Approach controller cleared canadair CL65 for descent to a lower altitude at pilot's discretion and ...

Attributes
ACN	433195
Time
Date	199904
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : msy.airport
State Reference	LA
Altitude	msl bound lower : 10700 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : msy.tracon
Operator	common carrier : air carrier
Make Model Name	Challenger CL604
Operating Under FAR Part	Part 121
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : msy.tracon
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 160 flight time total : 2940 flight time type : 605
ASRS Report	433195
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation
Independent Detector	aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	controller : issued new clearance none taken : anomaly accepted
Miss Distance	horizontal : 9000 vertical : 700
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

ATC told us to descend at pilot's discretion from 11000 ft to 4000 ft. We read back the clearance and I set 4000 ft in the altitude preselector. The captain elected to remain at 11000 ft so we could remain at cruise speed (approximately 320 KIAS) rather than having to slow to 250 KIAS passing through 10000 ft. Soon thereafter, ATC called and told us to 'descend now' to 3000 ft. We read back the clearance and 3000 ft was set in the altitude preselector. The captain brought the thrust to idle and deployed speed brakes to begin slowing to 250 KIAS. He then commanded the autoplt to begin a normal rate of descent. Passing 10500 ft, ATC called to amend our altitude and told us to climb back up to 11000 ft. In the same breath, ATC called B737 traffic at our 11 O'clock, climbing to 10000 ft and approximately 5 mi. I immediately read back the clearance and set 11000 ft in the altitude preselector while the captain disengaged the autoplt and pitched up. He then added thrust and retracted the speed brakes while the airplane transitioned to a climb. TCASII then issued a TA and when we brought up the display the yellow circle was at 11 O'clock and approximately 3 mi still in a climb. The captain acquired the target visually and we notified ATC. But the captain also stopped climbing at approximately 10700 ft even though the flight director showed a climb command toward 11000 ft. I told him that we needed to continue the climb to 11000 ft, but there was no response. By this time the traffic reached its closest point of 700 ft below and 1.5 mi from our aircraft. I again said to the captain that we had been assigned 11000 ft and asked why he was not climbing. ATC had said to maintain visual with the traffic and descend when passing clear. The captain at this point, and at approximately 10700 ft, asked ATC if we could continue our descent. ATC said we would continue our descent. The altitude preselector was reset accordingly and descent was initiated.

Original NASA ASRS Text

Title: APCH CTLR CLRED CANADAIR CL65 FOR DSCNT TO A LOWER ALT AT PLT'S DISCRETION AND THEN INTERVENED SHORTLY AFTER THEY HAD STARTED THEIR DSCNT AND SENT THEM BACK TO THEIR PREVIOUS ALT THEY HAD JUST LEFT. CTLR ISSUED TA FOR A B737 CLBING AHEAD OF THEM TO AN ALT THROUGH WHICH THEY WERE GOING TO DSND.

Narrative: ATC TOLD US TO DSND AT PLT'S DISCRETION FROM 11000 FT TO 4000 FT. WE READ BACK THE CLRNC AND I SET 4000 FT IN THE ALT PRESELECTOR. THE CAPT ELECTED TO REMAIN AT 11000 FT SO WE COULD REMAIN AT CRUISE SPD (APPROX 320 KIAS) RATHER THAN HAVING TO SLOW TO 250 KIAS PASSING THROUGH 10000 FT. SOON THEREAFTER, ATC CALLED AND TOLD US TO 'DSND NOW' TO 3000 FT. WE READ BACK THE CLRNC AND 3000 FT WAS SET IN THE ALT PRESELECTOR. THE CAPT BROUGHT THE THRUST TO IDLE AND DEPLOYED SPD BRAKES TO BEGIN SLOWING TO 250 KIAS. HE THEN COMMANDED THE AUTOPLT TO BEGIN A NORMAL RATE OF DSCNT. PASSING 10500 FT, ATC CALLED TO AMEND OUR ALT AND TOLD US TO CLB BACK UP TO 11000 FT. IN THE SAME BREATH, ATC CALLED B737 TFC AT OUR 11 O'CLOCK, CLBING TO 10000 FT AND APPROX 5 MI. I IMMEDIATELY READ BACK THE CLRNC AND SET 11000 FT IN THE ALT PRESELECTOR WHILE THE CAPT DISENGAGED THE AUTOPLT AND PITCHED UP. HE THEN ADDED THRUST AND RETRACTED THE SPD BRAKES WHILE THE AIRPLANE TRANSITIONED TO A CLB. TCASII THEN ISSUED A TA AND WHEN WE BROUGHT UP THE DISPLAY THE YELLOW CIRCLE WAS AT 11 O'CLOCK AND APPROX 3 MI STILL IN A CLB. THE CAPT ACQUIRED THE TARGET VISUALLY AND WE NOTIFIED ATC. BUT THE CAPT ALSO STOPPED CLBING AT APPROX 10700 FT EVEN THOUGH THE FLT DIRECTOR SHOWED A CLB COMMAND TOWARD 11000 FT. I TOLD HIM THAT WE NEEDED TO CONTINUE THE CLB TO 11000 FT, BUT THERE WAS NO RESPONSE. BY THIS TIME THE TFC REACHED ITS CLOSEST POINT OF 700 FT BELOW AND 1.5 MI FROM OUR ACFT. I AGAIN SAID TO THE CAPT THAT WE HAD BEEN ASSIGNED 11000 FT AND ASKED WHY HE WAS NOT CLBING. ATC HAD SAID TO MAINTAIN VISUAL WITH THE TFC AND DSND WHEN PASSING CLR. THE CAPT AT THIS POINT, AND AT APPROX 10700 FT, ASKED ATC IF WE COULD CONTINUE OUR DSCNT. ATC SAID WE WOULD CONTINUE OUR DSCNT. THE ALT PRESELECTOR WAS RESET ACCORDINGLY AND DSCNT WAS INITIATED.

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.