABLY WASN'T LISTENING UP VERY WELL EITHER AS I HAD TO ISSUE A PREVIOUS CLRNC TO HIM 2 TIMES. BUT THAT'S NO EXCUSE. SUPPLEMENTAL INFO FROM ACN 207848: DURING THE INITIAL OUTBOUND TURN AS I ENTERED THE HOLDING PATTERN AT MEINZ INTXN, CTR SAID TO CONTINUE TURN TO 310 DEGS, INTERCEPT THE ARR, MAINTAIN 10000 FT AND INCREASE SPD TO 270 KTS (HAD PREVIOUSLY BEEN MAINTAINING 250 KTS PER ATC). I READ BACK THE CLRNC AND COMPLIED. (FO WAS ON THE PA ADVISING PAX WE WERE NOW CLRED TO CONTINUE TO MSP). PASSING 11000 FT, CTR ASKED IF WE WERE AT 12000. TOLD FO TO REPLY NEGATIVE DSNDING TO 10000 AND DID THEY WANT US TO RETURN TO 12000. CTR TOLD US TO DSND AND MAINTAIN 10000. A LITTLE LATER, HE ADVISED US THERE WAS A 'POSSIBLE ALTDEV' AND GAVE A TELEPHONE NUMBER TO CALL IF PROBLEMS AROSE BECAUSE OF 2 THINGS: 1) 4 ITEMS OF INSTRUCTION IN 1 STRING, 2) FLYING PLANE AND RESPONDING ON RADIO AT SAME TIME IN BUSY PHASE OF FLT. I COULD HAVE PREVENTED THE SITUATION BY TELLING FO TO HOLD UP ON PA UNTIL WE WERE WELL ESTABLISHED IN HOLDING, AND QUERYING CTR ON ALT ASSIGNED AS THE ARR SAYS TO EXPECT TO CROSS PEPPER INTXN AT 10000 FT TO MAINTAIN 9000 FT LNDG ON RWY 29. APRIL 92 -- AFTER WRITING THE ABOVE, I FOUND OUT TODAY THAT MSP CTR HAD PULLED THE TAPES ON THIS INCIDENT. APPARENTLY, CTLR HAD IN FACT CLRED ME TO 12000 FT. I READ BACK 10000 FT AND THEY DID NOT CATCH THE ERROR IN MY READBACK.

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.

Air carrier Y unauthorized descent through occupied altitude descent to wrong altitude had less than standard separation from small transport X. Pilot deviation. Radar controller failed to hear air carrier Y incorrect readback of wrong altitude. System error.